wiggle drive propulsion application

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

  1. Boston

    Boston Previous Member

    Ahahahahahahahahahaaha

    no one eh, e gads you are delusional

    and I'd sooner trust a politician than an original idea with the likes of you

    so sorry but I gotta go.

    and remember

    Your a flaming jack *** with delusions of grandeur .
     
  2. spork

    spork Previous Member

    Your failing at life has had a very negative effect on you.
     
  3. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    I'm sorry, but this type of insult is not appropriate for the forum.
    It's been requested many times to please keep things polite here and refrain from the insults, a half dozen warnings have been given.
    Please, let's get the thread back on a productive note and no further insults. Thank you.
     
  4. kjell
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    kjell Senior Member

    In one way you are right. But don’t forget that they are different airfoils. One is rigid and works in a circular movement. The other one is flexible and works in an oscillating movement.
     
  5. kerosene
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    kerosene Senior Member

    And I asked clarification on why that would be different?
     
  6. kjell
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    kjell Senior Member

    The difference is the way the water mass is accelerated producing thrust. They are not producing LIFT
     

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  7. DCockey
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    DCockey Senior Member

    The first figure partially shows the simple "actuator disk" model of a propeller. It does not include the increase in average pressure across the "disk" which is used in the model. While the actuator disk model is very useful for looking at the overall behaviour of a propeller system, it does nothing to describe the mechanism by which the pressure increases across the disk.

    Each blade of a propellor functions like an airfoil, and when viewed from the reference from of the blade then the blade generates lift. This is using the definition of lift as a force generate normal to the direction of the approaching flow.

    Likewise, I expect that if the action of a blade on a wiggle drive if viewed from the reference frame of the blade then the blade generates lift.

    An example of a system where the blades are not generating lift would be the blade of an oar in "normal" rowing with the blade oriented perpendicular to its motion relative to the water. But if the same oar is used for "sculling" as in moving the blade back and forth with the blade at a slight angle to the motion relative to the water then the blade is generating lift.
     
  8. swashdrive
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    swashdrive Junior Member

    Hi blokes
    Great to finally see it back on topic, I wanted to post this like about 10 pages back but knew it would get lost with the infighting.
    These guys are doing ground breaking research in Cavitation, which occurs on ever screw and yes even fins.
    http://www.amc.edu.au/maritime-engineering/cavitation-research-laboratory
    They are working on super cavitation and making good steps forward !
    There's some good footage there to took at, its not helping my cause but still interesting !
    regards
    Craig
     
  9. Frosty

    Frosty Previous Member

    The blade of a surface propeller never cavitates but airiates. The blades are not like the conventional prop.

    Aplogies for repeating myself on numerous occasions but yet seems necessary here, the surface prop could be called a rotating sculling device. And is that not a basic mimic of a fin swimming.

    A Dolphin would swim with a beat of say 2-3 per second with a speed of 15kts. This would suggest a massive pitch.
     
  10. swashdrive
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    swashdrive Junior Member

    My fin device beats of say 4-6 beats per sec @ 15knots, this would also suggest a massive pitch and therefor different, or do you still consider it and elaborate toy that is just a crude mirage drive... such comments can be hurtful towards the cause for the sake of being smart you know, don't you think a lil credit is due and that what i'm dealing with is infact different to ur common surface prop ?
    regards
    Craig
     
  11. kjell
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    kjell Senior Member

    LIFT.????? Boats and swimming animals don’t need to produce LIFT. They are floating. To overcome DRAG they need to produce THRUST.
     
  12. MikeJohns
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    MikeJohns Senior Member

    There's always an elastic response to a stress, so yes they stretch and compress. But Frosty is a little lost here.

    If anyone is interested
    If we considered a frictionless system of say an internal combustion engine with no pressure differences then it will keep spinning perpetually. The effect of the reciprocating mass on a crank is analogous to adding rotational mass.

    The piston is accelerated from BTC. It reaches it’s maximum velocity half way up the bore and then decelerates from there to TDC the net energy in the must be zero. The piston and conrod receive energy from the crankshaft and then return it.

    With a dynamics problem like this just consider energy. If a mass on a crank was taking energy out of the rotational momentum that energy cannot just go away, it has to be stored. At that point you should realize there’s no where in the system to store the energy you imagine is being lost.

    Turning a flywheel for example is no different, the projection of any part of the wheel is changing direction sunusoidally, amd it’s under constant acceleration.
     
  13. swashdrive
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    swashdrive Junior Member

    Kjell, sorry old mate but gotta disagree on that, i think you'll find DCockey's explanation is good ! the fin is swimming with lift otherwise it would be a scull, just like a surface prop !
    But the fact that it swims is what should be questioned ?
    I don't think the penny has dropped just yet as to why it works !
     
  14. swashdrive
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    swashdrive Junior Member

    It has occurred to me after reading this quote that you guys may not realise "this is not so with a swashplate"
    heres the example;
    If the swashplate has 30 degrees deflection angle (Having a total throw of 60 deg through 360 deg shaft rotation, the pitch angle is 30 deg angle from line of flow, in propellor terms it would be 60 degrees pitch (extremely tall right).
    Once the swashplate goes past 30 degrees of shaft rotation from BDC the pitch angle of the fin is mechanically locked over and has reached its max velocity, it is then a constant velocity until it reaches 30 deg before TDC then decelerates to change of direction.
    The lock point and Max velocity coincide with the swashplate deflection angle.
    What i mean by lock over is its inability to straighten or flatten itself into the line of flow.
    There's another advantage, but i won't into that just yet.
     

  15. kjell
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    kjell Senior Member

    The surface prop is only making a half scull stroke in the same dirrction every time the propeller blade is sumerged.
    Sculling is made with a rigid airfoil, changing the direction and the AoA in every stroke.
    Your drive is not a scull drive. Your fins are altering the AoA during the stroke, produsing the “Kjell-Effect” that makes your boat move so fast. Your fins are not making any cavitation. When the fin is working in vertical position near the surface, they are sucking down air. Ventilation. To produce cavitation with the fin it must be working diper and very fast. The cavitation doesn’t affect the effisiensy of the fin, as it does on the propeller.
     
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