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  1. #21
    Join Date
    Dec 2005
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    Far S. Cornwall
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    10,995

    Default Re: Hydraulic emergency bilge pump or generator

    Next you need to know what flow rates are needed for your purposes, pump and motor. For instance, I have no idea what mine are, only that they are matched for driving the winch, slow speed high torque. The pump at 800 rpm drives the motor at about 80-120 rpm. The bilge pump above probably needs more revs than that for a good result.

  2. #22
    Join Date
    Aug 2012
    Posts
    231

    Default Re: Hydraulic emergency bilge pump or generator

    I got a book on hydraulics from the library. ... still working through it. Not quite sure yet how to control the speed of a hydraulic motor from a fixed engine speed. I suppose things like an anchor winch or a bow thruster we can live with one speed. It might explain why driving a generator is not common via a hydraulic link. A dedicated diesel engine is ideal as it is easily does fixed speed.


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  3. #23
    Join Date
    Dec 2005
    Location
    Far S. Cornwall
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    10,995

    Default Re: Hydraulic emergency bilge pump or generator

    Quote Originally Posted by Bi111ion View Post
    I got a book on hydraulics from the library. ... still working through it. Not quite sure yet how to control the speed of a hydraulic motor from a fixed engine speed. I suppose things like an anchor winch or a bow thruster we can live with one speed. It might explain why driving a generator is not common via a hydraulic link. A dedicated diesel engine is ideal as it is easily does fixed speed.
    A proportional valve will do that for you. I have one, set the winch speed, engine speed makes no difference. It does, however apply more torque at higher revs.

  4. #24
    Join Date
    Sep 2008
    Posts
    1,268

    Default Re: Hydraulic emergency bilge pump or generator

    Every valve you add increases the heat generated in the hydraulics, very soon you will need to add an oil cooler, with associated water supply. The gearbox will also need an oil cooler/ upgrade as its working harder.
    Maybe there is a reason not many have gone down this route?!

    edit- all this heat comes at a cost of fuel consumption ☺

  5. #25
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Durban East Coast Africa
    Posts
    5,598

    Default Re: Hydraulic emergency bilge pump or generator

    Quote Originally Posted by Bi111ion View Post
    I got a book on hydraulics from the library. ... still working through it. Not quite sure yet how to control the speed of a hydraulic motor from a fixed engine speed. I suppose things like an anchor winch or a bow thruster we can live with one speed. It might explain why driving a generator is not common via a hydraulic link. A dedicated diesel engine is ideal as it is easily does fixed speed.
    I have done this in the past with a variable displace pump of motor. Most common being axial piston pump with a swash plat displacement control. This overcomes the heating effect and in the end reduces the cost and reliability.




    This gives you some information on proportional valve

    http://www.hydraulicspneumatics.com/...control-valves
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