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Re: a few questions about secondary construction



Original poster: "R Heidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

on 11/02/01 12:26 PM, Tesla list at tesla-at-pupman-dot-com wrote:

> Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <vanyo-at-echoes-dot-net>
> 
> I just got my 9" by 30" spun aluminum toroid, and am considering
> rebuilding my coil to do it justice.  My current coil (dead by capacitor
> failure) has a 6.5" by 27.5" secondary, 1000 turns of 22 awg, and is
> powered by three 15/60 NST's (and has a static gap).  I'm adding a
> fourth 15/60 (for a total of 15kv/240ma).
> 
> I'm planning on winding another secondary, and here are some of the
> changes I'm considering.  I'd appreciate any feedback on these points.
> 
> 1) Diameter: Would it be better to have an 8" diameter secondary, as
> opposed to my current 6.5"?  Perhaps even 10"???  (the primary will, of
> course, be adjusted accordingly)
> 
> 2) Thick vs. thin walled PVC:  My current secondary is wound on thick
> walled PVC.  I've read that thin wall is better.  Is there really that
> big of a difference?  The new toroid is rather heavy, and it just seems
> like something solid would be better.
> 
> 3) Ground connection: I currently have a flat copper ground plate at the
> bottom of the coil (for the most part, I followed guidelines on this
> page: http://privat.schlund.de/s/skluge/coilbld.htm ), but am thinking
> about using a nut and bolt type terminal connection, possibly mounted
> through the wall of the pipe (below the bottom end cap).  With the flat
> plate, I'm not sure how to make a solid connection (early on, I made the
> obvious mistake of using a pipe clamp - a shorted turn that did some
> heat damage to the polyurethane).  Would a bolt through the wall, just
> below the botton end plate, be OK?
> 
> 4) end caps, toroid mount: My end caps currently consist of a sandwich
> of 3/4" plywood epoxied between two layers of some unknown type of hard
> white plastic I had laying around.  The top cap has a 3/8" bolt through
> the top layer of plastic.  I want to do something similar - a mounting
> bolt on top, to which the top end of the coil wire is permanently
> connected.  What I need is a reasonably priced source of the right kind
> of plastic.  Some of the online plastics catalogs seem to be
> exorbitantly priced, even for just enough to fashion a couple of end
> caps.
> 
> 5) epoxy: I used polyurethane the first time - many coats, applied and
> dried while turning on the winding jig - and the results were beatiful,
> but I want something more rugged (hence also why I'd like to go with the
> thick wall PVC).  I was looking at an epoxy at
> http://www.epoxies-dot-com/tech/20-3302.htm , for which they quoted me a
> price of $45/qt resin, 17.50/pt catalyst (2:1 ratio), which I think is
> enough if I'm careful.  Does it get a lot cheaper than that?  Can anyone
> recommend a good alternative epoxy available online?
> 
> 
> Thanks,
> Bill Vanyo
> 
> 
> 
I use a 1/4  plastic bolt tapped into the base of my coil to mount my ground
wire to avoid any internal coil connections.
 Epoxy resin mixtures must be mixed as per recomended ratios or it will not
harden correctly ever. Fiber glass resin can be varied to control hardening
time, but dont try that with epoxy.
    Robert H