Pedal Powered Boats

Discussion in 'Boat Design' started by Guest625101138, Jul 14, 2008.

  1. Sockmonkey
    Joined: Dec 2020
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    Sockmonkey Junior Member

    Having some trouble finding it. I'm basically brainstorming ideas rather than planning a specific build though.
    Ah, I suspected as much. Is there info on the performance of HPBs using treads with paddles on them?
     
  2. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Not much information available on tread power. Most likely if paddles and/ or Treads were truly significant at least in a general way, there might already be a commercial product developed along those lines, as that TUHH picture may be well over 20 years old.

    Available Currently, there are inefficient Sun Dolphin type water wheels, Hobie fin propulsion systems, kayak and oar paddle variations, Plus propeller systems from various different manufacturers. Some of these Concepts can be tweaked to fill someone's particular niche requirements, without having to reinvent a new kind of wheel.

    What is your statement of requirements, SOR, for your craft, which is not satisfied by a current human power commercial product? The approaches will be quite different depending on whether you are planning a craft that will race for a few hundred yards versus something that that has very long range under human power, for example.
     
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  3. Sockmonkey
    Joined: Dec 2020
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    Location: Michigan

    Sockmonkey Junior Member

    For the most part, I look at things and ask if it could be done just as well with fewer parts.
    I love mechanical things and I like problem solving and inventing.
    The thing I want most in a boat is that it be reliable and not a hassle to use.
    I don't care much about top end speed, but efficiency is still a priority.

    I'd be thrilled if something I thought of helped you guys.

    Latest thoughts on the ball cable.
    One possible way to keep the balls from slipping on the cable is to have the channel be curved and epoxy a peg in there.
    [​IMG]
    I can think of a few other solutions, but they're mostly variations on this. It's important that it be something easy to DIY by 3D printing or simple casting in plastic or resin.
    One could make the balls in left and right halves with a zigzag channel also.
    [​IMG]
    Press the cable into the channel and epoxy the other half on.
    You'd use a small jig to get the spaces between the balls right when you fit them on the cable.
     
    Last edited: Jan 21, 2021
  4. portacruise
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    portacruise Senior Member

    Sock, some good ideas on anchoring the beads, not quite sure about using plastic and epoxy... Myself thinks that the beaded cable probably should at least match the specifications of the steel drive chain and sprocket diameters which have proven themselves (as reliable) in existing twisted chain pedal systems. I would hazard a guess that well anchored metal beads would be required as a minimum, and that the repetitive stretch, torsion, and flex, characteristics of the (twisted/ untwisting?) wire strands cable part would have to be compatible, to this particular application.
     
  5. Sockmonkey
    Joined: Dec 2020
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    Location: Michigan

    Sockmonkey Junior Member

    Oh, I was thinking a kevlar cable or some other type of strong cord that won't stretch out of shape.
     
  6. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    I can see synthetic "rope" handling the force but plastic nubs would have hard time I think. you can easily press 50 to 100kg (110-220lb) with one foot and pedal leverage can double this for the chain. even if shared by several nubs the force is significant.
     
  7. Sockmonkey
    Joined: Dec 2020
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    Sockmonkey Junior Member

    There are some kinds of plastic that could handle it like ABS or polycarbonate. There's nothing wrong with metal, but we really want something that can be cast easily and cheaply. What would be ideal is if nylon is strong enough to make the nubs and the sprockets from because it's largely self-lubricating and corrosion-proof. It doesn't like UV, but you want a case over the whole thing anyhow for streamlining and to keep crud out.

    I don't see sourcing materials for the cord as being hard. It only takes a few feet of the stuff so you could probably get a bit left over from someone's other project.
     
  8. clmanges
    Joined: Jul 2008
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    clmanges Senior Member

    I would strongly suspect that 'nylon' isn't just one thing, but a whole family of formulations. You might want to try to find a plastics engineer who would talk with you about this. And for the cable, you might want to look at Dyneema; it's beginning to replace steel cable in some applications.

    Then you could run into a problem with bonding dissimilar materials and/or finding a solvent cement that will work. Toxicity can be a problem. As well, many plastic parts are formed by injection-molding liquid resin under pressure.

    I don't recall if it's been mentioned here, but have you looked at the Gates carbon drive belts used on some bicycles?

