http://www.teslauniverse.com/photos/wysock-13m#id=album-17&num=content-622The only difference between this and the ones us amateurs make is the surface area of the point of contact, there is nothing stopping someone from making an arbor capable of holding several tungsten rods in parallel and electrically binding them together so dwell time is tiny but conducting area is huge. It might be difficult to machine but it would perform superbly, and still be lighter than a disk. I'm going to say it, carefully built propellers are better in every way, I think there is room for improvement in the design of the "prop," making something special instead of just a rod in some PE, to correct issues like electrode spacing and as argued current handling capability, but I doubt I'll ever build a disk type. Just putting this out there.
Scott Bogard.
I'm not sure it's fair or useful to suggest that a propeller gap isn't up to the task of a 10KW or whatever, coil. I don't see how a disk holding short tungsten segments is inherently more capable than a propeller geometry. I think what matters is only the diameter of the tungsten rods. If the same diameter tungsten were used in a propeller gap, wouldn't it be equally capable as a disk-based geometry? I was going to suggest that maybe propeller gaps are limited because long welding rods don't normally come over 1/4" diameter, but just noticed that McMaster-Carr has lengths up to 12" and diameters up to 2". Wowza!
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