All, Here's the next installation in the bearing & platter digest. Chris will be out of town on business through February 10th and as a result, he may not be able to place this on the web site until he returns. Because we have so many new list members, many of whom missed the early part of this week, I thought it would be a good idea to spam you with this :-) Cheers, Thom ----- Original Message ----- From: Stewart Ono To: Sent: Monday, January 31, 2000 1:47 AM Subject: re TT project Hi Tom: Just did a real fast skim of the posts on Chris's website. Several points: larger bearing means it's easier to machine the well in the middle of the bearing. Secondly, you might want to ask Chris's brother about the possibility of placing one right hand twist groove on the bearing. This would pump oil up as the platter is spinning, although you'll have to place a small well at the top to hold the oil as it is pumped up if it doesn't drain fast enough. Just my $.02 Stu ----- Original Message ----- From: Chris Brady Sent: Monday, January 31, 2000 10:27 PM Subject: Re: Teres Bearing & Platter Welcome to the group Stu, Jon and Peter. Stu, I like your idea of a groove in the bearing to "pump" oil to the top of the bearing. My concern would be to not pump up too much oil. I'll run the idea past Bryce. You are right about the larger diameter shaft being easier to machine. Bryce and I discussed this but I didn't think to pass it on to the group. With a large diameter bore a larger, stiffer boring bar can be used resulting in more precise machining. However, the most significant benefit is from the large spindle shaft diameter. With a smaller diameter the shaft would flex slightly during the machining causing the shaft to be microscopicly out of round. This was part of the reason that Bryce suggested that we increase the shaft diameter from .625" to .75". With this diameter the shaft tolerance for roundness will be in microns! Thanks Stu for the input. Chris ----- Original Message ----- From: Stewart Ono Sent: Tuesday, February 01, 2000 1:45 PM Subject: Re: Teres: Palantir/bearings The Palantir was an interesting speaker that got killed when the Canadian government started sponsoring speaker research. I remember being very impressed with it (a small, slightly larger than a Rogers LS3/5 cabinet with its own integral stand) back in the early 80's. It was quite heavy, as I recall, but the manufacturer would not divulge the secret of its construction. The stands were also made of the same material, as I recall. For the TT base, the Sound Anchors people (Bob Worzolla, I believe) have an interesting concept. They use concrete but with varying mixtures of styrofoam and other materials in order to juggle the system resonance. Any consistent material will have one resonance frequency. He tries to have a spread of frequencies (hopefully all out of the audio range). This idea applies to the various legs of the stands he builds, but can be applied to the feet of the TT. Just food for thought, as I haven't done much experimentation or any deep thinking on the subject. The groove idea is not mine, BTW. Systemdek TT's employ it. In working with other TT's in the past, particularly the SOTA which employs an inverted bearing, one thing that always struck me was that the bearing always was dry upon inspection. The little dab of white silicone grease would be all dried up. A pumping action would continuously lubricate the bearing for an inverted bearing design. Also in regards to the tripulley idea a la VPI. While others have reported better results with out the tripulley, and I can attest to that, greasing the pulley bearings significantly increases the sound quality. The problem is that the PLC must be readjusted to compensate for the additional drag. Apparently the few thousandths of play introduced by the tripulley system does create a slight flutter leading to a loss of fine detail. The grease apparently takes up the slack and the original intent, motor isolation, does show its advantages. The problem is that with the VPI design, the grease or oil has a tendency to wick down and out of the bearing sleeves for the idlers (I've seen and heard a few squeaking idlers). An idea similar to the groove in the bearing would probably work wonders in a design like this. I've toyed with the idea of a precision ABEC bearing inserted into the pulleys, but the balls rattling would probably create more problems than an occasional greasing of the spindle. Perhaps some of the other more mechanically inclined members may have a better solution. The tripulley idea appeals to me because it would not put excessive wear on one side of the main bearing sleeve, particularly if it is machined out of any plastics (perhaps that is why the current TNT side bearings are made out of a ceramic material). Grease and Manfred's servo motor system may be just the ticket. Stu ----- Original Message ----- From: Chris Beck Sent: Tuesday, February 01, 2000 5:30 PM Subject: Re: Teres Bearing & Platter FWIW, Hunter Fans has used this idea for decades in their top of the line "Original" model. Just a big sleeve bearing with a ball thrust bearing at the bottom, and a spiral groove to pump oil. I believe there is a return channel for the oil to drain to the sump. They are quiet and last FOREVER. Chris ----- Original Message ----- From: jhlane To: Thom Mackris / Joan Panzella Sent: Tuesday, February 01, 2000 9:31 PM Subject: Re: Regarding the table project Thank you very much indeed, Thom. Sounds like things are as they should be, but you know how sometimes one has to be especially careful... And congrats now that Allen and Manfred have joined. I'd predict that those contributions will advance the project beyond even the best commercial fare to an entirely higher level of quality and performance. On a similar topic - and off-list - would you be in any way interested in the following: I've actually been plotting to fab up a different sort of 'table than the one you're looking at with the list. I hasten to add that I may very well abandon my plan if it proves impossible and I may well end up with a Teres-style unit after all. In fact, odds favor it. But my idea centers around a simple concept in need, I think, only of some expert machining. I want to consider making a large diameter platter of aluminum (of which I have a slab already) with an acrylic insert under the playing area. I envision a main platter diameter of 16" with tapered shoulders rising to meet a 12" dia playing platter. I want to then float this platter over a central puck of perhaps 2" thick x 6" in diameter centered under a mating inset in the underside of the platter(s). From there a simple air pump feeding this "puck" to float the entire affair. I have a source for a pump, and the rest is no different really than the Teres. Might your machinist be interested? Might the group be interested in an alternative to a post bearing design? Again, I submit this with the full understanding that we don't want to rock the boat. Further, I have no proof my concept would work flawlessly but since I design somewhat from instinct...I'm willing to risk it for at least my own personal project. Please ask your machinist if he would consider a variant on the Teres if you would be so kind. Meanwhile, I'll help keep up the good fight on behalf of the Teres and its fans. Respectfully, Jon Lane ----- Original Message ----- From: Anya & Fred Humphrey To: Sent: Tuesday, February 01, 2000 8:46 AM Subject: Teres Hi, Thom I was quite