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kilowattski 20th June 2005 02:54 AM

air bearings
 
I recently got alot of my other DIY projects finished and thought I may take a stab at a turntable this fall. I have been thinking alot about it lately and thought I would ask you gentlemen if anyone has contemplated using an air bearing as the main bearing? Has anyone tried using one? Is it cost prohibitive. I figure now is the time to ask if this idea is way out in left field before I commit myself to something that is not practical. Does anyone know how much they cost and if they are available on the surplus market? Lastly, what type of air supply is needed? Please let me know if I am way off base. Thank you all in advance.

frank2395 27th June 2005 02:10 AM

sorry not air but may be alternative
 
Sorry not air but.....

this guy has done his homework

http://aca.gr/paper37.htm

Thanks for helping me in past

Bare 27th June 2005 02:42 AM

The Foresell Air bearing TT. Years old... too late Mate.
Perhaps you might try a Magnetic Suspension bearing.. if you can negate the side effects on the Cartridge.. perhaps just in time for the V last Vinyl Lp .

koldby 11th July 2005 07:01 AM

Kilowattski:

I have toyed arund with airbearing main bearing a little. I have an Maplenoll turntable using just such a thing - too.
There were , in a Danish version of High Fidelity, a construction artikel from some students at the Technical University in Denmark, describing all the problems involved in constructing a fully air bearing main bearing.

The problem is to make it perfectly round, not have any relative temperature dependansy and to make the surface hard and even.
They used Aluminum that was later annodisized and had to calculate excatly the schrinking involved in the anodisizing process. Very difficult....

BUT do not dispare. The main reason for using an air bearing is to reduce friction AND noise from the main bearing and this is almost 100% comming from the vertical bearing (all the weight from the platter) and not so much from the horizontal bearing (the sidway pull from the belt).

The vertical bearing is easily made from acrylic or even better glass or a combination of the two materials. The horizontal bearing could be made from (as in the Maplenoll) a smal diameter brass sleave in the platter and a sligtly conical Teflon rod (?) in the stationary part of the bearing, that is adjustable in hight so it dosent stick and isen´t sloppy. A little silicon grease is the final touch here. Such a bearing is so frictionless that it will turn almost forever , without anything driving it and no noise at all.

If you use three motors (or one motor and two pullies) the side thrust is eliminated to almost nothing...

And aftre this , you should make an air bearing tonearm too :D


Koldby


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