Pod motor and large prop for electric motor drive

Discussion in 'Hybrid' started by Bookmaker, Feb 13, 2010.

  1. Boston

    Boston Previous Member

    hmmmm
    hadnt thought of the counter rotating thing
    kinda like a turbofan
    I wonder though if all that change in direction and edges would not also add to drag
    as would the spinning shroud
     
  2. sandy daugherty
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    sandy daugherty Senior Member

    It would have to operate at low rpm to avoid hellacious cavitation. and there would be a lot of pressure into the space between the rings.
     
  3. sandy daugherty
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    sandy daugherty Senior Member

    And it wouldn't have to be a very large diameter. The impellers in jet skis are only 4 or 5" in diameter and they soak up a lot of horse power. I suspect they are not very efficient.
     
  4. sandy daugherty
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    sandy daugherty Senior Member

    Prototyping something like this would be devilishly complicated, but its probably old hat for a turbine generator engineer.
     
  5. Boston

    Boston Previous Member

    I would think you could weld something up in a fairly short period of time

    its a ring with some turbo prop fan blades welded to it

    any old aircraft junk yard is likely to have some floating around and they would be plenty strong enough
     
  6. powerabout
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    powerabout Senior Member

    I read about a commercial thruster company that does this the other day, stating the lack of gearbox as the bonus.
     
  7. eric le marin
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    eric le marin naval architect

    [​IMG]

    brunvoll, a norwegian company
     
  8. kbowen
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    kbowen Junior Member

    motors

    You can get all kinds of torque out of an electric at low speeds while the ammeter goes through the roof. A permanent magnet DC motor (Minnkota etc, etc) is basically the same as a shunt-wound motor in terms of torque curve: It will try to turn at a speed commensurate with the voltage you feed it, and if you load it with a big prop, it will suck amps like crazy trying to turn at that same RPM. A series-wound motor, also called a traction motor has more gentle current demands with varying loads, which is why they are used in electric tools, but then you use energy in the field coils, which isn't terribly efficient. Electric model airplanes are increasingly going to 3 phase, brushless, high speed motors with electronic drives, geared-down to the needs of the prop, and I think this will eventually be the best answer for electric drives in boats. We are a tiny niche market, and we can't hold out breath for someone to manufacture these motors for us, but perhaps adapting future variable-speed industrial conveyer-belt drives will be the earliest hope.
     
  9. AOA
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    AOA Junior Member

  10. kbowen
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    kbowen Junior Member

    the first link you posted is terrifically interesting from a technological standpoint but their web-site makes it look like they are going for the megawatt market and the second link implies that the company is shooting for the military market, so I am not sure that individuals will benefit anytime soon. I think the magnetic gear technology is especially interesting for automotive drives where one might hit an obstruction and the magnetic gear could just slip a cog without breaking a gear tooth or over-stressing anything. We don't really need that benefit in driving a prop, because water is "ever-yielding and all-powerful" or however the saying goes.... of course, if one hits a rock.......
     
  11. AOA
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    AOA Junior Member

    Volvo, VW and other are also testing the PDD, but i'm afraid that there will not have enough neodymium for all on the market as more than 95% of the production is coming from China and this production is already saturated. Army, space, industry, and billionaires only will have access to energy saving, comfort, long lasting and efficiency offered by these advanced magnetic reductions that would also be smart if used with a compressed air engine like this one.http://www.mdi.lu/english/

    Pressurised air doesn't care about salt and water and large air tanks are far less expensive than batteries, and of course, will last many more cycles.

    It is a great mystery why this technology isn't used yet for sailing boats.
     
  12. FAST FRED
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    FAST FRED Senior Member

    "It is a great mystery why this technology isn't used yet for sailing boats."

    At sea there seems to be a lack of air hoses , connected to an air supply.

    FF
     
  13. AOA
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    AOA Junior Member

    Right, air hose supply is already in use around the neck of MDI that dare to develop this air motor technology. In 2010 MDI has had 4 state fiscal investigations... to encourage them and show we care, i guess.
     
  14. fastcat435
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    fastcat435 Junior Member

    Hallo Sandy

    that trip was finished May last year and the motors function better than expected , we have in mean while changed the props a few times and now use a 3 bladed 17 x 7 inch prop with a DAR of 70 % to give us a reasonable top speed under power ( about 8.0 knots ) with very good regeneration.
    So far in excess of 12000 NM experience , the second boat was launched recently and the owner is happy with the system.
     

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  15. sandy daugherty
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    sandy daugherty Senior Member

    Thanks Gideon.
     
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