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Re: Quarter shrinker electrodes
I am considering making my quarter shrinker firing electodes from 2" diameter brass stock. The firing assembly will operate much like the one that you use with the electrodes coming close but not touching. My question concerns brass erosion. In your experience, how quickly does the brass erode? I also considered using 10 mm diameter tungsten rods.
The most damaging fragments come from a radial cone of ejected fragments from the middle portion of the work coil (where the coil-coin repulsion forces are strongest). The total overall cone is perhaps 30-40 degrees wide. If your electrodes are not directly interception fragments within this cone, there's fairly little very little wear from flying fragments. I use copper bus bars, with bolts and flat washers made from silicon bronze. Pinching the coil wires between the washers reduces bus bar erosion from sparking during high-current peaks.
I use 1/4" and some 1/2" thick abrasion-resistant steel (AR-400) plates to intercept high-energy fragments that are in the direct path from the ejection cone. These are replaceable as needed. The outer walls of the blast shield are 1/2" thick Lexan polycarbonate. I also use a big chunk of 1" thick AR-400 with a semicircular cutout to intercept the high-energy coil fragments that would otherwise hit the floor of the blast chamber. The chunk of steel absorbs the most of the momentum and kinetic energy from the downward-flying coil fragments.
Unfortunately, I'm on the road for the next few days, so I can't take any pictures of some of these assemblies.
Apparently I wasn't clear about my question. I was referring to the two electrodes which make up the firing switch. I see that you originally used a trigatron but then switched to a pure mechanical switch with two large brass electrodes. How is the erosion rate?
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