Re: Rotary gaps -- machine work

To: tesla-at-pupman-dot-com
Subject: Re: Rotary gaps -- machine work
From: Chuck Curran <ccurran-at-execpc-dot-com>
Date: Wed, 07 Aug 1996 20:00:03 -0500
Tesla List wrote:
> 
> >From chip-at-poodle.pupman-dot-comTue Aug  6 20:28:50 1996
> Date: Tue, 6 Aug 1996 17:02:00 -0600 (MDT)
> From: Chip Atkinson <chip-at-poodle.pupman-dot-com>
> To: Tesla List <tesla-at-poodle.pupman-dot-com>
> Subject: Rotary gaps -- machine work
> 
> Greetings,
> 
> I've been working on a rotary gap for a while now (5 minutes at a time).
> The problem I'm having is making the disc run true.  The disc consists of
> two aluminum hubs with a 1/2" thick x 12" dia. disc of G-10 epoxy
> fiberglass.
> 
> After reworking the hubs, they are sitting in the 3 jaw chuck.  A dial
> gauge shows that they have been faced so that there is much less than
> 0.001" runout(?).  I then put the disc on the faced hub and put the dial
> gauge on it.  It shows about 0.002" at the center, and about 0.020" or
> more out of true at the edge.  Looking at the motion of the dial, I can
> see that the disc isn't just out of true, but is actually slightly warped
> or something. The needle indicates one "major" high point, and one
> "minor" high point.  These high points are not 180 degrees apart either.
> 
> After a little shimming, I can get things a little better, but not good
> enough.
> 
> This leads me to the reason for the posting.  How to true up the darn
> thing?  The three ideas that I have are
> 1) Face the G-10.  I don't like this too much because it may weaken, or
>    at least make it all fuzzy.
> 
> 2) Build up a rim of epoxy on both sides and face that.
> 
> 3) Ignore the out of true on the disc, put on my brass acorn nut
>    electrodes, and face the points of them.
> 
> Does anyone have any thoughts or suggestions?
> 
> TIA!
> 
> Chip

Hello Chip:

When I constructed my rotary using a 14" diameter disk of G-10 I had to
deal with the same problem you are facing now.  I picked up some shim
stock of different thicknesses and trued up the acorn nut runout in
order to minimize the difficulty.  My last step was to simply rotate the
rotary by hand and slowly bring in the two stationalry gaps until they
started to rub on the highest acorn nut.  At that point I simply backed
out the stationary electrodes about .006-.010" and checked things out
next for the largest clearance on my twelve acorn nut assemblies on the
rotating G-10 disk.  The worst spot was about .026" so I left it like
that.  Since these two rotary gaps are in series with seven stationary
gaps it seems to work O.K. so far.  Try that with yours system and if
possible give an update when you get it going.  Good Luck. 

Chuck Curran