Polymer bearings as turn table main bearings.

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
IMHO, you'd expect to find polymer bearings on the cheapest of turntables. They usually require greater clearances than metal bearings and unless the shaft is remarkably well polished, are probably noisier than an oil lubricated bearing. We're talking radial bearings here.

For the thrust bearing I've seen polymer bearings and they can work quite well. The loads are high, so a really hard hi-tech plastic like PEEK, using a lubricating filler (graphite/moly/teflon) might be a good choice to keep the contact area small. Expensive but probably even better would be DuPont Vespel with a filler. I still think a hard ball on a hard flat is a better solution.

IMHO again, I think people attribute too much to the tt bearing. Any vibrations in the bearing support (plinth) will get transmitted right through it to the platter. Way more effort should be put into motor isolation and tone arm isolation than is often the case. The tt I own is very well known and has an excellent bearing, but you can put a vibration pickup on the platter and listen to the motor vibration as clear as a sunny day. The design was a failure at the Engineering 101 level.
 
The other problem with polymer bearings is durability.

Because the bearing material is soft and the primary mechanism by which they keep their low friction at high loads is material shear and transfer, they wear very quickly if loaded heavily.

I replaced the idler bushings in my Garrard 301 with Iglidur G. They wore out very quickly indeed, IIRC I put the original bushings back less than a year later (and the originals are fifty years old).

BTW Conrad I disagree entirely about motor isolation and tonearm isolation. IMO the best tack for dealing with motor noise is to kill it at the motor. Once this is done the motor / platter coupling can be made far less lossy which has huge benefits.
 
I wouldn't disagree with that, but I don't know how to kill the vibes at the motor to the degree I want- other than by turning off the switch! IMO, an external motor seems like the best answer, but I want the convenience of a self-contained tt. I may next try something like a small iron-less DC motor, rather than the synchronous/stepper motors used by Project and later Thorens.
 
Hi,

IGUS is having a clearance free pre stressed bearing - JVSM. I am planning to try that one with a silver steel shaft. But, I am not sure on the bearing dimension. Will a 10mm or a 12mm diameter enough ?

What type of bearing should be used - Normal one/Flanged one ?

What is the best material for thrust pad ?

Best regards,
Bins.
 
Can anyone give us some feedback on Bill Firebaugh's teflon bearings in the WellTempered turntables?

For lack of teflon in my junkbox I have my TT running with nylon for both the sleeve on top and a ruby ball on a nylon pad for thrust bearing. both bearings are lightly lubricated with silicone grease. Seems to be a very quiet, low friction, bearing setup. I too wonder about longevity. Guess I will find out someday. Meantime I'm enjoying it. BTW it is very easy to replace.

Bill
 
I totally agree with Mark about killing noise at the motor end instead of motor and tonearm isolation. After switching to a quieter motor, everything sound cleaner and better focus.

I completely disagree with tonearm isolation because I firmly believe the tonearm should be rigidly couple to the same material the bearing is mounted so the platter and tonearm would vibrate in unison. Friends had experience with isolated tonearm mounting pods or blocks and they sound terrible.
 
Since my last post I've done some controlled tests on thrust bearings. More details are over at Vinyl Engine. The results are on my web site at ConradHoffman.com Basically, if you have a soft spindle shaft where the radius is cut and polished into the end, you want something that won't damage the radius over time. There are very few things that will do that. Teflon is good, but it lubricates by shedding layers of itself, and will eventually wear out. It also flows and I'm not a big fan of the stuff. I had high hopes for expensive high-tech polymers like graphite and Teflon filled Vespel (very expensive) and similarly lubricant loaded PEEK, but they didn't treat the radius as nicely as you'd think. For soft spindles, a small polished disk of Lignum Vitae can't be beat. It's harder than Teflon and will likely outlive both you and the turntable with no change in performance over time. It has to be the real stuff, not Argentinian. Run it in oil. I bear against the end grain because it's a bit harder and tends to save material when fabricating, but either way works fine. If you can't get that, vacuum impregnate a piece of rock hard maple or cherry with a good synthetic oil or possibly petroleum wax. My theory is that the grain structure gets lubricant right to the point of maximum pressure, which the other materials can't quite do.

