Here's the beginning of the dialog we had on the bearing and platter design. There some were preliminary drawings that Chris Brady had attached which I left of this out in order to keep the size down to just large. Additionally, they didn't change too much conceptually from what he has on his website. This ought to get you started. I tried to snip much of the redundancy that the respondents didn't bother to do on their own. As I assemble the digest, I may find other bearing/platter dialogs from earlier on, as people didn't always follow the subject conventions I tried to establish. Additionally, some e-mails crossed subject matter boundaries. This is going to be *work*. Mostly by indifference, (5 votes total) we decided to name the 'table The Teres. Note that much of this brainstorming began over a discussion of Thomas Scheu's inverted bearing 'table. Alex Mitaru had forwarded me a copy of Scheu's plans (in German). The drawings were useful. We quickly concluded that if we could design a non-inverted bearing that kept the line of the pull of the belt so that it was perpindicular to the center of bearing shaft, we would maintain all of the advantages of Scheu's inverted bearing, but at the same time have the advantages that an oil sump provides. I didn't feel bad about copying Scheu's plans because he practically gives them away (essentially charging copying & shipping costs). His table is a righteous deal at great prices and he knows that once you've seen the plans you won't decide to roll your own. As a matter of fact, if we had decided to go with his design, we would have ended up buying from him. I'll be picking up some 5x7 mailing envelopes this week and would be happy to mail you a copy of Scheu's plans. Cheers, Thom ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Thursday, December 16, 1999 11:41 PM Subject: Scheu-Bearing & Platter From: Igor Kuznetsoff [mailto:gorkuz@yahoo.com] I printed the thread, but fell asleep by the second page, so maybe more clues are there to this, but I am curious about one or two things re this subj. The existence of "kit" table parts is an exciting revelation, which brings up the question of why a new bearing is needed, if it is evident that the Scheu system must already be using something. Is the Scheu brg. a weak point, substandard, or just too expensive? Also, what are the proposed thrust surfaces? I'm used bearing of stuff like Sapphire on metal, metal on Teflon, metal on metal (steel/brass), etc. Finally, how will this brg. fit into the heavy looking acrylic platter I saw in the pictures? I ========================================= From: Mackris, Thom G. Igor, Because your question on thrust surfaces is important, I'm copying the "list" on this e-mail. I don't know the answer to this question, but it's certainly something we need to discuss and understand better. Regarding your question on us "producing" our own bearing, I believe this was further down in the "thread" I compiled for you, but just in case I didn't make it clear ... Chris is going to order the plans to see if designing our own bearing & perhaps platter (subplatter?) & or subchassis make sense in the sense that it is compatible with Scheu's standard design. This is important because we might consider ordering several additional assemblies to sell to Joe List members at *no* profit. We'd all benefit in the sense that we'd increase the volume discount from Chris' brother. As you know, in CNC machining, the first unit costs the most & each subsequent one distributes the cost of the CNCprogramming involved, bringing the price down. We don't want to step on Scheu's intellectual property rights here. The object is to bring the cost of machining down and not to start a turntable business stealing Scheu's knowledge. The advantage of us contracting out the bearing is that Chris' brother considers the tolerances required to make a wold class bearing to be trivial with his CNC setup. The price would come down from ~ $200 (for one unit) to ~ $60 is on a quantity of 6 bearings - more would be cheaper, but I'm not sure by how much. If we all agree that the bearing will be of = or higher quality to Scheu's, as well as easily fittable to a subchassis, then the decision to go with Chris' brother's work would seem to be the way to go. Obviously, this is a group effort & your input is desirable. We may all diverge in some areas (cosmetics, plinth or subchassis shape, etc.), but it seems as if we have to come to an agreement over the bearing & how the platter will fit on it. As I mentioned above the thrust surfaces and general bearing design are an open issue which remains to be resolved. . If contracting the bearing & or platter to Chris' brother doesn't allow additional Joe List members to use it with Scheu's off the shelf parts, then we'd probably only make up enough for our personal consumption (currently 5 units, I believe, including you). This would still get us to ~ $60.00 for a bearing assembly. I'm envisioning the bearing fitting into a sub-platter, much like the Thorens designs or my Merrill. The belt could drive this aluminum subplatter. lMerrill claims that acrylic is too dimensionally unstable with respect to temperature to use as a driven surface for a turntable. The main acrylic subplatter would then slide over this subplatter, and a material like sorbothane could be sandwiched between the two. Alternatively, the bearing might be a part of the main platter with the spindle passing through it. This design (which is perhaps Scheu's design) would prohibit future experimentation with different platter materials. Cheers, Thom ================================================ All, Responses to Igor's comments regarding bearing sump oil viscosity, bearings & compatibility with Scheu's design & plans ... 1) I like the driven subplatter idea also. Both George Merrill & Thorens are in this camp. This might affect compatibiltiy with Scheu's design (if he chose to go with no subplatter & the bearing spindle passing through the acrylic platter), but I'll bet we can work around this once we get the plans. 2) I also would guess that thicker oil (STP, etc.) is better than thin. This seems to be to common knowledge going back to the Garrard 301's, 401's & EMT tables, per. info in Sound Practices & the Joe List (haven't checked Analog Addicts list on this, however). 3) Compatibility with Scheu's design has the obvious benefits of allowing people to mix 'n match how much work they want to DIY. 4) Teflon bearing thrust surface. Is this durable enough? Isn't bronze preferable? I don't know the answer to this one ... Cheers, Thom Igor wrote ... [ snip ] For starters, it seems like it would be a very good idea to procure as much as possible in the way of info, diagrams, specs and, if possible dimensioned drawings of Scheu's stuff so that our designs can be made to interface neatly with his parts. The 20 DM plans seem like a good idea. Also, maybe Hartmut can be imposed upon to assemble some info sooner. [snip] I noticed mention of a "bearing (inverted, teflon, ceramic ball)" which sounded very interesting.... Certainly, I would vote for a teflon thrust surface. To expand on that, actually, I would like to see a bearing well which would include a sump arrangement which would allow use of STP-thick oil, not thin oil. [ snip ] (Igor is commenting on the option of a separate subplatter which is the driven platter, upon which the main platter sits, isolated perhaps by either a sheet of sorbothene or lead, or whatever ) ... Excellent idea! Decoupling the sonic main-platter from the driven sub-platter and its mechanical bearing noise (however little) is a capital plan! Thom's original comment ... > Alternatively, the > bearing might be a part of the main platter with the > spindle passing through > it. This design (which is perhaps Scheu's design) > would prohibit future > experimentation with different platter materials. Igor's comment ... I like the former (separate subplatter) idea much better. ================================================ From: Mackris, Thom G. All, There's another analog renegade who's joined this mini-list: Alex Mitaru. He's already ordered and received plans for the Scheu 'table and has had a platter machined for it (for $140.00). The plans are in German, although I didn't ask him if the Canadian distributor has any translations for it. It seems as if the idea of compatibility with Scheu's design (if we all end up liking it of course) is the way to go. I got to take a look at Johannes Chiu's website a bit today (http://www.columbia.edu/~jsc19/turntable.html ). He has some interesting ideas; like the one of adding external flywheel effect through the 3 VCR heads. I'm not certain that I like this much complexity. It seems as if you're adding a lot of potential for bearing noise to creep in after you've labored to move the motor off the plinth. Granted the TNT table has those 3 little idler wheels on the plinth, but the idea still makes me a bit uncomfortable. His thinking still makes for interesting reading and it might spawn fresh ideas from us. I recommend looking at it when you get a chance. Johannes mentions the superiority of a Delrin thrust plate over Teflon on his page (teflon having a tendency to flow according to him). I remember the derailleur on my first 10 speed bike in 1968 was made by Simplex and had a Delrin body. One weak point of these materials in the thrust plate position is in the weight of the platter assembly which they can withstand. This is one reason he went to a lighter platter, gaining flywheel effect from the VCR heads. Perhaps with a heavier platter, bronze is the way to go. I'm sure Chris' brother (the CNC machinist) will have some good information here. Cheers, Thom ================================================ ----- Original Message ----- From: Igor Kuznetsoff Yes, indeed there were some interesting comments. I was reminded, for starters, of my long term fascination for "distributed pull" belt/motor/idler systems of the TNT and Voyd systems, which I have always considered a necessity for stable platter operation. I was not, however, attracted to his implementation of the concept, as the friction pulleys he employed are sure to impart a great deal of bearing noise to the platter, which the use of belts should isolate. Also interesting were comments concerning the combination of Acrylic and Lexan (Polycarbonate) plastics, and aluminum, vis-a vis their ability to damp each other via different resonance characteristics. This is something we should consider in our designs, though I think that his avoiding sorbothane for fear of shear (displacement) is probably a mistake, given the area over which the pressure is distributed, although it does point out that it would be desirable to use the thinnest sorbo that could be found, certainly less than the typical 1/8" thickness that is commonly sold. Another interesting topic he brings up is the use of Delrin rather than Teflon as a thrust surface. Delrin, although a bit less slippery than Teflon, is slick, but he observes, is *harder*, and therefore less deformable than teflon under the type of concentrated load that the ball shaped end of the typical mating part (usually the spindle) presents. This is an important consideration if we are to mate a high mass platter to such a bearing system. My own experiences with Delrin in race car suspension linkages has left me with a great deal of respect for that material. I would suggest the combination of Delrin with the superior lubricative abilities of thick STP-type oil, which, if we look around, can even be found in microscopically teflon-laden formulations, which would cover all bases, probably more than making up for the slightly lower slickness of the Delrin. ================================================ From: Schei, Kenneth I was just in Eagle Hardware and I noticed that they had an assortment of ball bearings in their small parts bins. A possible option. Ken ================================================ From: Schei, Kenneth I've also used Delrin in model railroading applications, and it is very hard for a plastic, and quite slippery. Ken ================================================ From: Schei, Kenneth To All: I don't share Merrill's concern about the "dimensional instability with respect to temperature" of acrylic. What he's referring to is the fact that acrylic has a higher expansion coefficient than other materials like steel or aluminum. when the platter expands with temperature, the circumference gets larger, and the speed ratio between the motor pulley and the platter will will change, but ONLY if the pulley and platter are of dissimilar materials, e.g. they have different coefficients of expansion. Schei's "make it simple" solution is to make the motor pulley and the platter of the same material - acrylic. They will then expand or contract at the same rate and the speed ratio between the two won't change. That's not a bad idea anyway when a constant speed ratio is critical. Interestingly enough, the Master Reference turntable (see pic) seems to have acrylic pulleys. However, it's all somewhat academic: the coefficient of expansion of acrylic, according to the American Society for the Testing of Materials (ASTM) D696, is 0.00006 in/in/degree F. For a temperature swing in the listening room of 10 degrees F (due to a lot of sweaty CATS?) the dimension change would be only 0.006%. Cheers, Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ================================================ From: Mackris, Thom G. I like your thinking, Ken. Even if the difference between the dissimilar materials were a big issue, your DC controller as I envision it would have two fixed speed switch positions (a) 33 rpm and (b) 45 rpm with trimpots associated with each speed. You could trim the speed for Summer & Winter operation. One note about expansion coefficients. On my Merrill with its acrylic platter & aluminum outer periphery clamp, it does become a snug fit in the Summer and a looser fit in the Winter... big deal. Cheers, Thom ================================================ From: Thom Mackris / Joan Panzella This is a summary of some conversations I had with Chris & Ken this week... Platter: I'm thinking of sloped surface, a small rebate for the record label, perhaps a rebate milled into the bottom, and of course a center hole drilled for the spindle. The sloped surface would be in the style of many of the non vacuum clamping turntables like the Well Tempered. A drop of of perhaps .065" would allow a center clamp to flatten out most warps. Ron's Well tempered has a drop of slightly more than .100 from the edge of the platter to the edge of the record label (the thickness of one and a half quarters). Both Ron and I consider this to be too much. Ron finds that he does not fully screw down on his record clamp thereby losing bonding between the record and his acrylic platter. In my experiments with shimming cork record mats at the outer edge with crushable hobby foam (a ring about 3/4" wide beginning at the outer edge of the record), I've found that .065 (measured with my dial indicator) seems to work rather nicely. Extremely warped records are not completely flattened out, but there's no fear of clamping down fully in order to make good contact with the platter - an excellent compromise, IMHO. Bearing: Chris is leaning toward Delrin too, although his brother, the CNC machinist will be an invaluable guide here. The idea of a removable (from the subchassis) bearing is intriguing to both of us, in the event we need to redesign/change subchassis (see armboard discussion below). We all need to discuss the pros & cons of this in terms of integrity of the entire subchassis/bearing structure. For the record, Linn's bearing is removable from the subchassis, Merrill's is not. Record Clamping: Chris & I are leaning toward Ken's current record clamp: A Colorado Avalanche hockey puck. Your team may differ (basketballs and baseballs are not recommended). Chris