Magnetic turntable bearing - Page 11 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 1st April 2007, 10:04 AM   #101
YNWOAN is offline YNWOAN  United Kingdom
diyAudio Member
 
YNWOAN's Avatar
 
Join Date: Jan 2007
Unfortunately Iain you are not the first person to ask about 'looking after' my prototypes.

I know Les W quite well and am passingly familiar with the Genesis turntable. To implement a magnetic bearing the top plate would have to be re-fashioned and the specific dimensions of the magnetic bearing would have to be re-made to fit the main bearing and sub-platter of your deck - I don't think you would find either of my prototpes to be of much use - also it depends on the weight of your platter.
  Reply With Quote
Old 1st April 2007, 11:08 AM   #102
diyAudio Member
 
Join Date: Dec 2005
Location: essex
All going well then
My system is back up and running now so im happy.

Did you decide on some speakers?
  Reply With Quote
Old 1st April 2007, 01:38 PM   #103
YNWOAN is offline YNWOAN  United Kingdom
diyAudio Member
 
YNWOAN's Avatar
 
Join Date: Jan 2007
Good to hear your system is working again.

I managed to get my ES14's fixed but I am intending to replace them now - not decided with what though.
  Reply With Quote
Old 17th April 2007, 02:22 AM   #104
YNWOAN is offline YNWOAN  United Kingdom
diyAudio Member
 
YNWOAN's Avatar
 
Join Date: Jan 2007
Well, I've made yet another version of the magnetic bearing. This time it uses a large(ish) ring magnet and 20 5mm cylinder magnets. The advantage of this approach is that residual cogging is elliminated. The much smaller number of magnets (20 instead of 40) used in the upper section of the bearing should reduce the magnetic field projected above the bearing and make the shielding even more effective. I've not had a chance to ft or listen to it yet

I'm auditioning a pair of ATC SCM40's o Tue or Wed with a view toreplacing my much loved ES14's
  Reply With Quote
Old 18th April 2007, 03:34 PM   #105
diyAudio Member
 
Join Date: Jun 2004
Location: VA
I've been very interested in this project and are thinking of doing something similar.

Has to be nice to have your own CNC machine!

I have a few questions about your latest project. How large was the ring magnet you ordered? Do you have any idea roughly how much magnetic force is devoted to repulsion? I understand that you are simply relieveing the bearing of friction, and not floating the platter. How heavy overall if the linn platter with your additions?

If you know the answers to any of these questions I'd sincerely appreciate it!

Thanks
Zach
  Reply With Quote
Old 18th April 2007, 05:59 PM   #106
YNWOAN is offline YNWOAN  United Kingdom
diyAudio Member
 
YNWOAN's Avatar
 
Join Date: Jan 2007
Hi Zach, i'm in a real hurry at the moment but I will answer your questions shortly. One thing though, I AM floating the platter completely; the end of the bearing is a couple of mm above the thrust plate.
  Reply With Quote
Old 20th April 2007, 10:10 AM   #107
YNWOAN is offline YNWOAN  United Kingdom
diyAudio Member
 
YNWOAN's Avatar
 
Join Date: Jan 2007
OK Zach, here are a few answers which may (or may not) be of help to you:

"How large was the ring magnet you ordered?"

http://<a href="http://www.engconcep...agnets.asp</a>
Part R1410, 114.3mm OD, 101.6mm ID, 6.35mm thick. Many thanks to the forum member who posted this link. Plus 20 of the cylinder magnets CYL0350 provide 5mm of lift on the linn platter. Approximately 1mm of lift is still possible with only 10 of the cylinder magnets but the field is much more compliant.

"Do you have any idea roughly how much magnetic force is devoted to repulsion?"

I'm not sure what you mean by this. All of the magnetic force avaliable is radiated all of the time - therefore, all of the force is being devoted to repulsion. Perhaps you mean, what is the strength of the magnetic field? I'm soory but I haven't a clue as to this answer.

"I understand that you are simply relieveing the bearing of friction, and not floating the platter."

No, this is not true. It was never my intention to simply relieve the bearing of friction. The platter is completely lifted clear of the thrust plate although the bearing is still held in allignment by the bearing sleeve.

