Velvet drive prop shaft brake

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

  1. JamesKoss
    Joined: Nov 2008
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    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
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    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
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    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
    Posts: 4,127
    Likes: 147, Points: 0, Legacy Rep: 2043
    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
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    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
    Posts: 731
    Likes: 96, Points: 0, Legacy Rep: 1324
    Location: MD

    bntii Senior Member


  7. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, 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
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.