Re: Cylinder Static Spark Gap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Glen,

Wow, all these methods everyone has brought up is neat. Hey, but my 
own is the easiest and will ensure a perfect spacing (if that's what 
your after).

First, I've built these gaps using screws to attach the copper tube 
to the pvc - yes, it sucks. The problem is too much variation bolting 
down a cylinder onto a cylinder. There is a lot of effort to maintain 
tight tolerance (drilling, hole position, etc.). And yet, even when 
perfect, it can be warped by the screw.

I finally just epoxied the copper tube electrode into place (and into 
a coupler which as you will find, has an internal lip which can be 
used to set the electrode end onto for positioning). I epoxy the 
first electrode into place and try to get a nice 90 degree angle in 
relation to the internal lip ring. Then, I epoxy the rest of the 
electrodes (one at a time) into position by placing a predetermined 
spacer between the set electrode and the new one. I let it dry in 
place. I usually turn the pvc so that gravity helps hold it in 
position. Perfect spacing every time.

I worried about heat causing the epoxy to loosen. But, that has never 
happened. I use 30 minute 2 part epoxy available at any hardware 
store. There is a type that bonds to plastics and metals. That is the 
best to use. I simply add a 1/2" coat along the electrode (where I'm 
going to bond it) and set it in place pressing it against the set electrode.

I've built these type of gaps that didn't work well, but lately, the 
gaps are doing very well! Use 1" to 1.25" size copper tubing and 
preferably "precut" at the store (couplings about 3" long). Their 
ready to go. However, you will need to mount wiring to the gap. So 
first drill a hole near the outer end and attach a brass screw and 
nut into position. The electrodes will exit the coupler about 1/2" 
which is perfect.

Anyway, epoxy is great stuff for this hobby. BTW, it's important that 
the electrode is fully set before putting the next electrode into 
position (too hasty and you'll move the electrode you thought was set).

Take care,
Bart

Tesla list wrote:

> Original poster: "Glen McGowan" <glen.mcgowan@xxxxxxxxx>
>
> Trying to build a Cylinder Spark Gap out of a 6" piece of PVC (it's 
> actually a coupler not an actual piece of pipe). Currently using 1" 
> x 4" (ish) OD Copper pipe. Between 6 and 8 electrodes. There must be 
> an easy way to layout and drill the holes. I've tried to use exact 
> measurements but I didn't get the results I was looking for (which 
> means I can't figure out the measurements). I've resorted to trial 
> and error which I'm not particularly impressed with. This stink'n 
> thing is making me cross eyed.  I'm almost to the point of 
> unplugging the dremel and beating it against the garage floor. 
> Figured I'd drop the list a line and see if some of the veterans 
> could show me some tricks.