excited to read your platter and bearing message in the joenet digest yesterday. I was an active participant several years ago, but current work demands limit me to a few weeks a year and reading the digests whenever I can. My thoughts on TT design: the Verdier is far and away the best I've heard so I'm glad to see you're incorporating a large diameter, viscous-damped bearing. the Verdier's main weakness, other than price, imo is the vertical instability of the magnetic suspension. the ideal TT would use an airbearing ala Maplenoll but with a large diameter shaft for damping and horizontal stability. However, I have neither the time, money, or skills to pursue this idea. The Delrin thrust pad sounds like a good choice for medium weight platters (but it would probably deform with the 100# Maplenoll accessory platter.) So please sign me up. Who do I send money to? What form? I'll probably also be interested in whatever motor and controller you eventually decide on, but I also want to try rim drive with a 5#, 1/100 horse synchronous motor off an old transcription TT. Thanks for sharing your work. Yours truly, Fred Humphrey ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Tuesday, February 01, 2000 10:45 PM Subject: Re: Regarding the table project Zowie Jon, You are full of imaginative ideas. Feel free to comment to Chris on matters like this. I understand why you'd be hesitant to mention this to the "list". I started a side thread two days ago on the Merrill clamping scheme which resulted in 47 e-mails on Monday. Fortunately, there was no impact to the design. BTW, I'll be preparing a short clamping overview for the website - nothing extensive at first (we'll wait for the discussion to unfold), but just some teasers. Chris' brother Bryce is certainly sympathetic to our goals. I honestly don't know what to say about the machining or whether there would be any interest. I'm trying to envision a worst case scenario: that you present it to the list as an alternative architecture and that no one is interested. The one-off price for our bearing and spindle was ~ $550. I can't recall what percentage the platter was, but I believe it was about 55% of the cost. Anyhow, I think you follow my line of reasoning here. It could get quite expensive. Cheers, Thom ----- Original Message ----- From: Tony Bombera Sent: Wednesday, February 03, 1988 10:32 AM Subject: Re: Teres Turntable - A Group Project Hi Thom, I have subscribed. I am an electronic engineer by profession and I am playing with audio for 25 years. For past few years I am into single ended directly heated triodes and I am going into horns. I also happen to distribute AVVT tubes. For a day I have Scheu's bearing and motor in my hands so you can ask any questions about them. It is an inverted bearing (shaft going up with a ball on top, all made from stainless steel). I have Scheu's plans but his 1995 bearing was normal type, made from bronze. I have read your Digest #4 so I have a bit more to read. A few comments: 1. I vote for the tightest tolerances and thin oil. 2. Why was brass chosen vs. bronze? 3. What is the surface area of the "final" Teres bearing vs. Scheu? I would vote for the largest area. (4. I still have to find out what is the purpose of the reservoir in the centre.) I have all documentation of Manfred's speed control and I plan to use a Maxxon motor. What is the "final" cost - I have seen $220 and $460($560?)? I guess I could just get the bearing and heave my own platter made. Or would Chris' brother make me a slightly different platter? Where did you source the 3" acrylic? I was having problems, 2" was the maximum and even that was a problem. And unfortunately on this continent, all is sold in feet. Since the platter is a bit over 1 foot, I was being forced to buy either 2'x2' or 18"x18" ie. 2 to 4 times as much as needed. I have only 3 small "problems" concerning my audio hobby: 1. I am married. 2. I have a very nice 10 month old son. 3. I have reecently moved so there is a lot of work to be done in the new house. So, what used to take a couple of days to make now takes months. Regards, Tony Bombera Toronto, Canada -----Original Message----- From: Stanley Goudge [mailto:sgoudge@cisco.com] Sent: Thursday, February 03, 2000 1:07 PM Subject: Re: Teres Purchase Me too, I want one Teres bearing, spindle and platter. I just started to read the email archives so am not up on the all the evolving ideas that went into the design. But my further concerns are on the thrust bearing, I believe delrin was to be used, a self lubricating plastic which is cheap and easy to machine. I'm not conviced of this as to the best solution, rather a jeweled surface that can transmitt vibrations to a ground is what most designers use. So I can only guess there is a good table out there that uses delrin or you guys wouldn't recommend it. As far as rotational drag goes, its a must have, but there are many ways to do this other than using thick oil at the spindle, I guess this came from the Townshend design that Moncrief raved about many years ago. My experiments with my Star using a pair of needles glued under the platter dragging (at steep angles for low turbulance) in silicone filled circular channel of acrylic under the plater. The first thing I noticed was there was a lot more bass and overall sound improved. I don't recommend this approach, (too messy) however VPI uses damped idlers, Well Temperd uses direct contact 5 point bearing. How about using Oracles new 6 point bearing using nylon screws, you could adjust the bugger for any oil. As for oil try http://www.pdt.net/le/ LE and Red line oils are the best in the business. Thanks, Stan ----- Original Message ----- From: Mackris, Thom G. Sent: Thursday, February 03, 2000 3:40 PM Subject: RE: Teres-Bearing & Platter Hi Stan, I changed the subject in my response to "Bearing & Platter" in order to facilitate message threading (we've been discussing the bearing and the platter as an integral unit). Delrin was arrived at like Goldilocks & the three bears: (a) Teflon: too soft (b) Bronze: too hard (noisey) (c) Delrin: juuuust right. Seriously, I don't know much about bearings other than what I've learned through this list and what I've read in the popular journals as and from George Merrill's writeups. George discusses jewelled bearings from the perspective of lubrication. He contends that the only advantage of a jewell bearing is that is performs well with no lubrication - an advantage where you can't change the oil as needed (like on a sattelite). He is a firm believer in the superiority oil bathed bearings in any application where the oil can be maintained periodically. This doesn't of course address the thrust plate which you're talking about, as there is certainly no oil cushon in this area. The idea of making the thrust plate field replacable had been brought up recently, although I'm not certain of the state of this proposal. Would there be disadvantages to having the thrust plate removable (vibration, chatter, etc.) ? Perhaps another question for machinist, Bryce. This is the second question we've tabled for him this week, the first one being the machining of a spiral in the central (non-contact) portion of the shaft to distribute the oil throughout the bearing. Hartmut changed his Scheu bearing from teflon (PTFE) to scintered bronze. The group felt in general that he may have overshot the sweet spot between soft/quiet (teflon) and hard/noisey (scintered bronze). Delrin is extremely tough. Igor reports