Schematics for an easy frame-mount. Pls to be help.

Discussion in 'Frame Mounted Engines' started by itsrabid, May 16, 2008.

  1. itsrabid

    itsrabid New Member

    I've drawn up a basic design for a [hopefully] simple conversion. The idea is that instead of bothering with complicated gearing and sprockets, I will simply run the bike chain through the chain drive of a chainsaw. (removing that metal guide thing that gives the blade its shape) The saw would be bolted to the vertical support that the seat is mounted on, and a small gas tank would be strapped to the rear rack. Going to wire the saw's controls to the handlebars, so when a button is held down, the engine is put in gear, when I release it, it will disengage. This will allow me to keep the original brakes (ie: release button, THEN brake).

    Please excuse the messy handwriting!

    COmments, suggestions, and criticism welcome!

  2. Keep the pedals. And the gearing would be too high I think. You're gonna need a larger rear sprocket. If you drive the rear sprocket to your right,you can keep the pedals.
    You want the pedals to keep you within the laws of Motor assist bicycle.
    I like the utilizing the chain saw manual clutch idea.
    You should give your bike a LeatherFace theme!
  3. HoughMade

    HoughMade Guest

    Yep- a chainsaw bike can be done, but a chainsaw running at 8,00, or 10,000 or 12,000 rpm will have to be geared down for sure....way down.

    Even the happy times at a max of around 7,000 (give or take) and my Honda at 7,800 have to be geared down.

    Best of luck!
  4. itsrabid

    itsrabid New Member

    I could solve the gearing problem by getting an 18-speed and removing the front dérailleur....

    But having it go through the chainsaw would render the pedals useless anyway...
  5. HoughMade

    HoughMade Guest

    Nope. That won't do it. Run the math, do some searches on gear ratios. You'll see what I mean.
  6. kerf

    kerf Guest

    Chain saw could work but there are better engines for a bicycle. A 78 mm three shoe clutch would work much better than a stock saw clutch and you will need major gear reduction. At least 18 - 20 to one, even with a jack shaft that's gonna be rough without a very large wheel sprocket. That's the reason the bike engines use gear boxes for primary reduction.

    Ain't as easy as it looks.
  7. itsrabid

    itsrabid New Member

    But if a large sprocket is turning a small sprocket, that means more RPM, but NOT necessarily more torque. The speed would be lower when the thing actually has to MOVE something.
  8. HoughMade

    HoughMade Guest

    The small sprocket must turn a large one.

    Take my bike- the engine turns over 7000 rpm, buthere is a gearbox that reduces rpm and increases torque 3.7:1- even then, there is an output sprocket with 11 teeth and a wheel sprocket with 48 teeth to reduced rpm more and get enough torque.
  9. srdavo

    srdavo Active Member

    We've built a few chainsaw powered bikes. Trust me....chaindrive is not a simple process.
    check this post & pics of what we did to get the right gear reduction for our build.
    Yes...we did it the hard way:lol:....but we did it with parts on hand, so no out of pocket cash!!
    IMO, friction drive is much easier.
  10. BSA

    BSA Guest

    Or you could go for belt drive like a GEBE engine. You don't have to worry about having a gearbox then. Go for a toothed belt to prevent slip.