has adopted this technique. They've both drilled holes in their pucks which make a tight friction fit on the spindle. With a threaded spindle, the clamp probably wouldn't even need to have a threaded insert, althtough this is obviously an option. The puck seems like it could only be superior to my acrylic screw on clamp on my Merrill in terms of both mass and damping. Drilling the hole on center could require some creativity. Stock up on your pucks now before both the NHL & the Mpingo dudes find out. ================================================ From: Igor Kuznetsoff How about bonding two 1" thicknesses with an appropriate vibration fighting glue/agent, and keeping costs down & results up ? Also, how about Johannes Chiu's suggestion of mating acrylic and Lexan (polycarbonate) for dissimilar resonance characteristic reduction ? Who uses these sheets? maybe they can be persuaded to part with less than a full sheet. Security contractors might have the Lexan, as it is "bulletproof glass". ================================================ From: Schei, Kenneth That's a great idea. I think that a 2" thick bonded platter on a 1" thick base would be most excellent. Since I personally want my TT to be a visually aesthetic showpiece, I would like to be able to laminate the platter and still have it look pristine. I think that if we gave the platter a translucent matt finish, and kept the base clear with polished edges, we would achieve that. A matt finish on the edge of the platter would probably be required anyway to provide adequate belt traction. Looking for "scraps" is also worthwhile. We only need about a square foot of material to do each platter. Ken ================================================ From: Mackris, Thom G. All, A note about mats. I've been playing around with cork mats in order to simulate a sloped surface to effect record clamping. I'm shimming the mat at the record lead-in groove, making this area about .065 higher at the lead in groove than at the edge of the label. I'm using a ring of hard foam as a shim which sits under the cork mat. It supports the outer edge of the LP and is 3/4" wide. While this is certainly not as effective as a continuous slope, it's giving me a handle on how much slope is too much. Ron Welborne's Well Tempered has a .010 drop from the lead-in to the label which is approximately the thickness of one and a half quarters. We both agree that this is too much. Ron rarely clamps down fully on an LP as a result & loses some of the benefits of bonding the LP to the acrylic platter. While this helps to flatten severely warped records, you sacrifice the bonding effectiveness for moderate records when you back off from this extreme clamping. I need to check out my friend Blair's Sota (non-vacuum) to see how his reflex clamp works. It's been a while since I owned one. Maybe there's something to be learned from it. George ... is the surface of your VPI platter sloped? For ideas on turntable mats, check out the TNT audio site at: Main Page: http://www.tnt-audio.com/ Tweak Page: http://www.tnt-audio.com/clinica/tweaks.html Direct link to the mat design: http://www.tnt-audio.com/clinica/januse.html Cheers, Thom ================================================ From: Mackris, Thom G. Hi Brian, Note that I've taken Blair Hansen of this reply. He's too challenged at the moment managing his e-mail and asked me to cease and desist copying him for a while. Blair is definitely in on the first round of 'tables, but just doesn't want to involve himself at this stage of the discussion. I find this unfortunate, but I'll bug him offline about matters like how his reflex clamp works on his non-vacuum Sota. As I had mentioned, it's been a while since I owned my Star Saphire (1991) and I'd like to revisit this reflex clamp. This whole clamping thing ... maybe we need to talk to Dave Scott of Thornton. He's currently not online, otherwise I'd include him in this list. He had machined a new platter for his Sota Star Saphire. He used the same stuff that bowling balls are made out of. It would certainly be interesting to see his thoughts on this & how he pulled it off with respect to the vacuum clamping. As you know, the jury seems to be out on whether or not vacuum helps more than it hurts. I'm aware of the tanks that folks have built for the Eminent Technology arm, and I'm certain that there are equivalents designs out there for vacuum pumps (to filter out the pump surge). It would certainly be interesting if we could provide for the option for those inclined to go in this direction. ================================================ From: Steve Zettel I'd tend to decline the vacuum clamping; mostly on the KISS principle. I have no problem with the concept or the sonic effectiveness, but I am leary of the added complexity and the possibility of raising the noise floor. I am happy with the clamping system of the Delphi. >Regarding vacuum, once we talk with Dave Scott we can see what's involved, >as it might be able to be provided as an option for those who are so >inclined. It might end up being just some additional milling for which >those who want to undertake it can pay extra. That seems fair if it is do-able as an "extra cost option" Thanks, Steve Z ================================================ From: Mackris, Thom G. Vacuum: I'm extremely happy with simple mechanical clamping also. I've owned a Sota Star Saphire (vacuum) in the past, and it worked nicely, but I don't think that I personally want to tackle this approach for my table. One question I posed to George Munger is whether his VPI has any slope on his platter ... a straight line slope with the edge of the platter being higher than the area at the record label. How is your Oracle configured. One correction from a prior post: Ron Welborne's WTT is about 0.100 higher at the edge than at the label area and *not* .010. Reiterating my earlier comments I'd say that .065 (or 2/3 of the drop in the Well Tempered) is a more favorable number. An alternative for those who really want solid clamping would be to order a periphery clamp from George Merrill. It's a bit cumbersome to use, and mine is currently out of service. Envision an aluminum ring with a tapered, thin lip that sits over the outer half of the record lead-in goove. This lip is very thin in order to allow for cantilever/cartridge body clearance in the first few grooves of the LP. I could take mine to a machine shop and find out how much it would cost to machine one. The Merrill platter has a slight rebate (~ 1/8" wide & ~ 1/8" deep) that allows you to fit the clamp directly on the platter & underneath the record when you don't want to use it. The reason mine is out of service is that I used to hang the clamp by a plastic covered hook on an old turntable stand I once built. The delicate lip had bent (rippled all around at random points) and when I tried to straighten it, I cracked it in some areas. Although the clamp works incredibly well, I'm leaning toward not using it as it adds an extra step to playing a record. Additinally, some arms get dangerously close to the surface of the clamp as the arm traverses toward the inner groove. George's production is either seat of the pants or has undergone revisions over time, because when I asked about a replacement, he said that I should send my platter in so that the clamp could be matched to it. I think that this is unacceptable for our project, unless we spec'd out exact dimensions to him. I would certainly expect George to have a spec on this clamp with fixed dimensions. Perhaps he did have one but made several production run revisions. For this is the reason I'd lean toward spec'ing out our own version of this clamp ... for control over the project. Additionally, I'd have the clamp designed so that it would not have the tonearm clearance issues that George's clamp has. Having said all of this, I'm still in the KISS (keep it simple stupid) camp - leaning toward not using a periphery clamp and staying with a center clamp and a sloped surface. whew !! For the same reasons, I'm shying away from vacuum clamping, although we definitely should research this on Brian Day's (and others?) behalf as a machining option. Cheers, and thanks for the feedback, Thom ================================================ From: Mackris, Thom G. I received a copy of the (German) plans from Alex the night before last. Yesterday evening, I tore free to take a quick look at the drawings. The first thing that struck me is that the bearing is inverted. I wasn't sure about this when I first looked at the drawings but I checked the first e-mail that Chris compiled from the Joe List posts and confirmed this. Just about no one uses inverted bearings, and I have to wonder what Thomas Scheu's thinking is on this matter. Perhaps someone can comment on this. It would appear to me, that given two bearings of equally high quality, the non-inverted bearing would be quieter, due to the fact that it has an oil sump to damp vibrations. I now understand the comments made about the Scheu using a light coat of thin oil in its bearing. Igor used to work for Revox one Summer (high school) job & made a comment early in this thread about bearing lubrication. The decks which failed to pass speed control tolerances had their motor bearings filled with a *high* viscosity oil. I forget if he said that they used STP, or whether it was STP-like in viscosity ... same difference. George Merrill in a treatise on turntables categorized 3 main bearing lubrication methods: a) Air bearing - he didn't like it and I forget why. b) Dry (e.g. saphire like the Sota 'tables) bearing - good for applications where lubrication is not possible - space craft, etc. c) Oil bathed (sump) - High durability, lowest noise due to oil damping. I'm not sure if a full discussion of this is on George's site, but you might want to reference it: Underground Sound (George's Retail Shop): http://www.ugsaudio.com/index.html Merrill section: http://www.ugsaudio.com/merrillaudio.html I'm with George, Linn, and VPI on this one. Non-inverted, oil sump is th way to go. If you all agree with me about the bearing, this turntable is going to become *our* design and not that of Thomas Scheu. I may be wrong of course. If we get a split on this, say 6 for non-inverted & 5 for inverted Scheu design, I suppose we could end up specifing two bearings, as long as we can come up with a platter that accepts both. Comments? ================================================ From: Alex Mitaru yes, I do know that Scheu uses an inverted bearing...now, I'm mechanically challenged so I don't know what is an inverted bearing; if it is not too difficult I would appreciate an explanation...I also remember from the French magazine L'Audiophile that has a review of the "best" audio installations in the world (75% were in Japan), there was a description of a turntable that used no oil for lubrication (some very clever mechanical engineer invented that...BTW, some gorgeous turntables in that issue, maybe I should sent it to Thom so you guys could droll over it...;-))) alex ================================================ From: Mackris, Thom G. Sent: Thursday, December 16, 1999 4:32 PM Subject: RE: Scheu Turntable Project Alex, Regarding inverted bearings. The ascii drawing you originally sent me was of a standard, non-inverted bearing. The female section is mounted in the subchassis and the inner male shaft is attached to the platter (or a subplattar) and slides down into it. Because the female portion is open at the top, lubricant won't spill out. This is how Merrills, Linns, and Thorens are laid out. An inverted bearing is the same thing turned upside down. In your drawing below, the female portion would be attached to the platter, and the male would be attached to the subchassis. I honestly can't understand the benefits of an inverted bearing. Below is a (fixed font) copy of your ascii art representing a non-inverted bearing: Note: When I use Outlook Express from home, I can't turn on fixed font for sections of mail unless I change this message to HTML format. Cut 'n paste the following into another e-mail package & change to fixed font (e.g. courier) to view. ___ ________________________| |________________________ | | | | | acrylic 1.5" | | | | | | | |_______________________| |_______________________| | | |0.5" | |steel| _______________________]~~~~~~| |~~~~~[_______________________ ] | | [ ]2.5" | | [ ]teflon| | [ glass 1.0" ] | | [ _______________________] | | [_______________________ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] | | [ ] |_____| [ ] | ce | [ ] |ramic| [ ] | ball| [ ]__________________[ ================================================ ----- Original Message ----- From: Igor Kuznetsoff Facing *up* and slippery, by me, no doubt about it. One thing I am sure of, and that's that dry bearings make a ,well, *dry*, husky noise because, on a microscopic level, they grab/let go/grab/ let go, etc. Of course, conventional (upward opening) bearings are less dynamically stable (they want to teeter-totter like a top on its point) and create larger side loads on the bearing sleeves (as opposed to the "thrust" point), and so are more prone to a "wow" type of distortion by allowing (a microscopic) teetering wobble of the platter. This is one of the reasons I consider distributing the belt tension with idler pulleys to be absolutely essential in the creation of a turntable of above mundane capability. An inverted bearing would have to be in the platter, up high, closer in line with the pull of the belt, reducing the the lever arm effect the belt's pull would enjoy against the bearing. This would result in better dynamic stability, an elegant way to reduce (but not obviate) the need for the extra complexity of the belt idlers, but, then there would be that pesky dry, husky noise, and the lack of opportunity to use thick oil to damp / swamp the effects of the varying pull of the stylus as it drags its tortuous way through the groove. The only way to avoid the dry noise would be to pressurize the bearing with something, like air, so that there is no hard material contact, and the parts ride on a film of pressurized fluid (like air as it behaves under pressure), and that is a serious complication of the design. Not to mention the stylus drag damping thing. I vote that we a) go with idlers (at least 1 as in the Voyd, preferrably 2 for a 3-point system as in the TNT) *regardless* of any other aspect of design and b) go with the bearing facing receptively up & delightfully slippery with thick oil. ================================================ From: Mackris, Thom G. Wow Igor !!! In addition to your brilliant analysis (at least to this dumb guy), the presence of a microscopic layer of lubricant (especially a viscuous one) would tend to reduce the teeter-totering even further. So ... now we have potentially 3 more parts - high quality idler wheels. Thom ================================================ From: Igor Kuznetsoff > So ... now we have potentially 3 more parts - high > quality idler wheels. > > Thom > As per Ken's excellent suggestion, they should be made of the same acrylic to synchronize expansion, however little. But, then, we're going to have all those scraps of acrylic around , anyway, aren't we ? I think that thick, heavy acrylic idlers ought to look rather interesting,as well, and if not made too small, might add some flywheel effect. Perhaps they could be cut out of the same bonded two layer acrylic I commented on in Ken's price post, and the same belt grooves were cut into the join for a cool, unified, massive look... It must be kept in mind that they will need bearings of some sort also. ================================================ From: Mackris, Thom G. Regarding 3 idler wheels, I'm having problems with the geometry & visualizing the belt contacting the platter. I can easily see how one idler, 180 degrees away from the pulley would work ... I have to get out my pencil & paper. Regarding