Hydraulic drive problem

Discussion in 'Sailboats' started by CaptainPhil, Mar 25, 2011.

  1. CaptainPhil
    Joined: Mar 2011
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    CaptainPhil New Member

    Have a FD12 (50' Flying Dutchman)
    Instead of a transmittion, she has a Hydraulic Pump
    Hydraulic hoses are attached to a hydraulic motor which drives the shaft

    1st Problem: when sailing and our speed goes over 8 knots, the Propeller (fixed blade) starts to rotate, which in turn drives the shaft & motor, which drives the pump and turns over the engine

    Question: 1. would a feathering (folding) prop correct this?
    2. do I need to install shut off valves on the hoses to prevent rotation?
    3. Do both

    2nd Problem: If I install valves, I will have to go below to shut or open, which could be a problem in an emergency
     
  2. Adler
    Joined: Jan 2010
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    Adler Senior Member


    Pay attention,

    Do not install Shut off Valves.
    You need to Install a by pass circuit.
    In case that you install shut off valves you will block the propeller.
    Take in account that the torque which applied to the propeller when you are sailing with a given speed is equal to the torque that produced from the Hydraulic System to achieve the same speed.
    So your duty is to let your system run free and the hydraulic Oil to pass free in Closed Circuit just to Lubricate the moving parts.
    In case that you need a plan for the logical circuit please scan the Installation drawing of the existing Hyd. Circuit to add the by-pass sub-circuit.
     
  3. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Adler..yep...NO valves.
     
  4. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The Hyd shop will call what you need a motoring valve.

    There common and probably $75 in about 1 inch .


    The drag of the spinning prop will be higher than dragging a drogue of the same diameter.

    A folding or featherig prop will help your speeds.

    FF
     
  5. Lister

    Lister Previous Member

    Captain, are you happy with the hydraulic motor beside the problem of the prop?
    Lister
     
  6. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Hydraulic drives are about the most convenient, space saving, and easily controllable systems available. Too bad that hydraulic drives are the least efficient of any of the alternatives. If you motor a lot, and if you care about fuel consumtion, the hyd. is a bummer. If you are not in the mood for major changes in propulsion powering then get a feathering prop and you will be pleased with the improvement in sail powered performance.
     
  7. kenJ
    Joined: Jul 2005
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    Location: Williamsburg, VA

    kenJ Senior Member

    shaft

    You can also install a shaft brake to lock the shaft when not motoring.
     
  8. Frosty

    Frosty Previous Member

    And what doe's that do then?
     
  9. kenJ
    Joined: Jul 2005
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    kenJ Senior Member

    The installations I have seen have used a small brake disk like you would see on a motorcycle mounted to the shaft, sometime using the coupling bolts. A small disk brake caliper is hard mounted so that the disk spins in it. Caliper is attached to a small manual hydraulic pump, like you would see on an automotive floor jack. When you want to stop or keep the shaft from turning apply a couple pumps of hydraulic fluid. When ready to motor again, release the pressure.
     
  10. CutOnce

    CutOnce Previous Member

    Answer: Create a lot of drag and slow the boat under sail.

    A bypass makes a lot more sense. Better to keep the wheel spinning freely if there is no feathering. If you have to spend money to fix the problem, might as well spend it in a way that isn't going to slow you down.

    --
    CutOnce
     
  11. Frosty

    Frosty Previous Member

    Ah --just checking. I thought you might be one of those people that think braking the shaft reduces drag when sailing.

    There are some about you know!!
     
  12. Adler
    Joined: Jan 2010
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    Adler Senior Member

    Hydraulic Circuits

    Dear All,

    Based to thoughts were noted from "messbaout" I would like to write the causes that are established the basis of Hydraulic effect:

    1. The main idea to use the Hydraulic Transformation of Energy is locked to the fact, that we will be able to control the Speed independently to the Torque Vector. Describing that, by simple way, we can define by manner that in "Hydraulics" the speed control of a turning shaft or a linear moving rod and the control access to stabilize the speed at any given value, are depended only from the liquid's "Flow Volume" and has nothing to do with the produced torque (in case of turning shaft) or the applied force (in case of moving rod) that are directly depended only from the liquid's "Pressure".
    Take a note that in "Hydraulics" when the speed limits to "zero" the Torque could be applied at Max. Value.
    This gives an advantage that couldn't be reached at any other transformation form of energy.
    For example on Internal combustion Engines or Electric Motors the Speed and the Torque Control are strong related.

    2. The Hydraulic Transmission Efficiency - last 25 years - is increased to 0.97 (97%).
    That is based on Piston Variable Flow Pumps Design, on which the flow is regulated by Controllable Variable Piston's Stroke. On these Cases the Hyd.Pump could be driven from an Electric Motor or Diesel Motor or Steam Turbine or Gas Turbine and to have a controllable produce of Flow from 0 to Max. independent to "Pressure".
    Equal to that the Piston Motors also, have very low level of leakages and very low Pressure losses.

    On this kind of transmission where no valves are involved to regulate the Power, is obvious that the Efficiency should be High.

    3. The noise level is too low because the energy source (for example Diesel Engine coupled with the Hyd.Pump.) is installed into a Sound Sealed Canopy and all of that based on Rubbers so it's not necessary to by rigged on the Hull Load Carriers transmits the Engine's Vibration to the Hull Structure.

    4. In Latest designs the Hyd.Motor drives a CPP (Controllable Pitch Propeller) where it's Ability to produce Max. Torque at Very Low Speed is full applicable.

    5. The Sector under development in Hydraulics Industry on present times is to increase the Power at a Level higher than 1.500 kW /per unit - motor.
    It is easy to understand that the Pressure increases the Thickness and the low Volume increases the Diameter of the Pipes that transfer the Hyd. Liquid.
    This factor makes the Hydraulic Systems limited.
     
  13. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    ...I am one of them Frosty, a locked prop has less drag than a rotating one...rotating shafts also wear out parts for no reason...lock the shaft.
     
  14. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    ....it also depends on the prop size actually, little props, lock the shaft big ones, free wheel. The Kiwis did a good study on this, and it was decided that the freewheeler was the best, but on yacht props, . "little ones", it is still best to lock them.
    see this link for their results.
    http://www.kiwiprops.co.nz/documents/Drag-Thesis.pdf
     

  15. Frosty

    Frosty Previous Member

    You do not know what you don't know.
     
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