If you have a replaceable ball, get a hard ceramic one like silicon nitride. That eliminates the wear problem on the ball. Then choose whatever thrust surface suits your fancy. I haven't done controlled tests on this, but my guess is hardened tool steel may be a good choice.

Why tables with soft spindles and integral radi even exist, I don't know, but there are a lot of them out there, including both of mine.

The journal section of the bearing is, I think, even more important than the thrust surface. More on that later if anybody's interested.

Best,
Conrad
 
Not to mention shaft bearings for submarines and destroyers, plus water turbines. When you sand the disk, be careful not to embed abrasive particles in the surface. I usually sand on 500 grit paper, then finish polish on 12 micron metallurgical paper. It's getting rare, but there's lots of reclaimed wood available. I figure one old policemans night stick would yield enough Lignum Vitae disks for hundreds of turntables, so I don't worry too much about the environmental issues. Heck, an old Lignum bowling ball would probably supply a disk for every vinyl player in the world who wanted one!

On the journal bearings, IMO there isn't a bearing made that can compete with an oil film in terms of noise. That means that the material isn't very important, but the geometry is. IMO, Oilite is probably not a good choice. It wears well but I'm not sure about the noise. I wouldn't waste my time with polymers of any type. I'd want a honed bronze bore with perfect geometry (reaming isn't good enough) and a highly finished shaft (needs to be external honed or superfinished- grinding and soft polishing isn't good enough) running with a couple tenths clearance, lubricated with a good synthetic oil. Anything that isn't floating on a film of oil will create rubbing noises that get transmitted to the platter. FWIW, I've tried Lignum sleeve bearings and they work extremely well, but you can't beat an oil film. Very few bearings achieve the necessary float, either because they aren't made to sufficient accuracy, or because they didn't put enough thought into how the oil reservoir would work. My Thor-ject, after some mods, achieves a good float, but only if I pay close attention to the oiling.
 
Ex-Moderator R.I.P.
Joined 2005
For those in the UK old bowling woods:)spin:) are a good source of Lignum Vitae.

Man, I would like one of those:)

I think that hardwood is called "pukkenholt" here

But maybe its "puckenholt", or "puckenhol"

Anyway, I dont think the major issue with a bearing is wear, but more the problem with "rumble" noise
And maybe friction
Which made me think about air supported bearing, back then
I was close to trying it, but didnt
I hated those airpumps
 
Well, IMO whatever wonderful performance one can get when the parts are perfect, degrades as they wear. That's another thing about oil films and air bearings- they don't wear. Does anybody actually get rumble anymore? I associate that with the little rolling bearing rings used in cheap changers. A decent point contact system shouldn't rumble, but the journals can certainly generate a scratching noise that gets transmitted to the platter. Motor noise is another issue. The plinth mounted motor in my Thor-ject is easily audible if you remove the belt, rest the stylus on a record, listen with headphones, then turn it on and off. There's nothing "wrong" other than the motor should have been better isolated.
 
Hi,
I just made a 55lb. aluminum platter and used Vespel as the sleeve and polished 5/8" tungsten carbide shaft. Check the price of Vespel on ebay---just make sure you are sitting down with a seat belt when you see the price !!!!! i used a .6255' reamer and it works perfectly. I also used 2 types of bronze for the bearing and that also works well but has much higher friction. Vespel comes in a few grades, I used Sp-22 and Sp-211 which has graphite and / or moly disulfide mixed in. Delrin, Nylatron, PEEK can't hold a candle to Vespel which is self lubricating, can take 500 F degrees, extremely low drag coefficient ( even lower using lube ), machines beautifully.
 
Hi,

Almost forgot, I made an inverted bearing and used Vespel for the thrust pad. The 5/8' carbide shaft has a ground / polished 5/8" radius on top and sits at the center of gravity of my 5.5" thick platter. Vespel can take many thousands of pounds of pressure so no problem for thrust pad use. The lack of friction is amazing !!!!
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.