bearings, George Merrill talks a bit about them in his AR turntable FAQ's page. Of course, we're hearing his particular biases. It would be interesting to research the comments of his ex-employee at Underground Sound, the maker of the highly acclaimed Walker Proscenium turntable. Merrill's AR FAQ's are at: http://www.ugsaudio.com/arq-a.html Thom ================================================ From: Igor Kuznetsoff By three point, I mean *2* idler wheels, one driven wheel, 120 degrees apart. The limiting factor in this configuration would be the possibility of slippage of the belt due to the smaller contact area this geometry allows. With a 2-point version (1 idler, 1 driven pulley) the belt (of whatever cross-section) wraps around much more of the platter edge. ================================================ From: Igor Kuznetsoff I bought the new issue of TAS today, doing my homework for a business talk, and what's on the cover but the Clearaudio Reference System turntable. With what looks like a 2" or so machined acrylic platter in matte finish, a *three point* belt drive using *acrylic pulleys* on massive flywheel looking looking spindles, with the belt running very low on the platter suggesting a minimization of the teetering effect I was talking about and suggesting (I can't tell) an up-turned (non-inverted) bearing, and clear flame-polished trilobial ("Y" shaped) acrylic plinth pieces (or "elements" would be more descriptive) arranged in three stacked tiers. This is easily the sexiest TT I have ever seen. I don't know what it costs, that is not mentioned, but it is considered to be the best ever made by Harry Pearson, and others. Of more interest to us, doesn't this description sound an awful lot like some of the elements we've been discussing ? I was quite startled to see this thing on the cover (it was my first look at it, I'd only first heard of it recently) only a few hours after posting the last few thoughts...All this soon to be second best 'table is missing is a built-in phono stage to wire the tone arm wires right into.... Igor ---------------------------------------------------- Ken said ... One point to remember is that we need enough contact length between the belt (or string?) and the platter for adequate traction. I always find that the maximum traction requirement is when I'm cleaning a record with a brush. There is also the opposing school of thought that embraces an unbalanced pull from the belt. The theory is that the unbalanced pull preloads the bearings in one direction and helps prevent Igor's teeter-totter effect. Just being the devil's advocate. :>) Ken ================================================ ----- Original Message ----- From: Mackris, Thom G. Sent: Saturday, December 18, 1999 9:34 AM Subject: Re: Scheu-Bearing & Platter Guyz, This is great stuff! I pasted your (Igor) two e-mails into one & gave it the subject "Scheu-Bearing & Platter" so that we can find it later :-) I think that any issues relating to how the belt runs fall logically into this subject (rather than Scheu-Motor for example). Not trying to nitpick ... I just want to be able to find this stuff next week ! Thanks for the thoughts, Thom ============================================== From: Igor Kuznetsoff [mailto:gorkuz@yahoo.com] Sent: Saturday, December 18, 1999 12:41 AM Ken: The Clearaudio, of course, ours will be better. How about *one-piece* idlers made right out of the thick bonded (scrap) sections as per previous suggestion, with the belt groove matted, and the rest glossy smooth fire-polished (that's how that's done), and the outer section/surface of the bearing insert made of polished brass so that it can glisten visibly through the "flywheel/idlers" ? Sexy ?? As for the exotic suspension, a fabulous pneumatic suspension can be made for $3 using a K-Mart 12 x 2.25" inner tube layed in between the layers of trilobial fire-polished acrylic plinth pieces. ( About $5-6 at most bicycle stores). All that needs to be done cosmetically to the tubes is to remove the printing from them with lacquer thinner. They can also be painted in a variety of colors using flexible paint available quite commonly from many auto stores, meant for painting vinyl upholstery and bumpers. I use these under everything, and nowadays most of the NJ Audio Society has taken to putting them under all sorts of pieces of equipment. They are amazingly effective (they work *much* better than Seismic Sinks, which cost around $360). They do their best work under the most microphonic equipment, of course, and I have gotten the most stunning results from using them under my 'table and CD player, as well as under everything else nowadays, but with less improvement under those. There is also a secret trick I have for amplifying the outstanding-out -of -the-box performance of the inner tubes which is almost as equally cheap & simple, but I will keep that to myself as a stock-in trade at least until you are convinced of what I am telling you. Go ahead and try this. what have you got to lose / $3 and a few minutes of time trying the idea out? Throw a tube under a 'table if it is simple, or your CD player, and give it a listen. You can throw it directly under some equip., but be aware of not blocking critical cooling vents. If such are on the bottom of the unit, or the piece does not easily sit on the tube (like a 'table might not directly), just put a piece of MDF or whatever is handy on the tube, and the piece on that (& balance/level it). For large equipment, like some 'tables, more stability can be had using the next size up (16 x 2.25"). Inflate loosely (don't make it too stiff), and play with the inflation to tune the resonance passband. Cheeeeap! And speaking of price, having read the article, I still don't know what the thing costs, but the Clearaudio Reference *cartridge* riding the Souther arm it's equipped with is priced at $10,000 ! I ============================================== -----Original Message----- From: Igor Kuznetsoff [mailto:gorkuz@yahoo.com] Sent: Saturday, December 18, 1999 1:17 AM That's a practical thought. Fortunately, there are lots of possible grippy coatings that can be applied neatly to the contact area for pennies, so that's probably a non-issue. The pre-loading theory is a pause in the considerations until one realizes that reality of the situation is that the belt has some stretchiness, and that means that on a microscopic level what will really happen is that a cyclically repeating chain of events will occur. First impetus will be applied by the motor, then the belt will stretch, then impetus will be applied to the platter, then the platter will move while rocking the bearing onto its "loaded" position (pulled towards the origin of the pull), and now, finally (we're talking about microseconds), the platter will move, releasing, for a moment, the radial pull which loaded the bearing, allowing the platter to rock back the other way, and , now this chain of events will repeat, at a frequency dependent on the physical parameters (sizes/masses) of the parts. This is reality on a microscopic scale . All moving things develop harmonic cycles related to their physical parameters, and the only way to reduce/stop the rocking of such an inherently unstable configuration would be to to build the bearings with zero clearance, as in a solid piece, but, then, they won't turn too well...Or use a balanced system in which the pulls & vectors are *balanced*, and there is therefore no inclination on the part of the platter to rock & roll, so that we can. I'm glad you brought that up, Ken, it's good to analyze this so that we can get a handle on the uncertainties of such details, decide them, and go forward with confidence in our choices, once that is done. What do you guys think about this? I ----- Original Message ----- From: Mackris, Thom G. To: Mackris, Thom G. ; 'Boehler, Brian' ; 'Brady, Chris' Sent: Saturday, December 18, 1999 11:38 AM Subject: RE: Scheu-Bearing & Platter All, I'm trying to digest this bearing belt/ force vector thing, and upon a careful re-read of Igor's comments, it appears that Chris & I are stumbling on the same conclusions that Igor's analyisis describes. Driving to work this morning (yes, Saturday ... end of year computer fun), I was talking with Chris & trying to describe Scheu's inverted bearing to him. The shell (female part) in Scheu's bearing nests inside the platter with the outer portion being a slightly tapered conical shape. Picture a tip-toe with the flat surface down & the point facing upward. Now lop off the point so that the surface is parallel to the base and flush with the platter surface at the record label. Now drill a hole from the bottom (base), pointing upward - this is the inverted bearing well. The entire affair nests into a reciprocal conical hole in the platter, buffered by rubber (Bill Mollard pointed out to me that one of Hartmut from Munich's tweaks was to replce the rubber with an unspecified, less lossy material). One final refinement - the angle of this cone is very slight, perhaps 5-10 degrees, much less than that of a tip toe. Chris hit on what Igor has been talking about with respect to how Scheu solved the problem. You see, with Scheu's inverted bearing arrangement, the shaft and the female are all "inside" the 2 inch thick platter. This is a convenient way of side loading the bearing so that there is no (or little) tilting force on the shaft... the belt is set up to pull at a point perpindicular to the middle of the bearing shaft. Although this is an elegant solution, accomplishing this side loading is by no means limited to use of an inverted bearing. I am still in the George Merrill, Linn, Thorens, and Igor camp that all other things being equal, an oil sump is superior in *every* way to any dry (or nearly dry) bearing. The trick is to make all other things equal. I think that we can design a bearing in which we accomplish the same force vectors that Scheu achieved *without* using an inverted bearing. Bill's comments that he received from Hartmut point to the fact that Scheu is using the outer shell of the bearing the way George Merrill (and others) are using a subplatter. George uses a thin lead sheet between the subplatter and the platter. Scheu uses rubber (replaced by Hartmut) in the same position. I think that the use of a subplatter offers several advantages: (a) the ability to experiment with different interfacing surfaces (sorbo, lead, etc.) between platter & subplatter much more easily - cutting a disk is a whole lot easier than wrapping something around a cone. (b) a larger surface with which to ensure that the platter is perpindicular to the bearing shaft - no wobble (c) the possibility that the table can be driven by the subplatter, assuming that the goal of side loading the bearing is accomodated by this geometry. In a phone conversation last night with Terry Gesualdo, Terry brought up the idea of researching sealed bearings from commercial distributors. I know nothing of sourcing something like this or whether a product suitable to this task is even made. I thought I'd throw it out since Terry is apparently too shy to speak up ... no one ever accused me of being shy. Cheers, Thom ------------------------------------------- Igor's earlier comments follow: ------------------------------------------- [ snip ] This is reality on a microscopic scale . All moving things develop harmonic cycles related to their physical parameters, and the only way to reduce/stop the rocking of such an inherently unstable configuration would be to to build the bearings with zero clearance, as in a solid piece, but, then, they won't turn too well...Or use a balanced system in which the pulls & vectors are *balanced*, and there is therefore no inclination on the part of the platter to rock & roll, so that we can. I'm glad you brought that up, Ken, it's good to analyze this so that we can get a handle on the uncertainties of such details, decide them, and go forward with confidence in our choices, once that is done. What do you guys think about this? I ----- Original Message ----- From: Mackris, Thom G. Sent: Saturday, December 18, 1999 3:58 PM Subject: RE: Scheu-Bearing & Platter This is great stuff Steve! BTW, I changed the subject to "Scheu-Bearing & Platter". Your threaded two part clamp is like my Merrill clamp in some respects, and I suspect like George's VPI clamp too. One key difference is that my Merrill clamp does not extend as far out toward the edge of the label, nor is it tapered since the cartridge doesn't get that close to it. This clamping method is the inverse of the Well Tempered & the mockup of it which I created using a shimmed cork mat. I like Oracle's idea better than WTT's & my mockup, especially for the flexibility it offers. By adding or removing a humped washer over the spindle, in conjunction with the "inverted saucer" clamp contacting the record at the outer edge of the label, you accomplish exactly the same thing **and** you get a little anti-skating for **free** where you need it the most - near the end of the side! I'm going to mock this up with some cork & foam tonight. I'll create a ring for my record clamp & a small raised washer for the spindle. One could have a set of two washers, one of which is more raised than the other, and only to be used for extremely warped records. The best part of this is that it leaves you with a great baseline of a flat platter from which to experiment - greater flexibility than machining a slope into it and cheaper. This is absolutely great! One machining option would certainly be the threading on the spindle. I have no problems going with an Oracle threading, as long as it's a standard (English or Metric) thread that we could duplicate. There may be some who want no threading to accomodate their Sota Reflex clamps, but they'll have to pay extra, just like you pay extra for leaving the sugar out of your soft drinks :^) I met Chris for lunch today and to gave him a copy of the engineering drawings. I'll shoot copies for anyone else who is interested. I'm in heavy debugging mode at the moment (work) and so I'll comment about my state of confusion on our lunch a bit later, or sometime tomorrow. One note, however. Sheu's bearing design, whether it's the best approach or not is an outright steal at the prices he's charging. There's a lot more machining in this bearing than in a more conventional bearing that Chris & I had envisioned & *if* we wanted to duplicate it, I'll bet we'd only be saving $50-$60 (IOW, I'll bet the quantity deal on these bearings would run in the $140 range ... it's that complicated). None of this means that its the best solution, of course. I'm thoroughly confused about it, and the vector algebra course I took in college is ancient history by 25 years :-( More to follow guyz ... getting there is half the fun 8-) Thom -----Original Message----- From: Steve Zettel [mailto:zettel@libby.org] Sent: Saturday, December 18, 1999 3:32 PM At 15:59 -0500 12/18/99, ken schei wrote: >Igor: The best way to find out what's best is to run a turntable both with >and without idlers and let our ears decide. > >Ken I concur; I note with interest that one of the latest tweeks for the VPI-set on the Phonogram mailing list is the removal of the idlers which they claim makes an improvement in the sound. They have also gone through recent upgrades in bearings and platters, and now everyone is raving about the SDS, a variable voltage power supply. . . I wouldn't know about all of this, I run an old Oracle Delphi II 8^) Ken, I am finally catching up with the archives on this project. I concur with your analysis of the motor selection. I think a quality DC motor not only gets us more, but avoids expenses and noise elsewhere in the system, too. Re: the platter contour and clamping issues. The Delphi II uses a threaded spindle and a two part system for securely clamping the record to the mat: the clamp is two parts: a knob that is captured in the larger outer clamping fixture, which