[MHml] Outdrives

[Allied]

>commercial 55hp outboards and replacing their busted gasoline
> power head with a hydraulic motor.  I have not figured out the mounting 
> yet,

I sort of did this, using only the bottom (right angle gearbox) of two very 
old 40 HP Johnson outboard drives. I fabricated the parts to go between this 
and the hydraulic motors, from aluminium tubes and plates, I profiled on our 
machining centre. I used the Johnson drive shafts and joined this to the 
hydraulic motor with a splined coupling which I wire cut in two half's and 
welded together. I used two SS tubes, with plastic bushes, in my fabricated 
parts, to act as a slide and the units are on the inside, rear of each hull. 
Currently I use a small pulley system I made to lift them, but I am about to 
modify this to a threaded rod system, I can use a battery powered drill to 
drive up and down. I thought of using hydraulic rams, but simplicity is 
best.

>It seems that a part of the trick in achieving a quiet and efficient
>hydraulic system is to make sure fluid velocities are not too high as would
>makes for much heat loss and noise.  High pressure also has a noise &
>reliability cost.

There is only one type of hydraulic motor and pump that is suitable and that 
is the radial piston sort and these do work on high pressure. These are far 
lighter and much more efficient than any other hydraulic system. I use a 
twin swash plate pump, off a Bob Cat digger, that has a lever on each side, 
that controls the flow rate from full one direction, to stop and full 
reverse direction. I have these connected to twin Morse control levers, that 
I normally operate with my feet, as I can see much better when standing up 
high. I have two fixed displacement radial piston motors for the legs. The 
Old Johnson drive has a 1.6 to 1 gear reduction, but you can design any 
maximum propeller speed into the hydraulics you want and then have full 
variable from there.

Colin