Human powered submarine

Discussion in 'Boat Design' started by Beezer, Aug 16, 2022.

  1. Barry
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    Barry Senior Member

    I would consider a 90 degree set up with a round belt that uses v pulleys. Light weight, cheap and accommodates setting up a gear ratio.
    I noticed on one site that they use a segmented belt instead of a pure round belt (possibly for less "belt strain" loss) and I expect you may find a Kevlar belt as well
    Off the driven shaft you would be able to mount pulleys and transfer power over to the two shafts that you are considering. And with a twist in the belt on one of the belts, you could make one prop counterrotating
    There are quite a few options available on the internet.

    I understand your wishes to use two props but you would not be able to have two different rpms to enhance steering. The extra prop will add a bit more power transmission losses, belts, friction etc and with a finite available power source, you might find a single larger prop the higher efficiency route.

    You could pm Baeckmo and ask if he thinks that a set of stators behind the prop would get you "free" thrust? Ie free meaning that you have already accelerated the fluid and may be able to get a bit more thrust out of the input.
    Jet pumps use this method (and for other reasons) though a jet by itself may not be the best for your application.

    Or counter rotating props on a single shaft

    The upper picture shows the configuration a bit better
    [​IMG]


    upload_2022-8-16_19-8-50.jpeg
     
    Last edited: Aug 16, 2022
  2. Beezer
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    Beezer Junior Member

    Someone else mentioned the Kevlar belt drive thing on a different forum. I’m trying to wrap my head around what that would look like and how it might fit on the boat. Has any one tried discarded outboard motor lower units? This is a 5 day event so even without oil maybe they could last long enough without getting too corroded?
     
  3. Barry
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    Barry Senior Member

    You replace the sprocket from your bike with the gray pulley (lower picture). For a single prop shaft, add another pulley and install the belt. If you have to put two props on, you could put two drive pulleys on where the sprocket is on the bike and then turn them to two offset shafts. So from the front say at 12 oclock is the driving tandem pulleys and one of these pulleys drives a 90 degree shaft say at 4 oclock and the other at 8 oclock when viewed from the front (or back)

    Obviously, you would have to see if there is interference with the belts and the persons legs.

    Any gear sets with anything but a 1:1 gear rations will involve the gear faces to slide on each other. So your outboard gear set would require a very light oil to minimize this friction
     
  4. Beezer
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    Beezer Junior Member

    Hmm not a lot of room for 90 degree belts within the wing structure that we had hoped to mount the props in. It’s an option if we go single prop though. Has anyone used peg gears (like the old time wooden gears) to transmit power? I could get a hunk of thick stainless and tap holes for stainless bolts with smooth shafts and cut the heads off to create gears pretty easily. I imagine these could be made fairly small? I’m not discounting any of the great suggestions just trying to figure out what has been tossed out as a decent idea. Machining a full bevel gear is out of reach but if I could source big enough gears making a gear box should not be too hard
     

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  5. rnlock
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    rnlock Senior Member

    That twisted belt seems like a good idea, but it would need lots of vertical room inside the sub, wouldn't it? Or am I just imagining it too large? It might be tedious, but maybe, since the race is short, you could wind Kevlar cord or something around a pulley on the prop shaft and have the other end fastened to a pulley on the axle the cranks are on. Pedaling would wind it up on the crank axle pulley, making the prop shaft rotate. You'd probably need a couple of ball bearing pulleys in between to route the cord between the prop shaft and the crank axle. I believe this idea came up when the guys who did Decavitator were considering a water prop and were trying to reduce underwater volume, so as to reduce drag. I heard it from one of them. Instead, they used an air propeller.

    Does anyone show up at the sub races with a Goldschmied style sub, where the prop is used for what I think is boundary layer control on the hull? Or is that beyone everyone's budget and/or patience?
    If you haven't heard of him, here's a link that has a bunch of his papers:
    https://cafe.foundation/v2/tech_enablingtech_dragreduction.php
     
  6. rnlock
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    rnlock Senior Member

    BTW, I'm sure the gears from the lower unit of a very small outboard motor should be usable, but you'd either want to cut away most of the aluminum surrounding them or mount them in something else.

    Just had a thought. Could the twisted belt be made more compact with the use of idler pulleys? Maybe there's some sort of round belt with teeth or other feature for grip.
     
  7. Beezer
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    Beezer Junior Member

    I would just need to source some broken outboards… question, I’d it the gears in the angle grinders that are too weak or the housing? If the gears are usable then We could just build a stronger box to house them.
     
  8. dustman
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    dustman Senior Member

    Is it possible to use an electric generator and electric pod motor? I wonder how the efficiency would work out given that you can eliminate gearing, seals, etc.
     
  9. Beezer
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    Beezer Junior Member

    Good thought, but it is required to be direct drive. No stored energy allowed.
     
  10. Barry
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    Barry Senior Member

    So a small hydraulic pump and a couple of motors would not meet the requirements? With the limited distance, heat build up would not be a problem therefore a reservoir would not be required
     
  11. Beezer
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    Beezer Junior Member

    From the race requirements document…

    “Submarine propulsion systems shall be directly coupled to a human being and shall not employ any energy devices. All power trains shall be direct-drive without the use of any de-coupling devices.”
     
  12. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    That does preclude hydraulic systems, which is too bad.

    Torque in an angle grinder gear box is the limiting factor. They turn at several thousand rpm, and very low torque.

    Is there a strict LOA limit, because the drag of that transom will be massive?
     
  13. Beezer
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    Beezer Junior Member

    Yes we have been thinking that we need to maybe chop it down to be much narrower. Kind of a mistake in the original design. We were never thinking human powered at first, so it’s designed for multiple dive tanks.
     
  14. portacruise
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    portacruise Senior Member

    Beezer and BlueBell like this.

  15. BMcF
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    BMcF Senior Member

    We were running model tests in Carderock's Carriage 3 (something I once did fairly often) while some human-powered sub folks were practicing/testing in the adjacent channel. Had to go over and watch, of course. Looked like fun..and a lotta work. Not something this old man would attempt, that's for sure. Good luck!!
     
    Beezer likes this.
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