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Variable speed vacuum fan spark gap

Original poster: gary350@xxxxxxxxxxxxx I have seen several posts about spark gaps so I decided to post this again. I posted this many years ago I beleive it was about 7 years ago.

I built an RQ spark gap, 8 gaps about .030 between each gap. Built from 3/4" copper tubing pieces 2" long all mounted inside of a 4" diameter PVC pipe 6" long. I removed a vacuum cleaner fan and motor from an old vacuum cleaner. I mounted the vacuum motor on the end of the 4" PVC pipe. A variac is used to adjust the speed of the motor.

This can be used on a small 360 watt TC or a 10KW TC. It is interesting that as the motor speed is increased with the variac you can see the output of the TC get longer and longer. At some point the spark output will reach maxium length and if the motor speed is increased more the output sparks will get shorter. You can tweek the TC for maximum output with the variac.

Another interesting thing is to use a variac on the power supply too. Turn the power down so the output sparks are only 1 inch long. If your output is 1" sparks and you adjust the tap to tweek it to 1.25" sparks that is much easher to do than trying to increase a 23" spark to 24" because it is much easier to see the results of your primary tap adjustments using short sparks. Once you find the correct location for the primary tap turn up the VSVFSG =Variable Speed Vacuum Fan Spark Gap motor speed to get maximum output.

Here are some pics.
Pic #1 is of the RQ spark gap.
Pic #2 shows the vacuum fan spark gap next to the 4" TC on the left. I had a good close up pic but I must have deleted it when I wiped my hard drive a few weeks ago. I can take another close up pic if anyone needs it.



Gary Weaver