Propeller blades turning

Discussion in 'Props' started by A_Appleyard, May 13, 2012.

  1. A_Appleyard
    Joined: Oct 2005
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    A_Appleyard Junior Member

    I am sorry to appear silly, but have any of you heard of a ship or boat or submarine propeller where each blade can rotate on its support and back each time the propeller turns, like the blades of a helicopter's rotor? That would seem to let the propeller make sideways propulsion.

    http://en.wikipedia.org/wiki/Helicopter_rotor
     
  2. SheetWise
    Joined: Jul 2004
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    SheetWise All Beach -- No Water.

    I wouldn't think there's enough leverage given the relatively small diameter -- one side pushing and one side pulling would just stress the shaft.
     
  3. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Interesting idea and in theory a sideways thrust would be developed but it may not be much.

    Keep in mind that helicopters move sideways by the helicopter tilting so that the lift vector of the main rotor has a component in the desired direction of motion. The cyclic variation in main rotor blade pitch and therefore lift causes a moment which causes the helicopeter to tilt.
     
  4. baeckmo
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    baeckmo Hydrodynamics

    Actually, there was a prototype tug (?) built (or maybe only projected) on this principle a couple of years ago, in order to evaluate the principle. If I recall correctly it was patented, but as far as I know it did not "make it to the market".
     
  5. liki
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    liki Senior Member

  6. Frosty

    Frosty Previous Member

    Of course there is variable pitch props. The maxi prop is one.

    Most ships and especially tugs have them with no gearbox, all done on pitch adjustment.
     
  7. baeckmo
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    baeckmo Hydrodynamics

    Nope, Frosty and liki, this is a "conventional", horizontal shaft CP prop where the pitch can be varied individually around the perimeter sectors. Looking from aft for instance, the port sector of the propeller disc may have maximum forwd pitch, while the starboard sector simultaneously is given zero pitch. This will produce a longitudinal turning moment, due to the asymmetrical propeller loading, as if there were a rudder in stbd position.

    The effekt, of course is similar (but not identical) to the operation of VS vertical shaft propeller, with the higher propulsion efficiency of the horizontal shaft prop, but with a reduced manoeuvering capacity compared to the VS prop.
     

  8. Frosty

    Frosty Previous Member

    Yup there is those too. I forget the name of the drive -I think they had problems and went. It was a Uk company. Its on the forum somewhere with VDO of its maneuverability.
     
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