Is this doable?

Discussion in 'Propulsion' started by bgeddes, Oct 7, 2007.

  1. bgeddes
    Joined: May 2007
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    Location: NE PA

    bgeddes Junior Member

    I was on a cruise a few years ago. The 900'+ boat could maneuver with grace and precision beyond what I thought possible in a vessel this size. After inquiring into the abilities of the ship, I was told the ship uses 'pods' containing electric motors, capable of 360* rotation. The two of them can been turned and powered up and down to get the ship where it needs to be.

    So one I was thinking about this while cutting grass with my push mower. If I could send the power down through a center shaft, and steer with a top mounted sprocket perhaps I could recreate this for small boat use. Using dime-a-dozen vertical shaft four stroke mower style engines. This could be either direct drive, OR clutched through a centrifugal friction type drive. The steering would need to be done though a horizontally mounted chain. This would provide 360* of direction.

    I have drawn a simple concept, without the clutch pictured. Please let me know what you think.

    [​IMG]
     
  2. Jratte
    Joined: Jul 2007
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    Jratte Junior Member

    Did you ever ride "Bumper Boats"? Like bumper cars but small round boats, they pretty much ran off of a lawnmower engine with handle bars that you would turn in the direction you wanted to go in. There was a scene in "Jaws" were they were riding them I believe.
     
  3. bgeddes
    Joined: May 2007
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    bgeddes Junior Member

    Yes I know of bumper boats. However, the bumper boats I am familiar with could NOT turn 360*. My plan could in fact do that, making the infinite maneuvering possible, based on the Captain's skills. Ideally I would use two of these setups on a tiny (novelty) tug or trawler.

    I do appreciate the feedback. The journey from concept to completion is typically a rough trip. A friend of mine always said, "Thomas Edison knows 1000 ways how NOT to make a light bulb."
     
  4. Jongscx
    Joined: Oct 2007
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    Jongscx Junior Member

    Technically, you could mount 2 outboard motors on a rotating bearing, put an electric motor to rotate each one, and you'd be all set... Main problem would be having both deliver the same force, so that your boat doesn't drift to one side when you want it to go forward...
     
  5. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Great concept. It should be totally doable, and very usefull
    It should also be easy to make it retractible, (like a periscope) so when sailing it reduces drag.
    I would vote for a hydraulic engine at the top of the shaft, and have one or two of these driven by hydraulics from an engine elsewhere in the boat, for increased flexibility of design.
    The main design work will be the controls, to be a simple joystick like the new Volvos.
    Why hasnt it been done before ?
     
  6. bgeddes
    Joined: May 2007
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    bgeddes Junior Member

    Retractable! I had not thought of that. It has been done on a huge scale. But for a smaller craft it has not (to my knowledge). My idea was for a small S&G novelty boat, but hydraulic and retractable would be both possible and practical. My original thought was to build a dirt cheap boat. Something propelled by a lawn mower engine.

    Initially, I was planing on a simple chain and sprockets for steering and basic throttle cable.

    Back to the drawing board!! Thanks for you support.
     
  7. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Dirt cheap is good. If you leave enough 'meat' at the top of the drive shaft, then you could put anything on it - from cheap sprockets through to hydraulics or a warp drive.

    The steering or 'directiononometer' : - ) only has to be a pulley or two around the top, and a chain drive would be easy to fit (see attached sketch)
    First thoughts are to make the main body (black) able to slide up and down a greased shaft (yellow)

    Years ago there was an attachment you could put on the bottom of a drive shaft that looked like a UFO. It was basically a pelton wheel spinning horizontally, sucked water up near the shaft end, and spat it out a single orifice. Very much like the Yamaha jet drive in the principle. Its main virtue was propellor protection from weeds and rocks, and low silhouette when unpowered.

    One of the Yamaha's jet drive downfalls is the poor reversing - attached to a unit like yours, that would never be a problem.

    I mention these options as they are easier to retract into a hull, which is my little 'nice to have'

    Do you know any engineers who could draw this up ?
     

    Attached Files:

  8. Jongscx
    Joined: Oct 2007
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    Location: Atlanta, GA

    Jongscx Junior Member

    ...what if you didn't move the propeller at all and just had to redirect the flow...

    What I'm thinking is pretty much the same as a centrifugal pump. Have a propeller (impeller?) inside of a vertical cylinder sucking up. On the other side of the propeller, have a hole and a nozzle in that cylinder, so that the water has to go out through that hole... rotating the cylinder would be easier than figuring out how to rotate a spinning prop...
     

  9. Guest625101138

    Guest625101138 Previous Member

    I think I understand what you are wanting to do. It would be like the old Evinrude and Johnson 3HP or the new 2.5HP.
    http://www.brp.com/en/Products/Johnson/Showroom/ProductSpecs.htm?productID=J2_5
    Look down to steering - 360 degree rotation.

    Any motor with self contained fuel tank and throttle can do this providing the underwater exhaust runs down in the same outer tube that houses the drive shaft.

    Soon after lawn mowers became common the motors were converted to outboards. 40 years ago you could buy a leg and fit your own motor. They are much noisier unless you do something with the exhaust than a modern outboard and their air cooling is not as efficient as a water cooled outboard so will inevitably overheat if used up around full throttle continuously.

    Ruck W.
     
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