it's use in the suspension bushings of F3 race cars he used to work on back in the '70's. I had a bicycle in 1968 that had a delrin rear derailleur. Ken Schei is a structural engineer and an advocate of delrin's toughness. Later on in the digests you'll see that we finally clarified the matter about bearing clearance: make the best bearing (clearance) that is possible within reasonable budget constraints. The oil will take care of itself through experimentation. Red Line does indeed have a good reputation. Cheers, Thom ----- Original Message ----- From: Igor Kuznetsoff Sent: Thursday, February 03, 2000 4:29 PM Subject: Re: Teres Purchase Welcome, Stanley, Believe it or not, but a lot of this design was actually *original* thought. Looking to the work of others is a practical way to validate ideas and save a good deal of time, but progress is rarely made by merely copying. Prior art is a legitimate basis for beginnings, but if you don't hump your sand up to the height of Mohammed's mountain, all you can ever accomplish is dragging it to the beach, and that mountain's not going follow you there! I look forward to the benefit of your obvious knowledge base, but let's move *forward*, that's how real progress is made. There are indeed many ways to effect drag. What is your objection to oil in this capacity? It is an excellent way to accomplish this-it is *quiet*in itself, *and* it quiets *other* noise. Plus, it is changeable within a limited viscousity range to adjust the coefficients. And it didn't come from someone elses design, it came from *experience*, although its prior use can be considered a validation. Personally, I wasn't even aware of that detail, you are evidently better versed than I in the wider scope of existing design details. I look forward to the benefit of your expertise in referencing, this will be a valuable contribution. As for Delrin vs. jewels, well, it may not sound as fancy in a glossy brochure, but it is not only practical for our technological resources, but it is also a darn *good* materal for this purpose, by any standards. We don't have to eat cake to be stylin'. I look forward to checking out the oils site, that sounds like an interesting tip. Igor ----- Original Message ----- From: Stewart Ono Sent: Thursday, February 03, 2000 6:32 PM Subject: Re: Teres bearing material In reading Stanley's comment, I realize that I passed over the obvious, thinking that Delrin was the material to line the side bearing walls. I believe, in considering the impact of the thrust bearing material choice, several considerations have to be made. The first is machining capability and cost (we don't want Bryce to have to buy special tooling for jeweled inserts, for example). Second would be the weight of the platter assembly versus the surface area of the contact point, as that would determine how much the bearing will crush the Delrin pad. Perhaps a compromise for some members can be made by using a threaded insert for the thrust bearing. By drilling and tapping for a standard thread, a screw or set screw of various materials can be inserted to give a thrust pad for various member's tastes (something they could do on their own, rather than tying up Bryce's time excessively). You could still use the Delrin pad, but would have options. It would also allow the members to change the thrust pads bit easier (for those who worry a lot....8^) ). Sealing could be done with standard plumbers Teflon tape. As an aside for the noise consideration in using Delrin, perhaps a rubber pad could be inserted between the bearing flange and the platter and this could be done by the individual members who prefer a metal thrust pad. Again, judging from the predicted costs, it looks like Bryce is being very generous with his time, and I certainly wouldn't want to take advantage it. regards, Stu ----- Original Message ----- From: jhlane Sent: Thursday, February 03, 2000 8:41 PM Subject: Re: Teres-Bearing & Platter > The idea of making the thrust plate field replacable had been brought up > recently, although I'm not certain of the state of this proposal. Would > there be disadvantages to having the thrust plate removable (vibration, > chatter, etc.) ? Perhaps another question for machinist, Bryce. This is > the second question we've tabled for him this week, the first one being the > machining of a spiral in the central (non-contact) portion of the shaft to > distribute the oil throughout the bearing. In the spirit of DIY, please make the end of the cup removable so as to offer users the opportunity to play with varying materials for the thrust pad. An entire discussion among the members may result some months down the road on the relative sonics of different materials... Two more points come to mind: First, the use of Delrin seems to mean we're assuming that bearing drag is a given. This is a good thing, as many have pointed out, for the damping of the rotating system it provides even though the viscous drag of the lubricant itself may be many times more. However, would not this mechanical drag also indicate a higher noise floor? That is, contrasting a point-contact bearing with hard surfaces - traditional 'table bearing - with what will become in time a large bearing area in a relatively soft material like Delrin - the Teres - are we concerned about the noise that may creep into the system? I offer this not as a mechanical engineer, but instinctively, I feel we might actually want to take this a step further. But first, point two: A spiral groove in the side of the spindle, I think, is not needed. Oils (especially modern synthetics) have such a high shear that I'd be extremely surprised if a smooth bearing shaft in a smooth sleeve operating at very low speed and load, and at room temp would ever suffer from lack of lubricant. It just ain't gonna happen. If (and with the experts looking at this project's mechanicals, there is no "if" in this regard) the two parts are machined to the correct dimensions, oil WILL find its way to all parts of the assembly and stay there forever, assuming the cup is filled to the right level in the first place. This cushion of oil will be the most symmetrical if the shaft and sleeve are also, yes? Which brings me back to point one. Would a very large radius at the end of the spindle actually support even Teres' thrust load on a similar oil film? I don't know the math but presumably at some larger contact area (maybe as would be formed if the entire end of a large diameter shaft were contacting our Delrin thrust pad) the oil will actually float the end load imposed by the platter weight. Seems to me that an analysis of oil shear strength, rotational speed, and bearing contact size would be the only variables needing to calculate this problem. Any lubricant engineers in the team? One of my reasons for asking for a removable end to the sleeve is because I actually want to try metal-to-metal with only oil in between. I think it may work if the end of the shaft is nearly flat. Play around with a precision shaft in a precision sleeve with your fingers sometime. With only fine machine oil, its virtually impossible to make the two touch. Oil gives amazing protection. The same is even true for air bearings under enough pressure. Jon Lane ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Thursday, February 03, 2000 11:44 PM Subject: Re: Teres Bearing & Platter Hi Tony, You raise a couple of points which are bound to be asked by a few other people so I'll include those parts of your e-mail