Pedal Powered Boats

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

  1. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Your reply suggests the greater problem at hand.
    You make many bold claims, yet provide no supporting evidence.

    It is YOUR claim, no one else's. Thus unless YOU are able to support YOUR claim with evidence - it shall be treated like all the other harebrained ideas and solutions and holy grails by endless Posters/dreamers that have come before you and shall after you.

    No engineer/scientist would reply in such a manner....
     
  2. W9GFO
    Joined: Dec 2014
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    W9GFO Senior Member

    Reference to this study? I suspect that the 67% number is misleading. Hard for me to believe that cyclists are wasting 33% of their available energy in that manner. If that number is your basis for thinking that you have a superior idea then I would strongly suggest you look further into the efficiency of pedaling.

    They use this method because it has been proven to be very efficient. Other methods have been tried but they all come up short.
     
  3. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    QED :(

    I rest my case...not a single piece of evidence to support YOUR claim....utter nonsense and a waste of bandwidth.
     
  4. W9GFO
    Joined: Dec 2014
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    W9GFO Senior Member

    I have given you the opportunity to discuss one of these asserted flaws, instead you are arguing with another member.
    I am not in agreement with you, is that why you did not respond?
    What was your role, how did you contribute to these patents and what are the patent numbers? I would like to look them up. Are they at all related to human power propulsion? If not then they do nothing to increase your standing with regards to human powered boat design.
     
  5. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Haggsway,

    People are trying to find information to have a conversation.
    There can be no conversation and no "working out disagreements" unless we can see what you are talking about.
    I think this is "Reddit" style BS from a 10 year old.
     
  6. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    I never suggested I have any miracles or secrets.

    That's your claim.

    I hoped you would reply to my comments and show some details.

    You didn't which has led to this being a total waste of time.

    Finished

    PS: anyone on a forum is a party to the conversation. What kind of idiot thinks they can exclude anyone who wants to comment?
     
  7. DHaggsway

    DHaggsway Previous Member

    Do you really think that name calling is productive? Do you think that when I said that you were an observer, that it indicated that I didn’t know that the text was viewable by all? You could give me an answer to these questions.
     
  8. Boat Design Net Moderator
    Joined: Feb 2010
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    Boat Design Net Moderator Moderator

    I don't think it will work very well to discuss how a secret compares to existing designs in this forum thread.
    It would work better to continue the discussion of your project in the existing thread and then maybe come back to this thread when you have design elements to discuss which are not secret. Look forward to seeing what you are working on when you can reveal it. Until then, please continue the discussion of your project in that thread. Thanks.
     
    kerosene and BlueBell like this.
  9. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    That one is just as useless as this one.

    In answer to the questions above.
    1. I'll resort to anything finally to try to get a factual discussion.
    2. You said I was not a part of the conversation - that is wishful thinking on a public forum. Your total of 14 posts seemed to indicate with your statements that you did not understand.
    3. If I had a valuable secret, I would not mention it on a public forum in an attempt to get other peoples good ideas you could improve your secret with.

    Ideas are dime a dozen - what counts is producing something.
    I'll be waiting until you publish, since it is faintly possible I'll have to apologize. Not holding my breath.

    If you really wanted to have a conversation - you could send me a PM.
     
  10. W9GFO
    Joined: Dec 2014
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    W9GFO Senior Member

    In an attempt to compensate for recent bloviating I offer some actual content for discussion.

    I have been working on two pedal powered boats recently - sort of. I have two hulls, they each started as a 20' temporary catamaran that we built over three days for Edensaw's wooden boat challenge at the Wooden Boat Festival in Port Townsend. The intention from the beginning was to use these hulls to build two pedal boats similar to what Rick W. has designed. We took second place, I used the prize money to buy a drum sander.

    For the first hull, which will be the solo pedal boat, I cut about three inches off the top so that it would end up with about 3" of freeboard. The second hull (the red one) I cut in half and inserted a five foot section to stretch it to 25 ft. Other than working on the hulls, most work has been on the pedal drive for the solo boat. Since I am deviating somewhat from the standard way of doing things I want to use the solo boat to test my ideas before committing to building two more pedal drives.

    [​IMG]

    The most obvious thing I am doing differently is I am using a very large diameter pulley on the crank with a belt. Here is my reasoning;
    1. Belts are maintenance free and quiet. Being quiet is important to me, which is why I have also taken steps to isolate the gearbox from the hull.
    2. The action of the belt bending around the pulley takes energy, the less severely it has to bend, the less energy wasted.
    3. A larger pulley reduces the likelihood of the belt skipping - more teeth engaged, which enables a lower belt tension - which wastes less energy.
    4. A large pulley significantly reduces the forces the belt has to carry, allowing a much thinner belt which further reduces the bending losses. I currently have a 15mm belt installed, I also have a 9mm belt which is what I hope to use.
    The single biggest challenge with using such a large diameter pulley is that they are not available, you must make them yourself. I used Fusion 360 to create the pulley. After several iterations I ended up completely defining the tooth profile so that I can now easily make a pulley with any number of teeth. The Pulley itself is 3d printed on a large format 3d printer. Many test prints were required to dial in the precise size to that the belt would mesh properly, a fraction of a millimeter change in diameter makes a big difference.

