Re: Re: [PSUBS-MAILIST] external Motors for depths of 1000ft

[rjune@fuse.net]

Rob, you are basically correct.

1. If the correct oil is used (low viscosity and dielectric)
    there is no appreciable reduction in rpm.  By the way
    the oil that I use is Biodegradable.

2. Is Dave at DC Marine still around ??? 
    I’ve  tried to locate him, with no luck.

3. The Aluminum prop that I sell, should only 
    be used on the 80# and 107# motors as it will
    burn up the smaller motors.


> 
> From: "Captain Nemo" <vulcania@hawaii.rr.com>
> Date: 2002/06/19 Wed PM 04:17:07 EDT
> To: <personal_submersibles@psubs.org>
> Subject: Re: [PSUBS-MAILIST] external Motors for depths of 1000ft
> 
> Rob,
> 
> I don't have an exact number, but drag-induced RPM reduction on the armature
> isn't much at all due to it's shape.  A guy to ask might be Dave at DC
> Marine, or Casey at trollingmotorparts.com.
> 
> BTW: Casey is presently selling the complete MK Riptide 101# 36VDC unit for
> about $550.  This is a saltwater motor, and for this price you get the
> factory potentiometer, prop, the whole tamale.
> 
> MK's are factory rated to one additional atmosphere: 33FSW.  People have
> been using them to 100 feet with a 95% success rate, but the company won't
> cosign that.  One tech I know of is modifying the motors to work
> uncompensated at 300 feet by polishing the shaft and matching it to a better
> seal; I've got no info on the success / failure rate of those modifications,
> but he says people have been using them for a while and didn't mention any
> complaints.  One thing, though; if you open the case to modify the innards,
> you need to reassemble it correctly: time the brushes and torque the covers
> down properly.  Otherwise, she no runna so well.....
> 
> Regarding props: one problem MK had years back with the 4HP (just a name,
> not a horsepower rating) occurred when they went from the plastic weedwacker
> to the an aluminum prop.  Large numbers of burned out motors started coming
> back the shop; MK finally returned to the original prop.  Something to keep
> in mind when thinking about modifying the prop arrangement from what the
> design engineers originally decided on.  Not saying it can't be done, but
> possible overheating is something to be aware of.
> 
> The pressure compensation of any of these motors should make them
> serviceable at homebuilt-sensible depths.  If in doubt about oil
> compensation, you could always use air.
> 
> Pat
> 
> 
> From: "Rob Innes" <innespace@jett.net>
> To: <personal_submersibles@psubs.org>
> Sent: Wednesday, June 19, 2002 10:03 AM
> Subject: Re: [PSUBS-MAILIST] external Motors for depths of 1000ft
> 
> 
> > Does anyone know how much resistance is caused on the trolling motors by
> > filling them with the oil? Approximately how much thrust could expect  to
> be
> > lost on a Motorguide 107lb thrust unit? Has anyone fitted one or more of
> these
> > motors to a sub or DPV?  I'd be very interested in the results
> >
> > Rob Innes
> >
> >
> >
> 
> 
> 

Roger June
REJ and Company
rjune@fuse.net
513-300-1189