PSN-L Email List Message

Subject: Re: Digest from 07/07/2008 00:01:28
From: ChrisAtUpw@.......
Date: Tue, 8 Jul 2008 09:46:36 EDT


In a message dated 2008/07/08, rpratt@............. writes:

> My experience is that support flexure or lose threads in supporting legs 
> are the barriers to settup stability and the floor of the basement is the 
> controlling factor over days or weeks. 

Hi Randy,

    Agreed! I put a wavy spring washer and a lock nut on the top of the 
baseplate to keep the threads under a fairly high tension at all times and to 
prevent any rocking or slipping of the threads. These are better than the ordinary 
split spring washers and give a force along the thread axis. This seems to 
work fine. I set the level etc, tighten the lock nut to ~1/2 compress the spring 
washer and then make any final level adjustment. 

       You can only try selecting areas of the floor away from load bearing 
and particularly external walls, if possible.

 I am also finding that with the stronger magnets I have obtained that I am> 
> fighting magnetic effects not seen before where even my damping plate may be
> causing instability.

       This suggests that you are using an Aluminum damping plate and that 
the edges of the plate are getting close to the edges of the magnets, during 
normal operation. There is a very high field gradient here. Increase the width of 
the damping plate so that it always completely covers the magnets? Aluminum 
is paramagnetic, some alloys more than others. I use 1/16" Copper sheet. Copper 
is very slightly diamagnetic and is ~free of this force problem. 

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/07/08, rpratt@............. writes:

My experience is that support f= lexure or lose threads in supporting legs are the barriers to settup stabili= ty and the floor of the basement is the controlling factor over days or week= s.


Hi Randy,

    Agreed! I put a wavy spring washer and a lock nut on the=20= top of the baseplate to keep the threads under a fairly high tension at all=20= times and to prevent any rocking or slipping of the threads. These are bette= r than the ordinary split spring washers and give a force along the thread a= xis. This seems to work fine. I set the level etc, tighten the lock nut to ~= 1/2 compress the spring washer and then make any final level adjustment.

       You can only try selecting areas of the= floor away from load bearing and particularly external walls, if possible.<= BR>
I am also finding that with the stronger magnets I have obtained that I am<= BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT:= 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">
fighting magnetic effects not seen before where even my damping plate may be=
causing instability.

       This suggests that you are using an Alu= minum damping plate and that the edges of the plate are getting close to the= edges of the magnets, during normal operation. There is a very high field g= radient here. Increase the width of the damping plate so that it always comp= letely covers the magnets? Aluminum is paramagnetic, some alloys more than o= thers. I use 1/16" Copper sheet. Copper is very slightly diamagnetic and is=20= ~free of this force problem.

       Regards,

       Chris Chapman

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