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DIY linear tonearm
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Old 10th February 2019, 01:27 PM   #2731
niffy is offline niffy  England
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Join Date: Nov 2013
Location: Dartmoor
Hi Coolerooney,

Thanks for the link. The German site is more comprehensive though Google translate seems to think it's in Dutch. I'm not actually looking for any new bearing materials myself but like to keep my eye on what is available. It's also helpful to have accurate specs if I'm trying to advise anyone else on their application.

All the resent discussion about arm bearings (and the off topic main spindle bearings) has galvanised me into finally making a new set of idler wheel and bearings. This is the one aspect of my deck that I am least pleased with. The new bearings are based on the work I carried out whilst developing the pin bearings for my arm. I won't be going the full jeweled route with these (not yet anyway). These will be the same as the bearings I made from sewing pins and grub screws. If these work as intended I have a further plan for the way the drive belt is run that should eliminate any problems with off balance records.

Niffy
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Old 10th February 2019, 08:10 PM   #2732
hottattoo is offline hottattoo  United States
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Join Date: Sep 2006
The Best "space age" polyimide for thrust pads / turntable bearings is VESPEL, some grades are graphite or moly disulfide loaded but $$$$$$$$$ followed by TORLON $$$$. Best to look on ebay for small pieces, just make sure you are sitting down when you see the price !!!! I made my turntable bearing ( inverted ) using polished ultra micrograin carbide 5/8" diameter 5" long. The sleeve is made from 1" diameter Vespel 3" long. The platte is 6061 aluminum and weighs about 55 lbs. I cannot detect ANY noise, much quieter then any of the 3 bronze alloys tried, it wasn't even a contest.

Carbide Rod – Centennial Carbide: Carbide Blanks, Rod and End Mills
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Old 10th February 2019, 09:17 PM   #2733
niffy is offline niffy  England
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Join Date: Nov 2013
Location: Dartmoor
Hi Joe,

You weren't kidding about the cost of vespelŠ. The properties that I've seen so far look excellent. Teflon like friction in a much more robust package. Your recommendation of tungsten carbide was spot on so I'd definitely trust your recommendation for vespel. My arm now has tungsten carbide wheels running on the rods you gave me. The bearings are tungsten carbide pivots running in sapphire jewels.
I have toyed with the idea of replacing the main bearing of the deck with tungsten carbide. The question is how to make a perfectly spherical indentation (1.5mm radius, 0.6mm deep) in the end of a short rod. The hardened steel version I'm currently using offers very low friction and is silent so there probably wouldn't be any great difference. Having said that, going from steel to carbide in the arm made a big difference so it might in the main bearing as well.
55lb platter!!! That must be a solid billet over 5"thick. Are there any benefits to going that massive? The load on the bearing is going to push the friction and noise inevitably higher than for a more modest platter. The increase in inertia will be offset by the increased bearing load so speed stability probably won't improve with the increased mass. The benefit I can see is that there is more mass to sink the energy from the stylus into. What are your thoughts on the advantages of higher mass?

Niffy
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Old 11th February 2019, 02:27 AM   #2734
hottattoo is offline hottattoo  United States
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Join Date: Sep 2006
Hi, Niffy

I kept my platter bearing fairly simple, .625" diameter carbide shaft with a .625 " radius on top using 1" diameter Vespel as the bushing and thrust pad. I made thrust pads of Nylatron, Vesconite, and Torlon with Vespel being the clear winner after spinning the platter for several days on each material. Torlon was a close second. I got a deal on 3 pieces of 6061 aluminum 12.5" diameter and 5.250" thick so that is what I used. That is my "scientific" answer for using that size platter, why make unnecessary chips !!!! My platter also has a mag-lev option that uses a pair of 4"OD x 3" ID x 1/2" thick N48 neo ring magnets which can pull 130lbs. I bought the 3 motor unit / controller from my friend who is a TW acoustic dealer here in N.Y.C. This is the same motor / controller used on their Black Knight turntable. My platter is a light weight compared to my friend in Las Vegas who is a Triangle Arts dealer and has their 750 lb.Reference turntable with a 135lb. Platter !!! Last month we spent 5+ hours at his house listening to the big reference turntable against the "smaller" reference turntable (250lbs with 50lb+platter) using the same tonearm / cartridge / phono stage / electronics on his horn system. It's hard to believe, but the bigger turntable sounded better every time, with all 4 people in 100% agreement. There was a little more of a solid image, more overall weight and presence, not by a great amount but easy to hear. I will not even speculate how this was possible, but there it was. This was an experience I will not forget !!!

I must confess, I "clipped" your carbide ring / axle (size 5 for me) / jewel bearing wheel idea because it is the best design possible for the purpose. My carriage will ride on 3/16" polished carbide rods. The carriage will be more conventional, 4.5" long and made of magnesium with a 7" long precision 7075 aluminum .420" diameter arrow shaft. I listened to the 250K Clearaudio reference turntable at audio shows with their 25K linear arm and it had excellent sound so my arm will be as good or better / lighter / less friction then theirs.

Niffy, thanks again for you precious input and time making this the best DIY linear tracking arm thread on the planet !!! I will be watching, learning, and contributing when possible.
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Old 11th February 2019, 11:28 AM   #2735
niffy is offline niffy  England
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Join Date: Nov 2013
Location: Dartmoor
Hi Joe,

Sounds like you've been having fun. My limited experience with heavyweight platters, though nothing as heavy as yours, is that there is a definite advantage in the lower octaves but they seem to loose a bit of delicacy in the higher frequencies. With a short listening session the bigger bottom stands out though with a more extended listen the short comings higher up become more obvious. I haven't had any experience of super heavy megabucks tables. My platter is just shy of 4kg with record and clamp fitted, seemed like a good compromise to me. My entire deck weighs in at 30kg so is no lightweight.
Are you currently using the maglev on your deck? And do you have any materials specs for vespel? I was specifically looking for Youngs modulus and poissons ratio. The website has the coefficients of friction with load variation.