that are relevant to the group and attempt to answer them. Additionally, some of your questions are probably addressed in e-mails which I have not had an opporunity to consolidate into digests yet. Getting everyone "caught up" is keeping me from building more digests, but I think it's important that we stay in the present squeeze this bearing/platter design to its necessary completion. Note - Stu Ono and Jon Lane have just opened up an interesting dialog which I'm curious to watch unfold. (Jon, I just may know an "audiophile" petrolium engineer. I'm going to e-mail him from work tomorrow). I may be wrong about the brass vs. bronze sidewall issue, but if I recall, scintered bronze has advantages when lubrication is problematic. Maybe Chris or Igor or Ken can help my memory here. Tolerances - Yes !! After some confusion (partly my fault) we agreed with you - the *tightest* tolerances possible. Oil - some minor disagreement in the group here, but based on the above unanimous agreement on the tightest possible bearing tolerance, some want to experiment with viscosity. Bearing area: Quoting from the web page (disclaimer - this number is one of the few that I have not personally verified) - "The bearing spindle provides a large surface area to maximize viscous damping. The bearing surface area for the Teres bearing is 75cm^2 compared to the Platine Verdier at 60cm^2. " The resevoir is serves two purposes: (1) to clear out some contact area from the bearing in order to reduce noise, while at the same time (2) serving a damping function. There was some dialog about how much viscous resistance the resevoir would provide and whether we wanted to create the resevoir by necking down the shaft vs. grinding away the female part of the bearing. Cost was not a determining issue between the two methods. The issue had to do with the increased speed that the bearing surface travels if it is not necked down due to it's larger diameter (resistence is proportional to the square of the velocity). Regarding thick pieces of acrylic, 3" thick is hideously expensive. During the discussion, we surfaced the information that there is a type of bonding agent designed for acrylic that makes a perfectly transparent weld ... totally invisible even if one is using it in an application with flame polished edges (the platters will be matt or frosted, BTW). We are planning on using 3 layers of 1" acrylic to get to 3". The bonding will happen first and the machining will occur afterword for obvious reasons. The (approximate) $550 price is what a single unit would cost if someone missed the boat on this order and Bryce had to do it as a one-off (this takes into account that he will have already done the CNC programming). Setting up apparently take a whole lot of time and only part of the benefit comes from already having the CNC programming. I would guess that Chris's brother Bryce could do a one-off platter ... the price is another question. Bryce doing the platters is serendipetous. We were shocked that he agreed to do it. The fit between the bearing and platter will have a tolerance specified - "as tight as can be done with manual assembly" (i.e. no press fitting, or cooling the bearing and heating the platter required - in order to not stress the platter). Imagine having an acrylic shop put up with our nonsense in order to do this. Cheers, Thom ----- Original Message ----- From: Chris Brady Sent: Friday, February 04, 2000 12:31 AM Subject: Re: Teres-Bearing & Platter I just had a long conversation with Bryce (our machinist) about details of the turntable design. As usual he had some very good insights and suggested some minor adjustments to the bearing design. He also had some minor concerns that he wanted me to pass on to the group. I confirmed with Bryce that the Delrin thrust plate will just drop into the bottom of the bearing housing and will be trivial to remove. There is no need for a press fit since the contact area with the bottom of the bearing housing will be much larger than the contact with the shaft (i.e.. it will not move at all). So if anyone wants to try a different material it will be very easy. Bryce also feels confident that Delrin is the best material for the thrust plate, but we will be free to try anything we want. I talked to Bryce about the idea of the spiraled groove in the bearing surface to "pump" oil to the top. He liked this idea but thought it unnecessary since we have an oil bath. However, the discussion got him thinking about how we could better insure complete lubrication of the top portion of the bearing. He suggested cutting a shallow well into the top of the bearing to hold a small pool of oil at the top of the bearing. This would insure liberal lubrication of the top bearing surfaces. This seems like very very good idea. I will try to update the bearing drawing soon to better illustrate this concept. He also indicated that the diameter of the recessed area in the bearing needs to be reduced from 1.0" to about .81" due to machining constraints. This seems to be of little consequence especially since there will be an additional oil reservoir at the top. For those new to the group the platters will be made from three layers of 1" acrylic laminated together. The reason for this is the huge cost of acrylic more than 1" thick. With proper glue and clamping a joint in acrylic is invisible even when the acrylic is polished. However, Bryce is uncertain about being able to force all of the bubbles out of such a large surface area to make an invisible joint. This is purely a cosmetic issue and with the machined finish it is unlikely that small bubbles (if there are any) would be visible. Also the raw material for the platter will be 3" thick but after machining both sides the final thickness will be roughly 2 15/16 not 3". An item of little consequence but we don't want anyone to be surprised. A couple of list members have expressed interest in having Bryce do some extra "one-off" machining for them. Bryce has too much on his plate to do this kind of work and also thought that for one of a kind machining we would be better served to use a local machinist. Bryce has been a valuable resource in the design process and has spent a many hours providing us with free, expert advise. I for one am grateful. Chris ----- Original Message ----- From: Igor Kuznetsoff Sent: Friday, February 04, 2000 1:57 AM Subject: Re: Teres-Bearing & Platter --- Chris Brady wrote: > There is no need for a press fit since the > contact area > with the bottom of the bearing housing will be much > larger than > the contact with the shaft (i.e.. it will not move > at all). So if > anyone wants to try a different material it will be > very easy. > Bryce also feels confident that Delrin is the best > material for > the thrust plate, but we will be free to try > anything we want. I thought the drop-in fit is what we had been talking about all along. I was surprised by all the complications that surfaced today. I had expected that, at worst, removing it would require a straw & a little suction to grab it & pull it out. > I talked to Bryce about the idea of the spiraled > groove in the > bearing surface to "pump" oil to the top. He liked > this idea but > thought it unnecessary since we have an oil bath. > However, the > discussion got him thinking about how we could > better insure > complete lubrication of the top portion of the > bearing. He > suggested cutting a shallow well into the top of the > bearing to > hold a small pool of