Aluminum vs steel electrodes
Benjamin, Mon Nov 02 2015, 10:04PMI 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?
Re: Aluminum vs steel electrodes
Hazmatt_(The Underdog), Tue Nov 03 2015, 04:23AM
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.
Hazmatt_(The Underdog), Tue Nov 03 2015, 04:23AM
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.
Re: Aluminum vs steel electrodes
Benjamin, Tue Nov 03 2015, 04:38PM
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.
Benjamin, Tue Nov 03 2015, 04:38PM
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.Re: Aluminum vs steel electrodes
hen918, Tue Nov 03 2015, 05:49PM
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.
hen918, Tue Nov 03 2015, 05:49PM
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.
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.
Re: Aluminum vs steel electrodes
Benjamin, Tue Nov 03 2015, 06:32PM
Ok I'll go for steel then. Do you think half inch electrodes will handle 8 kVA? I don't plan to run it for more than 30 seconds at a time.
Benjamin, Tue Nov 03 2015, 06:32PM
Ok I'll go for steel then. Do you think half inch electrodes will handle 8 kVA? I don't plan to run it for more than 30 seconds at a time.
Re: Aluminum vs steel electrodes
loneoceans, Wed Nov 04 2015, 12:54AM
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.
loneoceans, Wed Nov 04 2015, 12:54AM
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.
Re: Aluminum vs steel electrodes
Benjamin, Wed Nov 04 2015, 05:30AM
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
Benjamin, Wed Nov 04 2015, 05:30AM
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
Re: Aluminum vs steel electrodes
hen918, Wed Nov 04 2015, 05:45PM
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!)
hen918, Wed Nov 04 2015, 05:45PM
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
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!)
Re: Aluminum vs steel electrodes
dexter, Wed Nov 04 2015, 07:00PM
what about making the disk from a non conductive material?
dexter, Wed Nov 04 2015, 07:00PM
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
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?
Re: Aluminum vs steel electrodes
Benjamin, Wed Nov 04 2015, 08:28PM
Because I don't have any g-10 or phenolic to make a disc with so that's why I was going with a propeller gap design.
Benjamin, Wed Nov 04 2015, 08:28PM
Because I don't have any g-10 or phenolic to make a disc with so that's why I was going with a propeller gap design.
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