Re: Rotary Spark Gap.

From: 	Adam[SMTP:absmith-at-tiac-dot-net]
Sent: 	Wednesday, December 03, 1997 1:06 AM
To: 	Tesla List
Subject: 	Re: Rotary Spark Gap.

>TC list,
>I just got a 1' dia  1/2" thick Plexiglas plate and a 1/3 hp -at- 3000 rpm
>motor  (4.7 amps) for my rotary spark gap.
>I have seen pictures of gaps with a metal ring configuration so that one
>electrode on each side (1 foot away) of the
>disk makes up the gap,  and ones with electrodes that go through
>straight through disk.  Which method, if any, is best?

The latter type is more common, and more electrodes means more cooling 
surface.  Many coilers have a single rotary disk with more than one pair 
of stationary electrodes in series to increase break rate, gap distance, 
quenching performance or all of the above.  Often, rotaries are used in 
series with static gaps as well.

It should be noted here, that non-syncronous RSGs are not recommended for 
neon/obit powered coils.  Since you have a non-syncronous motor, you 
should really save this until you get into higher power projects.  Neon 
sign transformer powered coils have been shown to work well and safely 
with syncronous gaps, which use motors that are synced to the AC line 
frequency at either 1800 ot 3600 rpm.  The syncronous motor, once 
adjusted to the right phase, makes sure that there is always a chance for 
a spark when the voltage on the cap is at maximum, saving your cap and 

>Does anybody know of a good piece of hardware suitable for electrode

Brass bolts or bullet nuts (like cap nuts) are often employed for 
electrodes.  Also, Plexiglas is not an acceptable disc material since the 
electrodes will melt it and fly off the disk at extreme speeds.  An 
electrode in a 3000 rpm 1ft diameter disc will launch itself with a 
linear velocity of 100 MPH- dangerous!!!  Safe coilers use 1/2" G10 
Fiberglass board for their rotary discs, and polycarbonate shielding 
(1/2" Lexan, which I've seen stop a .45 slug) around the disc.


Adam Smith
Epoch, Inc. Digital Music Project

www.tiac-dot-net/users/absmith/     Now with MP3!     Musik. Macht. Macintosh.