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Smoking RS-550 motors
We smoked an RS-550 motor last night, and were not near the stall point, as far as I can tell.
This is somewhat puzzling. We used the RS550s a couple years ago with no issues, so I thought I would throw this out here to get some opinions. Here's what we have: Banebots RS-550 with a 25:1 gearbox, driving a 3" diameter timing belt pulley which raises our elevator. The design load is supposed to be around 30 lb, but we have some binding, as I will show below. Banebot RS-550 spec 19300 RPM Free speed RPM 70.55 in-oz Stall torque 85A Stall current When connected to 25:1 gearbox 772 RPM Free speed RPM 1763 in-oz Stall torque 85A Stall current We were running the elevator up at roughly 8 feet in 2 seconds, using a 3" diameter pulley with a 1:1 timing belt between the pulley shaft at gearbox Belt speed = 4 ft/sec Pulley/gearbox RPM = 306 RPM (4 ft/sec/(pi * 3" diameter)*60 sec/min * 12 in/ft) This is 40% of the free speed RPM. From the motor curves: The motor current should be roughly 51A (60% of stall current) The motor torque should be roughly 1057 in-oz (60% of stall torque) With a 3" diameter pulley, and ignoring gearbox efficiencies, this should create a lifting force of 66 lb (1057 in-oz/1.5" radius/16 oz/lb). (Clearly we have some binding to get rid of.) Even so, this is just over the normal, max power operating point of the motor. Any ideas why this motor smoked? -Jeff |
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