FWD 700c Road Bike w/ Chain Driven Freewheel

Discussion in 'Rack Mounted Engines' started by lowracer, Jul 11, 2014.

  1. lowracer

    lowracer Member

    I just got done with this bike project. This time I found a throw-away 700c road bike and decided to mount the engine to a front DIY rack using pieces and parts I had laying around. I didn't have to purchasing anything new for this project. Its got a 44T chainring mounted to a SickBikeParts freewheel allowing independent pedaling & motoring (or both at the same time). The pocket bike 5:1 tranny is driving a 12T sprocket. At this gear ratio it should do around 32-26 mph. I might even drop it to a 10T. I took it on its maiden voyage yesterday & aside from the gearbox needing some break-in (whining) it ran great. The Tanaka PF-4000 is a great little engine especially when the stock catalyst muffler can is replaced by an expansion chamber.
    Cheers,
    -Lowracer-
     

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  2. lowracer

    lowracer Member

    Here are a few detail pics of the 'in-front of the fork' mount and handlebar engine mount. The blue 'in-front of the fork mount' is actually a seatstay cut-off from a discarded Cannondale caad 3 frame. The engine mount is some 1/4" angle aluminum, 1/4" aluminum bar, 3/16" angle steel/bar & one muffler clamp.
    Accelerating from a dead stop while both motorizing & pedaling (in the highest gear) is quite brisk.
    -Low-
     

    Attached Files:

  3. Bonefish

    Bonefish Member

    How is the 44/12 combo working for you with the 5:1 pocket bike tranny? You happy with the ratio? I was considering doing the same with a rear axle mount using a dual threaded electric bike hub/wheel and converting it to gas.
     
  4. lowracer

    lowracer Member

    Bonefish,
    The ratio worked out well @ 12T/44T on a 27" wheel for the engine I am using (40cc Tanaka). I since have switched to a 10T to lower my top speed. On this no suspension bike, I really don't have the need for high speed. On your dual threaded hub, I'm assuming you are mounting to the left side of the bike with the engine hanging off to the left? If so, are there left handed threads? If not you may need to lock your left side drive freewheel onto the hub with green bearing lock-tite to prevent unthreading since it will be driving it counterclockwise.
    Cheers,
    -lowracer-
     
  5. darwin

    darwin Well-Known Member

    Low looks like you used some dimension edge parts on that build lol. What's up with that muffler? Looks like it just awoke from a mummy's grave. How do you like the 700 wheels? I like the ride they give better than the 26in wheels.
     
  6. lowracer

    lowracer Member

    Darwin,
    Thank for the encouragement (I think)...lol
    The muffler was a pocketbike expansion chamber prior to the embalming & mummification.
    The black 2" header wrap for $12 was a worthy investment considering the leg scar I received for free that I'm still hoping goes away (from a previous build pre-header wrap).
    -Low-
     
  7. lowracer

    lowracer Member

    The pocket bike 5:1 gearbox I had on here was a noisy little booger. I've had about 5 of these gearboxes but none noisy like this one. I lubed it and tried to give it chance to 'Break-in' but decided to remove it. I purchased a new one & received it yesterday. I installed it today after adding some very thin grease. I took it for a test drive & Ahhhhh..., nice & quiet now & a pleasure to ride. I also re-installed the engine shroud I had removed when installing the header pipe & expansion chamber.
    -Low-
     
  8. lowracer

    lowracer Member

    I've been asked many times if the handling is difficult having the extra weight up front & with the engine off center.
    The engine weight being mostly behind the front axle allows it to handle very well both on the gas and engine freewheeling.
    I compare it to when I was a paperboy with a large plastic milk crate hose clamped to a BMX handlebar loaded with newspapers out for delivery.
    The bike handled well. The extra weight on the front wheel actually balances out the weight on the bike & gives good higher speed stability.
    I don't think I've ever had to true a front wheel on any of my pedal only bikes over many years, just rear wheels...
    Here are some new pics.
    I still want to swap saddles to the leather spring loaded Gyes I've got on another bike.
    I may install a larger 53T front chainring (46T now).
    I enjoy pedaling and motoring at the same time.
    Bystanders realize you're pedaling a bicycle as you go flying by at 30+ mph.
    -Low-
     

    Attached Files:

    Last edited: Aug 3, 2014
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