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Spark gaps




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From:  Justin Oliver [SMTP:joelec1-at-ozemail-dot-com.au]
Sent:  Wednesday, February 18, 1998 11:02 PM
To:  tesla-at-pupman-dot-com
Subject:  Spark gaps

I am having trouble with my spark gap. My xfrmr is a 10Kv 10ma ignition and
I put the two leads together to see how big a spark I could get and it was
about 1cm. I then made my gap - I got two screws and cut the heads off them
leaving me with about an inch of screw with thread and 1/2 inch without. I
then cut two bits of brass bar about 1/4 inch long, drilled a hole through
the middla and silver solded the bare end of the screw through it with about
1/8 inch of the screw end sticking out. I drilled a hole through two L
shaped bits of steel and screwed the terminals into the holes. 
                      |        ||||         ||||        |
*****|*****8888|||88     88|||8888*****|
|        ||||         ||||        |
|                                 |
|                                 |
____________|                                 |_______________
Legend:
* = Screw with thread
8 = Screw without thread
                ||||
Bit shaped like  ||| = Brass heatsink 
                ||||
Using this setup I can only get a spark 2mm long and it sounds like a swarm
of bees. The spark is all purple like  it is giving off ultraviolet. I have
been told a spark gap works better with an airflow going through it so I put
about 75 psi through it and the spark turned white and hissed like a snake
though I could still only get continous sparks at 2mm with short bursts at
3mm. Why can I get a 1cm spark from the terminals of the xfrmr yet using my
gap I can only get 2mm spark. Will this change when I finish my coil and
there is a capacitor in place? Also, I was told that you can change the
frequency of a primary by changing the distance of the spark gap because the
capacitor discharges faster. Is this true?

Justin Oliver