Re: [PSUBS-MAILIST] Hydraulic Drive Unit

["Gary R. Boucher" <engineer@sport.rr.com>]

    No, not accurate ones off the top of my head. 
The pump and motor combo weighs about 50 pounds.  I would say that
the control system with valves etc weighs about 40 pounds.  The
lines another 20 pounds with the motor about 20 pounds.  You will
also have to cool the fluid.  Hydraulic systems typically cool the
fluid by requiring a minimum number of gallons.  This requires a
minimum number of square inches for the reservoir's outer surface. 
This area will allow heat to leave the system.  Thus, if you follow
the guidelines, you will have a large reservoir full of oil.  If
inside the hull it will keep you toasty, too toasty!  You will need
to have an outside reservoir to allow the water to cool the fluid. 
I run just two or three quarts in total of fluid and it stays cool. 
However, running a small amount of fluid (This also keeps you from
looking like the Exxon Valdez if you have a rupture) will generate
bubbles from the return flow into the outside reservoir.  The
bubbles will cause something similar to cavitation in the pump because
they are trapped in the fluid after returning to the reservoir. 
This can be minimized by using a cylindrical reservoir and having the
returning fluid injected into the reservoir almost tangential to the
outside wall.  I used bent copper tubing for this.
    Trolling motors looking better?

G. Boucher

At 12:30 AM 11/19/2002, you wrote:
> Thank you
> Mr Boucher for your quick reply.  By the way, do you have any
> guestimates on the wieight of your drive
> system?