oil at the top of the bearing. > This would > insure liberal lubrication of the top bearing > surfaces. This seems > like very very good idea. I will try to update the > bearing drawing > soon to better illustrate this concept. He also > indicated that the > diameter of the recessed area in the bearing needs > to be reduced from > 1.0" to about .81" due to machining constraints. > This seems to be > of little consequence especially since there will be > an additional > oil reservoir at the top. The oil groove is an elegant concept, but I don't see any serious need for it, either. I have to admit I did spend a few minutes musing about whether a *reversed* spiral, i.e. *downward* pumping, could be employed to create enough pressure to effect either a pure pressurised oil bearing system, or perhaps one at least assisted enough by the pressure to reduce the force on the thrust surfaces. Anybody have any idea if this is possible? A well sounds ok, but *only* if it is extremely shallow, so as not to shorten the distance between the contact surfaces any more than than very minimally, as per previous discussions. But: reducing the sump area volume sounds very undesirable. At .81 minus .75"(spindle)/2= only .03", which is no longer a sump, hardly more than just clearance. This, I fear, will impact the noise damping possibilities of the oil bath, however unproven that capacity may be. Is this change absolutely necessary? What machining consideration does this change address? Perhaps we should change to Ken's previously expressed preference for machining that area out of the spindle instead, in order to preserve the larger clearance, or, if this doesn't affect the cost significantly, both. I would very much prefer *not* losing that larger clearance, as I feel it is beneficial. Is this reduction *absolutely* necessary ? > > For those new to the group the platters will be made > from three > layers of 1" acrylic laminated together. The reason > for this is > the huge cost of acrylic more than 1" thick. With > proper glue and > clamping a joint in acrylic is invisible even when > the acrylic is > polished. However, Bryce is uncertain about being > able to force > all of the bubbles out of such a large surface area > to make > an invisible joint. This is purely a cosmetic issue > and with the > machined finish it is unlikely that small bubbles > (if there are > any) would be visible. With the frosted matte finish, this may not be visible, anyway, but at the risk of suggesting what Bryce already knows, I would suggest the following. Rather than spreading the glue over the entire surface prior to clamping, if he were to put a good dollop of it in the center of the area, and then proceed to clamp down, the glue will tend to force the air out ahead of it as it spreads outward. No offense meant if this is already second nature to him, I don't wish to re-teach him how to tie his shoe laces. > Bryce has been a valuable resource in the design > process and has spent > a many hours providing us with free, expert advise. > I for one am > grateful. I second that. Igor ----- Original Message ----- From: Igor Kuznetsoff Sent: Friday, February 04, 2000 2:24 AM Subject: Re: Teres bearing material --- Stewart Ono wrote: > In reading Stanley's comment, I realize that I > passed over the obvious, > thinking that Delrin was the material to line the > side bearing walls. I > believe, in considering the impact of the thrust > bearing material choice, > several considerations have to be made. The first is > machining capability > and cost (we don't want Bryce to have to buy special > tooling for jeweled > inserts, for example). And of just how much value would this type be in an oil bath environment, anyway? Jeweled bearings are usually used in *dry* applications. Also, seems I remember, vaguely, something about VPI's TNT sapphire bearings having some sort of trouble back around '90 or so... Stanley, do you know anything about this? Second would be the weight of > the platter assembly > versus the surface area of the contact point, as > that would determine how > much the bearing will crush the Delrin pad. Delrin is pretty hard, Stewart > Perhaps > a compromise for some > members can be made by using a threaded insert for > the thrust bearing. By > drilling and tapping for a standard thread, a screw > or set screw of various > materials can be inserted to give a thrust pad for > various member's tastes > (something they could do on their own, rather than > tying up Bryce's time > excessively). You could still use the Delrin pad, > but would have options. It > would also allow the members to change the thrust > pads bit easier (for those > who worry a lot....8^) ). Sealing could be done > with standard plumbers > Teflon tape. Actually, the Delrin is just supposed to drop in, I believe. > > As an aside for the noise consideration in using > Delrin, perhaps a rubber > pad could be inserted between the bearing flange and > the platter and this > could be done by the individual members who prefer a > metal thrust pad. You probably haven't gotten up to that point in the posts yet, but Ken & I examined that issue recently. I am planning to use a lead washer, after experimenting with a pair of concentric O-Rings, which should have just the right Durometer rating, I am guessing. Igor ----- Original Message ----- From: Igor Kuznetsoff Sent: Friday, February 04, 2000 2:44 AM Subject: Re: Teres Bearing & Platter > I may be wrong about the brass vs. bronze sidewall > issue, but if I recall, > scintered bronze has advantages when lubrication is > problematic. Maybe > Chris or Igor or Ken can help my memory here. Ah, well this isn't exactly my subject, but it seems that I do remember that Sintered Bronze is the material that is known as "Oilite", and is used commonly as a bearing surface because the sintering process, one of heat + pressure applied to powdered material, produces a somewhat porous result, which has the capability of holding lubricant in a sponge-like manner. This is desirable in harsh duty/low maintenance app's. Whether this is desirable for us vs. the smoothness of brass (or non-sintered bronze), which I would think will produce a *stronger*, more coherent, film of oil with a better capability of keeping the surfaces separated, and the operation quieter, is a question probably answered better by Bryce. Or, perhaps, if we have an appropriate engineer / expert on this subject. Igor ----- Original Message ----- From: Brian Sent: Friday, February 04, 2000 8:21 AM Subject: Re: Teres-Bearing & Platter > For those new to the group the platters will be made from three > layers of 1" acrylic laminated together. The reason for this is > the huge cost of acrylic more than 1" thick. With proper glue and > clamping a joint in acrylic is invisible even when the acrylic is > polished. However, Bryce is uncertain about being able to force > all of the bubbles out of such a large surface area to make > an invisible joint. This is purely a cosmetic issue and with the > machined finish it is unlikely that small bubbles (if there are > any) would be visible. A vacuum bag press would work best here. It would ensure no bubbles, but more importantly even distribution of the adhesive. With conventional clamping, adhesive thickness variation and bubbles will make for possible balance issues. I wonder if Bryce might know of a contractor or furniture builder that does work with large veneering jobs that could do the laminating of the acrylic with a vacuum