Hydraulic Motor In Water

[Mark Emaus]

Ok, picture this....I have built a proto-type case that in housing a hyd. geared motor that is hexagon in shape. If you look at the hexagon that is aprox. 9 inches in Dia. form the back, a shaft protrudes out the back somewhere in the middle, (of the hexagon back plate) and attaches to a bearing unit and shaft that holds the prop. Now on top of the hexagon is another shaft that has 2 purposes. The first is to attach to the boat and pitch and steer the hexagon unit. 2 is to take the hyd lines up to the hyd. system. Now my question is this...Can the hyd. motor be ok if water gets down the shaft/pipe and settles in the hexagon case that houses the hyd. line/ motor? If not, what would you recommend as a way to have the hyd. lines come out of the pipe and still seal the top of the pipe so no water can get into the pipe?

thanks

Mark

[Mako2]

Is there any reason you can not allow the unit to be open to the water? If the hydraulic oil can't get out the water can't get in. I would use biodegradable hydraulic oil in the event of any failure.

Mark

[Mark Emaus]

no, there isn't any reason. That is a great point about the if the oil can't get out...water can't get in. We are using bio-hydro oil for the system. My concern is the motor sitting in salt water for long periods of time. The motor is Aluminum though...

[goodwilltoall]

Maybe the motor being submerged would also help with cooling.

[TeddyDiver]

Originally Posted by Mark Emaus

My concern is the motor sitting in salt water for long periods of time. The motor is Aluminum though...

Protective sinks helps, and there's surely also steel parts thou casing is Al..

[mydauphin]

Growth on seals is biggest issue, sooner or later they will die. Better use a longer shaft and keep motor out of salt water.

[Mako2]

I agree with the cooling aspect of the set up, ours will be used in fresh water so we are building the lower unit in an open tube on the end of the shaft. Almost like a bow thruster would be set up with the motor submerged. Also in the fresh water we don't seem to have the need for zincs but we would used them in salt water.

[wardd]

what is the source of hydraulic pressure?

[Mako2]

On our we are planning to use (2) 16hp honda engine driven power pumps. Each unit is rated at 10 gpm at 2000psi. This will only be for the test trials as I already had them. If the system works as planned we will be looking for a single diesel driven power pack rated at around 60 to 80 hp and able to deliver 40 gpm at 2500psi which would supply 20 gpm to each submerged hydraulic motor. This would be the sweet spot for the charlene motors.

[wardd]

then a cooler downstream just before the return would be a good idea there wont be any pressure there

and 2 pumps may not be all that efficient , is it an open center system?

[WestVanHan]

I trust the motor/unit has a thrust bearing???

Also kind of curious what you plan on using it for...for an occasional move or with much use.

[Mako2]

As far as the two pumps go it will only be for testing as we already owned them, at 10 gpm they are a little undersized for task. Each pump will power its own motor one on each of the two outboard legs.

If the testing goes as planned we will purchase a single larger hydraulic unit which would supply a total of 40 gpm with 20 gpm for each motor which is in line with the design specs for the Charlene 104-1023 hydraulic motors.

We chose the Charlene 2000 series motor because they are designed for the axial loads that should be encountered.

In our case it will be for movement of a barge around a dock.

[wardd]

what kind of controls do you plan to use ie. valves

I've built my own farm implements some of which had hydraulic motors run from the tractor

[Bglad]

Originally Posted by Mark Emaus

no, there isn't any reason. That is a great point about the if the oil can't get out...water can't get in. We are using bio-hydro oil for the system. My concern is the motor sitting in salt water for long periods of time. The motor is Aluminum though...

Only if it has two seals already. The one that holds the oil in won't necessarily keep the water out

[wardd]

and crud build uo on the shaft may abraid the seal