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

itsrabid

New Member
Joined
May 14, 2008
Messages
7
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!
 


L

Large Filipino

Guest
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!
 
H

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!
 

itsrabid

New Member
Joined
May 14, 2008
Messages
7
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...
 
H

HoughMade

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

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.
 

itsrabid

New Member
Joined
May 14, 2008
Messages
7
Hmm.
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.
 
H

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.
 

srdavo

Well-Known Member
Joined
Nov 4, 2006
Messages
3,161
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.
http://www.motoredbikes.com/showpost.php?p=78789&postcount=47
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.
 
B

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.

BSA
 
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