Has anyone seen this?

Discussion in 'Propulsion' started by cthippo, Nov 21, 2010.

  1. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    I stumbled across this design on youtube looking for cool old engines.

    Apparently what these guys are doing is using a fixed piston with a moving cylinder. They claim it's the greatest thing since sliced bread, but if nothing else it's interesting.

    http://www.shepherdengine.com/
     
  2. PAR
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    PAR Yacht Designer/Builder

    Just about every curious engineer has fooled with this. It's called a sleeve engine. They have a number of issues (surprise!). Fernande Porsche got fair close (refined) with a 2 cylinder, but eventually abandoned it for excess heat problems. Looks good on paper or now in 3D animation, though reality works best.
     
  3. dougfrolich
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    dougfrolich Senior Member

  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    These slipper cam and axial engines have been around for a century or more and you'll note that development pretty much stops in the 1920's and 30's as gas engines became more refined. Though some clever thought processes went into them, they have a host of "issues" from an engineering view. The common problems are what to do with all the heat they create and of course the huge frictional issues of the slipper style of engines.
     
  5. aranda1984
    Joined: Jan 2010
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    aranda1984 aranda1984

    New type of engine

    I have seen a few different variations on similar engines in the past few decades.

    Everey single idea that used a cam and cam follower type application had major limitations. RPM is being one...

    There was one from England in the 60's where the cylinder assembly was rotating and they used opposing pistons. Heat problems, too much rotating mass, vibration etc..
    Cam followers were rolling on the inside flange cam.. Similar to the large multi-piston hydraulic motors.
    They are best used for slower hydraulic applications.

    I have seen the evolution and testing of the opposing square piston type engine, where the pistons moved down on twin arc paths....
    That went nowhere fast also.
    The most promising excercise was the Vankel engine...
    You don't see many around.. except in car collections.

    ...Almost every engineer will play with new and revolutionary engine ideas, early in their professional life. (This person included.)

    This excercise is great for the understanding of what's taking place in an IC engine, but eventually they see the evolution that has taken place in the past 100 or so years and abandon their quest.
    The first engines on the horseless carriages had around one horsepower. The same size engine today can deliver about 50 times that...

    The lighter the reciprocating parts, the more balanced the rotating parts, the better engine you have.
    See today's race cars, it is insane, just compared to the 60's what they can do! (RPM & HP!!!)

    ... Some people must have been convinced to sink a lot of money into this project, if they are already at the testing stage.
    I guess, they should patent it!:D:p

    The second idea of the axial multi-cylinder engine is another example of some clever engineer trying to make a better mouse trap.
    It is very neat, but the swash plate type system is not a very efficient way to transfer the energy...
    ...The animation in both cases was cute, ... anyway...

    With respect,:p

    Stephen
     
    Last edited: Nov 22, 2010

  6. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    Somewhere out there some young engineer or backyard inventor has the next big idea, it's just a matter of recognizing it.

    No question the reciprocating engine works, but it has always struck me as ungodly inefficient to start and stop that big piece of metal a few thousand times a minute. Just because someone has yet to come up with something better does not mean that something better does not exist.
     
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