Re: More rotary gap questions..

To: tesla-at-poodle.pupman-dot-com
Subject: Re: More rotary gap questions..
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 29 Apr 1997 02:27:05 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: More rotary gap questions..
  Date:   Mon, 28 Apr 1997 15:38:58 -0500
  From:   "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
    To:   Tesla List <tesla-at-pupman-dot-com>


> <snip>
>  
> >> Now I'm wondering about the rotating electrodes, I've heard mentioned
> >> brass pins, brass screws with stainless acorn nuts, and some sort of
> >> threaded holder with tungsten rods.
> 
> <snip>
> 
> >Daryl,
> >
> >I can supply you with matched .250" dia. solid tungsten studs ground to
> >1.5" length within .002" for $7.00 each. I use, and recommend, nothing
> >but solid tungsten studs on any of the gaps that I use because of the
> >durability and safety factor. Screw in inserts can work loose because
> >the two different materials involved expand at different rates when
> >heated.
> >
> >I have 6 continuous hours of run time at 8 to 10 KW on the .250 dia.
> >studs in the rotor on the series rotary gap I use with my magnifier and
> >the stud erosion is minimal. In addition, when the studs do errode
> >sufficiently all you have to do is pull them out and face them off on a
> >belt sander or grinder and it only costs you the time it takes to do it.
> >No extra cost to replace inserts!
> >
> >Safe Coiling Always,
> >
> >Ed Wingate
> 
> Thanks for the info !
> 
> I'd considered using Tungsten studs, but I'm still trying to figure out
> how to hold the studs to the rotor.
> 
> I thought of drilling out a 1/4" hole in some stainless bolts and then
> useing a setscrew through the side to hold the stud in place. 
> 
> But I worry about the balance of the rotor, 'tho I could machine them
> till they weigh the same. The other big problem is whether the setscrews
> will hold well enough in something as hard as Tungsten. I also worry
> about
> haveing so much weight at the edge of the disk
> 
> The ideal situation would be something like a collet, which would hold
> the stud in place by compression, while makeing sure they were
> concentric.
> 
> Alas, if I had enough equipment to make such a holder, I wouldn't have
> enough money to make a coil !
> 
> The hardest part of all this, is finding out what is 'good enough'.
> ('Tho the same can be said for most enginering...)
> 
> Daryl
> 
 
Daryl, All (with the explicit exception of  DR.WHO),

There IS a type of collett available from radio/electronics parts 
stores.  This device is designed to thread onto a standard, 1/4 inch 
shaft, panel mount potentiometer, the kind that use a 3/8th inch fine 
thread.  Made of nickel plated brass, they are split several places
around and
when their hold-down nut is tightened they prevent the setting of the
pot from 
being changed.  You can get 'lockable' pots with this already on them,
or 
buy these after market screw-ons as a retrofit.  If you could figure 
out a way of embedding these in your rotary disk they would be 
terrific I suspect for holding replaceable 1/4 inch tungsten flying 
electrodes that are mounted 90 degrees to the disk.

rwstephens