Re: [PSUBS-MAILIST] Re: looking for trolling/thruster motors

["Captain Nemo" <vulcania@interpac.net>]

PS:  I've talked props with the techs at MK, and guys with shops who tweak
E-motors for special purposes like ROV's and subs.  General line of thinking
is: it would be nice to have a more "submarine orientated" prop for, say,
your MK trolling motor (which is matched to a prop optimized for pushing a
surface boat around), but it causes problems.

MK had an aluminum prop for the 4HP (just a model designation, not a power
rating) about 15 years ago, but it kept burning up lower ends, so they
canned it and went back to the plastic weed whacker.  The trouble is the RPM
ranges and loads that the lower end is designed for don't correspond well
with larger heavier props.

 If you could find a big, coarse prop intended for slower RPM that would fit
on your MK shaft, when you kick the potentiometer up to Warp 9, the load is
going to fry the motor after not much use.  So then guys start thinking
about gear drives; but if you're going to do that, why start with an MK?

Really, the thing I like about trolling motors is that they are something
you can pretty much just bolt on and run (compensation notwithstanding).
And they aint bad, by and large.  But if I'm not satisfied with performance,
I'm not going to mess around trying to adapt a gear reduction to an MK, I'm
going to piece together a much more powerful motor / reduction / prop/
controller setup, and run the shaft outside through a watertight coupler.

Dave at DC Marine is really sharp on this particular aspect of things.
Knows what components work well for guys in our LEAGUES.  (sorry, one track
mind)...   If you can get him on his cel phone, he's a good brain to pick.
I bet Jack in Texas would be a good, too.  I've found that a lot of E-motor
techs are really interested in submarines; and when you tell them what
you're building, they start talking and the next thing you know is you've
just put some telephone company exec into a new income tax bracket.  Worth
it, though.

Pat


----- Original Message -----
From: "Michael B. Holt" <mholt@richmond.edu>
To: <personal_submersibles@psubs.org>
Sent: Thursday, August 02, 2001 4:03 AM
Subject: [PSUBS-MAILIST] Re: looking for trolling/thruster motors


> Alec Smyth wrote:
> >
> > The stock speed controls should be fine, they're pulse width modulation
> > (hence efficient). If you buy another model do check that the controler
is
> > PWM, as the resistor controllers on cheaper motors waste an awful lot of
> > energy.
>
> As long as we're talking about this sort of thing, would not a larger
> and low-speed screw work better submerged?
>
>
>
> Mike Holt
>