An Innovative System

Discussion in 'Propulsion' started by amateur mariner, Oct 28, 2009.

  1. fcfc
    Joined: Feb 2005
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    fcfc Senior Member

    "Universal joints can't transmit the kind of axial loads a prop shaft must handle"

    I am not sure of this. In this design, seems that the universal joint has to transmit torque and axial load only when the two shafts are aligned. So no move in the U joint.

    I have also seen kind of a saildrive system that retracts by rotating lateraly, pivoting around the input shaft.

    There are also hydraulic pods that are in a dwell, not specifically made to be retractable, just removable for maintenance. but can be adapted.

    There are a bunch of reduced draft system, look at military landing craft. It just depends on how much money you have to spend. :p
  2. amateur mariner
    Joined: Feb 2009
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    amateur mariner Junior Member

    I just want to transmit power when It is straight.Retract the shaft and propeller when the vessel is stopped.Can somebody give a suitable idea?
  3. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Yes, I have a very small one which I use in shallow river waters and even thru rapids. Why not use the principle of long tail motors used in Thailand? No need for any complex univeral joints, puncturing the hull, hydraulics, leaks, rudder, etc. Mine is "porta"- compact enough to carry as baggage in an airplane, but I have seen them big enough to be powered by automotive engines!


  4. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    Google cam.a.propulsion or pivotal drive
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    After 19 posts it seems there is nothing ready-made on the market, so your application must be a very special one.
    If only the berth is the problem, dredging could be the solution. It is probably cheaper than constructing an exotic propulsion system.

    On the other hand the thrill of making something unusual is of course priceless.
    Imagine a prop shaft with a disc attached to it in the style of the old OMC stern drives. They used hemispheres to maintain propulsion with the drive lifted, but if that is no requirement any shape of teeth will do.
    Attached to the stern is a hinged triangular frame with a second disc, a short stub, bearings and a prop, everything nicely lined up with the prop shaft. A hydraulic or pneumatic cylinder can raise the frame to near or above the waterline.
    With the frame lowered, the discs can transmit both axial and radial forces. If I remember correctly, OMC used a diameter of approx. 10 inches or less to transmit several 100 horse-powers. But that was before the reduction gear, so in your case it should be a bit larger, say 12' to cope with the torque. Or instead of aluminum you could use stainless steel.
    The rudder can be attached to the hinged frame with a forked construction. If hydraulic steering is used, no mechanical construction with gears that engage in lowered position is needed, although that may be required by law.
  6. Frosty

    Frosty Previous Member

    Ive been toying with this idea myself. This could be done on a surface drive system, something like an Arneson that the hydraulics were set up so the shaft could be drawn up out of the water. This could only be possible on a shallow draft vessel and even than not all the shaft could be removed.

    What does cover this criteria is the Thai long tail. A marvelous piece of boat propulsion.

  7. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    There are all types of propulsion systems about which are easy enough for a handyman to make.If you had a good engineering shop a super model is easy to make to.Using established and proven mechanics.

    Attached Files:

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