bag press. A note to Sound Practices subscribers. Joe has a couple of articles from the yet to be released 1999 Yearbook available for download in pdf at soundpractices.com. Some good stuff! My shipping info is: Brian Day 1321 15th St. Greeley, CO 80631 ----- Original Message ----- From: Sent: Friday, February 04, 2000 10:27 AM Subject: Re: Teres-Bearing & Platter In a message dated 00-02-04 10:15:01 EST, briday@uswest.net writes: << A vacuum bag press would work best here. It would ensure no bubbles, but more importantly even distribution of the adhesive. With conventional clamping, adhesive thickness variation and bubbles will make for possible balance issues. >> I think this stuff bonds too quickly for a vacuum press to help. I also wonder about the possibility of building stress into the platter that will cause problems later...regardless of how it is bonded. Cheers/Carron ----- Original Message ----- From: Mackris, Thom G. Sent: Friday, February 04, 2000 10:44 AM Subject: RE: Teres-Bearing & Platter If we're truly welding the layers together, is there really any stress? Anyone? Thom ----- Original Message ----- From: Stewart Ono Sent: Friday, February 04, 2000 11:10 AM Subject: Re: Teres-Bearing & Platter:misc thoughts In regards to Jon Lane's comments, I once received a Linn LP-12 brand new where the bearing was machined 2/10,000th's oversized. It spun well when cold but would actually freeze up solid (you couldn't pull the inner platter out without employing considerable force after playing just one side of an album). This was with the recommended amount of oil inserted in the well and I believe the Linn uses Delrin inserts for the bearing well. I do not claim to be very cognizant of the temperature coefficients involved here, but tight tolerances mean some consistent temperatures must be maintained. It seems to me that a slight pumping action coupled with an oversized well and oversized bearings insures more of a temperature constant and also means less long term maintenance. Of course, a large oil sump may probably be equally effective. As for the problem of the bearing spindle radius to thrust pad contact patch, my experience with other fields indicates that the bearing will quickly wear a pattern in the pad material large enough to suspend the weight and, barring actual disintegration of the materials, stop wearing for a significantly long period of time. As far as a one shot project is concerned, as this one is, we ought to plan for every contingency, or, at least be aware of possibilities. However, it is not necessary to have every option already built in. A spiral groove can be machined later and is not a necessity for initial production. A replaceable thrust pad insert on the well bottom, if it involves simple drilling and tapping, should still be able to be fairly easily incorporated. It can be machined in after the basic initial fabrication for those who really want it. Again for Bryce, time is of essence. Most suggestions can be done in the field by any competent machine shop or many hobbyists with decent bench tools. Laminating the thick pieces of acrylic calls for the use of a vacuum chamber or vacuum pump in order that no air be trapped between laminations. I would advise experimenting with smaller pieces and scraps first, before attempting the very expensive thick stuff. The bonding agent is something like diethylene chloride and literally melts the mating surfaces. I built a TNT table top by laminating 1/4 inch sheets of acrylic to a total of 1 1/4 inch thickness and have experimented with building arm boards of laminates. It was difficult and really impossible to do it at home without trapping varying amounts of air between layers, even though I predrilled a number of holes so as to be able to bolt the assemblies together (in lieu of clamps). On the other hand, I have some "bulletproof" glass, actually plastic, a built up laminate with two 1/2 inch layers and two 1/8th inch layers of polycarbonate. Commercially made, it is optically clear. Structurally, it is not very strong in that it is rather flexible, so I would not recommend it for a platter. It feels much more 'dead' than acrylic and may be interesting to experiment at a later date as mentioned in previous posts (if bonded to acrylic, however, be warned that the acrylic glue causes poly to turn cloudy: no amount of drying time will clear it). The glue used to bond the polycarbonate is very unusual in that it is much softer than the polycarbonate which in turn is softer than acrylic. It is spread on very thick (1 to 2 mm) and doesn't seem to dry hard. It reminds me of a thicker version of RTV. Personally, I would be satisfied with two inch thick platters in the machined finish. While laminating thinner sheets may be a cheaper option, using one thicker sheet will be cosmetically much more pleasing and probably easier on Bryce (except for moving a 4 x 8 sheet around for the initial rough cuts). Flaming the machined edges will obviously change the dimensional tolerances. The new 'clear' Basis models have a frosted finish rather than clear to avoid the polishing and possible dimensional changes. Like many other acrylic platters, they employ brass plugs fitted into holes drilled at the peripheral edges of the platter in order to increase mass. Again this can be done by individuals with a good drill press in the field. regards Stu PS. Sorry if some of this is redundant, I wrote a day and a half ago, but forgot to push send! ----- Original Message ----- From: Mackris, Thom G. Sent: Friday, February 04, 2000 2:28 PM Subject: RE: Teres-Bearing & Platter:misc thoughts Hi Stu, If memory serves, the end of the LP 12 male bearing (spindle) is shaped like a tip toe (conical) rather than speherical, FWIW. You report yet one more reason to have an oil resevoir - cooling / dimensional stability. Ken Schei (Structural Engineer) is our man with respect to thermal expansion coefficents (brass female bearing vs. stainless steel male). I would have to guess that Bryce is cognizant of these issues and that in the case of Linn, the male and female was at opposite extremes of their allowable tolerances, or perhaps machined at different room temperatures. I can see where at .0002 tolerances, this could make a difference. Fortunately, ours will be machined in the same shop in a moderate climate at the same time of year. Take these rantings as not those of a bearing expert, but just my humble prognostication. I had a brief conversation with Chris about the thrust plate and other bearing related issues. I'll let him report back in full when he gets a chance. If I understand him correctly, Bryce is comfortable with an easily removable delrin thrust plate from the perspective of: (a) It not chattering or otherwise compromising the performance of the bearing. (b) that delrin is plenty tough for this application. If (a) is true, we have field replacable components so (b) is not an issue and everyone can experiment to their heart's content. With respect to flame polished vs. a machined surface, you correctly mention the possibility of dimensional changes. Another concern we have about going to clear is one of providing a good frictional surface for the belt. With a rubber belt, this is probably not an issue, but it certainly would be instructive to be able to experiment with string, floss, and magnetic recording tape (Sound Practices #10 - "Turn Your Table" article). It seems as if while most of the early group liked the look of clear (flame