I'm glad you have found my work on bearings useful. My purpose in posting is to share the knowledge and hopefully help others to build a better tonearm. You will definitely get a better bearing than the clearaudio ballrace on glass design. The friction should be between a third and a quarter of their design. I think the biggest advantages are the elimination of chatter and much superior mechanical grounding. Please let me, and everyone else, see what you build and your opinion on the sound.

Niffy
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Old 11th February 2019, 02:00 PM   #2736
super10018 is offline super10018  United States
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Join Date: May 2010
Quote:
Originally Posted by hottattoo View Post
Hi, Niffy

I kept my platter bearing fairly simple, .625" diameter carbide shaft with a .625 " radius on top using 1" diameter Vespel as the bushing and thrust pad. I made thrust pads of Nylatron, Vesconite, and Torlon with Vespel being the clear winner after spinning the platter for several days on each material. Torlon was a close second. I got a deal on 3 pieces of 6061 aluminum 12.5" diameter and 5.250" thick so that is what I used. That is my "scientific" answer for using that size platter, why make unnecessary chips !!!! My platter also has a mag-lev option that uses a pair of 4"OD x 3" ID x 1/2" thick N48 neo ring magnets which can pull 130lbs. I bought the 3 motor unit / controller from my friend who is a TW acoustic dealer here in N.Y.C. This is the same motor / controller used on their Black Knight turntable.
I will love to see some photos or drawings of your table. It sounds like a very nice table.

My ideal table is air bearing table. Please see the drawing. I have all the air bearings, but since the project involves too much with mechanic parts and additional air supply, etc. I think it is beyond my capacity.
Attached Images
File Type: jpg table.jpg (14.3 KB, 200 views)

Last edited by super10018; 11th February 2019 at 02:13 PM.
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Old 11th February 2019, 04:46 PM   #2737
hottattoo is offline hottattoo  United States
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Join Date: Sep 2006
Niffy,

A bit off topic but for a complete review of my Vegas listening session, I left out that we also listened to a highly modified, custom, Technics SP10 MK 2 turntable / electronics with the same arm and cartridge. The turntable was absolutely stunning, with a very large cocobolo base. However, sound wise it was a distant 3rd place. To be fair, the Technics table was about 18K IIRC. The overall sound was a bit thin, less presence, less relaxed sound, almost as if the entire sonic presentation was on a diet !!! In all fairness, if we did not have direct comparisons to the 2 other monster belt drive tables, anybody else would be perfectly happy with the sound of the Technics table.

The Vespel I used was grade SP22. I caught a break on ebay for two 1' x 1" diameter lengths for $310 about 2 yrs. ago. I am not using the turntable at the moment as I think about a final finish (or not) for the platter. I was thinking about anodizing or powder coating but have reservations on both. The platter has a 6" x 1" well machined in the bottom to fit a ring containing the ring magnet with stainless screws. The bottom bearing assembly has the same type ring for the opposing magnet. I can raise and lower the spindle shaft to change the contact weight on the thrust pad. I can install the magnetics in 10 minutes and it works very well. The platter can completely float but I want a constant zero point and a few pound of weight on the thrust pad for energy drain. I even made provisions to add some mu-metal in the magnet well if needed. The plinth is made from a 3" thick x 18" x 20" piece of gray granite with 1/2" stainless steel plate epoxied to the bottom. One of the club members son works for a high end granite company that has a water jet machine who cut the plinth and 5 holes for me, one 2" for the bearing assembly and four 1.250" for the foot assemblies. The plinth is set up to use up to 4 tonearms. The naked plinth weighs 138 lbs. !!! Each foot / arm stanchion assembly weighs 11.5 lbs ( copper / bronze with Nylatron for foot). The bottom line is I got the plinth for free !!!! Of course, I gave a few hundred dollars for the favor.

super10018,

Unfortunately, my computer skills are not good as far as CAD, drawing programs go. I make simple sketches of what I need and measure as I go. My projects are "one of" but I make others without much trouble. I will have one of the computer guys from the audio club show me how to upload the pictures I have. Your air bearing arm and turntable are works of industrial art and I very much admire your skills and out of the box thinking.
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Old 11th February 2019, 05:11 PM   #2738
carolus is offline carolus  Belgium
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Join Date: Jan 2005
Location: Brussel
Quote:
Originally Posted by super10018 View Post
My ideal table is air bearing table. Please see the drawing. I have all the air bearings, but since the project involves too much with mechanic parts and additional air supply, etc. I think it is beyond my capacity.
Welcome in the air bearing TT club.
Good idea.
I wish you perseverance in realizing your musical dream ....
Music on a heavenly cloud ... super.
My experience ... I like (& build) TT air bearing (& TA)
Karel
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Old 11th February 2019, 07:11 PM   #2739
walterwalter is offline walterwalter  Ukraine
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Join Date: Mar 2011
Hottatoo, I think what everyone here will be glad to see some photos of your turntable here. As to heavy platters, I do have my own experience of upgrading several vintage belt drive turntables by installing heavyweight platters (from 4 to 10 kilogram), and sonic results are always huge improvements, with no exceptions.. My last project will be a complete DIY turntable with DIY linear arm and DIY MC cartridge (halfway through for now). Will post it here.
My contribution to off-topic
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Old 11th February 2019, 07:53 PM   #2740
hottattoo is offline hottattoo  United States
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Join Date: Sep 2006
walterwalter,

Nobody will be happier then I to post some of the pictures I have. Next time I have a computer person from the club over I will learn how to do it.
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