Hydraulic Winches

[Salty Sailor333]

I am considering human powered hydraulics to turn winches for a long distance short handed racing sailboat. I imagine using your feet to drive a pair of pumps to create hydraulic pressure which would be used to drive pistons or winches. The main sheet and traveler could be activated with a hydraulic ram. Halyards would have to be driven with a hydraulic motor. The pilot could remain seated while pedaling. Valves could be opened and closed to direct pressure to various cylinders or motors. Computer controls could easily open valves to ease sheets. Changing gears would be easy by changing the mechanical advantage to the pump. Ultimately the goal would be to control the whole boat or at least the main from a single seated position.

I see there are well experienced hydraulics experts on this forum so I would like to ask a few questions about hydraulics. I understand hydraulics are not the most efficient means of transferring mechanical energy. Where are the losses? What percentage of the losses come from viscous losses in the fluid? What percentage of losses come from leaks of fluid? What percent of loss comes from seals sliding in pistons? If a system were optimized for human power (a pair of piston pumps connected with some hose to a hydraulic motor), what are the top efficiencies one could expect from such a system?

Regarding hydraulic motors, which is most efficient; radial piston? Axial piston? Rotary Vane?

It appears that all of these hydraulic motors use some sort of rotary valves. Do these valves leak? Is there a lot of friction with these valves?

To avoid return hoses and reservoir, could sea water be used as a fluid?

Thanks;

Roy

[alan white]

Have you thought about electric winches? I realize you're asking about hydraulics, but my guess is that electric would be easy to run by human power, since the pedalling would be turning a generator and charging a battery----- and wind and solar power might replace tired legs as well.
It also allows pedalling between uses, so no extreme excersise would be required. Also, electricity can be used for other things besides winches.

[TeddyDiver]

Originally Posted by Salty Sailor333

1.Regarding hydraulic motors, which is most efficient; radial piston? Axial piston? Rotary Vane?

2.It appears that all of these hydraulic motors use some sort of rotary valves. Do these valves leak? Is there a lot of friction with these valves?

3.To avoid return hoses and reservoir, could sea water be used as a fluid?

1. Depends of the specs.. basicly you define what you need and then look what would work best for that specific purpose.
2. Leaking happens mostly throw axial lubrication
3. Yes but no. There's a thread here about the subject but it's a waste of time and money..