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High power spark gap 3kva

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Vigh holtage

Sat Dec 16 2017, 12:49AM

Registered Member #61739 Joined: Wed Aug 23 2017, 04:43PM
Location:
Posts: 44

Again thank you i will get the new tungsten electrodes within 1mm and ground dead flat on one end and 45ed on the other to a point then try bolth sides.

Okay here is a link to a YouTube video of the motors I have the tungsten carbide I have access to and what I can do with what I have if you have any information on my best route of action please comment let me know oh and mind the way I speak I have ADHD and can never find the right words

What do you think its my first try at a REAL... spark gap

profdc9

Sat Dec 16 2017, 01:42AM

Registered Member #58522 Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50

A couple of comments. I've never made a synchronous spark gap, so take this with a grain of salt.

From what I've read, you need to get the position of the spark points to correctly phase with the AC cycle so that when the capacitors are charged to their peak, the spark gap fires. You might need a way to rotate the disc with the points relative to the shaft to do this.

Because the acceleration of the disc is velocity^2/radius, and the spark gap point should achieve a particular velocity I would think so that the spark quenches as the point moves across the static electrode, this would favor the 1800 rpm over 3600 rpm, but the diameter of the disc will need to be twice as large. A larger disc would help prevent arcing into the shaft as well, and you could add more points if you want to increase your repetition rate.

The downside I see to a larger disc is the possibility of wobble and runout, so you have to balance everything carefully. But you have good tools and skills available to you so you can probably handle this.

It looks like its going to be a great spark gap.

Dan

Vigh holtage

Sun Dec 17 2017, 06:23PM

Registered Member #61739 Joined: Wed Aug 23 2017, 04:43PM
Location:
Posts: 44

Well I'm going to try and Tackle this until I succeed or fail whichever comes first LOL

All I need to do is grind the Two Flats that's simple enough make sure it runs synchronous which is simple also and then cut out a disc and lay it out for for electrodes drill and tap some set screw to hold the electrodes in place and then comes the hard part

I will need to change the position of the motor in small increments until I find the best firing position on the AC waveform the problem is I do not have a oscilloscope or a functions generator to actually select the right position with so it's going to have to be trial and error making tiny adjustments and testing I figure it's pretty much the same principal as the adjustable aluminum flywheel on my cart you loosen it up make a tiny adjustment maybe one degree tighten it all down and run it to check the difference in performance then rinse and repeat until you get the best performance and then Mark that position on the rotor

Getting it built will not be that hard I do have the tools for that unfortunately finding the best position for the rotor on the shaft so that it fires at the peak of the AC waveform will be difficult for me to do without an oscilloscope so I can actually see where it is firing

Coronafix

Thu Jun 07 2018, 10:43PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Try sharpening the 4 electrodes to a point. This should help with the quenching, not sure how much though. Magnetic field will also help quenching, or a fan to blow the ionized air out of the way.

MRMILSTAR

Sat Jun 09 2018, 03:27PM

Registered Member #62119 Joined: Sun Feb 04 2018, 04:59AM
Location: Cedar Rapids, Iowa
Posts: 136

Building a RSG capable of reliably handling high powers with good quenching is not an easy task. Mine uses a 0.5" thick 10" diameter G10 (FR4) disk with 4 flying tungsten electrodes. There are 2 stationary tungsten electrodes. The motor is a 1/2 HP induction motor modified for synchronous operation by milling 2 flat spots on the armature. The rotation speed is 3600 RPM. This was a difficult thing to build. The hardest part is achieving a precision balance of the rotor with the electrodes other wise it will shake itself apart. My SGTC is powered by a pole pig presently limited to 4.8 KVA. The RSG is very reliably handling 4.8 KVA of power. The rotating disk with electrodes generates a considerable air flow for cooling. I have yet to see any wear at all on the 0.125" tungsten flying electrodes. I only get minor wear on the stationary electrodes. I have attached some pictures of my RSG.

1528557916 62119 FT180967 Rsg Assembly Mounted In Tesal Coil Base

1528557916 62119 FT180967 Rsg Front View 1

1528557916 62119 FT180967 Rsg Front View 2

1528557916 62119 FT180967 Rsg Stationary Electrode Holder Cooling Fins

1528557916 62119 FT180967 Rsg Stationary Electrode Holder Detail 1

1528557916 62119 FT180967 Rsg Stationary Electrode Holder Detail 2

1528557916 62119 FT180967 Rsg Top View 1

1528557916 62119 FT180967 Rsg Top View 2

1528557916 62119 FT180967 Rsg Top View 3

Hazmatt_(The Underdog)

Sat Jun 09 2018, 05:06PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Yes, rotaries are no walk through the park, especially ones hurling heavy rotors, but I managed to build mine with little more than a drill press, a Dremel tool, and some machinist's tricks to get around needing highly precise machining.

The rotor is 2 1/8" thick FR4 sheets bolted together for more rigidity. The little sewing machine motor is variable up to 5000 rpm, but has trouble
swinging the rotor because of its mass, a smaller 3-4" rotor with custom hub works fine though (this one was made with real machining though).
1141963127 135 FT3662 Mdkrotaryvariant

This is the smaller one that I made for a customer and I had a milling machine so I could do machining at this point.

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