Pedal boat drives, talk about yours

Discussion in 'Boat Design' started by MarkX, Mar 27, 2010.

  1. MarkX
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    MarkX Junior Member

    Following on from my thoughts about building a pedal fishing Kayak/boat/canoe I am now thinking about drives. Having established that a good starting prop is an APC 16"x16" model plane prop geared at 6-1 my fave plan is to try flexible stainless wire rope drive (7x19), about 1.5 to 2mm onto pulleys. This would be an extremely cheap and versatile method if it works because cable pulleys are easy to make, low loss and the cable can be routed at will between prop and pedals. Plus the cable is cheap and you can make it any length you want.

    This is presuming I can make it so it doesn't slip, which means urethane covered pulleys (thinking skateboard wheel turned down to 40mm on propshaft and airhose cut in half, stuck+pinned around pedal pulley). I may wind the wire more than once at least around the prop pulley.
    The compromise of the prop pulley is between small diameter for streamlining and extra radius for minimum bending (longevity of cable) and grip of the cable. I'm aiming at 40mm prop and 240mm pedal pulley sizes.

    The continuous cable loop:
    Rather than joining the cable with horrid crimps to make a loop, I will be making a continuous ring by unravelling one long strand of cable and re-winding it back into a 7-strand loop, hiding the ends in the middle, hooked around each other.

    I haven't made this yet, so we'll see how it turns out but meanwhile do talk about your own drives and make suggestions for others who are investigating DIY pedal drives in future.
    PLEASE STAY ON TOPIC !!! Or the thread will be too bloated to read.
     
  2. Squidly-Diddly
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    Squidly-Diddly Senior Member

    This MIGHT be on or off topic, but how about a 'fish tail' instead of prop?

    How about just attaching a semi-flexible extension, possibly cut from a scuba-flipper, to a typical kayak rudder.

    All kayak rudders I've seen only need a couple inches of heel-to-toe movement, and the cables wouldn't be up to propulsion duty, so longer low friction "sliders"(possibly running on little wheels/tracts taken from sliding rowing seat) would be needed to give legs enough room to work, and the ratio would need to be changed by adding an extension on top of the rudder(so instead of 5" between the cable connections at the rudder you might have 16", so 6" of stoke at the foot-rests would give 45' rotation of the flipper).

    This might work better with long slender flipper maybe 3 feet long by 6" tall, and placed with the top about 6" below the water's surface.

    I'm thinking of this set-up on a SOT such as Ocean Prowler.

    Instead of cables it might be better to use solid connecting rods, or a combination of rod and cables. Mounted either inside or outside the hull.

    One advantage of this set up would be both rudder and power control strictly with the feet, leaving hands completely free for fighting fish.
     
  3. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    I'm gonna start building a small pedal boat, when the snow desides to melt. I'm gonna use a tunnel for the prop, so I have a straight 15 mm shaft connected to an angle gear with 2:1 to 5:1 ratio. The gear is driven by bicycle chain, standard mountain bike cranks. Overall gearing is 1:10, around 600 rpm on the prop.

    Rick W did the math for the prop, 8x9''. It'll be placed 2/3 of diameter inside the tunnel.
     
    Last edited: Mar 27, 2010
  4. portacruise
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    portacruise Senior Member

    What system will be used for keeping proper tension on your cable? Seems like over tension means more friction losses plus unpredictable cable sheath deformation and failure exposing the SS cable underneath. My experience with chain and toothed belt systems would seem to favor minimum tension- just enough to prevent slippage. A spring loaded idler positioned in just the right place allowed for changes in temperature and moisture with some of my systems, and may work for cable?

    Porta
     
  5. MarkX
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    MarkX Junior Member

    I expect to have a sprung idler pulley like you say plus the prop part will be lowered below the keel though a small rectangular box. The further down it's pushed, the more tension there will be in the cable. I don't know how many turns I will need to put over the prop pulley as I've only just started making the drive. I have some polyurethane coming next week that will hopefully do the job.

    I don't think cable has been used before but if it works, it should make it easier for other builders. It might also be possible to use more than one cable.

    Squiddly Diddly, sounds like a plan. The fin thing needs testing to get the motion right, it could also flap up and down rather than side to side.
    I won't be trying it though because there are some big shark where I will be using it so I want to look and sound as different to a fish as possible.
     