    Another challenge was how to keep the belt on the large pulley. Adding a flange for the belt to rub against doesn't work so well on such large diameters unless the flange is quite tall, and rubbing would be another energy loss. The solution was to put a slight crown on the pulley like you would find on bandsaw wheels. This has been working very well.

    As it is now the belt drive is at a 7.5:1 reduction, I think too much. It is a 240 tooth main gear and 32 tooth on the gearbox. I also have a 36 tooth to use which will give a 6.67:1 ratio.

    I think this is enough for one post. Other changes include gearbox mount and vibration isolation, method of attaching the flexible shaft to the gearbox, retractable drum rudder and propeller support strut.
     
  11. upchurchmr
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    upchurchmr Senior Member

    Looks like an interesting project.
    Just remember that although you spread the force out over more teeth on the biggest pulley, the small pulley has very few teeth to spread the load.
    Its really not all that bad of an issue, since belts stretch.
    You are probably only getting drive force in the first 3-5 teeth of engagement. The rest of the belt teeth will be in loose contact.
    When you drive the cranks, you will probably see the return leg of the belt be loose. Showing a curve where the other side will be absolutely straight.
    Is the final drive to the drive shaft a right angle gearbox?

    Thanks for the details to talk about.
    And I promise, I personally will not steal anything off your work.
    But I'd like to hear how the whole project works out.
     
  12. W9GFO
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    W9GFO Senior Member

    Right, that is the primary reason for the very large pulley - to allow a larger sized pulley on the gearbox.

    Yes the return side of the belt is slack. I expect that I will need to install a nip roller (only contacts the belt if it lifts away from the pulley) to keep from jumping teeth on the gearbox pulley when pedaling hard, but I will wait and see if it is truly necessary before putting one on.


    [​IMG]

    The final drive is a Mitrpak 1:1 right angle gearbox filled with 00 weight grease, with a shaft extension.

    The gearbox extension is a length of aluminum tube with a bearing in the end welded onto a flange for bolting to the gearbox. Around that tube is another tube which is bonded using 5200. The mounting bracket clamps onto this tube to secure the gearbox. The idea here was to isolate the gearbox and provide some noise damping. It has the added benefit, being a tube, that the clamping mount allows the gearbox to be infinitely adjusted so that the output can be easily adjusted to the proper angle for the flex shaft.

    As an afterthought I decided to mount the gearbox assembly to the hull using rubber anti vibration mounts. While the 5200 does offer a slight bit of noise reduction it was nothing compared to what the rubber vibration mounts provide. For the next one I make I won't bother with the tube within a tube idea and instead use only the rubber mounts. Another necessary change is that the mount needs to have a much wider stance due to the flexing of the rubber mounts. Tension on the belt causes the gearbox assembly to tilt. It is workable as-is but I intend to change it so that at least one mount point is on the other (port) side of the hull.
     
  13. kerosene
    Joined: Jul 2006
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    kerosene Senior Member

    Copying here from “the other” thread. Not sure the problem of oscillating force and rpm is an issue on pedal boats but just a mental exercise. Might be of interest here.

    Here pictured the moment when the muscles provide the peak torque to the crank. Elliptical gear accelerates the flywheel even if the crank (and power output) axle is rotating at steady rpm. This acceleration of the flywheel puts an additional resistance, lets call it negative torque to the crank.
    When the axles turn 90 degrees the force from pedals dips to it’s minimum. Yet the flywheel tries to maintain steady speed and provides positive, assistive, torque to the crank.

    Essentially you store peak torque and release it 90 degrees later.

    This should even out the bursts of force much better than a simple flywheel. And in case of pedal boat steady the prop rpm. Naturally the ratios would need be optimized.
     

    Attached Files:

  14. W9GFO
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    W9GFO Senior Member

    That reminds be of the biopace chainrings, they were popular for a while but now no one uses them. I remember reading the reasons why they (and other elliptical chainrings) fell out of favor but I cannot recall what those reasons were.

    If the two elliptical gears were sized so that the torque would be more even, then the power portion of the stroke would be substantially slower than the "coast" part of the stroke. That might be hard getting used to.

    There will be added losses via the meshing of the elliptical gears along with additional losses in the extra set of bearings required to support the additional axle. My gut feeling is that whatever efficiency is lost due to the pulsing power, it would be measured in the low single digits. The added losses via the extra moving parts would likely make the efficiency gain a wash. However, in an application where there is a low cadence and low ratio between pedals and prop (maybe paddlewheel) I can imagine that the gains could outweigh the added losses.

    I would like to try adding a small flywheel on the output side of the gearbox as an experiment. It would be interesting so see if it has any impact on efficiency. That won't happen for quite a while though.
     

  15. kerosene
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    kerosene Senior Member

    Of course practical solution might make no sense due to gearing effuciency.
    But the rpm shoukd be more even than currently. A little more resistance during power stroke to carry over the coasting.

    I remember the elliptical bike sprockets. But I think those had different goal. They actually added to the oscillation but optimized the moment of best mechanical advantage.
     
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