is a sort of shallow inverted saucer with diameter equal to the record label, and only touches the record label at the outside edge. The edge of the clamping ring where it comes closest to the record leadout groove, and thus the cartridge at the end of play, is very thin and doesn't present a hazard to the cartridge. The knob turns freely independently of the larger clamping part, to avoid marring the record label, and threads down on the spindle. The metal platter is flat and uses a mat. Placed under the mat is a washer which fits over the spindle, the bottom of the washer is flat, the upper surface is curved -- thickest in the middle, thinnest at the edge. When the knob of the clamp is tightened down, the center of the record bottoms out first on the mat and washer, but the area at the edge of the label is forced down farther and very securely bonds the record to the mat. So effective is this that with the original, smooth sorbothane mat the mat usually came off the table with the record and had to be peeled off. Even with a compressible mat, the clamping action seems quite effective with warped records. Some very severely edge-warps (the kind that want to launch the whole arm, then bottom the cartridge) have been tamed by removing the mat and placing a sheet of paper over the bare metal, then really reefing down on the clamp. My understanding is the newer Delphis went to an acrylic "mat" that is still placed on the metal platter, but is very shallowly dished, slightly deeper in the center than the rim. The same clamp is used, but no washer is necessary, as the outer rim of the record contacts the outer edge of the mat first and the album is stressed against the acrylic when the clamp is tightened down. I have played around with both the original "sticky" sorbothane mat, the Audioquest pebbled finish ("non-stick") mat of a somewhat less dense sorbothane, and a flat disc of acrylic in place of the mat. On most records, the ridge at the outer edge seems enough to cause a slight stressing effect when the clamp is tightened down, though the acrylic does not have a relief for the record label. I have also placed the washer on top of the acrylic mat and under the record label, though unless the record is an RCA dynaflex (dynafloppy), there is probably somewhat larger surface of the record not in contact with the mat or platter. Sonic differences. Yes. As one might expect the two sorbo mats are pretty much the same. I couldn't reliably tell them apart. Perceptable difference between sorbo and acrylic and the plain metal platter with the paper sheet. No surprise. Which is better? I don't think that is answerable. All I was doing with the various methods was varying the amount of energy reflected back into the record from the discontinuity of the record/mat or record/platter interface. The sorbo, as a lossy medium, and as perhaps the most closely "bonded" to the record by the clamping mechanism, probably reflected less energy back, and hopefully transmitted less enery from the platter to the LP. Certainly, it sounded less "extended" than the acrylic or the metal platter. But I think this is a false extension, due to the increase in energy getting back to the stylus with the harder materials. So depending on the system, especially the cartridge, but certainly the arm, compliance, tracking ability, tracking force, antiskate setting, and every other parameter one can fiddle with, it may or may not sound "good" to a specific end user. I kind of liked the harder materials when I was using an AudioNote IQ2; with a new Clearaudio Sigma, I find the additional high-frequency energy to be artificial. Short of making the platter out of the same vinyl as the record, and bonding the record to it, we are probably always going to have that discontinuity reflecting some amount of energy back into the LP. And even with good bonding, we are simply then adding mass, and shifting resonances and energy transfer modes around. Adding in the different variables of individual record thickeness, weight, composition, and throwing the additional universe of cartridge and arm unknowns into the mix, and I don't think we can predict what results a given individual will get with a unique setup. I would propose that we make the design of the platter flexible enough to accommodate a variety of tweeks, mats and clamping options for the end users. Certainly the lucite or plastic material would seem to be a good selection for all the reasons you've discussed before my appearing on the scene (ease of machining, availability, cost, relative inertness, decent immunity or freedom from propagating outside vibrations, etc). I sure don't want to second guess that. A slight rebate for the label to accomodate those who wish to leave the platter nude, a threaded spindle for positive clamping (I propose we use the Oracle threading 8^) unless there is some other standard). Enough of a spindle to allow mats for those that subscribe to the lossy/absorbent theory of mats. A shallow dish to the face of the platter would assure positive contact of the record to the mat/platter, with or without a mat or the Oracle-style raised washer to stress the LP on clamping. I like the matte finish all over the platter, if only because a polished surface on soft, plastic material which will be subject to even small amounts of dust, airborne contaminants, fingerprints and record surfaces will ultimately get scratched, just like my present 'table's base, just like my glasses, and just like everything else plastic I own. And I find it a PITA to keep clear finishes looking clean and dust/fingerprint free. YMMV of course. Enough of my rambling for now. Some other time I will bore you with my bio. . . Steve Zettel near Libby, MT USA ----- Original Message ----- From: Mackris, Thom G. To: Boehler, Brian ; Brady, Chris ; Collier (w), Dave Sent: Wednesday, December 22, 1999 11:47 AM Subject: RE: Scheu-Bearing & Platter All, Some furthor thoughts from Igor on belts, & pulleys. Note that these are still in their formative stages. When Igor wrote, it was late at night & he was in a stream of consciousness writing style. I edited his e-mail, primarily by eliminating run-on sentences and clarifying areas where I thought necessary. The changes were minor and I think I did justice to his thoughts. Comment from Thom (read this after you read Igor's analysis). The off center platter experiment could be carried out in a one motor, balanced system. With a motor on a movable base, different length belts could be substituted to vary the distance from the motor pulley to the platter vs. the fixed distance of the idler pulley to the platter. Thom ---------------------------------------------- Igor's (edited) thoughts follow ... ---------------------------------------------- [ snip ] Also, I will be on the lookout for an old-style AR motor to try some things with an old AR 'table I was given, in decrepit state. The AR table has a T-shaped sub-chassis which carries the bearing, platter, arm (an old style that is not useful), and the spring suspension. I thought from when I first got it that the subchassis could be removed from the ridiculous metal plinth, and simply set *nude* on top of an inner tube, with the springs removed entirely for quieting. The tube/subchassis could then be placed on an MDF plate which would also carry the motors. This version 'table used 1 motor (some of the old ones used 2), which will not work with the inner tube by itself as the tube is much too soft laterally. Using 2 motors, a balanced 2-point system could be built with almost no effort. Such a set-up would allow an easy way to experiment with an idea I have about tuning the location of the platter within the system. One would naturally assume that the platter should go equidistant between the two pulleys which would be 180 degrees apart. I have the sneaking suspicion that moving the platter closer to one of the pulleys would result in even quieter operation. The rig I am describing would not fix the position of the sub-chassis relative to the motors. The motors *would* be fixed to the base plate but the inner tube/sub-chassis would just sit on top this plate and could be repositioned. I did not want to muddy the decision waters too much further, not to mention that I didn't want to spend any more hours last week writing micro-analyses of micro-movement such as I did for the way a 1-point (unbalanced) drive system works. Unfortunately, I realized that my analysis of balanced systems was not complete. In a balanced system, the belt stretches with impetus in sections between the items it contacts in just the way I said it does between the motor pulley and platter in the 1-point system. In a balanced system, the belt then sequentially, stretches between the platter and the next idler; then between that idler and the other side of the platter, then from there back to the motor. All this happens sequentially just like with railroad cars bumping back and forth against each other as the locomotive starts to pull them from rest. The motion smooths out of course, as the train gets under way, and the string of cars "pre-loads" under tension, but that back-and forth bumping never quiets completely. What this means to us is that a balanced system is not perfectly balanced because the opposing forces are not applied in synchrony. Does this make sense as I've explained it ? I believe that the amplitude of resulting imbalances will still be much smaller in the balanced system and at a higher frequency, which rotating mass can damp more easily than lower freq's, but....For this reason, I am thinking that off-center platter placement on a common center line (the pulleys would still be 180 degrees apart, but the platter would be closer to one pulley than the other ... Thom), *could* but only *could* result in the best results, but the actual spacing would be a matter of tuning. (Note from Thom - I think we have enough agreement from everyone on the advantages of DC motors - Me, Ken, Chris, Steve Z., Igor, Scheu, Origin Live. For this reason, I'll leave the following comment out of a separate e-mail with "motor" in the subject. This is one area in the design that's a "done deal" methinks). Also, I found mention of the pricey 6V DC motor that Origin offers to be of great interest for the "ironless non-cogging" description, plus all the other stuff that comes with it. "Non cogging"" makes a lot of sense as what that means is that the motor pulls smoothly, rather in pulses as most others, even many DC motors do. This is something we should be aware of in choosing a motor. ----- Original Message ----- From: Schei, Kenneth To: 'Mackris, Thom G.' ; Boehler, Brian ; Brady, Chris Sent: Wednesday, December 22, 1999 12:21 PM Subject: RE: Scheu-Bearing & Platter Igor: I agree on the need for a non-cogging motor; that is one of the foremost requirements. Cogging occurs when the driving force (electromagnetism) is transfered from one armature pole to the next. There are several ways reduce or eliminate cogging. One way is to skew the poles so that their forces overlap. That reduces but does not eliminate the cogging. The best way is to have a pole-less motor, which the coreless motors such as the Faulhaber are. In a permanent-magnet motor, you can feel the cogging or lack thereof by rotating the shaft with your fingers. The shaft of a good coreless motor will rotate freely with uncanny smoothness. Incidently, Faulhaber invented the coreless motor in the 1950's. Maxon is another brand that produces high-quality coreless motors. I think that using two drive motors would be a problem because the platter would always be "hunting" between the slightly different pulls of the two motors. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Igor Kuznetsoff Sent: Wednesday, December 22, 1999 5:36 PM Subject: RE: Scheu-Bearing & Platter Ken, I'm glad that you are on top of it. It is good to have a range of talents pooling on a project. I'm used to having to slog it out with the research necessary every time I run into a discipline I am not well enough versed in at the start of a project. I have been aware of the cogging problem for some time now, but was not aware of what was out there for a solution. I agree with you completely about not using two motors in this project, and had no intention whatsoever of suggesting the use of a second motor (or wanting to buy a second one, either!). I am looking for a second AR motor (AC) only as a means of more easily mocking up a simple test bed for checking out the idler/platter position thing, see the other of today's posts. Should I do this mockup, I may even not power the second motor (probably try both on & off), just use it as the idler, *if* it idles freely. AR actually produced a model for a while (see Merrill's site) with 2 motors, but that was to make up for "torque-challenged" motors. I ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Friday, December 31, 1999 2:09 PM Subject: Re: Scheu-Bearing & Platter All, A couple of comments from Igor are attached, taken from a private e-mail. I added one minor clarification, enclosed in brackets - [ .... TM] . Also, at the end of this e-mail is a copy of a response that Bill M. received from Hartumut of Munich regarding tweaks he made to his Scheu. I think this gives some insight as to which of the (apparently 2) platter/bearing designs are in the production model. I believe I neglected to forward this e-mail to the list so it is attached at the end of this e-mail. You'll note that Igor references pages 5 & 6 in his e-mail. Chris & I numbered the drawings from 0 to 7 for ease of reference (being computer folks, we *had* to start counting with zero ). Those of you who already have copies of the plans can follow along in your hymnals. Regarding two different upper bearing / platter designs. Yes, it appears to be the case to both Chris & me that there are two distinctly differrent bearing/platter interfaces. The lower bearing assembly appears to be identical for both designs. On one design, the upper bearing has a slight conical taper with a reciprocal female taper/socket in the platter (shown on pages 1-4). The other bearing top is cylindrical in shape with a flange, resembling a tiny subplatter ... a reciprocal cylindrical hole is in the platter (shown on pages 5 & 7). I think that Hartmut's comments (below) about replacing the washer impiles that we're talking about the surface where the flange rests/seats against the platter and that the version with the *cylindrical* upper bearing housing/platter interface is the production version. This coupling is similar to how George Merrill couples his subplatter to the platter with a thin lead sheet (thicker than foil). Also note that Hartmut replaced the teflon with scintered bronze. Here is my recollection of my lunch with Chris two weeks ago & our preliminary observations about the drawings: Page 0: laufwerksbasis = drive base. General layout of subchasis showing relationship between bearing hole & arm hole. Note 227 mm distance for Scheu arm. Regas are 220mm. Pages 1 & 2: The top & side views of the conically shaped upper bearing & platter. Pages 3 & 4: Detailed sketches of motor mounting (pod), bearing, bearing mounting pulley, etc. Shows conical upper bearing again. Page 5: Detailed drawing of cylindrically shaped (vesion #2) upper bearing along with shaft. It appears that in both of upper bearing designs, the shaft is separate from the bottom of the bearing. Page 6: Lower half of the bearing in more detail (bohrung werden 2 kalibrierte sinterbronzebuchsen = drilling become 2 calibrated sinter bronze sockets). Apparantly a teflon thrust bearing (fur teflonstopfen mit feingewinde und teflonband = fur teflon-pot with fine thread and teflon band). Chris & I concluded with respect to pages 3, 4 & 6, that the lower bearing part feeds in from the top of the subchassis, identified by the part Lager mit Achse (= Stocks with axle). From the bottom of the subchassis, it is fixed by the