JACOBEIS wrote
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[b]How do they open with that spring[/b].
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Normally the motor sheaves open and close in response to the idler sheaves opening and closing, which is under the control of the speed control. As you decrease speed you close the control sheaves, increasing belt tension. The motor sheaves have the spring so they open in response to the increased tension, compressing the spring. Increasing speed, everything is opposite and the motor sheaves close in response to reduced belt tension allowing the spring to expand. The floating sheave on the motor simply moves to balance spring tension to belt tension.
From the description, your next step is to determine if something, like a bearing, is creating mechanical resistance that the motor cannot overcome. That can be anywhere from excessive drag to a seized bearing. IIWM I'd put a sanding disc on and just spin the headstock by hand. It does not take a lot of mechanical resistance to be a problem.
Note: We tend here to presume 'traditional' circuit breakers which provide over-current protection only. If yours are 'new fangled' that's something else to look into. Generally, Arc Fault and/or Ground Fault or any combination breakers may trip for reasons other than excessive current for excessive time.
- David