    Finally, I don't recall mention of this either, but I believe there are cable drives that don't use any kind of toothed wheels at all, but simply wrap the cable around a drum for several turns. I could be wrong about that. But do a search for 'string bike', also 'cable drive mechanisms'.
     
  9. Will Gilmore
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    Will Gilmore Senior Member

  10. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    The other thing you will need is a tensioner, a freeing device, and an idler to take up slack. Think of this as two self tailing winches, one provides the tension to the other. But one of the winches is free spinning 3-4 times as fast as the driving winch.
    Edit to add, This is not unusual during the steam belt drive era of the late 19th century. I'll need to find it, but there are several books I've seen on mechanical mechanisms of the are that are quite ingenious, but not really useful for most things. We used a spring balanced foot lathe as the inspiration for SUBHUMAN III's "stair step" drive.
    Second edit...if it's mechanical and you think it's new, it most likely is not.
     
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  11. Sockmonkey
    Joined: Dec 2020
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    Sockmonkey Junior Member

    True, there are many types. I've snagged an engineering paper on plastics that covers the basics.
    A belt drive would be my second choice after a ball cable for a twisted drive setup.
    The zigzag channel itself is supposed to provide most of the securing friction. The cord doesn't have to be chemically bonded in there, just having something sticky in there is enough to be sure it doesn't slide.
    Hopefully.
    I've heard of the string bike. Thought about using a cord wrapping around a drum but rejected it because then the cord has to be able to "slide" down the length of it to prevent it from binding up. Also, I think it relies on the ratcheting action in the rear hub.
    Huh, I've heard of lignum vitae but I didn't know it was still used in industrial applications.
    Fun fact: It's tough enough to make bullets out of for killing vampires.
    Most of my research started here. 507 Mechanical Movements http://507movements.com/toc.html
    I did a quick model including all those things back in post #2097 on page 140. It was for a chain with bi-directional flexing but is fine for a ball cable too if twisting it 90 degrees is a problem.
    Sure, balls on a cord have been used for plenty of other stuff, just not this particular thing.
     
  12. Tiny Turnip
    Joined: Mar 2008
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    Tiny Turnip Senior Member

    Seems to me that the ball chain solution would be the easiest, and lowest friction, but is problematic because the maximum size of ball chain available is not strong enough. But... how about using conventional link chain, with the pulley wheels that are used in chain hoists to engage with the chain ?

    [​IMG]

    [​IMG]

    That sort of thing?
     
  13. Skyak
    Joined: Jul 2012
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    Skyak Senior Member

    I don't want to squelch any innovation, but the ideas in the last page or two look highly unlikely to be suitable due to friction and wear issues. For right angle bevel gears there are dirt cheap drill parts and (for higher quality) pneumatic tool spares. They are quite small but suitably strong. Will Fraser did a nice job characterizing them in his solar racer.
    For something new I am looking at reciprocating pedals with high strength cord to a rectifying clutch setup on the prop shaft. For clutches I am thinking of bike freewheel parts.
     
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  14. Sockmonkey
    Joined: Dec 2020
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    Location: Michigan

    Sockmonkey Junior Member

    Redid the design for the ball cable.
    This way you can pull it the cable tight through the zigzag channel when assembling it, and get the spacing just right without it wanting to pop out or force out the plug bit.
    [​IMG]
    The edges of the hole formed where the cable comes out on either side would be rounded off a tiny bit to prevent abrading the cable.
    Oh, if I'm not going into enough detail on anything, by all means ask me to elaborate.
     
    Last edited: Jan 25, 2021

  15. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Would there be a tendency for the Spheres to slide out of the sprocket pockets due to etching wear as layers of self lubrication are lost plus imprecise alignment due to stretching and torsion forces UNuniformly shortening or lengthening distance between spheres? Depending on how the Kevlar cable is constructed, be it twisted , braided, or somehow uniformly extruded it may age to having uneven stretching sections? How to increase the total sphere in pocket contact grip area to get a better grip equivalent to that possible by widening in the Gates sprockets and tooth belts? Using bigger spheres mean wider spacing needed between them, and smaller spheres have more of a tendency to hop or slide ? It may require building a prototype and load testing in order to see if some of these things could be issues?
     
    Last edited: Jan 26, 2021
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