part labeled Mutter (= nut/mother) which screws into it. I'm guessing that both bearing designs (tapered & cylindrical) use this same lower assembly. Page 7: Cross sectional view of platter with cylindrical bearing housing interface. Cheers, Thom ========================================== ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, December 30, 1999 5:11 PMT I looked at the plans, got some translations. Didn't help much, the elderly, totally non-technical, lady had more trouble than I did, as I, at least, could guess what those things *should* be. [regarding the Scheu diagrams ... TM] You were quite right about the alignment of the belt and bearing being an elegant means of minimizing (but not eliminating) the teeter - totter effect. The way the bearing and seat are shaped, there will still be a cyclical "riding up" within clearance existing, only the amplification of the lever arm is eliminated. Pages 5 & 6 have what appears to be an alternate bearing / spindle affair that I haven't caught on to the purpose of, but I haven't had time to look very closely or really study all of this yet. Maybe you've figured out what that is about is already ?? The motor housing appears to be filled with "Moosgummi". My translator had no idea what that was, she evidently left Germany before foam rubber became common. I could not tell, however, just how much Moosgummi is supposed to be in there, and how this might affect the motor's heat dissipation. I'll look at the drawings more closely when I can find time, if I have somewhere to do that & and have the plans handy. ========================================== ----- Original Message ----- From: WilliamB Sent: Friday, December 17, 1999 8:42 AM Subject: Harmut improves the Scheu Hey Thom, As mentioned... I contacted Harmut regarding his comment. FWIW William, first I have to say, that now the Scheu in USA is only available over a distributor. Mods in decreasing effectiveness soundwise: replace the rubber ring between platter and bearing with a washer of same thickness use thin oil For myself I use a Cotter slate/rubber suspended base and a Swiss Maxxon motor. I also have a special bearing with ceramic ball riding on a brass piece instead of PTFE. Then I have a special platter from higher density (but that makes only the least improvement) regards, Hartmut best bill ========================================== ----- Original Message ----- From: Steve Zettel Sent: Friday, December 31, 1999 4:32 PM Subject: Re: Scheu-Bearing & Platter on 12/31/99 2:09 PM, Thom Mackris / Joan Panzella at tmackris@earthlink.net wrote: > All, > > A couple of comments from Igor are attached, taken from a private e-mail. I > added one minor clarification, enclosed in brackets - [ .... TM] . Also, > at the end of this e-mail is a copy of a response that Bill M. received from > Hartumut of Munich regarding tweaks he made to his Scheu. I think this > gives some insight as to which of the (apparently 2) platter/bearing designs > are in the production model. I believe I neglected to forward this e-mail > to the list so it is attached at the end of this e-mail. > > Here is my recollection of my lunch with Chris two weeks ago & our > preliminary observations about the drawings: > > Page 0: laufwerksbasis = drive base. General layout of subchasis showing > relationship between bearing hole & arm hole. Note 227 mm distance for > Scheu arm. Regas are 220mm. > I received my set of drawings day before yesterday (thanks, Thom!) but confess I haven't done more than skim over them. But, the above caught my eye in reference to the Rega 220mm measurement. This is apparently in error, according to the skimpy Rega setup data for the RB-300 arm and also some consultation with other Rega users, and the redoubtable Wally Malewicz (designer of the Wallytractor, among other things). The proper distance is 222mm. This may or may not be a problem, but if using the shorter length and a long-bodied cartridge, the overhang might not be able to be set at the headshell. The OriginLive website is one source of the wrong measurement. FWIW, Steve Z ----- Original Message ----- From: Thom Mackris / Joan Panzella Friday, December 31, 1999 7:58 PM Subject: Re: Scheu-Bearing & Platter Indeed, I was quoting from the Origin Live site. You bring good news on this eve of the millenium kimosabe. My Audiocraft also needs to be 222 mm from the spindle. It's a big center hole drilling just like the Rega which essentially means the drillings for the two arms are *perfectly* compatible !! Happy gnu ear ... Thom ----- Original Message ----- From: Chris Brady Sent: Wednesday, January 12, 2000 5:24 PM Subject: Re: Scheu-Bearing & Platter It's time to move toward finalizing the design of the turntable bearing and platter. From the e-mails I think that there is general consensus for a simple non inverted, oil sump bearing. I talked at length with my brother about the bearing and based on his credible advise came to the following conclusions: 1) Since we are using a oil sump, brass will work fine for the bearing surfaces and there would be no advantage for using sintered bronze, Oilite or any other exotic materials. 2) Since the material cost for the bearing is low it will be more cost effective to turn the bearing from a single piece of brass rather than make an aluminum bearing case and then insert bronze/brass bearings. 3) My brother strongly recommended delrin for the thrust plate. He agreed that teflon would be too soft. He was confident that delrin would be smoother (quieter) than brass but also very rugged. 4) The shaft should be made of stainless steel. Stainless is a little more expensive and more difficult to work but it will not corrode. The other options of plating or painting would be more expensive in the long run. With this information and using the Sheu plans as a rough guide for dimensions I created a draft design for the bearing and shaft. The drawing is attached. Note that the top of the bearing is inside of a recess in the bottom of the platter. This lowers the center of gravity and places the drive belt below the top of the bearing. Not shown in the drawing is a 3/8" ball bearing inserted into the bottom of the shaft. For the platter we could simply use the Sheu plan modified to fit our spindle. This drawing is intended to be a starting point for the design and not the final answer. Please feel free to suggest changes. Even nit-picking is acceptable. However, lets move toward finalizing the design and not get side tracked by what if's or other theories. Also, can anyone recommend a reasonable program for creating mechanical drawings? Being spoiled by computers I hate drawing by hand. Chris ---------------------------------------------------------------------------- ---- ----- Original Message ----- From: Mackris, Thom G. To: 'Chris Brady' ; Thom Mackris / Joan Panzella Sent: Wednesday, January 12, 2000 5:27 PM Subject: RE: Scheu-Bearing & Platter Chris, Does a bearing of this configuration still keep the pricing (for 6 or more) in the $70 range? My only suggestions would be: (a) to consider expanding the horizontal disk in to be more of a true sub platter (b) we need to consider whether the top of the spindle will be threaded or threaded as an option (for VPI, Oracle & Merrill style screw clamps) Cheers, Thom ----- Original Message ----- From: Steve Zettel Sent: Wednesday, January 12, 2000 7:28 PM Subject: Re: Scheu-Bearing & Platter on 1/12/00 17:24, Chris Brady at cbrady@sgi.com wrote Great work, Chris! All of the material choices seem reasonable to me. Recessing the bottom of the platter to lower the center of gravity is a very good idea. My only nit to pick is the diameter shown for the recess is the same as the diameter of the bearing housing. Don't we want a few thousandths clearance to avoid any possibility of drag or binding. Only other comment, realizing that this is a preliminary drawing, is threading the top of the spindle to accept a thread-on record clamp, a la Oracle. I will determine the pitch mine uses if desired. Now we can obsess over lubricants! 8^) Thanks, Steve Z ----- Original Message ----- From: Alex Mitaru Sent: Wednesday, January 12, 2000 6:08 PM Subject: RE: Scheu-Bearing & Platter At 05:27 PM 1/12/00 -0700, Mackris, Thom G. wrote: >(a) to consider expanding the horizontal disk in to be more of a true sub >platter I tend to agree with this, though I'm concerned that it can't machined then anymore of a single piece of steel, so it might add to the cost (but, remember I'm totally incompetent in mechanical things...) Also, I don't understand what it is gained by pushing the disk within the platter, I feel that cutting in the platter will weaken it... alex ----- Original Message ----- From: Alex Mitaru Sent: Wednesday, January 12, 2000 6:23 PM Subject: Re: Scheu-Bearing & Platter At 05:24 PM 1/12/00 -0700, Chris Brady wrote: >This drawing is intended to be a starting point for the design and >not the final answer. Please feel free to suggest changes. Even >nit-picking is acceptable. However, lets move toward finalizing the >design and not get side tracked by what if's or other theories. I completely agree with Chris, let's move towards finalizing, so please, take my previous e-mail just what they are, uneducated opinions... So, if I could have another uneducated opinion, I think it would very cool if we would have several brass pucks (7 or 8, didn't do the math), ohhh, about 3" dia. and maybe 1-1.5" thick that would be glued (or threaded into) the bottom of the platter on the circumference. It would give the platter a greater mass and inertia...plus it would look VERY COOL...I think Michel Gyrodeck has a turntable that has something like that... alex ----- Original Message ----- From: Chris Brady Sent: Wednesday, January 12, 2000 8:46 PM Subject: Re: Scheu-Bearing & Platter Thanks for all of the positive comments! It sounds like we are quickly zeroing in on the design. I need to comment on some of the suggestions/questions. > Does a bearing of this configuration still keep the pricing (for 6 or more) > in the $70 range? I sent my brother the draft design so that he can give us a better quote. I will try to reach him tonight. > (a) to consider expanding the horizontal disk in to be more of a true sub > platter I thought about this also. My brother indicated that we can have a spindle diameter of up to 2 inches from a single piece of stainless. Any bigger than this and it would need to be made from 2 pieces. That would increase the cost and also reduce the mechanical stability. Thom as you pointed out making the spindle larger also removes more of the platter creating a different set of problems. From the comments received perhaps the spindle diameter should be increased a little. Say 1.75 to 2.0 inches, but no more. Also as Steve pointed out the bearing housing needs to be smaller than the spindle so making the spindle a little bigger would give the bearing some clearance. > Only other comment, realizing that this is a preliminary drawing, is > threading the top of the spindle to accept a thread-on record clamp, a la > Oracle. I will determine the pitch mine uses if desired. I was unsure of what to do here since I had no idea of how the various clamps attach. Perhaps we need to provide a threaded hole (with an agreed upon size an thread pitch) in the top of the spindle that can accomodate everyones needs. Those not wanting to use a clamp would need to have a short shaft made to screw into the spindle. This would increase cost but would be a more flexible solution. > I'm guessing that the left side of the drawing (the female) will be threaded > on the outside, and a big honkin nut will bind it down to the subchassis as > in Scheu's design. Exactly! Thanks Thom for pointing that out. My brother was confident that the delrin could easily handle any platter we wanted to throw at it. I have no opinion if 3" would be better than 2" but Alex's brass puck idea sounds cool. It goes against my "keep it simple" approach but may have merit. Last of all we need to come up with a name for this project. It certainly is not going to be a Sheu and "the turntable" will not work for long. Lets get some suggestions so we can take a vote and find a name for our beloved project. Chris ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Thursday, January 13, 2000 2:07 AM Subject: Fw: Scheu-Bearing & Platter This is good work Chris! I suspect that you intended to send this to everyone. I note a couple of dimension corrections (thanks, Steve) that you picked up. The important one is the increase from 1.0 to 1.125" in the height of the wide part of the female bearing (the "collar" for lack of a better term). This creates necessary clearance between the bottom of the platter and the top of the subchassis. I'm guessing that the length of the shaft plus exposed ball bearing is in the vicinity of 2.625". This would put the clearance between the top and bottom bearing surfaces at the thickness of the delrin plate. If the delrin plate is as thick as .2" I think we have a safe margin here. So... assuming a 2" thick platter, the effective clearance between the bottom of the platter and the top of the subchassis will be: a) the clearance between the wide part of the bearing and the top of the female (.125") b) the thickness of the delrin (.2" ??) c) the depth of the rebate in the platter for the record label (0.05" ?). The threaded spindle insert looks like a good idea. Some of the light-grade lok-tite (or other thread locker) will certainly keep it from working its way loose - for those of us who use a threaded clamp. This would also allow experimentation with the Roxan school of thinking (although I doubt that I'm inclined do do so). Roxan uses the spindle to locate the record on the platter. The spindle then slides off the bearing stub so that there is no direct contact between the bearing and the LP. This is obviously an unclamped approach. Personally, I think we have enough damping with the platter to render this a disadvantage rather than an advantage, but someone out there might want to try it. Additionally, the damping effects of the clamp would not exist in this arrangement. I take it your brother doesn't see any problems in creating a precision fit between the platter and the upper bearing assembly? BTW, on your next update, fix the typo in the drawing (the spelling of delrin). Regarding names, do we have any mythology experts out there? Any unused gods or goddesses perhaps? The astronomy theme (as you've noted in the past, Chris) has always provided a wealth of names too. Cheers, Thom ----- Original Message ----- From: Chris Brady To: Thom Mackris / Joan Panzella Sent: Wednesday, January 12, 2000 10:38 PM Subject: Re: Scheu-Bearing & Platter I tried using my favorite schematic drawing tool (xcircuit) to create the bearing drawing and it work quite well. Here's the updated drawing. Chris ---------------------------------------------------------------------------- ----- Original Message ----- From: Igor Kuznetsoff To: Chris Brady ; Steve Zettel Sent: Thursday, January 13, 2000 2:55 AM Subject: Re: Scheu-Bearing & Platter Hey, it's great to go online last! You guys already covered most of the questions nicely already, but here's my two cents, following, anyway. I --- Chris Brady wrote: > > (a) to consider expanding the horizontal disk in > to be more of a true sub > > platter > > I thought about this also. My brother indicated > that we can have a spindle > diameter of up to 2 inches from a single piece of > stainless. Any bigger than > this and it would need to be made from 2 pieces. > That would increase the > cost and also reduce the mechanical stability. Thom > as you pointed out > making the spindle larger also removes more of the > platter creating a > different set of problems. From the comments > received perhaps the spindle > diameter should be increased a little. Say 1.75 to > 2.0 inches, but no more. My thoughts, and for all the same reasons, exactly. 