Where to start on a pedal powered boat?

Discussion in 'Boat Design' started by ryan808, Aug 4, 2008.

  1. Guest625101138

    Guest625101138 Previous Member

    If they were doing mid 40mph the wind was not a "problem". It would be needing to blow a gale in their direction of travel - termed assistance; not a problem.

    Rick W.
     
  2. BHOFM
    Joined: Jun 2008
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    BHOFM Senior Member

    It was on a narrow river and there was a cross wind!

    I wish I had the pictures, all my photos and negs and
    trophy's were stolen during a move. long story,,!

    The fellow that built it lived in St. Louis and worked for
    NASA. They used the boat to test drive units for a Mars
    Rover, a people powered rover!

    It seems the thing weighed 75lbs, but not sure about that,
    I know two people carried it with one hand each!

    It was a canoe hull with two wide out riggers on the back
    and two narrow one on the front, they were lowered in
    the water once it got away from shore and then it would
    raise the hull out of the water when it got up some speed.
    Then it really started to move! They said once you got up
    on the foils it didn't take much to keep it going!
     
  3. Guest625101138

    Guest625101138 Previous Member

    No doubting the statements above but 50mph on water with human power in anything other than a howling gale is nonsense. The fastest human powered hydrofoil 1-up did 21mph. Even then it was one way with slight wind assistance.

    A young fellow started this thread seeking good advice and ideas not to be given silly information.

    Rick W.

    Rick W.
     
  4. BHOFM
    Joined: Jun 2008
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    BHOFM Senior Member

    There may have been some current in the river, all I know
    is what the announcer was saying! I remember them talking
    about the Kitchenaid parts in it and later he needed some
    waterproof grease and I had some with me, I was running
    some of my RC boats!

    It was a fund raising thing for Special Olympics! They had
    a cardboard boat race and a contraption race, land and
    water!

    I was just trying to convey that there are all kinds of things
    we can use out there, we just need to look!
     
  5. alexlebrit
    Joined: Aug 2006
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    alexlebrit Senior Member

    Another thought for right-angle drives, which might be a bit more soild than the drill attachment above is to look at angle grinders. I'm not saying they're going to last forever, but they're more solidly built than the drill chuck.
     
  6. ryan808
    Joined: Aug 2008
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    ryan808 Junior Member

    Would a 16x16 APC prop work well in a ninety degree gear system? What about in a compact twisted chain HPB drive system? As I look into making a more efficient boat, it is clear that I need to rethink the overall design of it, not just the propulsion. Up until now, the planned design of the boat was to create a doubled hulled paddled/ propeller powered class 1/2 sea-worthy mode of transport between islets off the beach, rivers, etc. I realize that there is too much drag and weight for the propeller to even be effective. The layout was basically wood crates and plywood hull with plastic drums and b-boards with a centrally mounted bike with propeller. Any ideas for making the boat using these supplies plus or minus?
     
  7. Guest625101138

    Guest625101138 Previous Member

    A 16X16 APC prop will work OK.

    You can make a nice simple hull from ply that will work well.

    The Sears gearbox might last 5 miniutes if you use it carefully. I have seen many people try these boxes, including me, and they can give you a few minutes of fun. Other than that they are a waste of money. A decent right angle drive is a good investment. If you cannot afford the 200+ dollars to get one new have a look on Ebay. I know a fellow who got three nice little boxes for USD100.

    Twisted chain drives can be made to work but not easy to do with bicycle stuff. It is not the best way to use chain. There is also a lot of set up involved to get the leads to the sprockets right.

    If you have a gearbox, you can use a cutdown bicycle frame with the bottom bracket upwards as the crank support. Just need a plate welded or bolted on to carry the gearbox. The gearboxes have numerous mounting points; unlike the Sears drill stuff.

    The best boat for going places will be a long slender hull with stabilisers that looks something like this boat:
    http://www.boatdesign.net/forums/attachment.php?attachmentid=24110&d=1218255936

    You need to do some planning and have an idea of what you can spend on the project. You can waste of lot of time, effort and money for the sake of planning what you really need, to achieve what you aim for.

    Rick W
     
  8. ryan808
    Joined: Aug 2008
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    ryan808 Junior Member

    Dear Rick W,
    thanks for the reply! Whew, saved me some bucks on the Sears gear box cuz I need something that would work more than a couple of minutes. I redesigning the entire boat. I can't be thankful enough for your help!
    ryan
     
  9. grob
    Joined: Oct 2002
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    Location: Cotswolds Waterpark, UK

    grob www.windknife.com

    Rick,

    Do you have any experience of the tourque rating required for the right angle drive?

