Re: Trolling Motors

[Paolo Velcich <pavel@mail.nauta.it>]

Thank you Ken,
I didn't make any test on different thrust/propeller combination, I well
understand your point of view and it's certainly right. I wasn't actually saying
to change the propeller on a trolling motor but - better - considering about a
totally "new" design including the both components of a thruster: the motor and
the propeller.
I'm still thinking the trolling motors are a very good and cheap solution for the
early stage of experimental design, but if anyone is going in some more serious
development, something more reliable than an "off-the-shelf" trolling motor should
be considered.

Yes, the seal you're speaking about is on the group I was referring to.

Have a nice day

Paolo

Subscuba@aol.com ha scritto:

> Paolo,
>
> For what it's worth. The trolling motors are basically shunt wound motors made
> for constant speed, loading the motors down with another propellor  may
> excessively load the motor and degrade it's life. The high RPM you mentioned
> may be necessary for motor life and maximum motor use. I'm under the
> impression that in the marketing race of thrust versus motor size and cost
> that the trolling motor propellors are matched for the maximum thrust
> consistent with motor loading in a static environment. This probably changes
> when you are at speed but maybe not much. Have you performed any tests on the
> problem of thrust versus propellor and motor loading? Were you able to get any
> data from Motorguide on this subject? I think they make a propellor called a
> "Ninji" which is a three bladed propellor.
>
> I like what you said about the two seals on the Motorguide, that should be
> better than the Minnkota. I have considered placing two cup seals on my
> Minnkota. It looks like there is room but I haven't tried it. The Minnkota
> appears to be a more powerful motor from what I have found out.
>
> I once worked on D. Rebikoff's Pegasus and he used a ceramic seal which he
> said was in common use in the water pumps used on wells. The kind you find in
> Wal-Mart at about 1 HP. He showed me one and it looked like two rotating
> ceramic washers spring loaded and static O-Ring sealed. he said these seals
> lasted a very long time with few problems and were good for high pressures, at
> least several hundred to a 1000 feet. He is still around and can be contacted
> if anyone is interested.
>
> Have fun,
>
> Ken Martindale