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Results of new single static gap




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From:  Gary Lau  17-Aug-1998 0842 [SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent:  Monday, August 17, 1998 7:55 AM
To:  tesla-at-pupman-dot-com
Subject:  Results of new single static gap

All:

Last week I posted speculation that a single, well air-quenched gap may
offer better performance than a multi-stage gap, due to lesser gap losses
while acknowledging inferior quenching.

I have constructed a new, single stage static gap.  Imagine two 1.0" OD
brass cylinder electrodes with a hole through their axis, 0.5" ID.  A
vacuum cleaner motor is attached to a common manifold, so air is drawn
across the faces of the two cylinders into their central holes.  The
vacuum motor is on it's own variac.  Gap setting was 0.42".  Spark output
was directly proportional to gap length.

With this gap I have achieved a new personal best - 51".  Previously I
had been using a 10 x .03" fan cooled RQ-style gap, achieving 42".  Power
supply is 15kV/60 mA NST, 4.25" x 23" #22AWG secondary, two stacked
toroids- 4.5" x 15.5" plus 6" x 24".

With the gap set to 0.42", it did not ignite if I ramped the main variac
from off to on.  If I set the variac to at least 50% and then threw the
switch to ON, then it ran smoothly.  It was more than a little unsettling
to ramp the variac to 100% with nothing happening, reminiscent of a blown
NST or cap.  I guess this is nature's way of saying "Your gaps are too
wide, dummy!".

Also unexpected was the effect of the vacuum motor variac.  My goal in
designing this gap was to maximize the airflow through the gap arc,
believing that there was a critical value, above and below which would
diminish results.  It turned out that any airflow, from maybe 5% of
variac on up, produced the same performance.

To be fair, the 10 gap assembly was always operated at it's maximum
number of gaps, so it's unknown and probable that I'd get better than 42"
if I increased the number or setting of it's gaps.  I guess the next step
is to build and compare with a multi-gap with comparable total gap
length.

Gary Lau
Waltham, MA USA