Unique gearbox for weedeaters.

Discussion in 'Spare Parts, Tools & Product Developement' started by Garp, Aug 26, 2010.

  1. Garp

    Garp Member

    I recently posted details of my custom gearbox for weedeater type engines, I am quite proud of it. I got some great feedback and it started me thinking about building them from home to sell.
    would anyone be interested?
    It solves all your gearbox problems neatly, I couldn't break the prototype even though I tried, and it's easily adapted to a large variety of motors including electric.
    If you have any questions or suggestions put them here...
     

    Attached Files:

    Last edited: Aug 27, 2010

  2. SimpleSimon

    SimpleSimon Active Member

    Interesting. Give me some details please - gear ratios, final output gear size, suck as that.
     
  3. Garp

    Garp Member

    It is synched to the pedal speed so when you pedal flat out the motor will be at full revs.
    The front sprocket is driven so the gearing is determined by what is behind it.
    This one has a 100/1 reduction between the clutch and the crank. Power goes to a seven speed shimano, which has been excellent.
    It only has one chain and no extra levers, just a throttle. It's slim too, I only had to extend the pedal shaft a small distance to clear the motor. I don't even notice it till I ride my Giant.
    Check my other posts to see it going.
     
    Last edited: Aug 27, 2010
  4. loquin

    loquin Active Member

    Worm drive gearbox?

    Is there a freewheel on the peddles, so that you don't have to peddle when the engine is running?
     
  5. Garp

    Garp Member

    Yes it freewheels. Everything works fine.
     
  6. GearNut

    GearNut Active Member

    So it's a dual output, single speed industrial reduction box, most likely originally set up for an electric motor such as a 1hp? (I can't figure out how that would allow the left pedal to stay in synch with the right pedal and still freewheel though.)
     
  7. Garp

    Garp Member

    Magic, lol.
    You'll work it out, I did and I'm a plasterer.
     
  8. GearNut

    GearNut Active Member

    Ooooh! I get it now!
    I need to get plastered before I ponder the inner workings. :D (A corny joke, don't take it wrong.)

    Hmmmmm.......
    Freewheeling crank arms, sorta like what is on a shifter kit, on both sides would never stay in synch, but a jackshaft ran through the gearbox and geared internally somehow...... hmmmmmm....
     
  9. Garp

    Garp Member

    That could work!
     
  10. V 35

    V 35 Member

    I give credit to anyone who can supply power directly to the sprocket, and not use a Rag Joint. Safe Bikes are important. Your pictures don't show enough. I'd like to
    see an uninstalled one, and installed one, and a price / shipping cost ?

    Good luck, you seem on right track . I also must ask, can the deraileur take the
    torque of an Engine ? Extra, clutch side kill button, might make sense, kill mag,
    shift, release button.
     
  11. 5-7HEAVEN

    5-7HEAVEN Guest

    An new SRAM S7 derailleur can withstand full powershifts from a 2.8hp Tanaka 47R engine.

    Ask me how I know.:jester:
     
  12. 5-7HEAVEN

    5-7HEAVEN Guest

    I'm interested. Then I can move my engine off my lap, then lower into the frame.:jester:
     
  13. SimpleSimon

    SimpleSimon Active Member

    I've read that question, in diverse forms, so many times I am really tired of it.

    There is not a small engine made anywhere that can generate the torque levels produced by a 200 pound human standing on a pedal at the end of a 6 inch lever arm. Dérailleurs are designed to handle enormous per square inch loads on all components. Torque is NOT an issue - vibration can be.
     
    Last edited by a moderator: Dec 18, 2015
  14. GearNut

    GearNut Active Member

    Derailleurs never see any torque transfer anyways, unless you are pedaling backwards or trying to bump start an engine through one (don't bump start an engine through one, you will most likely ruin it). While propelling the bicycle forward the torque load is applied to the top run of the chain only. The bottom run is just the chain following through in a full circle.
     
  15. Garp

    Garp Member

    I have some other posts on this site you can check.
    As far as cost, I don't know. This is a one off built at exorbitant expense and uncounted hours.
    I used mostly off the shelf parts and designed it to be easy to manufacture, but the next one will be a prototype too.
    How much do you want one?? Seriously, if enough people were interested I'd love to take this project further.
    I did use it initially with a derailleur, it worked fine but I'm not a fan of external mechanisms.
    I didn't bother putting a killswitch on it but I do have one.

    "kill mag,
    shift, release button"
    I'm not sure what you mean here.
    I am using a gx31 which probably gives me about 700 watts at the rear wheel so it's not legal on the road in Oz. I use it in the mountains anyway.
    Thank you for your encouragement.
     
    Last edited: Sep 2, 2010
  16. V 35

    V 35 Member

    I was assuming, we were talking Gas Engines, my thoughts were to kill Magneto
    by pressing kill button, shift, release kill button, to allow Mag to fire, and resume
    power I think an Electric Bike is a different deal, electric motors make max
    torque at 0 RPM, minimizing need for gearing. The Electric Motor built in wheel
    solves all but battery mount issues, sure looks cool.
     
  17. Garp

    Garp Member

    I think I understand, you mean like an air shifter on a drag bike to cut power briefly as it shifts gear. No need, these boxes shift under power.
    Hub motors are unsprung weight, that's the main issue. I also feel an electric motor would be better with gears. I could be wrong, We'll see...
     
  18. ducatiluke

    ducatiluke New Member

    love your bike is it a worm drive ?
     
  19. Garp

    Garp Member

    Thank's a lot.
    Yes, partially.
     
  20. happycheapskate

    happycheapskate Active Member

    I have no idea what you did there but it looks awesome. That is serious style.

    I am a fan of the practical and reproduceable. I think you are really onto something.
     
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