Thinking of combining a chainsaw and bike

[Jstude]

Hi Folks, I thought I would take a break from tinkering with my usual stuff and tackle something that has been on my mind for years. I remember that when I was in Vietnam, and in other parts of Asia, there were tons of motorized bicycles. I see lots of store bought mopeds but don't think I have ever seen a motorized bicycle since then. I have several bicycles in my barn (some good quality and some not worth peddling). I also have a couple of old 2 cycle weed eaters, and chainsaws lying around. With gas like it is, the old creaky cogs in my mind got to spinning and now I want to cobble one of these engines on a bicycle. I'd love to see the expression on my poor wife's face when grandpa go whizzing by the window on a screaming smoky bike! Now I got on the computer and found that there is a whole world of interest and stuff going on regarding this subject. Right now I have removed the chainsaw bar and clutch cover from an old Homelite chainsaw. The first problem I have is the direction of shaft rotation for the orientation I would like to mount the motor and keep it relatively centered for weight distribution on the bike. If I used a friction drive, it probably would not be a problem. However, if I use a chain or belt drive, then I see a problem. Anyone have suggestions? I might be too old to learn, but I am not too old to listen.

 

[NunyaBidness]

nah never too old
welcome aboard
lots of folks have done what you're wanting to do, so while I'm sure the info is around, I have no idea where it is atm lol
someone will be around shortly to point you in the right direction I think

 

[SimpleSimon]

Homelite, eh? I will assume, that like every other chainsaw I've ever seen, the direction of crankshaft rotation (as you look at the exposed end of the shaft) is clockwise. Chainsaws rev pretty high to be in their power band, so using a small roller for a friction drive might work, but you are correct - the engine would be pretty far over to the left side. Might be possible to make a jackshaft arrangement, motor mounted above or ahead/behind the jackshaft, and roller below/behind it. Which would let you gear it to run a bigger roller, which means the roller lasts longer, you get better power transfer to the wheel, and best yet - the roller can be bearing supported at both ends.

Sort of like the sketches show, although they are obviously rough - You'd need to sort out sizes for your pulleys/sprockets to arrive at the final gear ratio you want. As shown, the base plate is 12" x 18".

 

[SimpleSimon]

Actually, looking again, depending on wheel size, roller diameter, engine rpm's, and output pulley/sprocket size, you can probably dispense with the jackshaft entirely.

 

[srdavo]

welcome to MBc.

have a look over here at some of our homebuilt contraptions
http://www.motoredbikes.com/showthread.php?t=4770

 

[Jstude]

homelite chainsaw bike

Thanks for all the suggestions folks. I have wandered around different threads in this forum and learned a lot. Of course, the more windows i open up with this old laptop, the more it reverts back to "hand crank" slow mode. It looks like with the direction of rotation and config of most chainsaw engines, friction drive is most practicle and potentially clean and simple. Some of the riggs i have seen make about as much sense as climbing over the roof of a two story house just to get to the back yard. So, now that I am thinking friction drive, the next step is figuring how to keep the clutch and add a roller.