Re: Rotary Gap

From: 	Steve Falco[SMTP:sfalco-at-worldnet.att-dot-net]
Sent: 	Sunday, August 10, 1997 6:56 AM
To: 	Tesla List
Subject: 	Re: Rotary Gap

> Thanks for this rotary gap construction information.  I have noticed
> that there seems to be two different types of contact cement
> available (but one may be an older type),  One type is flammable,
> and has a certain texture...another type is i think not flammable,
> and has a different texture.  Are both these types equally strong
> and suitable for this application?
> Thanks again,
> John Freau

The flammable stuff is the older formula - I'm not sure if it is even
available anymore.  We basically traded a toxic solvent for a flammable
one.  Both have had a similar texture to me (the newer type may be
slightly thicker).

I have used both the flammable and non-flammable types of contact cement
for various purposes over the years and found both to be extremely
aggressive adhesives.  I would not be too concerned using either in
construction of a rotary spark gap wheel, because as I indicated in my
first posting, I also used #10 bolts in addition to the glue to secure
the wood to the pulley.  (Four bolts with vibration-proof nuts).  So the
glue should never get a chance to separate.  This is a
belt-and-suspenders approach, but I have to get very close to that
cutoff wheel and press a sharp object against it, so I want it to hold
together. Having a spark gap come apart would not be fun either.

If you are still concerned about glue failure, I would try an experiment
with a scrap piece of wood and metal.  Glue them together following the
directions carefully, then see if you can break them apart.  I'm betting
you can't!  One more thing: make sure both surfaces are clean.  Any oil
on the metal, or dust on the wood will weaken the bond.

	Steve Falco