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Registered Member #54655
Joined: Thu Mar 19 2015, 05:56PM
Location: BC, Canada
Posts: 82
I am about to build a large arsg for a 5-10 kVA tesla coil system. Due to the design, my only options for electrode material are aluminum and steel. The electrodes will be 1/2 inch and it will operate at around 450 bps. It is a 16 inch diameter propeller gap design with a metal shaft on bearings. Which material would be better?
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Tungsten.
Steel will melt. My old rotary used 1/4 28 set screws for the electrodes and they are melted from 1kva. 5kva will cause a lot of erosion once the electrode heats up and starts to flow. They basically stand little chance of staying cool enough to operate for any length of time.
Aluminum will probably burn up pretty fast. It should be quite brilliant as the metal burns.
If you are going for the propeller type gap, you should look into using the Tungsten rods, they are available from welding suppliers, but they are not going to be 16" unfortunately.
Registered Member #54655
Joined: Thu Mar 19 2015, 05:56PM
Location: BC, Canada
Posts: 82
Hi hazmatt, I was planning on using a 1 inch steel shaft on bearings and belt driven and drill a 1/2 inch hole through it to weld in a 1/2 inch steel rod. It needs to be 16 inches to get the dwell time down and 1/2 inch to handle the power. I will use 10 stationary electrodes to get the break rate up as it will be spinning at about 2700 rpm. Apparently this coil uses 3/4 inch steel electrodes! I have used tungsten electrodes before but it's king of hard to in this case as it would ruin the simplicity of this gap. I just need to know weather steel or aluminum would be worse and if either would work at all.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
Benjamin wrote ...
Hi hazmatt, I was planning on using a 1 inch steel shaft on bearings and belt driven and drill a 1/2 inch hole through it to weld in a 1/2 inch steel rod. It needs to be 16 inches to get the dwell time down and 1/2 inch to handle the power. I will use 10 stationary electrodes to get the break rate up as it will be spinning at about 2700 rpm. Apparently this coil uses 3/4 inch steel electrodes! I have used tungsten electrodes before but it's king of hard to in this case as it would ruin the simplicity of this gap. I just need to know weather steel or aluminum would be worse and if either would work at all.
Definitely go for steel over aluminium. Aluminium has a lower melting point as well as being flammable. Steel will be a little vaporised but erosion should be slower overall.
If possible at all, go for brass. If you're going to be building a 10kW coil, I'd spare a bit more expense at the beginning and avoid using steel (aluminum will get destroyed extremely fast). Brass rod is inexpensive and easy to find as well and it'll do better than steel in every aspect.
Registered Member #54655
Joined: Thu Mar 19 2015, 05:56PM
Location: BC, Canada
Posts: 82
Ok thanks, I have another problem though, the v-belt that I was going to use turns out to be highly conductive. I tested it with a flyback transformer. how do I get around this? It needs to isolate the motor from the gap. Thanks for any help.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
Benjamin wrote ...
Ok thanks, I have another problem though, the v-belt that I was going to use turns out to be highly conductive. I tested it with a flyback transformer. how do I get around this? It needs to isolate the motor from the gap. Thanks for any help.
Benjamin
Belts are actually impregnated with carbon powder to make them conductive as an anti static precaution (nobody wants a Van de Graaff generator in a flour mill, for example)
You will have to find one specially designed to be non-conductive (or one not specially designed to conductive!)
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
Benjamin wrote ...
Ok thanks, I have another problem though, the v-belt that I was going to use turns out to be highly conductive. I tested it with a flyback transformer. how do I get around this? It needs to isolate the motor from the gap. Thanks for any help.
Benjamin
what about making the disk from a non conductive material?
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Aluminum vs steel electrodes
