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Re: [PSUBS-MAILIST] motor seals
I see what you're saying and I have not thought of that. In theory if
the prop didn't follow you because of the initial acceleration of the
shaft, it would sit there and just vibrate back and forth. It would be
like a surfer not riding the wave with the same velocity but allowing the
waves to pass under him not getting anywhere. I think it depends on the
strength of the magnets and the moment of inertia of the prop and its drive
shaft, also the resistance of the prop in the water. But, if I went to the
trouble to have a system retrofitted such as we are discussing, I would
want to have PWM to control it and that could be limited at start up to
slower accelerations.
At 09:37 AM 8/16/00 , you wrote:
>One thing it seems no one is mentioning is the
>limitation on maximum acceleration imposed by the
>magnetic coupling. No problem with a mechanical
>linkage, but with the field effect device, your
>starting RPM will be limited by inertia of the system
>downstream of the linkage (the prop) plus water
>resistance. If you accelerated the driving motor too
>quickly, it would be possible to approach a pole
>reversal (> 1/4 turn, for a two pole motor) before the
>prop had time to catch up. How significant an effect
>is this, and apart from trial and error, is there a way
>to exert some control over this, without PWM?
>
>-Sean
>
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