A Picture is Worth a Thousand Words

Discussion in 'Props' started by DogCavalry, Jun 30, 2021.

  1. comfisherman
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    comfisherman Senior Member

    I've minimal knowledge of the ring drive or the concept as the whole.

    However, a decade or so ago a local guy bought a barge style z drive from a surplus auction. It could rotate and vector thrust 360 and it worked really well. After a few years it started to have issues. Reality set in, the system was close to 150k usd new hr had purchased it for pennies on the dollar but parts were still normal price. The harsh reality of so many intricate parts immersed in salt water became evident in about 5 years of normal use. For an industry that needs and can afford the pinpoint thrust could warrant the price tag. Boat was converged to conventional gear as repairs were more expensive than conversion.

    Boats always have a reality of a harsh environment and a high cost to try keep at bay. The conventional prop is a tough one to beat even with all its shortcomings.
     
  2. Kayakmarathon
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    Kayakmarathon Junior Member

    The shaft driving the blades will have to rotate at a much higher RPM than the blades or have a gear much larger than the diameter of the blades. Both configurations are tradeoffs with removing a center shaft.
     
  3. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Everything in engineering is tradeoffs.
     
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  4. Will Gilmore
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    Will Gilmore Senior Member

    Perhaps it could be driven through EM induction. upload_2021-7-1_19-31-56.png
     
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  5. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    At least some of them are. Lots of outfits makes them. It seems they are extremely quiet, efficient, are resistant to FOD, but energy density seems low. Can't get as much power through the disk area as with a regular prop.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    It seems to have a similar problem with excess wetted area as a "ring" propeller, and the sealing also seems to me a real problem
     
  7. cracked_ribs
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    cracked_ribs Senior Member

    This is pure three-drinks-in zero math spitballing but I would be sort of interested to see an outboard application of this.

    Maybe it just wouldn't work, I don't know. But an outboard has a gearbox in the water already. If you could eliminate the lower in front of the prop maybe you'd save enough drag to make it worthwhile?

    Just a thought. It's Canada Day and I have been drinking.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't see how it wouldn't have the odd problem or three
     
  9. Will Gilmore
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    Will Gilmore Senior Member

    Most likely. I would be inclined to put a cone shaped hub in the center to direct water to the blades from the middle, but that might just lead to cavitation behind the hub. As has been pointed out, Engineering is filled with compromise. Satisfy one problem and create another.
     
  10. Heimfried
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    Heimfried Senior Member



    It is existing oviously, don't know if it was or is a success.
     
  11. Heimfried
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    Heimfried Senior Member

    The middle is left free purposely to provide room for passing of smaller objects of debris, which otherwise would block the prop.
     
  12. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    The space also makes the system much more efficient. Blade roots contribute far more drag than thrust, but they are a necessary evil, because blades must be connected to the hub. Unless they don't need to be. The hub contributes no thrust at all. I think the increased resistant to tangling up ropes and nets is a happy side benefit.

    The system as a whole would be better than a free shaft driven propeller at low speed, but the ring would have so much drag at higher speed that the regular prop would be better.
     
  13. upchurchmr
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    upchurchmr Senior Member

    It would be nice to see some real performance, weight, maintenence data instead of everybody's wishful thinking.
    Including my guess below.
    The original picture has a seriously large cross-section ring.
    Has to be a drag issue.
     
  14. comfisherman
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    comfisherman Senior Member

    Would stand to reason it could be an improvement for shallow draft bowthrusters. Gearleg and hub issues always plague small tunnel thrusters, seems a better use of the concept than propulsion.
     
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  15. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people


    The main use I see on manufacturers websites is, exactly as you say, thrusters.
     
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