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Old 21st February 2007, 08:47 AM   #21
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Wow, super stuff. Congrats on your ingenuity.

I've got a couple of magnet ideas on the drawing board too, but the idea suspending my platter was causing me sleepless designing nights due to the fact my TT motor is a direct-drive. (Paradoxically a type of design which would benefit the most, but with the magnetics of the motor being so close... <gulp!> )
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Old 21st February 2007, 11:20 AM   #22
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I dont think it would work well im my aplication either as my TT uses a lenco motor. This is idler and the idler wheel pushes againt the underside of the platter. In my head, im sure this would greate lots of problems.
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Old 21st February 2007, 11:32 AM   #23
YNWOAN is offline YNWOAN  United Kingdom
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Quote:
Originally posted by Vinyl-Addict


Actually I think that individual magnets would be more susceptible to cogging than 2 opposing ring magnets which offer a constant circular magnetic surface/field.
The challenge, as you mentioned, is to find large enough ring magnets. I did find a source recently that had magnets strong enough for my application but they are only 75mm in diameter. The inside diameter 25mm.

What do you think a ring magnet of those dimensions would do since the inside diameter of the ring magnet would be very close to the bearing shaft? In my case I use a 16mm shaft.
sorry, I didn't explain myself very well. You are quite correct there is potentially a cogging issue with using individual magnets; that is why I chose to use many small magnets. I cannot detect any cogging now even at very slow speed and very low load. It is possible that using an uneven number of magnets for the top and bottom elements of the bearing would reduce this effect even further as it when be impossible for the poles to line up and any time. The outer diameter of the ring is not much of an issue. It is possible that a larger ring aids stability but the main reason I chose the size I did was purely practical. i needed 80 magnets to provide sufficient 'lift' and that dictated the bearing diameter. I don't see a problem with using a single ring magnet as you suggest if they provide sufficient force.
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Old 21st February 2007, 11:40 AM   #24
YNWOAN is offline YNWOAN  United Kingdom
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Quote:
Originally posted by sq225917

does the platter height vary at all during a full rotation? i'd be interested to measure this visually with a laser level.

if there is no verticle variation then their should be no cogging either, as any varience in repulsion will manifest itself as changes in height.

No doubt you know the answer to this already YNWOAN.

care to enlighten us.

it certainly looks like particulalry well executed,do you have access to CNC or laser cutting for the jigsaw pieces?
No, the platter does not vary in height at all during rotation. However, I too would be very interested in measuring any variation if you have access to very accurate measuring equipment. I am happy that cogging is not an issue in this particular implementation unless proved other wise.

I do indeed have access to both a CNC router and a CNC milling machine. The router was used for both the platter mat and the main bearing - lucky me :-)
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Old 21st February 2007, 11:43 AM   #25
YNWOAN is offline YNWOAN  United Kingdom
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Quote:
Originally posted by sq225917
ps: re the fibrelam, if you lay this up yourself you might want to try backfilling the Nomex with sand loaded epoxy before you add the final skin.

nomex/carbon is very stiff, and has great mechanical damping to loads, but every little helps.

it adds an awful lot of mass to the composite, though it can be awkward for gassing out if you dont pin roller the carbon skins.

i can bring some samples of cast epoxy/mineral loaded blocks if you'd like to see a few.
I would be interested in the epoxy/mineral material you describe. However, I am less inclined to use it for the subchasis. The aim with this component was to achieve the greates siffness to mass ratio possible; this aim would be somewhat defeated if I then added a load of mass :-) - sounds very interesting though.
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Old 21st February 2007, 12:00 PM   #26
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I emailed you, i hope you got it. Maybe our other sheffield member could meet up also?
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Old 21st February 2007, 12:03 PM   #27
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if low mass is your ideal then i can't think of much to beat it than Nomex/Carbon.

Did you use uni-directional or biax?
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Old 21st February 2007, 12:16 PM   #28
YNWOAN is offline YNWOAN  United Kingdom
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Quote:
Originally posted by graeme uk
I emailed you, i hope you got it. Maybe our other sheffield member could meet up also?
Umm, I'm not sure, I'm getting all confused by people having one user name, then a different real name, and yet another e-mail name. I have received and responded to one e-mail about coming round to my house - if this wasn't to you then I haven't rec'd your e-mail - but you are welcome to come round.

Just seen your e-mail and will repond now - cheers matey :-)

I think it would be great if we could get together.
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Old 21st February 2007, 12:27 PM   #29
YNWOAN is offline YNWOAN  United Kingdom
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Quote:
Originally posted by sq225917
if low mass is your ideal then i can't think of much to beat it than Nomex/Carbon.

Did you use uni-directional or biax?
The stuff I used is manufactured for use in the aerospace industry. It consists of twin skins of carbon fibre laminate bonded to an internal structure of honeycomb paper. It is a version of the material used by Pink Trianhel but they used the aluminium bersion which uses aluminium skins and honeycomb. I have used two 12 mm layers bonded together for my suchasis.

I look forward to hearing all about it when we meet up though :-)
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Old 21st February 2007, 12:29 PM   #30
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Does that mean our other sheffield member wants to meet too?
I dont mind whose house/system we use, whatever works out easiest, but we'll arange via email and leave this thread to its intended purpose.

P.S. im not sure what e.mail address is registered with this site. The e.mail im using now is whtf812@aol.com

If you replied to a different address i wont get it.
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