Re: Square rotor disk on SRG

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi Paul,

I would use 2-part epoxy, with a 30 minute curing time or more
(epoxies with longer curing times seem to be stronger and less
brittle). "Devcon" brand epoxies, available from Walmart, K-Mart,
etc. are wonderful.

> Square should be OK but it does limit your firing times

I see no reason for this, as the electrodes are still moving at the
same speed (provided their spacing, in reference to the centerline of
the motor shaft, remains the same).

> Is it feasible to run a square disk? 

I imagine so.

> Has anyone done this? 

Not that I know of...perhaps kVA Effects has but I'm not sure. I want
to say I saw a picture of one of their RSG's (it was big..) that used
two cross members. I suppose this is essentially the same as a square
shape but weighs much less.

Anyhow it sounds like a great idea to me...because if the gap doesn't
quench for some reason and it "drags an arc", the disk (the square
disk!) won't be damaged. Being a square shape, there would be a
minimal surface area exposed to the arc if it drags.

Also: a perfectly balanced square disk would be much easier to obtain
than a round disk. Cut it out on your table saw vs. call the local
machine shop.

> If I don't cut it down to a circle my electrodes can be spaced out 
> in diameter by a further 5cm (1.5 inches) which will be beneficial 
> in my design. 

Sure. Spark "Dwell" time as they call it, will be shorter as the
electrodes will be moving faster. Up to a practical point, the faster
the better. This increases airflow over the flying electrodes, which
would help out with temperature problems if they exist.

> The disk will still be in balance but I don't know if the extra 
> drag from the increased wind resistance may be a problem?

The square......flying electrode holder (can't call it a disk
anymore!) will definately move some air. Whether the extra resistance
will be a problem or not depends on the motor torque.

> Is it structurally sound to have the electrode bolts mounted in the

> corners (rather than on a circular disk?

I'm no mechanical engineer, but it seems to me that a square disk
would be stronger (for lack of a better word). There would be more
material to fasten the electrode to...the corner of the square.
However, I think this is of little significance as the strength can
be increased greatly by simply moving the electrodes inward, towards
the center point....so there would be more material to crack/tear off
if it's going to fail at all.

I like the idea, mainly because it seems it would be easy to machine
to a perfect balance.

Take care,

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com