I've not had a chance to weigh the whole assembly but my Google search tells me that a Linn LP12 platter weighs 3.75KG the magnetic bearing element may bring it a bit closer to 4KG (I'm sure it would support that).
  Reply With Quote
Old 21st April 2007, 03:16 AM   #108
diyAudio Member
 
Join Date: May 2006
Hi YNWOAN. I love your work! Here is what I tried. I bought a bunch of These magnets from parts Express. ( http://www.partsexpress.com:80/pe/sh...number=329-217 $1.65 ea. X 2) I never thought it would work, but I duck taped one to the plinth of my RM-9 and the other to the underside of the platter. I put the platter back on, and sure enough there was about 5-7mm Clarence. Meaning they raised it up that far. Do to the thickness of them the platter was up to high to play it, (Darn!) but they did work.

Now the platter, magnet, and puck weigh in at 9-10#. Meaning that's how much weight two of them will lift. Another possibility is to stack a few of the magnets on the plinth to support even more weight, if somebody wants to make a heavier platter.

Dave
__________________
People in audio whom I admire.... Henry Kloss, Edgar Villchur, John Dahlquist, Bowers and Wilkins, Theil and Small, Don Keele, our own Nelson Pass. In short VISIONARIES.
  Reply With Quote
Old 23rd April 2007, 07:42 AM   #109
diyAudio Member
 
Join Date: Apr 2006
Location: seattle
Way to go Dave, duct tape, love it, very cool move………
I saw some speaker shielding cups somewhere but I can’t find them.
Nice work YNWOAN, I look forward to your updates
  Reply With Quote
Old 13th June 2007, 02:46 AM   #110
diyAudio Member
 
Join Date: Jan 2003
Location: Musicville
Default Mission accomplished.

Quote:
Originally posted by eeka chu


With the magnetic ring, my thoughts were along the lines of how easy it is for imperfections to make it wobble/tilt on its axis for the same field strength. The smaller the OD of the ring, the more it becomes like a plate spinning on a finger, so any slight mistake will make it start wobbling, even if it's virtually impossible to press the platter down any further against the magnet supporting it (think of a small OD magnet like a jewel pivot). For the same field strength, it'd be harder to make it wobble/tilt if the support was around the circumfrence, thinking about moments of forces rather than just the repulsive force alone. A small OD ring is more like a pivot, whereas a large OD (even if it has a large ID as well) is more like a support. For the same strength of magnet, it should be harder to make the platter wobble/tilt if magnets are round the edge of the platter.

I just completed my magnetic bearing using opposing ring magnets. It took me awhile to find the right strength and magnets that would fit my upper & lower bearing housings. I built my turntable with my own inverted bearing design that worked very well to support the 36 pound platter. I initially used a tungsten carbide thrust plate but I always wanted to relieve the immense force it had to undertake to support the high mass platter. Anyway, that was over a year ago and after searching on & off I finally found a pair of magnets that fit both my criteria.
After building a test fixture and measuring clearance, I was satisfied that machining the pockets and bonding the magnets would be the final test to see if the magnets would perform as I hoped they would.
I initially assembled the lower & upper bearing housings which was a challenge because of the 100 pounds of opposing force generated by the magnets. I had to machine a Delrin sleeve to extend the length of the inverted bearing shaft, after that I assembled both housings and placed the platter on top.
I did this on a granite surface plate so I could place a dial indicator on the platter to measure deviation. The total measured deviation from perfection was 0.1mm, hardly anything to be concerned with.
I then put it to the true test and actually played record after record. What an improvement! Ultra quiet and smooth as silk, well worth all the effort. Below is an image of the lower bearing housing that shows one of the ring magnets bonded to the lower housing. The magnet is nickel plated. Another image shows the complete turntable.


Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Air Bearing Spindle DD Turntable monsieurphot Analogue Source 18 12th April 2008 07:05 AM
Other bearing for turntable use? Zero One Analogue Source 4 27th May 2006 01:13 PM
DIY turntable bearing bigbulb Analogue Source 9 11th July 2005 02:16 PM
Turntable bearing Tee-Rex Analogue Source 3 5th May 2005 06:55 PM
turntable bearing design sc351cobra Analogue Source 1 24th March 2005 10:30 AM


New To Site? Need Help?

All times are GMT. The time now is 11:14 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2