polished) acrylic, the concern about friction as well as the eventual small scratches that will innevitablly get on the platter resulted in most of us nixing the idea of polished. Bryce had mentioned a concern about the cosmetics of the machined surface - if someone touches it with greasy fingers it might be difficult to clean. I know, we all keep our records in a clean room and wash our hands with distilled water before approaching the alter known as our turntable stand . As far as a 3" vs. 2" platter is conerned. We originally had spec'd out the platter at 2" for the reasons you state - making it out of one piece out of the thickest "reasonably" priced material. As we thought more about the stability (teeter-toter) issues, we decided to drop the center of gravity of the platter lower by use of a 3" bearing. I'm guessing that from an overall stability viewpoint that this is still a superior choice. I think you are correct in stating that we should really get clear about how the platters will be bonded. The question of a frosted vs. machined finish came up and no one knew how the frosting was accomplished or whether it would affect the precision of the machining. This is a piece of information we should obtain. ** Chris ** take ** note ** Perhaps this is a question for Bryce? A very real question arises here: If we agree that 3" is superior to 2" from a dynamic balance perspective, are we willing to take the risk of slight cosmetic imperfections, which for the most part will be masked by the machined (or frosted) surface? It seems to me that for reasons of form following function, that the answer is yes to a 3", machined (or frosted) surface. Thanks for the thoughts, Stu ... keep 'em comming. When we're all happy, we'll either have a bullet proof design, or one that is hopelessly compromised. I strongly suspect that it will be the former (bullet proof), however. Cheers, Thom ----- Original Message ----- From: Mackris, Thom G. Cc: 'Brady, Chris' Sent: Friday, February 04, 2000 2:59 PM Subject: Bearing Lubrication Technology ? Hi Steve, Bob had referred me to you. I don't know if he has mentioned this, but a group of us (it started with a half dozen, and now it's up to two dozen!) are in the process of assaulting the state of the art in a turntable. Check out my friend Chris Brady's web page (click on the link - "Teres DIY Turntable") ==> http://reality.sgi.com/cbrady_denver/audio/ This merry band of pranksters started out by considering building a kit turntable designed by Thomas Scheu of Germany. It has been reported by many to be better than the $7500.00 Platine Verdier. Pretty soon we realized that we had the talent on tap to design one ourselves. A recent post to the Joe List (Sound Practices list server) resulted in the number of tables committed to purchase approaching two dozen!! We have an electrical engineer who has designed a micro code controlled motor controller for his Thomas Scheu turntable. He has volunteered to help us adapt the design to our 'table. This controller promises to leave the Linn Lingo, Naim Armegeddon and VPI controllers in the dust from both a performance standpoint as well as one of convenience. It will even have motion sensing - if you give the platter a nudge, it will sense that you want to start it up !!! All for a cost of ~ $100.00 !! Anyhow, we've been going back and forth about lubrication for the bearing. My friend Chris's brother is a CNC machinist who has specialized in making computer disk drives ... the breadth of talent on this project has me dizzy !! The bearing is going to be a male, stainless steel spindle inside of machined brass female portion, with a delrin thrust plate. There will be a well in the central portion of the bearing to reduce bearing surface contact (lower noise) as well as to effect viscuous damping. The thrust surface of the male bearing will be a 3/8" ball bearing. The drawings are on the web page. The male surface of the bearing will be polished, and the tolerances are being specified as the tightest possible ... in other words, we will most likely be using a light oil. Some have expressed concern about delrin's suitability to the task, but our machinist agrees with others in the group (including a structural engineer and a former Formula 3 race car mechanic) that this is an ideal material for a thrust plate - extramely tough, and most certainly stronger than teflon (with less deformability) and quieter than brass or scintered bronze. The question of toughness, specifying the correct lubricant as well as a thrust surface interface which will permit a cushion of oil to be maintined between the thrust surfaces arose. Note the quoted text immediately following. Do you have any thoughts on the matter or resources that would be pertinent to the situation? Regards, Thom ---------------------------------------- Quoted text follows ...... Which brings me back to point one. Would a very large radius at the end of the spindle actually support even Teres' thrust load on a similar oil film? I don't know the math but presumably at some larger contact area (maybe as would be formed if the entire end of a large diameter shaft were contacting our Delrin thrust pad) the oil will actually float the end load imposed by the platter weight. Seems to me that an analysis of oil shear strength, rotational speed, and bearing contact size would be the only variables needing to calculate this problem. Any lubricant engineers in the team? One of my reasons for asking for a removable end to the sleeve is because I actually want to try metal-to-metal with only oil in between. I think it may work if the end of the shaft is nearly flat. Play around with a precision shaft in a precision sleeve with your fingers sometime. With only fine machine oil, its virtually impossible to make the two touch. Oil gives amazing protection. The same is even true for air bearings under enough pressure. End quoted text ---------------------------------------- ----- Original Message ----- From: jhlane Sent: Friday, February 04, 2000 6:15 PM Subject: Re: Teres-Bearing & Platter > << A vacuum bag press would work best here. It would ensure no bubbles, but > more importantly even distribution of the adhesive. With conventional > clamping, adhesive thickness variation and bubbles will make for possible > balance issues. >> > I think this stuff bonds too quickly for a vacuum press to help. I also > wonder about the possibility of building stress into the platter that will > cause problems later...regardless of how it is bonded. > > Cheers/Carron My first instinct, also. We're not dealing with adhesives as much as we're dealing with solvents. No margin for repositioning, and given the fair amount of surface runout in raw acrylics, this is an issue in need of resolution. Further, is a cemented bond really visually absent or will there be an uneven appearance to it as the cement seeks the high and low spots in the bond? Jon Lane ----- Original Message ----- From: jhlane Sent: Friday, February 04, 2000 6:35 PM Subject: Re: Teres-Bearing & Platter:misc thoughts Friends, In thinking over the platter bonding issue, I recalled a 'table I made in the mid 80's using a 3" solid polystyrene platter. Polystyrene is pure white in color, not unlike the effect the Teres acrylic platter has in the home-site Pov Ray rendering seen at, http://reality.sgi.com/cbrady_denver/audio/ With the issue of bonding multiple layers currently on the table (no pun), may I suggest that since most will use a mat (an