My biggest concern with nylon or 3D printing is the temperature resistance. The originals are a hard plastic, almost like bakelite. Would it be resiliant enough to put up with the running tempratures in the motor?

I found a pic on eBay of the brushes close up. They're an inch long, with a large hook on the brush end (for the brush to ride in) and a small hook on the opposite end to grab the motor frame. It's all held in place with a small spring between the two brackets which also squeezes the brushes against the commutator. You can see the small spring hook on the right side of the picture. Below that the bracket is squeezed against the motor frame by the spring and acts as the fulcrum. They are likely identical to the blower in a 122, but I can't compare directly.
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88 740ti 73 1800ES 67 122S