Re: Trolling Motors

[Albert Long <subview@mediaone.net>]

Hi,
The trolling motor, for me, is going to be nothing but a bow mounted directional
thruster !
My main propulsion is a westinghouse m18 41/2 hp motor mounted inside my pressure
hull, using compression seals for the shaft.
Thanks for your info !!!

Paolo Velcich wrote:

> Just to add some more to the general knowledge, but nothing really new.
> I know Minnkota and I didn't know Evinrude (as trolling motors I mean). But I'm
> dealing with MotorGuide which seems to have some more robust products than
> Minnkota.
> I also have all their technical specifications and drawings, about the shaft seal
> they use a couple of cupped seals on the shaft. Two should be better than one, but
> I agree that seal isn't the best for deep use.
>
> I also have a Scubapro DPV which mounts Minnkota (Scubapro is part of the same JWA
> group as Minnkota is) and there's another couple of small manufacturers which are
> using the same motors.
> I successfully dived the Scubapro Seashuttle to depths of 150/160 feet and it
> never failed (it's rated to 180 feet).
>
> There's another solution which should work much better, it's magneto-ceramic
> coupled seals and it's widely used on ROVs thrusters as well on some DPVs. I know
> this device as being really expensive (when purchased from the ROV market) but
> it's also widely used on hi-pressure pumps running at very high speed and pressure
> and it's a cheap spare part, even when using stainless steel spring and flange.
> This is just a seal - however - and needs an appropriate housing to work, but if
> you're building a life shell it should not be a problem to deal with a motor
> housing.
>
> I'm personally using MotorGuide for testing new DPVs design (the motor unit is
> cheap and almost ready to go) but I'm designing my own propulsion unit.
>
> Uh... and what about propellers? I don't really think the ones supplied on
> trolling motors being very efficient for underwater propulsion... in fact, the
> Scubapro is a pain (also due to its own design and mounting). I'm pretty sure the
> pitch of those (trolling) propellers isn't that good, in fact it's designed for
> high rotational speed. A variable pitch would work the best.
>
> Dive deep and safely.
>
> Paolo
>
> --
> Paolo Velcich
> industrial designer
> **********************
> KORUM DESIGN
> Viale Tricesimo 5/6
> 33100 - UDINE - ITALY
> Tel. (+39)0432-603654
> Fax (+39)0432-601213
> e-mail: pavel@mail.nauta.it
> http://www.x-plora.com
> **********************
>
> Subscuba@aol.com wrote:
>
> > Albert,
> >
> > Is it possible that the motor seals did have some sort of pressure
> > compensation across the motor shaft seal such that the actual differential
> > pressure across the motor shaft seal was less than 700 feet of Sea Water?
> >
> > Ken Martindale
> >
> > PS On this site it is always possible to misinterpret people's comments in the
> > wrong way. I try to assume the best or ignore what irritates me. I do find it
> > interesting about the big discrepancy between what you have implied about the
> > motor shaft seals and what I was told by Minnkota. I have also heard rumors
> > about the seals being good past the vendors statements, but I have to be
> > conservative for safety concerns and that I don't loose 3.5 years of work.
> > Bear in mind my Sub is a wet Sub that I can bail out and not loose anything
> > but the work and money. A 1 atmosphere Sub is a different story. If the motor
> > seals leak do you run the risk of flooding and sinking? Can you bail out?
> >
> > Have fun.