Magnetic pull kevlar suspension tonearm

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IslandPink
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Re: Magnetic pull kevlar suspension tonearm

Post by IslandPink » Sat Apr 22, 2017 9:46 pm

Good stuff. OK - I have found the magazine (2002) and the interview with Frank Schroeder. It is very detailed.
I will try & scan on Monday at work . Meanwhile , this may be of interest.
The magnets are surrounded by aluminium I think -
"every movement of the magnets relative to each other results in the magnetic force lines to move to the surrounding aluminium and that induces an opposing force. Another problem in designing the arm is that ideally, you do not need a lot of vertical movement in a tonearm. Initially I was concerned that I should have various a singularity magnets ( sic ) but in practice it does not make any difference. You would only induce more force lines. In the smaller arm there is high permeability, a pole piece in the back basically resulting in the force lines being restricted and contained. There is a thread here and a hole and a small countersunk dimple to take up the knot. The most difficult, even more difficult than drilling a hole through a twelve-inch piece of wood, is drilling a 0.3mm hole into a magnet of sintered material which has a hardness of 9 on the ( moh's - ed ) scale. Only a diamond bit can do it. The next problem is when you want to drill a hole in it you have to use a special method invented by the watchmakers in Britain. The next problem is that because the material is strongly magnetic , how do you get the waste material out of the shaft you are drilling ? It takes me now, and initially it took me an hour per millimetre and now four hours per 6mm hole. Every third or fourth magnet I throw away because the drill I use gets stuck and you cannot start from the beginning again"
Detail elsewhere says he's using Neodymium magnets for the 'Referenz' .
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pre65
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Re: Magnetic pull kevlar suspension tonearm

Post by pre65 » Tue May 02, 2017 4:27 pm

I saw these magnets with a 4mm hole on Ebay, any good ?

http://www.ebay.co.uk/itm/252501978805? ... RTM2473667
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Re: Magnetic pull kevlar suspension tonearm

Post by cressy » Tue May 02, 2017 6:04 pm

Probably be as good as ideal for an off the shelf buy. the rebate in the underside could be useful for a thin nylon washer or something to fit in that the kevlar string could go through, and the hole should be big enough that the the string doesnt hit it and bend when the wand traverses warps. As long as the hole above it in the wand is big enough to do the same

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Re: Magnetic pull kevlar suspension tonearm

Post by izzy wizzy » Tue May 02, 2017 8:54 pm

cressy wrote:
Fri Apr 21, 2017 10:04 pm
Which arms have a pivot point at the same plane as the stylus? Genuine question, the only one i can think of is possibly the well tempered arm
Triplanar and Eminent Technology come to mind

There are probably others.

cheers,

Stephen

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Re: Magnetic pull kevlar suspension tonearm

Post by IslandPink » Tue May 02, 2017 9:42 pm

Good link, Phil . Shame they only go down to 10mm dia, that's the smallest I could see on EBay. Not bad - probably workable as Ant says. The fact that Frank say's he's drilling 0.3mm holes suggests his magnets are a fair bit smaller diameter.
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