wiggle drive propulsion application

Discussion in 'Propulsion' started by SudorracMechEng, May 7, 2012.

  1. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    Mechanical designs aside - I would be curious to know why is it that oscillating device would be more efficient?

    Off hand I can see 2 issues
    1. Part of cycle when the blade/fin is only causing resistance as it has angle of attack of zero.
    2. Blades don't have twist so it is hard to see how both the tip and the root of thefin would be at optimal angle at the same time.

    It seems that in general prop has the benefit of essentially being a fin constantly at the best point if cycle. Also propeller fin can be designed to have the correct pitch variation along the length of the fin/blade.
    Obviously props have their own issues with shafts and hubs etc. but I cannot see what principle would make an oscillating system superior in efficiency.

    This has been discussed number of times here and I thought that the conclusion always was that propeller designed for efficiency beats any kind of oscillating version.

    Not trying to be argumentative but genuinely interested.
  2. Frosty

    Frosty Previous Member

    Good post kerosene.
  3. swashdrive
    Joined: May 2012
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    Location: SEQ, Aus.

    swashdrive Junior Member

    Hi Kero
    Thanks for ur input, i know exactly what ur saying and i totally agree !
    I really don't have an answer for you !
    I can only really speculate from my observations, which i don't think is gonna satisfy the critic.
    I have no way of calculating thrust as it doesn't develop much until the boats planing, maybe i could use an accelerometer or something ?
    The data i collect from the data logger and the run time i get from the battery suggests its better, but like i said i don't intend to prove this, i only want to prove that it actually works !
  4. spork

    spork Previous Member

    In the U.S. the inventor has 1 year from initial public disclosure to file a patent.

    Additionally, the fins are being asked to produce lift in both directions - thus they presumably have a symmetrical (zero camber) foil. That should cost a few points in efficiency as well.

    I was surprised to see that the fins were "rocking" side to side rather than translating. By translating, you could minimize the problem of inaccurate twist. With them rocking, they would be optimized with blade twist similar to that of a prop - but they obviously can't twist both ways.

    I am inclined to think that a prop designed for efficiency would almost certainly beat a reciprocating design. But there is one caveat... a prop with blades that long would have a diameter twice as great. That would be one big prop, and your center of effort would be well below the hull.
  5. Frosty

    Frosty Previous Member

    Hence the surface prop,-- a rotating wriggle drive if you like with perfect set pitch without stop start inertia.

    A wriggle drive out of the water would need considerable power just to move itself due to inertia.

    A surface prop if spun out of the water would spin freely with almost no energy except of its kinetic energy absorbed when set in motion.
  6. spork

    spork Previous Member

    I'm not sure what a wriggle drive is, but if it's what I think it is, the start/stop shouldn't require any additional power so long as it's kinematically constrained. Consider a piston on a crank-shaft - it doesn't take any external energy to make it stop and change directions repeatedly.
  7. Frosty

    Frosty Previous Member

    How can you think that it does not take energy to change direction of a piston.

    Go outside , start the car and put your foot on the gas. It will hold about 7,000RPM not go on for ever. Then it will throw a conrod out of the side dues to stresses of the pistons weight.

    Because all it power is being used to rotate the engine.

    Wankels are much better,--no pistons.

    Turbines --well even better.
  8. swashdrive
    Joined: May 2012
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    Location: SEQ, Aus.

    swashdrive Junior Member

    OMG you guys just aren't getting it, thats ok i don't expect you too !
    This propulsion units direction of rotation is perpendicular to the rotation of a prop, across the stern ! and i'm using swashplates, it changes everything !
    It doesn't follow the path of a conventional prop, it follows a cosine path, exactly the way nature does, that the difference !
    we only need look how well a penguin swims, or not !
    Frosty, what ever :p
  9. Boston

    Boston Previous Member

    Hmmmm, who yah goin to call.

    I'll have to go find some of those threads Kerosene
  10. Frosty

    Frosty Previous Member

    Thats why there is wiggle drives -(-what ever) all over the world.

    Four legged vehicles never got off the ground either (pun intended).

    You think a horse is more efficient than a car?

    The misunderstanding seems to be more on your side. To travel the sea in a proper boat you dont use fish drives. For a toy on a calm lake some kind of movement can be made and fabricated in cheap plastic so you don't hurt the kids.

    Muscular control will handle this,--mechanical reciprocation does not.
  11. Boston

    Boston Previous Member

    Took me a bit but I see how you did it. Nice job.

    I'm very curious to see how the efficiencies work out, Sodurra has some interesting input and Kerosene suggests there are some good threads around here somewhere concerning this very issue. Frosty, all new things take time, this ones got precedence in nature and seems like it ought to work. Never know until you try. My take on it is that if its close and the fins are so much cheaper then the difference in cost might make up for the increase fuel usage, in my case I pay about 17 cents a gallon for my bio-fuel blend and considering the cost of even a single 3 blade 22" prop let alone the two that I'd need for a cat. The up front savings might end up well within the range. Poor Mass just got his million dollar props and BAM !!!!!!! must have hit something cause now he's talking needing another. Yikes, and on a pension, thats gotta hurt ;-(

    The idea isn't that it has to be more efficient, but that its gotta be in the ball park, then if up front and maintenance costs are lower, might work.
  12. Frosty

    Frosty Previous Member

    Thing is here that you donr understand a prop very well and its shape, pitch , rake, foil, and even average pitch along the chord of the blade.

    All these you have none. A prop blade is so designed to suck its way through the water as in 'screw' it does not work well in reverse which is what you are expecting your fins to do and yet they can not.

    A Dolphin has muscle control over the whole fin and in control of sweep, pitch (up and down.
  13. swashdrive
    Joined: May 2012
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    Location: SEQ, Aus.

    swashdrive Junior Member

    Hang on
    I think Frosty must be right, there must be engines ever were throwing a leg out of bed cause they have pistons, <insult removed>
    maybe i need to go elsewhere, i'm banging my head here :confused:
  14. Boston

    Boston Previous Member

    which boils down to the efficiency thing again. You might reread Sodurra's comments about flexible fins when I brought up the spring steal idea.

    In any case its new and lots of R&D will be needed to actually pin down the best arrangement

    But if 87% efficiency is a real number then its well within the range of doable.

  15. Frosty

    Frosty Previous Member

    A swash plate is nothing new, helecopters use them and so does the compressor in your car refrigeration/.

    If you push something you have to stop it to go backwards, change direction, then push it again. If you can just keep pushing no stopping will be required.

    Stopping takes as much energy as pushing it in the first place.

    Rotation can absorb Hp through the entire 360degrees. Sine wave can not, How much power are you putting into the wheel of your bicycle when the pedals are at the top and bottom? the answer is zero.
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