T-Pain Is On A Boat: Re: [Electric Boats] Re: Trolling Motors

Thursday, July 30, 2009

Re: [Electric Boats] Re: Trolling Motors

These motors burn up when pushed hard.
They are designed for replacement every few years.
I designed a brushless motor for Minnkota years ago, but they had no interest
in eliminating their return business. Same for Motorguide. Both companies count on repeat sales to the same crowd. The motors cost about $10 to stamp and wind, including brushes and ferrite magnets. Add another $30 for all the other parts, then sell the bundle for $500 again and again. Perfect.

Arby

On Jul 31, 2009, at 3:29 AM, "Alycia & Kevin Miller-Lynch" <ak@twcny.rr.com> wrote:

àAnswer: All MinnKota and MotorGuide products (12v, 23v, 36v) are design to
spin at about 800 rpm for a max speed of around 3 mph . . . though they
claim 4 mph.

This doesn't make sense to me. If the 12, 24, and 36 all spin the same RPM,
and all use the same prop, they should all have the same thrust – so why
different voltages?

The only thing that would make sense is if the same prop on 12v makes 54lb
thrust and on 36v produces 108lb of thrust, it must be spinning a lot
faster. Thrust is somewhat like F=mv where F is force (thrust) m is mass
(amount of water moved by prop) and v is velocity (speed of the water moved
by the prop). The only way to increase F without increasing the mass (the
amount of water the prop moves, hence prop size or pitch) is to increase
velocity. Is anyone else following my logic? The only reason I'm beating
it to death, is I don't have access to a 24 or 36v motor, and I don't want
to spend the money to find out that John is right….

Anyone else care to comment?

Thanks for the tip on streamdancer

Kevin

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