RE: Screw size and speed

["asmyth" <asmyth@hsomail.com>]

Sure...

Guy Schavone
Prime Air Products
1211 Mall Drive
Richmond, VA 23235
Phone: (804) 378-0686

Please note that I have not even received the fan rotor yet, they have a 6
week lead time. It is purely my speculation I can adapt the blades for use
with a trolling motor, and I will have to machine the prop hub myself. The
rotors come in a very large selection of sizes, think from 6-24 inches or
more. Guy can fax you a spec sheet, but about the only thing that's useful
on it are the photographs, because the performance specs all refer to
performance in air and at super-high rpms.  In case you need to refresh his
memory, these are "Woods" brand small aerofoil fans. The final disclaimer,
of course, is that these things are pricey. I've ordered a 9.5" rotor and it
was just over $200.

I'll be happy to post detail photos, specs, etc. eventually if this
experiment actually works out. Unfortunately the photos on Guy's fax aren't
good enough to scan and post online.

-Alec

> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Paolo Velcich
> Sent: Friday, July 16, 1999 4:30 PM
> To: personal_submersibles@psubs.org
> Subject: Re: Screw size and speed
>
>
> Alec...could it be possible to have an address for that
> industrial fan/blades...
> I'm already interested on testing trolling motors for DPVs and
> always interested
> in existing spares like props, blades and so far.
> Thank you in advance for your kind help
>
> Paolo Velcich
> industrial designer
>
> *******************************
> KORUM DESIGN
> Viale Tricesimo 5/6
> 33100 - UDINE - ITALY
> Tel. (+39)0348-2611707
> e-mail: pavel@mail.nauta.it
> http://www.nauta.com
> http://www.polarexpeditions.org
> *******************************
>
> asmyth wrote:
>
> > Trolling motors have no gear reduction, hence the high rpm. You
> can get lots
> > of different props for them but they all have something in
> common, which is
> > a very small pitch. That's because they are designed for trolling, and
> > although I'm no fisherman, I think its safe to say that...
> trolling = slow.
> > The people who buy a BIG trolling motor use it to move a rally
> big boat just
> > as slowly as they would want to move their small boat -- sort
> of like buying
> > a big diesel which only has 1st gear. So if your sub is a conventional
> > design (slow), the standard trolling motor prop should work fine, but if
> > you're looking at something streamlined and fast, bolting on an infinite
> > number of trolling motors would still not make it go any faster than:
> >
> > trolling motor rpm * pitch * slip factor  (which I'm told is 3-5 knots)
> >
> > I've found and ordered a variable pitch prop for industrial
> fans, with the
> > intention of hacking the blades and building a high-speed prop
> for trolling
> > motors. But as you can imagine, my prop diameter will have to be even
> > smaller than the original.
> >
> > -Alec
> >
> > > -----Original Message-----
> > > From: owner-personal_submersibles@psubs.org
> > > [mailto:owner-personal_submersibles@psubs.org]On Behalf Of Michael B
> > > Holt
> > > Sent: Friday, July 16, 1999 5:40 PM
> > > To: personal_submersibles@psubs.org
> > > Subject: Screw size and speed
> > >
> > >
> > > I've been looking at the pictures of the Hunley.   It had a
> 30-inch screw
> > > that turned at . . . a low speed, I would think.
> > >
> > > I see other small subs with a pair or more of smaller,
> higher-RPM screws.
> > >
> > > It's my understanding that it's fairly easy and inexpensive
> to buy what
> > > seems to be large trolling motors as power.
> > >
> > > But is there an operational reason small high-speed screws are used?
> > >
> > > Why can't a large low-speed screw do the same thing?
> > >
> > >
> > >
> > > Mike Holt
> > > --
> > >
> > > ___________________________________________________________________
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