Transmission Question and Solution

Discussion in 'Frame Mounted Engines' started by Mike S, Sep 18, 2008.

  1. Mike S

    Mike S Member

    So I built a MB with the Grubee engine kit. It operates as intended but the take power is a little low, without a transmission. Does anyone know of a trans that could be added or used on a new build other than an expensive
    Nuvinci hub trans? I am starting to believe that using a kit like the Grubee without a trans or electrical system is not a good solution, when a Lifan 50 cc engine is available with full trans and electrical for $320. The Lifan engine seems to solve all the problems at a reasonable price. Any comments?

  2. Ghost0

    Ghost0 Guest

    Looks interesting but a couple of observations, adding 42 pounds to a bike frame may present a problem along with the width of the engine may not allow for pedaling. If these hurdles can be overcome it may be feasible.
  3. s_beaudry

    s_beaudry Member

    Lifan engines are very good and quite reliable...

    The weight and size issue are going to be a problem, you may wind up doing more work and spending more money trying to get it to fit correctly.
  4. Mike S

    Mike S Member

    Of course some problems would have to be worked out: Maybe the bike shouldn't have pedals. The Whizzer ambassador doesn't. Select a strong frame, wheel with 12 guage spokes, a good tire and that's leads to a solution. It would be less complicated and less cost than trying to put a trans on a lawn mower engine. I'm tempted to try it over the winter.
  5. hill climber

    hill climber Member

    i been thinking about a pocket bike engine with a cvt trans to a chain drive. ive seen some cvt trans with a ratio of 1:1 to 3:1 . take off tourque and top speed directdrive. HEY!! DO A WHEELIE! hill climber
  6. duivendyk

    duivendyk Guest

    It takes a 15 to 25 reduction between the engine (crank shaft) and the driven wheel to get the right gearing (26" wheel),which implies another reduction of about 10 to 1,this is not easy to come by with a single reduction.The relationship between engine rpm,overall reduction and road speed is the following:
    S= 0.075*rpm/R, R is the overall reduction.For instance R=17,
    rpm=5000, S= 0.075* 5000/17 or S=22mph . R=17 is based on an average CVT reduction of 1.7 and a further reduction of 10 in the drive train.So the speed could vary between 37.5 and 12.5 mph at 5000 rpm.
  7. hill climber

    hill climber Member

    duivendyk, the cvt i saw has a gear reduction also not just the cvt. wish i could remember were i saw it. search pocket bike cvt.
  8. duivendyk

    duivendyk Guest

    Seems likely that there is internal gearing,from the crank to a centrifugal clutch ?.If you knew the wheel size of these pocket bikes you could make an intelligent guess.Most likely 3-4 to 1, with another similar reduction in the chaindrive, and you are in the ball park.