There is no such thing as a dumb question. Brushes are seated in with fine sandpaper (NEVER Emory paper!)between the brush and communtator. The paper is pulled tight with the grit facing the brush to conform to the contour of the communtator and pulled through so the grit grinds the brush to the contour. Use compressed air to blow all the carbon dust and grit out. After that, it takes a little time for the brushes to fully seat and reach minimum noise.

B. Gentry

On 7/6/25 4:12 AM, Hubert Miller wrote:

If i may ask a dumb question, how do you accurately concave the commutator facing side of the brush ?

Purely a curiosity question only - i have no intention of using a dynamotor ever.

I recall using an ARR-15 some decades back, and i definitely recall the "dynamotor noise floor". Which made a noisy background when listening to a game show from BBC Kuching Malaysia in the 5 MHz band. ( Few ppl will remember that. )

-Hue Miller

Sent from my Galaxy
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