  6. unclenos
    Joined: Mar 2010
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    unclenos New Member

    Dear Friends,
    I'm new to this pedal boat's world and don't even have one finished yet. Hope someone can share their idea here.
    I have bought 3 APC nylon propeller 15 x 12, 16 x 14 and still waiting for my last ordered 16 x 16.
    A few months ago I decided to built an upright pedal powered catamaran with fiberglass hull, almost 50% done. After I go through this forum and Greg K's record attempt, now I have changed my mind to build single hull with outriggers similar to Rick Willoughby and Greg K. but my plan is more like 3 piece kayak for purpose of portability. Each section of the main hull is about 6 feet long (total 18 feet). The widest mid section is 13.5 inches wide and 12 inches high, combination of U shape(in the middle) and V shape(on the front and back). I will use quick release skewers to attach all the sections together. I have no idea how much will the hull weight soon. I'm 5'8" tall and my body weight is 60kg.
    I've bought 2 gear box from eBay, one is Mitrpak 1:2, another one is Boston 1:1. Usually on road and mountain bike my cadence choice was 90 rpm, I've never try a recumbent bike before. So I don't know what is my best cadence on that machine.
    I'm using s/steel and aluminum tubing for the drive train and seat frame.
    Can you please suggest to me what is the best gearing combination to begin, which prop to use, and details about the outriggers.
     
  7. MarkX
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    MarkX Junior Member

  8. Guest625101138

    Guest625101138 Previous Member

    It has been used before.

    Attached shows one variant. There are a few others. All variants have certain problems and certain features. The variant in the photograph is reasonable.

    Rick W
     

    Attached Files:

  9. MarkX
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    MarkX Junior Member

    Looks big and draggy but usable! This is a linear push-push pedal setup using one-way sprag bearings, right?

    Being Kayak-size I was thinking of doing linear so that the feet don't have to be raised so high, but it's rotary for now.

    I am doing it so that I can still change to other pulleys on the propshaft if the cable doesn't work.
     
  10. Guest625101138

    Guest625101138 Previous Member

    It is not big and draggy. The drums are 1" in diameter and get covered with a fairing and the leg turns as a rudder.

    I used a similar system with 3" drums in my V12 boat. The drums were inside and the shaft went through the hull.

    Rick W
     

    Attached Files:

  11. MarkX
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    MarkX Junior Member

    Ah, sorry! I couldn't get an idea of the scale! What diameter is the cable?


    Now also thinking of a potential plan-B. I saw someone mention angle grinder bevel gears somewhere and that they were too small/weak, well the chunky 9" /225mm angle grinders are bigger. I should think that salvaged gears from them are hefty enough to cope. I have used one and they can handle with stopping a 2kw motor dead repeatedly. I think the ratio is around 2.66 to 4 -1.
    The idea is to mount it at the prophaft with a sprocket fixed to the big gear and then run a chain straight up to the crankset.
     
  12. Guest625101138

    Guest625101138 Previous Member

    1/16"

    The gears from a large grinder are suitable for pedals connected to the large gear. The one I have is 1:3.3. These were made in India by Involute for George Tatum. I57 is currently using one. He has pictures on the Pedal Boat thread.

    Rick W
     
  13. MarkX
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    MarkX Junior Member

    Here are some pics of angle grinder gears made by chinese firms, it's possible to tell the ratios by counting and in some cases they even give the model of grinder it's made for:
    http://www.alibaba.com/showroom/angle_grinder_gear.html

    They look the cheapest option for anyone who wants to make drives commercially.

    They also look thin enough to be mounted to drive the propshaft and a sprocket fixed to them with the chain going up direct to the crankset chainring. I think it would be difficult to make a more efficient drive.
     
  14. Guest625101138

    Guest625101138 Previous Member

    A pinion about 20+mm in diameter made from high grade hardened steel will be suitable to drive the prop. The main gear is connected directly to the crank. There is no need for a chain.

    Making the box is not trivial but also not impossible if you have a good workshop.

    A box with cranks driving a curved shaft is the best set up providing you use a folding prop that ditches crap when you stop pedaling.

    I used a standard DZ 1:2 "T" box on the V10 boat. It was really smooth. It is much nicer feel than a chain.

    I bought an Involute box but have never set it up. It is a bit heavier than I would like for a cruising boat but perfect for a sprint boat. It will take huge loads as you can see in the drag race photo. Those guys got to 18kph in hulls that were not the best and had very large appendages for dynamic stability. They would have been peaking at over 1kW.

    The gears would be OK with regular grease if you did not want to go to the effort of a fully enclosed box. One guy has drilled holes in the casing of an Involute box to get it lighter.

    Rick W
     

    Attached Files:


  15. Guest625101138

    Guest625101138 Previous Member

    This has been done roughly as you describe:
    http://www.tailboats.com/propulsion_technology.html

    There are some videos on the site. The problems become somewhat apparent. It is not very efficient due to the yaw of the boat. The fact that the foil ventilates is also a serious drawback.

    The Hobie flappers are the best variant of oscillating foils I have seen.

    I made an oscillating foil that was very simple with a single large rigid foil and this worked efficiently to the point of the boat oscillating up and down - about 8kph. It is a simple way to drive a heavy boat that has low resonant frequency. It is the simplest drive system to make with basic tools and no expensive parts. My best blade was 1m wide and 120 chord. It work at cadence. The stroke was 600mm.

    The Hobie flappers overcome the oscillation problem because there are two smaller blades that work in opposing motion for most of their travel - at least in the high thrust part of the stroke.

    Rick W
     

    Attached Files:

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