T-Pain Is On A Boat: [Electric Boats] Re: Brushed Trolling Motors not a good idea for primary propulsion!

Saturday, August 1, 2009

[Electric Boats] Re: Brushed Trolling Motors not a good idea for primary propulsion!

I agree With Arby!!!

The brushed trolling motors are not designed for primary propulsion.

I had a 105# thrust motor and used the Aluminum 3 bladed prop and it made awesome speed and power (48 amp draw @ 36 volts)....for 50 minutes then burned up the armature and commutator! I have been told to NOT run at max power for extended periods. I am rebuilding and will use a "weaker", more flexible plastic prop and shoot for 40 amps. Even still, the harder you work them the shorter they live.

I run a bushless Parsun 4 hp electric outboard and can run WOT continuously. I never worry about brushes again!

Joe M

--- In electricboats@yahoogroups.com, Arby Bernt <arbybernt@...> wrote:
>
> 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@...> wrote:
>
> Ã Answer: 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 doesnâ€™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 â€" 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 Iâ€™m beating
> it to death, is I donâ€™t have access to a 24 or 36v motor, and I donâ€™t want
> to spend the money to find out that John is rightâ€¦.
>
> Anyone else care to comment?
>
> Thanks for the tip on streamdancer
>
> Kevin
>
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