1.5" did not feel stable enough for the mass & size of platter we have been talking about. My immediate thought ( I started from the earliest post, and read through to this one before putting my foot in mouth) was 2". Looks that must be an agreeable #. > Also as Steve pointed out the bearing housing needs > to be smaller than the > spindle so making the spindle a little bigger would > give the bearing some > clearance. Yup. > > Only other comment, realizing that this is a > preliminary drawing, is > > threading the top of the spindle to accept a > thread-on record clamp, a la > > Oracle. I will determine the pitch mine uses if > desired. > I was unsure of what to do here since I had no idea > of how the various > clamps attach. Perhaps we need to provide a > threaded hole (with an agreed > upon size an thread pitch) in the top of the spindle > that can accomodate > everyones needs. Those not wanting to use a clamp > would need to have a > short shaft made to screw into the spindle. This > would increase cost but > would be a more flexible solution. Personally, I have nothing against a lengthier spindle, with , or without, the threading. There are other clamping systems than the threaded types that also like a bit of extra spindle to grab. Would the excess be a problem to anyone ? I am undecided myself as to whether I do or don't want the thread, but am 100% certain that I *do* want the flexibility of being able to change that to accomodate all needs, and, *especially*, to be able to take advantage of any hot new *future developments* the market may offer us. Let's not commit ourselves to an inflexible design, only to have some hot new gotta-have clamp show up on the cover of some magazine next week, and us sucking lemons because we can't interface with it. The bit of extra cost for this has gotta be worth it. > > > I'm guessing that the left side of the drawing > (the female) will be threaded > > on the outside, and a big honkin nut will bind it > down to the subchassis as > > in Scheu's design. > > Exactly! Thanks Thom for pointing that out. Ditto, absolutely ! > > My brother was confident that the delrin could > easily handle any platter > we wanted to throw at it. No sweat. With the kind of pounding I've seen Delrin take in race car suspension bushings, I'd guess we could almost put a 10-pony carousel complete with the calliope on one of those. I have no opinion if 3" > would be better than 2" > but Alex's brass puck idea sounds cool. It goes > against my "keep it simple" > approach but may have merit. I'd suggest saving the money from this to put into the threaded spindle tips. In fact, to take advantage of scale economy, perhaps we should consider a complete dual (with/wo thread) tip package with every bearing set for everyone. This way, no regrets for anyone later when they discover that they have to pay to get a single part machined, or if they are willing to get one machined for a hot new clamp, only it can't be screwed in. >There is good rationale for keeping it imbedded, >Alex. The idea behind getting part of the bearing >surface inside the platter is to accomplish what >Scheu is doing with his inverted bearing - to allow >the pull of the belt to approximate pulling at the >middle of the bearing shaft, thereby minimizing the >teeter-tottering effect. This does appear to be a >brilliant solution, irrespective of whether idler >pulleys are in the design Yup. Stability is good. >I feel that cutting in the platter will weaken it... So let's be sure that our platter is at least 2" thick, so there will be plenty of "meat" left after cutting. Now, a couple of thoughts about design details : >Not shown in the drawing is a 3/8" ball bearing >inserted into the bottom of the shaft. 1)The little ballbearing cup in the bottom of the spindle : the drawing shows it as a square cut well. perhaps this was just an artifact of sketching, but my thought is that the well should be radiused so as to encourage the ball to center, rather than wander within the well, improving (however microscopically) the stability of the spindle shaft movement within the (main) bearing well (or outer shell, to be sure that I am causing no confusion). The radius should be significantly larger than the diameter of the ball, so there is point contact for minimum friction. If the ball is to be pressed in, ignore the previous. For the same reason, perhaps the Delrin insert can also be radiused ? >1) Since we are using a oil sump, brass will work >fine for the bearing surfaces and there would be no >advantage for using sintered bronze, Oilite or any >other exotic materials. 2) This is an upward facing bearing that *can* *hold* oil, but I see no provision for a *sump*. A sump is a storage area, like an oil pan in a car. We do not need a *large* sump, but the thin film the present design allows will not give us the long-term viscosity breakdown-free quieting and smoothness that a true sump system can give us. Off the top of my head, to keep this simple, go along with other concepts discussed today, and because it is getting very late (I will think about this some more in the next few days) my suggestion would be to take advantage of the increased 2" spindle disk diameter, and increase the top of the bearing well diameter from 1.5" to just *under* the 2" size. This will allow enough room between the spindle shaft and its outer edge to sink 2-4 largish "sump" bores around the perimeter plus smaller angled (oil) feed holes going from the bottom of those into the spindle cavity. > Last of all we need to come up with a name for this > project. It > certainly is not going to be a Sheu and "the > turntable" will not work for > long. Lets get some suggestions so we can take a > vote and find a name > for our beloved project. > Chris Perhaps, if we go with some of the flame -polished, clear as a glass slipper acrylic subchassis parts, we can call it "The Spinderella"....JUST KIDDING ! >Now we can obsess over lubricants! 8^) I ----- Original Message ----- From: Schei, Kenneth To: 'Chris Brady' Sent: Thursday, January 13, 2000 7:34 AM Subject: RE: Scheu-Bearing & Platter Chris: I will be glad to draw the final design in AutoCad 14. AutoCad is an industry standard and can also be translated into other formats. I like the use of the ball bearing. Questions: There appears to be a recess machined into the bottom of the shaft. If the shaft will bear on a ball bearing, why not make the bottom of the shaft perfectly flat for minimum contact area and thus minimum friction? Also if we have a ball bearing, do we really need the delrin pad? Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Schei, Kenneth Sent: Thursday, January 13, 2000 8:30 AM Subject: RE: Scheu-Bearing & Platter I would rather not have a shrink fit between the spindle and the platter for several reasons. You have already noted the difficulty of disassembling them. Also, as the spindle expanded inside the platter, it would stress the platter somewhat. That stress would make the platter a little less inert, thus losing some of the advantages of using acrylic. Also, I think a shrink fit would couple the vibrations of the spindle to the platter more efficiently, which is what we are trying to avoid. I would prefer a reasonably close slip fit. Ken ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 9:25 AM Subject: RE: Scheu-Bearing & Platter First a note about the threaded bearing stub, and then a suggestion about the platter. Regarding the threaded bearing stub: I agree with Igor - a threaded and non threaded stub would be fairly cheap if done as a production run and expensive if done later. Issuing both (allowing for a threaded clamp and a non-threaded clamp) at the outset for each bearing set produced makes sense in terms of cost and flexibility. A bit long is also good, just in case some people want to experiment with mats. Stress fitting the platter to the bearing shaft: I defer to Ken's structural engineering background on this matter, although I still have concerns about platter stability and how to ensure this. Does anyone else share my concerns, or have additional thoughts on the matter? The shape of the platter: Those of you who have the Scheu drawings, will note that there's a small rebate around the periphery of the platter. This would serve at least two purposes: (a) To facilitate gripping the record by the edge, and (b) To allow the record to contact the platter - remember that the very edge of the record is a bit thicker. I propose that we do the same thing, but follow Merrill's dimensions in this area for (a) platter diameter and (b) the dimensions of the rebate. This will permit the use of his periphery clamp for those of us who are so inclined. I'll either get together with Chris in the next couple of days to get a diagram out or perhaps play around in Paint to diagram this. Cheers, Thom ----- Original Message ----- From: Chris Brady Sent: Thursday, January 13, 2000 10:02 AM Subject: Re: Scheu-Bearing & Platter I also like the idea of a shallow rebate for the record label. Chris ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 10:03 AM Subject: RE: Scheu-Bearing & Platter The bearing/spindle interface is certainly an area for tweakery & experimentation. Hartmut's substitution of a less-lossy substance (than the original Scheu rubber), Merrill's use of a thin sheet of lead - which would tend to validate Hartmut's findings. While I can agree with a more stress-less fit, I'm still struggling with the idea of platter stability on a disk that's only 1.75 to 2.0 inches in diameter. Someone help me here ... Thom -----Original Message----- From: Chris Brady [mailto:cbrady@sgi.com] Sent: Thursday, January 13, 2000 9:53 AM Subject: Re: Scheu-Bearing & Platter The interface between the spindle and the platter is something that I have been thinking about. I can see 3 possible approaches. 1) A net fit with no clearance. This would give a friction fit but if the tolerances are good it could be inserted and removed with some effort. There would probably be minor thermal stresses and no decoupling. 2) Minimal clearance. With 1 or 2 thousandths of clearance there would be some friction during assembly. This would be easy to disassemble and there would probably be a small amount of decoupling. 3) Greater clearance with a decoupling medium. Placing a thin layer of rubber, felt or whatever between the spindle and platter would provide some decoupling. This would be more like the Sheu design. However, we need to remember that one of the Sheu tweaks was to replace the medium with something more rigid. Like Ken, my leaning is for a minimal clearance, slip fit. If we wanted to play with decoupling a thin washer of some lossy material could be placed between the bottom of the platter and the lip of the spindle. With the close fit between the top of the spindle and the platter the decoupling would be a bit limited, but perhaps beneficial. Chris ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 10:11 AM Subject: Re: Scheu-Bearing & Platter on 1/12/00 20:46, Chris Brady at cbrady@sgi.com wrote: > Thanks for all of the positive comments! It sounds like we are > quickly zeroing in on the design. I need to comment on some of > the suggestions/questions. Well, as I see it, this part of the design is key -- I might be able to fabricate most of the other parts of the turntable, but it is doubtful that I could do the bearing and spindle at work (and our best machinist there just retired on a medical retirement). Without a quality bearing, the whole project is just pretty acrylic sculpture. No matter what we do with dampening, mass loading, vibration isolation, or sand boxes, if we have a noisy bearing we can't overcome that. So thanks again, Chris. > >> Does a bearing of this configuration still keep the pricing (for 6 or more) >> in the $70 range? > > I sent my brother the draft design so that he can give us a better quote. > I will try to reach him tonight. I am on a budget with this project, but I would consider paying more for the bearing (and economizing and doing more DIY elsewhere) than to cheap out on this part. > >> (a) to consider expanding the horizontal disk in to be more of a true sub >> platter > > I thought about this also. My brother indicated that we can have a spindle > diameter of up to 2 inches from a single piece of stainless. Any bigger than > this and it would need to be made from 2 pieces. That would increase the > cost and also reduce the mechanical stability. Thom as you pointed out > making the spindle larger also removes more of the platter creating a > different set of problems. From the comments received perhaps the spindle > diameter should be increased a little. Say 1.75 to 2.0 inches, but no more. > Also as Steve pointed out the bearing housing needs to be smaller than the > spindle so making the spindle a little bigger would give the bearing some > clearance. I am not sure, given a certain tolerance, how enlarging the spindle will give any more accuracy or precision. Granted, 0.001 in 2.0" mathematically is a smaller error than 0.001 in 1.5" or 1", however when talking about runout or eccentricity, I don't think it makes a material difference. Bottom line, we have to make sure the platter hole for the spindle is as precisely concentric with the outside platter edge as possible. With CNC machining, this a trivial matter for the spindle/bearing assembly. For the platter, the only method that comes to mind is to mill the center hole/bearing hole in the platter and turn the outside edge of the final platter assembly on a lathe or a cutting jig, using the actual bearing assembly as the pivot, or a lathe chuck of equal or better tolerance. Perhaps this has already been addressed and I am getting ahead of myself. > >> Only other comment, realizing that this is a preliminary drawing, is >> threading the top of the spindle to accept a thread-on record clamp, a la >> Oracle. I will determine the pitch mine uses if desired. > > I was unsure of what to do here since I had no idea of how the various > clamps attach. Perhaps we need to provide a threaded hole (with an agreed > upon size an thread pitch) in the top of the spindle that can accomodate > everyones needs. Those not wanting to use a clamp would need to have a > short shaft made to screw into the spindle. This would increase cost but > would be a more flexible solution. I had the concept of a spindle with the initial part of the shaft unthreaded as it exits up through the platter, at least to height that would account for a small dished washer placed next to the platter and the thickest label area (MOFI UHQR?) plus a little, then threaded with a *male* thread, with sharp edges chamfered at the top. This would be less of a fabrication hassle than internal threads, and though it sounds less elegant than a plain spindle for those who opt not to clamp, in practice, it does not look obtrusive at all. Or, for those not wanted the top threaded, that step could be eliminated at a slight cost savings. (In all the experiments I have done I have *always* perferred clamped over unclamped, but YMMV). > >> I'm guessing that the left side of the drawing (the female) will be threaded >> on the outside, and a big honkin nut will bind it down to the subchassis as >> in Scheu's design. > > Exactly! Thanks Thom for pointing that out. > > My brother was confident that the delrin could easily handle any platter > we wanted to throw at it. I have no opinion if 3" would be better than 2" > but Alex's brass puck idea sounds cool. It goes against my "keep it simple" > approach but may have merit. Not wishing to be a party pooper, you are on your own with this one! I like the looks, too, but we are adding multiple requirements for maintaining tolerance with individual masses, maintaining tolerance with balance/concentricity, attachment decisions, etc. It may be possible to have a wide, very shallow band machined into the underside of the platter to serve as a precise locating area for brass weights, dampening material, etc. But this is turning into a platter discussion, and not bearing final decision. > > Last of all we need to come up with a name for this project. It > certainly is not going to be a Sheu and "the turntable" will not work for > long. Lets get some suggestions so we can take a vote and find a name > for our beloved project. Actually, "The Table" makes kind of a nice, proud statement about the project. 