assumption of mine - please correct me if I'm wrong), that we are not really all that fussy about a perfect transmission of energy through impedance matching anyway. In fact, it could be argued that the only way to do that would be by using a vinyl platter... Polystyrene is mechanically stable (harder that acrylic), inexpensive, and serves the same function. Is acrylic the standing choice or is there room for discussion? Jon Lane ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Friday, February 04, 2000 9:38 PM Subject: Re: Teres-Bearing & Platter:misc thoughts Hi Jon, Early on, a couple of folks had reported that nearly perfect welds are possible. Perhaps this is something that Ken (who had been doing research on the plastics side early on in the game) or I should research locally. If it is do-able but is out of the realm of Bryce's specialty and/or tools or time constraints, we might want to have a local plastics shop create 3" thick blanks for Bryce. This might add a few dollars to the price but would certainly be cheaper than 3" thick acrylic and we'd have a higher comfort level that it was done right. I honestly don't know the characteristics of polystyrene. With respect to mats, the best performance both Bob Pickwoad and I have achieved with our Merrills has been with the full Merrill clamping system (center clamp and periphery clamp) against the bare lead platter surface (the Merrill has an acrylic platter with a thin layer of lead bonded to it). I am generally a mattless kinda guy, although others have had success with mats on their tables. Obviously, this is one area where we need to allow for choice. Can anyone answer Jon's question about polystyrene? ----- Original Message ----- From: Stewart Ono Sent: Friday, February 04, 2000 6:48 PM Subject: Re: Acrylic bonding The recommended procedure for the bonding of acrylic is to float the solvent on one sheet and gently drop the other sheet from an angle onto the bottom sheet. Easier said than done in real life. Of course we can use excessive amounts of solvent since we will still have to machine the final surface. You don't have the luxury when you want to preserve the factory surface. The other method is to tape the sheets together and then inject the solvent into the space between the layers. That will guarantee visible bubbles. I use this method to glue smaller pieces together in order to get a certain thickness for armboards, but then I don't use clear acrylic either , at least not after my first attempt with clear acrylic (you can alternate colors to get interesting effects). The bond is still strong however. The appearance incidentally is similar to splashing water onto two pieces of glass lying against each other. If I'm not mistaken, the frosted appearance may be due to bead blasting. regards Stu ----- Original Message ----- From: Steve Zettel Sent: Friday, February 04, 2000 10:28 PM Subject: Re: Teres-Bearing & Platter on 2/4/00 00:31, Chris Brady at cbrady@sgi.com wrote [snip] > Also the raw material for the platter will be 3" thick but after > machining both sides the final thickness will be roughly 2 15/16 not > 3". An item of little consequence but we don't want anyone to be > surprised. > > A couple of list members have expressed interest in having Bryce do > some extra "one-off" machining for them. Bryce has too much on his > plate to do this kind of work and also thought that for one of a kind > machining we would be better served to use a local machinist. > > Bryce has been a valuable resource in the design process and has spent > a many hours providing us with free, expert advise. I for one am > grateful. > > Chris > Chris, Once again, thanks for the work and the liaison with Bryce. I hope you are passing along all our appreciation for his insight and concern for our project. We are very fortunate to have the Brady brothers working on this! For my part, I would be proud to have him sign his work on my bearing housing, or even the platter, if it doesn't affect the balance. Best regards, Steve Z ----- Original Message ----- From: Thom Mackris / Joan Panzella Sent: Saturday, February 05, 2000 8:47 AM Subject: Re: Teres-Bearing & Platter - Open Items All, As we were getting in the final days of solidifying the bearing and platter design (the first time around), Chris put together a list of issues, both open and closed. I think it's a good idea to do the same at this point. I don't really see any of the following items as true issues, more as requests for clarification as well as for "refinements" in the design. Correct me if I'm wrong on this one. There are indeed some action items arising from these "issues", which I've noted as best as I can. I have not plowed through the last week's e-mails, and so I may be missing something here. Additionally, I'm rushed to get out of the house at the moment, but I think this should get out as soon as possible - not waiting until tonight. Please don't be shy with your comments. Having said that, I continue to be amazed at the how the major elements of this design have held up the the scrutiny of this highly competent group. Let the group know if I've missed something or you have more to add. 1) Use of Delrin as a thrust plate: ## closed ## . We are using Bryce's vast experience in this area in conjunction with the experiences of Ken and Igor with this material. Delrin is an excellent compromise between quiet (teflon) and strong (brass/bronze) and may be the compromise that Hartmut was looking for when he replaced his teflon plate in his Scheu with a hard substance. It is more than robust enough for a 15 lb. platter, and it is field replacable (see below). 2) Field replacable thrust plate: ## closed ##. Bryce indicates that there is no problem with a drop-in thrust plate replacement with respect to bearing perfomrance (noise & chatter). Replacement will require no tools other than perhaps a pencil with a piece of "blu-tak" on the end of it to retrieve the plate from the bearing well. I suspect that this would be done by cooling down the bearing and allowing the differing thermal expansion coefficients to "loosen up" the fit. Action item: Make clear the specifics of replacing the thrust plate. 3) Decreasing the size of the bearing well ## closed ##. This must be done due to material costs. Bryce indicated that we have specified too large of a piece of brass as far as cost threshold is concerned. The price would jump significantly if we maintained the current size. We are only marginally above this dimensional threshold, and the space needs to be recoverd by sacrificing part of the bearing well. Igor would like to have as much oil damping as possible and suggested that some of the well volume be recovered by "necking down" the bearing shaft. Bryce indicated that this would compromise the excellent tolerances he expects to attain on the shaft. These tolerances are attributable to the thickiness (and hence rigidity) of the shaft. To date, we've had no one question that the #1 priority is to machine the absolute best tolerances possible. 4) Use of three layers of acrylic for platter ## closed ## Action items: (4a) We need to confirm that the glue will ensure a good weld, that is cosmetically and structurally acceptable with respect to the platter having a machined finish. (4b) We may learn that Bryce will need to subcontract out the task of making 3" thick blanks to work from. I have to sign off ... there may be more, but this will certainly get us started. Thanks for your feedback, Thom