I've been playing around with Hurst 24V, 300 rpm (250 in Europe) motors for a turntable I'm designing. Like others here I'm concerned with the 240 Hz. (200 in Europe) vibration characteristic of this type of motor. I discovered that merely touching the motor to my cast iron drill press vice diminished the vibration significantly, I gently clamped the motor into the vice. The vibration became virtually inaudible and was barely perceptible to touch. Now I'm thinkin: a cast iron motor mount and a cast iron flywheel attached to the pulley? Eh?
This is my initial test setup. The capacitor bank allowed me to trim for the lowest vibration. The best value was near 6 mf as opposed to the recommended 10. Incidentally, the best value also displayed the most symmetrical waveform. I used an old ceramic phono cartridge as a vibration sensor.
This is the resulting waveform. It is a surprisingly clean sine wave. It wasn't this clean everywhere on the motor top plate but the cleanest spot was also the highest amplitude.
This is the motor in the vise. I'm applying very little pressure, I got similar results with the vise horizontal, gripping the motor by the sides.
Waveform with the motor in the vise. A 20X reduction in amplitude!
This is my initial test setup. The capacitor bank allowed me to trim for the lowest vibration. The best value was near 6 mf as opposed to the recommended 10. Incidentally, the best value also displayed the most symmetrical waveform. I used an old ceramic phono cartridge as a vibration sensor.

This is the resulting waveform. It is a surprisingly clean sine wave. It wasn't this clean everywhere on the motor top plate but the cleanest spot was also the highest amplitude.

This is the motor in the vise. I'm applying very little pressure, I got similar results with the vise horizontal, gripping the motor by the sides.

Waveform with the motor in the vise. A 20X reduction in amplitude!