8^) Steve ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 10:22 AM Subject: Re: Scheu-Bearing & Platter I should have read my mail before posting my last message about threaded spindle tips. Igor's suggestion about a set of unthreaded and threaded is right on the mark. Steve Z Igor said: Personally, I have nothing against a lengthier spindle, with , or without, the threading. There are other clamping systems than the threaded types that also like a bit of extra spindle to grab. Would the excess be a problem to anyone ? I am undecided myself as to whether I do or don't want the thread, but am 100% certain that I *do* want the flexibility of being able to change that to accomodate all needs, and, *especially*, to be able to take advantage of any hot new *future developments* the market may offer us. Let's not commit ourselves to an inflexible design, only to have some hot new gotta-have clamp show up on the cover of some magazine next week, and us sucking lemons because we can't interface with it. The bit of extra cost for this has gotta be worth it. I have no opinion if 3" > would be better than 2" > but Alex's brass puck idea sounds cool. It goes > against my "keep it simple" > approach but may have merit. I'd suggest saving the money from this to put into the threaded spindle tips. In fact, to take advantage of scale economy, perhaps we should consider a complete dual (with/wo thread) tip package with every bearing set for everyone. This way, no regrets for anyone later when they discover that they have to pay to get a single part machined, or if they are willing to get one machined for a hot new clamp, only it can't be screwed in. ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 10:42 AM Subject: RE: Scheu-Bearing & Platter On the subject of platters, and how they fit into the bearing spindle assembly, heres a quick sketch of the platter. I'm thinking that a thicker (3") platter would lend to more stability as most of the mass would be below the 1.75" disk. Anyhow, 2" or 3", I think this is what the basic layout of our platter is going to look like. I'm *still* concerned about platter stability/wobble, however. This might be one reason why Hartmut's less-lossy tweak sounded better ... less wobble. Of course, an idler wheel or two would solve this problem... methinks. Thom ----- Original Message ----- From: Schei, Kenneth Sent: Thursday, January 13, 2000 10:55 AM Subject: RE: Scheu-Bearing & Platter I agree that the bearing is the critical part to be fabricated precisely. Regarding the platter, it was my impression that it also will be CNC milled for adequate precision. That would also make the rebates for the rim and label easy. The brass pucks in the platter sound neat, but they don't fit into my personal KISS philosophy so I will probably opt to go without them. Ken ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 10:59 AM Subject: Re: Scheu-Bearing & Platter on 1/13/00 09:53, Chris Brady at cbrady@sgi.com wrote: > The interface between the spindle and the platter is something that I > have been thinking about. I can see 3 possible approaches. > > 1) A net fit with no clearance. This would give a friction fit but if > the tolerances are good it could be inserted and removed with some > effort. There would probably be minor thermal stresses and no > decoupling. > > 2) Minimal clearance. With 1 or 2 thousandths of clearance there would > be some friction during assembly. This would be easy to disassemble > and there would probably be a small amount of decoupling. > > 3) Greater clearance with a decoupling medium. Placing a thin layer > of rubber, felt or whatever between the spindle and platter would > provide some decoupling. This would be more like the Sheu design. > However, we need to remember that one of the Sheu tweaks was to replace > the medium with something more rigid. > > Like Ken, my leaning is for a minimal clearance, slip fit. If we wanted > to play with decoupling a thin washer of some lossy material could be > placed between the bottom of the platter and the lip of the spindle. With > the close fit between the top of the spindle and the platter the decoupling > would be a bit limited, but perhaps beneficial. > I vote for 1), net fit, no clearance. Given the minimal amount of decoupling that would be provided with the 2) or 3), and Scheu's experience, I think the chance of intoducing an additional source of eccentricity outweighs the damping possibilities. With a very slight temperature differential and either a dry teflon lube, or a liquid tef lube, brand name "Tetra Bike" (also available as "Tetra Gun"), manufactured by FTI Corporation, Annapolis MD, distributed by KBV, Arnold, MD (phone 301 757-7094) a zero clearance fit is easily assembled and disassembled. What we DON'T want is an interference fit, for all the reasons already identified. Stress rises at a dramatic rate with each 0.0001, let alone 0.001". Even given the plastic deformation of the acrylic, I don't think we want that. A little note about Tetra Bike -- this stuff is amazing, For open applications a drop applied, spread, the surfaces worked together, then wiped off results in a dramatic lessening of friction, stiction, and of course, squeaking! In a closed system, such as our bearing, several drops in the well and distributed along the bearing shaft will better than almost any other lube I can think of. In my turntable, cleaning the bearing well out and using Tetra Bike made a very noticable reduction in friction over even the Oracle lube. The coast down time for the platter with belt off when up significantly, and the "feel" of the platter when spun was even more silky and ultra-smooth. Addressing the bearing sump issue briefly -- I really don't think any perceived advantages justify the expense and added complexity. In our application, the speed, load and heat involved is negligable -- certainly not enough to concern us about oil breakdown. About the only thing that would require an oil change is the intial contamination of the oil with the first wear products when running in, and the eventual ever so slight build up of dust and "dirt" in the oil from atmospheric contaminants. A simple swab-out and a few drops more of Tetra Bike and away we go again. A two ounce bottle of Tetra Bike will probably last until I am no longer to struggle out of my chair unassisted and hobble over to the turntable. Steve Z ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 11:20 AM Subject: Re: Scheu-Bearing & Platter on 1/13/00 10:03, Mackris, Thom G. at tgmackris@vicorpinc.com wrote: > The bearing/spindle interface is certainly an area for tweakery & > experimentation. Hartmut's substitution of a less-lossy substance (than the > original Scheu rubber), Merrill's use of a thin sheet of lead - which would > tend to validate Hartmut's findings. > > While I can agree with a more stress-less fit, I'm still struggling with the > idea of platter stability on a disk that's only 1.75 to 2.0 inches in > diameter. Someone help me here ... > > Thom Thom, The platter will be plenty stable, even without a 2" "disk" to rest on. Actually the very slightest of shoulders would be enough to secure the platter rigidly, as long as clearances between the upper bearing assembly and platter do not get excessive. The platter is not resting balanced on a 2" disk, it is located both axially and radially by the part of the bearing that extends up through the platter and ultimately becomes the spindle protruding from the platter's upper surface. The horizontal shoulder, or 2" disk of the bearing takes care of supporting the platter weight and locating the platter in the vertical plane. The *vertical* part of the upper bearing assembly locates the platter side to side and resists tipping. The longer the vertical surfaces of platter and bearing in contact, *and* the tighter the fix, the more stable is this location. This quite effectively resists and "tilting" of the platter on the bearing, as if one were to grab opposite edges of the platter and lift on side and push down on the other. Additionally, stability of the platter is enhanced by having the bearing recessed into the platter, both statically by lowering the center of gravity of the platter, and dynamically by lowering the belt/platter interface in relation to the bearing, as already identified. The platter "hangs" from the bearing assembly, rather than resting on top of. I could see how resting the platter on a "washer" of some very uniform, lossy material might add some minimal dampening, but I don't see how we can line the inside of the hole in the platter with another substance, get a snug fit, and avoid eccentricity problems. But I could be wrong 8^) Please put me on record (pun intended) for advocating very strongly, the snuggest fit between platter and bearing assembly, short of an interference fit. Steve Z ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 11:22 AM Subject: RE: Scheu-Bearing & Platter Well said Steve (Steve's description of the distinction between the vertical and horizontal locating forces on the bearing/platter interface). I'd also like to go on record for as tight as possible without an interference fit. With respect to "as tight as possible", we briefly covered temperature coefficients of expansion before, but we might want to address this again prior to spec'ing out the final dimensions (Ken?). I know that my (aluminum) periphery clamping ring on my Merrill feels snug against the acrylic platter in the Summer (say ... 80 deg F) and looser in the Winter (~ 68 deg. F.). Cheers, Thom ----- Original Message ----- From: Steve Zettel To: Mackris, Thom G. ; Chris Brady Sent: Thursday, January 13, 2000 11:32 AM Subject: Re: Scheu-Bearing & Platter Well, besides my other arguments, clamping the record by pulling against a threaded insert in the top of the bearing assembly, also effectively clamps the platter that much tighter to the bearing assembly as well! 8^) Steve ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 11:29 AM Subject: Re: Scheu-Bearing & Platter on 1/13/00 10:56, Mackris, Thom G. at tgmackris@vicorpinc.com wrote: >> From a cosmetic standpoint, the pucks would not be visible since the edge > and top of the platter will be frosted. Adding more mass would most easily > be accomplished by a milled ring, although it's my preference to gain this > extra mass by increasing the thickness of the platter to 3". Any of the > above solutions would drop the center of gravity to lower down the bearing > shaft, but the deeper platter would get us closer to having the pull of the > belt at the center of the bearing shaft. > > Thom > Which is justification to having the clearances between the bearing shaft and the sides of the bearing well as close and as smooth as possible, since the delrin and ball bearing at the bottom will be supporting the weight of the platter, but the shaft and the inside of the bearing housing will be supporting all side loads. The clearances of the Oracle bearing assembly (which is a long shaft pressed into the platter, and terminated in a ball which rests on a flat, hardened steel plate at the bottom the bearing well) are so close that the lubed shaft very slowly sinks down into the well whether pushed in or allowed to settle of it's own weight, due to the pneumatic cushioning of the air trapped below. It takes some appreciable time to rest on the bottom. Steve Z ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 11:36 AM Subject: RE: Scheu-Bearing & Platter Of course, with Roxan 'tables, the spindle is completely removed after the LP is placed on the record. This isolates the LP from the bearing. But then their bearing isn't as good as ours is going to be 8^}. Roxan's entire approach is a traditional Brittish/Scottish one - isolate the LP from everything via a felt mat - the hell with sinking any vibes from the record back into the platter. We have 10-15 lbs. of acrylic that will be damping any bearing vibration that does occur, although, I personally agree with Steve that our bearing will be silent and that there will be nothing to damp. With respect to seating the bearing, my Merrill also takes about 5-10 minutes to come to rest against the thrust plate, as Steve mentioned that his Oracle does - this being due to the pneumatic pressure and *slow* displacement of the lubricant along the side of the bearing shaft. With respect to record clamps, Ken's & Chris's hockey pucks (actual hockey pucks) add some very nice damping from above. Thom ----- Original Message ----- From: Schei, Kenneth To: 'Steve Zettel' ; Chris Brady ; Schei, Kenneth Sent: Thursday, January 13, 2000 11:49 AM Subject: RE: Scheu-Bearing & Platter I thank that the goal of a net fit with no clearance would be difficult to achieve and would be troublesome because of the significant difference between the coefficient of expansion of acrylic and that of steel. A close slip fit with Tetra-Bike or other lubricant (it must be acrylic-compatible) shouldn't allow any appreciable eccentricity. Ken ----- Original Message ----- From: Schei, Kenneth To: 'Mackris, Thom G.' ; 'Steve Zettel' ; Chris Brady Sent: Thursday, January 13, 2000 11:53 AM Subject: RE: Scheu-Bearing & Platter The reason for enlarging the spindle is not because it increases the tolerances significantly but because it increases the interface bearing area thus resulting in greater structural stability. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 12:20 PM Subject: RE: Scheu-Bearing & Platter Yes, let the lube take up the slop! Keeping in mind that I did experience a difference in fit at the edge of the platter (12" diameter) between the acrylic platter and the aluminum periphery clamp (Summer vs. Winter ... maybe 12 degree room temperature change). Thom ----- Original Message ----- From: Schei, Kenneth Sent: Thursday, January 13, 2000 1:43 PM Subject: RE: Scheu-Bearing & Platter > -----Original Message----- > From: Steve Zettel [SMTP:zettel@libby.org] > Sent: Thursday, January 13, 2000 11:30 AM > Subject: Re: Scheu-Bearing & Platter > > > The clearances of the Oracle bearing assembly (which is a long shaft > pressed > into the platter, and terminated in a ball which rests on a flat, hardened > steel plate at the bottom the bearing well) are so close that the lubed > shaft very slowly sinks down into the well whether pushed in or allowed to > settle of it's own weight, due to the pneumatic cushioning of the air > trapped below. It takes some appreciable time to rest on the bottom. > > Steve Z The same thing happens on my lowly (?) Thorens TD166 Mk II. Ken ----- Original Message ----- From: Brian Sent: Thursday, January 13, 2000 2:12 PM Subject: Re: Scheu-Bearing & Platter It appears that thickness greater than raw 1" acrylic have been ruled out? It seems the idea is to bond multiple sheets of 1" acrylic to arrive at a 2" or 3" platter. I like the idea of as large a platter as possible, but I'm concerned about the balance of bonded multiples. I have read where companies go to lengths to make sure their platters are perfectly balanced. Will we be able to assure the balance of our multiple bonded platters? How? If so, it would seem to make sense to add the mass loading brass pucks(I think I read something about that). Would these brass pucks also break up resonant modes in the platter such as the brass rod inserts in the Merlin speaker cabinets? Brian Day ----- Original Message ----- From: Schei, Kenneth To: 'Steve Zettel' ; Mackris, Thom G. ; Chris Brady Cc: Thom Mackris / Joan Panzella ; Terry Gesualdo ; Brian Boehler ; Bill Mollard ; Brian Day (h) ; Dave Collier (w) ; George Munger (w) ; Grant Gassman ; Igor Kuznetsoff ; Jeremy Epstein (w) ; Mitaru, Alex ; Ron Welborne ; Thomas Martin (h) ; Thomas Martin(w) Sent: Thursday, January 13, 2000 1:43 PM Subject: RE: Scheu-Bearing & Platter > > -----Original Message----- > > From: Steve Zettel [SMTP:zettel@libby.org] > > Sent: Thursday, January 13, 2000 11:30 AM > > To: Mackris, Thom G.; 'Schei, Kenneth'; Chris Brady > > Cc: Thom Mackris / Joan Panzella; Terry Gesualdo; Brian Boehler; Bill > > Mollard; Brian Day (h); Dave Collier (w); George Munger (w); Grant > > Gassman; Igor Kuznetsoff; Jeremy Epstein (w); Mitaru, Alex; Ron Welborne; > > Thomas Martin (h); Thomas Martin(w) > > Subject: Re: Scheu-Bearing & Platter > > > > > > > > The clearances of the Oracle bearing assembly (which is a long shaft > > pressed > > into the platter, and terminated in a ball which rests on a flat, hardened > > steel plate at the bottom the bearing well) are so close that the lubed > > shaft very slowly sinks down into the well whether pushed in or allowed to > > settle of it's own weight, due to the pneumatic cushioning of the air > > trapped below. It takes some appreciable time to rest on the bottom. > > > > Steve Z > > The same thing happens on my lowly (?) Thorens TD166 Mk II. > > Ken > ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 2:03 PM Subject: RE: Scheu-Bearing & Platter I can't recall the exact price, but I seem to recall Ken quoting something like $300 for a 4x8 sheet of 1" and six times that for 1.5" (or was it 2" thick). I believe that it's a special order item too, which means we'd have to make use of all 32 square feet. Balancing (i.e. material uniformity) is something we have yet to touch upon. Anyone? Thom ----- Original Message ----- From: Schei, Kenneth Sent: Thursday, January 13, 2000 2:33 PM Subject: RE: Scheu-Bearing & Platter The coefficient of expansion for acrylic is 0.00006 inches per inch per degree F. Stainless steel is 0.000008 "/"/F. The difference is 0.000052 "/"/F. If we have a 2" diameter collar on the spindle and experience a 12 degree temp variation, the differential would be 0.000052 X 2 X 12 = 0.001248". If we designed our fit with 0.001" of play, at 12 degrees cooler we would see a 0.000248" interference. Something to think about. Ken Ken Schei, P.E. Project Engineer Antarctic Support Associates Email address: scheike@asa.org Phone: 303-643-0163 ----- Original Message ----- From: Chris Brady To: Schei, Kenneth Sent: Thursday, January 13, 2000 4:33 PM Subject: Re: Scheu-Bearing & Platter My brother thought that it would be a good idea to enlarge the shaft from .625" to .75" for quieter operation. Also in response to the "oil sump" issue he suggested removing some material in the middle of the bearing. This would reduce friction and make room for more oil. See the updated drawing for details. After some thought I also like the idea of using a 3" platter. Since it will be machined after it is laminated there should be no problem with balance. I am not sure if the greater mass will help, but I really like the idea of lowering the center of gravity relative to the bearing. The only disadvantage I can see is the cost of the extra material. Besides, a 3" platter would look way cool! The attached drawing has been modified to work with a 3" platter. With the thicker platter I increased the height and diameter of the top of the spindle from .75 x .75 to 1.0 x 1.0. Comments? Chris ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, January 13, 2000 4:45 PM Subject: RE: Scheu-Bearing & Platter I agree, Chris - a 3" platter would look way cool. After hearing your brother's suggestion about removing some material from the middle of the bearing, I seem to recall that Scheu did the same thing with his bearing (I don't have the plans on hand for reference). I can't figure out why removing material would result in a quieter bearing , since even without the material removed there is a cushion of oil surrounding the entire shaft. Strangely, my intuitive feel for a thicker bearing is supported by your brother. I can't reconcile the above two facts, but the important thing is that we have two experts in this area (Scheu & your brother) coming up with the same solution ... good enuf fer me. I'm *loving* the price! Cheers, Thom ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, January 13, 2000 5:39 PM Subject: RE: Scheu-Bearing & Platter --- "Schei, Kenneth" wrote: > Questions: > There appears to be a > recess machined into the bottom of the shaft. If > the shaft will bear on a > ball bearing, why not make the bottom of the shaft > perfectly flat for > minimum contact area and thus minimum friction? Because the bearing will want to wander around on this (microscopically, of course). A slightly concave surface will not increase contact area noticeably, but *will* encourage the bearing to to stay put, improving stability. > Also if we have a ball bearing, do we really need > the delrin pad? It is more slippery, and *quieter* than metal. ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, January 13, 2000 5:44 PM Subject: RE: Scheu-Bearing & Platter --- "Mackris, Thom G." wrote: > I can't figure out why removing material would > result in a quieter bearing , > since even without the material removed there is a > cushion of oil > surrounding the entire shaft. Removing metal from the middle still leaves the top & bottom supported where the mechanical advantage is best, while removing some drag / contact area from the middle, and allowing us to set up a true sump . Oil baths are great for quieting things, and that's what a sump would be. ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, January 13, 2000 5:54 PM Subject: Re: Scheu-Bearing & Platter > > My brother thought that it would be a good idea to > enlarge the > shaft from .625" to .75" for quieter operation. > Also in response > to the "oil sump" issue he suggested removing some > material in > the middle of the bearing. This would reduce > friction and make > room for more oil. See the updated drawing for > details. > Excellent ! I thought of just this detail late last night , but didn't know how this could be machined, and, as it was very late, decided to let it go for the moment. My vote is with this method . We probably don't need to remove very much, only a small sump would be beneficial, and that interesting sounding bike oil probably comes in small quantities. > After some thought I also like the idea of using a > 3" platter. > Since it will be machined after it is laminated > there should be > no problem with balance. I am not sure if the > greater mass will > help, but I really like the idea of lowering the > center of gravity > relative to the bearing. The only disadvantage I > can see is > the cost of the extra material. Besides, a 3" > platter would look > way cool! I'm for this also. ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, January 13, 2000 6:06 PM Subject: Re: Scheu-Bearing & Platter --- Brian wrote: > It appears that thickness greater than raw 1" > acrylic have been ruled out? > > It seems the idea is to bond multiple sheets of 1" > acrylic to arrive at a 2" > or 3" platter. I like the idea of as large a platter > as possible, but I'm > concerned about the balance of bonded multiples. I > have read where companies > go to lengths to make sure their platters are > perfectly balanced. Will we be > able to assure the balance of our multiple bonded > platters? How? They get machined *after* bonding. > > If so, it would seem to make sense to add the mass > loading brass pucks(I > think I read something about that). Would these > brass pucks also break up > resonant modes in the platter such as the brass rod > inserts in the Merlin > speaker cabinets? > > Brian Day Folks, brass is what *gongs* are made of. Let's skip the resonances and expenses of these "pucks" and go with the quieter, more reasonable all acrylic construction. ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 9:10 PM Subject: Re: Scheu-Bearing & Platter on 1/13/00 09:22, Chris Brady at cbrady@sgi.com wrote: > Comments below: > >> I'd suggest saving the money from this to put into the >> >> threaded spindle tips. In fact, to take advantage of >> scale economy, perhaps we should consider a complete >> dual (with/wo thread) tip package with every bearing >> set for everyone. This way, no regrets for anyone >> later when they discover that they have to pay to get >> a single part machined, or if they are willing to get >> one machined for a hot new clamp, only it can't be >> screwed in. > > I like this idea. A screw in tip as part of each bearing > assembly. We need to pin down the specs for this part. The dimensions from my table are: 11/32" from top surface of the table to the top of the smooth, unthreaded portion of the full-diameter record spindle (don't have an accurate way to measure the diameter, but it fits a standard record hole snugly, but doesn't require pushing to put the record on), the thread portion extends up from there another 11/32". The threading and diameter is standard 1/4" X 20. The top is chamfered a little to knock off the sharp edge of the top thread. > >> >> 1)The little ballbearing cup in the bottom of the >> spindle : the drawing shows it as a square cut well. >> perhaps this was just an artifact of sketching, but my >> thought is that the well should be radiused so as to >> encourage the ball to center, rather than wander >> within the well, improving (however microscopically) >> the stability of the spindle shaft movement within the >> (main) bearing well (or outer shell, to be sure that I >> am causing no confusion). The radius should be >> significantly larger than the diameter of the ball, so >> there is point contact for minimum friction. If the >> ball is to be pressed in, ignore the previous. For >> the same reason, perhaps the Delrin insert can also be >> radiused ? > > My plan was for the ball bearing to be press fit into the > shaft. I don't follow you about the delrin. If the bottom of the bearing spindle is slightly concave, and the delrin plate at the bottom of the well is also slightly concave, a loose ball bearing between the two will be self-centering. As long as the radius of the concave surfaces is sufficiently larger than the radious of the ball bearing, there will still be low-friction point contact between the ball and the surfaces. > >> 2) This is an upward facing bearing that *can* *hold* >> oil, but I see no provision for a *sump*. A sump is a >> storage area, like an oil pan in a car. We do not >> need a *large* sump, but the thin film the present >> design allows will not give us the long-term viscosity >> breakdown-free quieting and smoothness that a true >> sump system can give us. Off the top of my head, to >> keep this simple, go along with other concepts >> discussed today, and because it is getting very late >> (I will think about this some more in the next few >> days) my suggestion would be to take advantage of the >> increased 2" spindle disk diameter, and increase the >> top of the bearing well diameter from 1.5" to just >> *under* the 2" size. This will allow enough room >> between the spindle shaft and its outer edge to sink >> 2-4 largish "sump" bores around the perimeter plus >> smaller angled (oil) feed holes going from the bottom >> of those into the spindle cavity. > > Good point. I had not thought of providing any sort of well. > Unfortunately, this would add quite a bit to the cost since > the drilling and then cross drilling would be separate setup > steps. It may double the bearing cost. I need to think about > this and also run it by my brother. All that need be done is to neck down the diameter of the bearing shaft the last half inch, so that there is some clearance between the sides of the well and the shaft to hold some oil. Steve ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 9:34 PM Subject: Re: Scheu-Bearing & Platter on 1/13/00 12:04, Chris Brady at cbrady@sgi.com wrote: > For the specification of tolerances (fit) we can rely on a machinist. > However, we need to be able to describe the kind of fit we at shooting > for. I agree with the idea of a tight fit. In my layman terms I would > describe tight fit as "tight as we can get and still be able to > insert/remove without use of tools". > > I don't think that temperature will be as much of an issue with the small > diameters we are working with. > > Steve's description of the fit of the shaft into the bearing is exactly > what I have had in mind. I don't know how to spec this, but I am sure > that this description will tell a machinist exactly what is needed. > > Chris I agree, a machinist has specific language to describe the "fits" available. An "interference" would require heating the platter and dry icing the spindle, as the spindle diameter would be slightly larger than the hole in the platter. A "press fit" or "zero clearance" fit would probably require the use of a press fixture to fully seat the spindle in the platter. I honestly don't know what the proper terminology for a fit that can be assembled by hand yet have as little clearance as possible, nor more importantly, what the clearance in thousandth necessary is. Maybe I'll look it up tomorrow at the library. Or the 'net. Steve ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 9:44 PM Subject: Re: Scheu-Bearing & Platter on 1/13/00 13:43, Schei, Kenneth at SCHEIKE@asa.org wrote: >> -----Original Message----- >> From: Steve Zettel [SMTP:zettel@libby.org] >> Sent: Thursday, January 13, 2000 11:30 AM >> To: Mackris, Thom G.; 'Schei, Kenneth'; Chris Brady >> Cc: Thom Mackris / Joan Panzella; Terry Gesualdo; Brian Boehler; Bill >> Mollard; Brian Day (h); Dave Collier (w); George Munger (w); Grant >> Gassman; Igor Kuznetsoff; Jeremy Epstein (w); Mitaru, Alex; Ron Welborne; >> Thomas Martin (h); Thomas Martin(w) >> Subject: Re: Scheu-Bearing & Platter >> >> >> >> The clearances of the Oracle bearing assembly (which is a long shaft >> pressed >> into the platter, and terminated in a ball which rests on a flat, hardened >> steel plate at the bottom the bearing well) are so close that the lubed >> shaft very slowly sinks down into the well whether pushed in or allowed to >> settle of it's own weight, due to the pneumatic cushioning of the air >> trapped below. It takes some appreciable time to rest on the bottom. >> >> Steve Z > > The same thing happens on my lowly (?) Thorens TD166 Mk II. > > Ken > Not so lowly, Ken. And it certainly has a good bearing, then! 8^) Steve Z ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 10:05 PM Subject: Re: Scheu-Bearing & Platter Chris, it looks great and I learned long ago to trust the recommendations of mechanics and machinists or any skilled craftsmen in their areas of expertise -- the recommendations are most usually based in practical and pragmatic experience of what works and what doesn't. Prices are right in there. The changes look super. I second the motion on the 3" platter, and Thom's recent drawing looks good. The rebated edge is a must. The label recess is a good touch. Though I favor mats so far, I plan to experiment with with the bare acrylic platter. Who knows, I might like it! Steve Z ----- Original Message ----- From: Steve Zettel Sent: Thursday, January 13, 2000 10:11 PM Subject: Re: Scheu-Bearing & Platter on 1/13/00 17:54, Igor Kuznetsoff at gorkuz@yahoo.com wrote: > Excellent ! I thought of just this detail late last > night , > but didn't know how this could be machined, and, as it > was very late, decided to let it go for the moment. > My vote is with this method . We probably don't need > to remove very much, only a small sump would be > beneficial, and that interesting sounding bike oil > probably comes in small quantities. > Tetra Bike or Tetra Gun comes in 2oz bottles most typically. Couple of bucks a bottle. I will get in contact with the factory and distributor and see what kind of deal I can get on a dozen or more. Every good turntable has an accessory kit! Steve