T-Pain Is On A Boat: [Electric Boats] Re: Relays to replace a controller

Thursday, July 9, 2009

[Electric Boats] Re: Relays to replace a controller

--- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@...> wrote:
>
> > Comment: If the drive train is so weak that turning on the motor, with its momentary high torque, would break something, then the drive train is not nearly strong enough.
>
>
> OK well at least hold onto your beer :)
>
> I'm curious though - is that why you put a jackshaft onto your system? (to allow for belt slip) Or was it just that the motor RPM was so high to start with that there was no practical way to reduce the RPM vs an overly large pulley ratio?
>
I needed an overall ratio of about 4.5:1, but only had room enough for a 7 inch pulley on the main prop shaft. Withour a jackshaft, that would translate to a pulley on the motor less than 2 inches diameter, which would not do the job according to the belt manufacturer's data. Putting in a jack shaft, I could go about 2:1 on each reduction, which is reasonable.

This setup also allows the use of adjustable pitch pulleys on the motor to jackshaft belt, and thus allows for ratio adjustment to get a selected load on the motor. Using an ampmeter to get 28 amps (very nearly rated load) I get just about full motor output by trial and adjustment.