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Saturday, July 23, 2011

Money pains

Just checked Big Blue Saw for water jet cutting costs. My rotors will cost almost $17 a piece for regular cutting and over $20/piece for low-taper cutting...and that's without the bolt holes, which add another $6/part (and cutting 24 out of 1/8" makes the prices worse). I'd have to do the bolt holes on the mill anyways, because of the waterjet's taper, so I took those out. At first, I thought this was insanely expensive. Then I realized that if I did my own waterjetting, it would probably take 4 minutes/part, and at $3/minutes, that's $12/part in just cutting costs. Add $5/part in steel, and that's the same price as Big Blue Saw. Wow, waterjetting is expensive.

In contrast, I can turn four 3/4" long rotors out of steel tube for $65 and a few hours. But I won't have the nice magnet notches.

Waterjetting Pros: Very handy little magnet notches that conform to the magnet geometry. No effort on my part.
Waterjetting Cons: $200+ dollars. Over triple the cost of turning rotors. I have to put 12 parts in a mill instead of 4.

Turning Pros: Cheap: $65. I only have to put 4 parts in a mill afterwards (instead of 12).
Turning Cons: I have to spend probably 3-4 hours turning (even if I take time off work to do this, it's still cheaper than waterjetting). No little magnet notches, so add an hour to magnet gluing time.

I'm fairly certain I can glue the magnets in the right place without the notches (I've done it before). And I REALLY don't want to spend $200 on the rotors, when I'm already spending $220 on the stators. I'll sleep on it.

But speaking of stators. The stators I'm getting are from Scorpion Power Systems . They started out by producing lower cost brushless outrunner motors for the R/C aircraft market, but are now expanding to larger motors and wind generators. They're currently developing the "65" (65mm) and "85" series motors. You can purchase the 65mm stators from (they are the ones I used in ELB). Apparently they're developing a 70mm and 130mm line, too, or at least the R&D guy I talked to suggested that by letting me purchase a couple stators from them. So far, they are the only source I know of for stators in the famed "70mm-130mm" gap (where copier motors and turnigy motor stators are on one end, and alternators and ceiling fans are on the other end).

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