Velvet drive prop shaft brake

Discussion in 'Inboards' started by JamesKoss, Nov 19, 2008.

  1. JamesKoss
    Joined: Nov 2008
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    Location: Richmond, CA

    JamesKoss New Member

    Does anyone have a design, a comercial product, or plans for a prop shaft brake on this transmission? Ideally one that positions the prop behind the dead wood as well.
     
  2. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Commercial prop brakes attach directly to the shaft , not usually the tranny.

    When installing one it is EZ to index it to hie the prop.

    However what "looks" good behind the deadwood, may not be lowest drag.

    With a big wrench its best to slightly move the locked prop while sailing at your cruise speed.

    Sometimes the drag is least with the blades in a position they prefer.

    When you are holding the LEAST amount of force from the shaft , and the prop wants to not rotate very hard at all, lock it there!

    FF
     
  3. JamesKoss
    Joined: Nov 2008
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    Location: Richmond, CA

    JamesKoss New Member

    Attached to the shaft it would spin. The brake assembly attaches to a stable site and clamps on to the shaft to keep it from spinning. Like brake calipers on a car, nothing attaches to the axle or shaft except the spinning disk. The caliper grips the disk when activated. It is the caliper attachment idea I need help with. I do not want to use a vice grip or wrench. I want to remote control it. Any ideas out there?
     
  4. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hi James,

    Just curious, for what purpose do you need a shaft brake?

    I've only ever seen shaft brakes in two types of applications. One is what Fred says- a simple fitting attached to the shaft, somewhere between transmission and stuffing box, so that you can lock the prop while under sail. I don't think you ever actuate this kind of brake while the shaft is powered.

    The other is for gas-turbine engines driving jetpumps, in which case a car-like disc brake is often used at the reduction gear output so that power to the jet can be killed quickly. (These turbines take a long time to slow down, so putting a brake on the shaft is an easy way of controlling them without affecting the turbine itself- the turbine rotor from which power is extracted usually spins separately from the compressor and its power turbine, and so can be quickly brought to a halt while the engine spins down to idle.)
     
  5. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A shaft brake is a great tool to keep the tranny from dieing , as many should not freewheel, to reduce the drag of the spinning prop, or best of all to hide the prop behind the deadwood on a cruiser for almost Zero drag.

    Look in a copy of Sail , or Cruising World , if they still exist , and you should locate a few suppliers.

    FF
     
  6. bntii
    Joined: Jun 2006
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    Location: MD

    bntii Senior Member


  7. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 111, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    That looks like it will work, but there are other styles that do not require the end coupling to be removed to install the unit.

    FF
     
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