    Gareth
     
  10. Guest625101138

    Guest625101138 Previous Member

    Gareth

    The Mitrpak 1/2" box is close to perfect for typical application:
    http://www.mitrpak.com/product_datasheet.php?product_id=34
    With 4:1 step up from a crank they spin at say 300rpm for aggressive cruising. Their continuous rating for this condition is 0.25HP (190W). This is in the very well trained category for cyclist. The box has about 10X overload on torque so very hard to damage using a prop.

    These boxes have stainless shafts and weigh just 3lbs.

    The one major problem with them is that they are not shipped to Australia so I use something else that is slightly poorer value.

    Mitrpak have been sponsoring Greg K and he has not had any problem with the boxes in regular use. Probably done well over 1000km on two boxes now in different applications. He removed the seals on the one he has on CP2 to reduce drag. Saved about 3W. I just wear mine in as they eventually free up but it takes many hours of use.

    Mitrpak are building Greg a two box set up for the Ocean boat using a 3/4" box for pedals and the 1/2" box for the prop. They will be shaft connected with 1:2 step up in each box to give 1:4 overall. These would make a very good cruising leg if they were put into production but they would not be cheap.

    Rick
     
  11. Village_Idiot
    Joined: Oct 2007
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    Location: USA

    Village_Idiot Senior Member

    Conventional wisdom is that direct drives (chain, belt) are more efficient than, say, a beveled 90-degree shaft drive. From motorcycle drive data, it seems chain/belt drives are typically 7-15% more efficient than shaft drives.

    Has anyone considered twisted belt drive? Has a few advantages over twisted chain drive, components should be relatively light. Any slippage should be easily controlled with an adjustable idler pulley. See a lot of twisted belt drives on old farm machinery...
     
  12. Guest625101138

    Guest625101138 Previous Member

    Have done measurement on twisted chain versus high quality bevel drive. A standard bike chain is 97% when twisted. A new gearbox is 95% and gets better as the seals wear in. If you remove the seals it is better than the chain at 97% including the straight chain reduction. So as the box wears in it gets similar efficiency and does not jump off or wear out prematurely. Neither case measured losses in the crank bearings but these would be less than 1%.

    The Nauticraft uses a twisted toothed belt and it is a commercial product regarded as durable:
    http://www.nauticraft.com/propulsion.htm
    So not only considered, it is in use. Do not know the efficiency but unlikely to be better than the precision spiral bevel box.

    Rick W
     
  13. Village_Idiot
    Joined: Oct 2007
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    Village_Idiot Senior Member

    Good to know that it is being considered. Those Nauticraft don't appear to be built for speed. It would be interesting to compare belt drive to bevel drive on similar craft.

    I rather like the idea of using discrete (non-continuous) belts, or ropes even, that are attached between pedals with linear travel (like a stair-stepper) and the driven assembly. The belt, or rope, is wrapped around the assembly (we'll use a paddlewheel for simplicity sake). The axle of the assembly contains a ratchet mechanism and may even be spring-loaded. Each push of a pedal may turn the wheel 1/4-rotation or so, depending on design. The design could incorporate either a fully-turning paddlewheel or even just a part of the wheel where the wheel would spring back to its original position with collapsing paddles (although engineering for reverse would get interesting). Granted, it probably wouldn't be fast, but would be extremely simple and robust, and probably easier on the legs and joints.
     
  14. clmanges
    Joined: Jul 2008
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    clmanges Senior Member

    Hey, V.I.,
    Not to be harsh, but that sounds a lot more complex than a simple direct chain or belt drive. If you want a different pedal motion than circular, there are much simpler ways to do it than with ratchets or freewheels or some other one-way clutch. Just run rods or maybe even cables from the pedal levers directly to a crankshaft.

    Any time I try to design something, I quickly get into a battle with complexity. It just seems way too easy to get off on some tangent of Dr. Suess / Rube Goldberg stuff. You're likely having the same problem; from what I've seen, it's pretty common.
    Fight it. Count the moving parts in your design, and try to eliminate as many as possible. Each one costs you, in manufacturing expense, cockpit clutter, extra framing/mounting parts and stresses, friction, wear, maintenance, weight, and possible failure.

    Curtis
     

  15. Guest625101138

    Guest625101138 Previous Member

    Here is an outboard drive using a ratchet system:
    http://www.boatdesign.net/forums/attachment.php?attachmentid=23596&d=1216703448
    This is very efficient if it uses roller clutches and propeller. I expect it to be the cheapest system that can be built but there is a good degree of engineering involved.

    Rick W.
     
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