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How to design a dolphin propulsion swimsuit?

  1. Jun 30, 2004 #1
    I'm not an engineer, but I want to design this all for my self. So I have a few questions, for the bright out there. :-) [excuse me for my bad english, I'm not a native speaker].

    I want to design a swimsuit (more a lightweight aerodynamic "rack" which you strap yourself into) which has a dolphin tail attached to it, which is thrusted up and down by an electric tubular linear motor. Only, I'm not sure how powerful the motor should be.

    The idea is to have a suit with which you can swim up and down in the water, using your arms to gain initial speed (just crawl), and once you attain sufficient speed you let the tailfin do the rest. (You then keep your arms close to your body or keep them straight ahead of you). You use your arms and the weight of your head to steer (like you would driving a motorbike.)

    How much power would you need to have such a horizontal tailfin (not a vertical one like that of sharks) kick up and down and push a person of average weight (say 80kgs - 175 pounds) through the water (say one meter, 3 feet under the surface) at a fun speed (say 30km/h - 20miles/ph)?

    I'm at a loss.

    Would the strongest tubular linear motor of this company suffice?

    Brushless direct drive technology

    1180 Lb. Peak Force

    180 In/Sec

    40G Acceleration

    Strokes up to 20 inches

    The motor would be powered either by batteries (say good for a ride of up to 15 minutes) or by a fuelcell and hydrogen.

    [By the way, how much does a good engineer cost? How much would it cost to have an independent engineer design this kind of toy in its entirety?]
    Last edited: Jun 30, 2004
  2. jcsd
  3. Jun 30, 2004 #2


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    You would be much better off to use a simple trolling motor for a fishboat and a motorcylce battery.

    A linear motor with encoder designed for industrial use from a 220V 3-phase powered controller. You may want to check on price (guessing $1000+ each) and you'll exhaust a 60lb car battery in very little time (5-7 minutes) if you'd need to run them at full power.

    Sorry to be a buzzkill, but pretty tall challenge for a toy. Neat idea though. :)

  4. Jun 30, 2004 #3
    Thx cliff.
    I was just thinking, the biomechanics of a dolphin kick movement is a rather linear one (in reality it works with a kind of a muscular "spring", like that of kangooroos), so I thought I'd look into linear motors. They're very powerful when it comes to accelerating, which is basically what the dolphin kick is about. But indeed, these motors are more for precision work, while this toy needs raw power.

    I needed the realism of an engineer, and that's what I get. Thx :-). (I think when an engineer starts with: "you would be much better off with...", then I think I've heard enough, lol).

    Anyways, more comments welcome.
  5. Jun 30, 2004 #4
    If you're not going completely underwater, the hydrogen powered has potential. Maybe you could employ some sort of pneumatic actuator for quick, forceful, intermitant movements.

    I think side to side motion would be easier to facilitate because the forces and stresses in either direction would be similar where up and down would differ somewhat (gravity working against the up motion and with the down motion, etc).

    Cool idea.
  6. Jun 30, 2004 #5


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    Just a word of warning; do not strap yourself into this thing unless it is positively bouyant! When it runs out of power, you will be trapped and helpless underwater.
  7. Jun 30, 2004 #6
    Yes, I've thought about that. The rack should be positively or neutrally buoyant. The entire lightweight aluminum rack will be mounted inside a fiberglass case, with a nice shape. It shouldn't be too difficult to have a few airpockets in this "backpack". The backpack ends in this long tailpiece, at the end of which your feet are strapped (and behind that, you have the tailfin).

    The advantage of the design is that in water, things weigh less, and you still have your arms free (your feet are strapped but I'll design some system -- like with ski's-- where you can kick your feet loose, something like that.)
    Last edited: Jun 30, 2004
  8. Jun 30, 2004 #7
    Yep, additional pneumatic thrust would be very interesting.

    And indeed, shark motion (side to side) would be easier from a mechanical point of view (more equal load distribution), but if this ever gets off the drawing table, I think a dolphin toy has bigger market potential. :-) (Maybe not, I'm not sure).

    Anyway, the most important thing is raw power. I don't want to use a combustion engine, since that's directly polluting (and if I ever want to market this, I will want to use metaphors and lines like "become a dolphin" "feel the dolphin in you" "they're your friends" etc... so I obviously can't use a gasoline engine.)

    The thing should be battery powered or have a fuelcell (but I think fuelcells are quite heavy).

    Ok, thx a lot for your remarks :-)
    Last edited: Jun 30, 2004
  9. Jul 23, 2004 #8


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    "Feel the dolphin in you"?

    I think Ann Summers have already registered that marketing slogan as a trademark...
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