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Do you need help with the math to the back wheel, or how to set up the jackshaft.
I went with chain the first try but had the math all wrong so i switched to belts, the hoop from a 20'' rim makes a fine pulley.
 
Hey there.
Thanks for the reply.
Dowie Soetenga, another fellow builder, already had made the math for me on a previous arrangment (see older posts on this topic).
The thing is that I changed to a new engine and this one has a conical engine shaft with a 11 teeth sprocket, so I have to run a chain from there to a 26 teeth input sprocket on the jackshaft. On the other end of the jackshaft will be my centrifugal clutch, runnin a chain to a final 35 or 44 teeth sprocket.
Here's a sketch:


Uploaded with ImageShack.us

The problem is that I dont know if the shaft will acquire enough rpm for the clutch to engage, since the a 11t to 26t arrangement gives torque, not speed. This would be reached with the 11t to 44t setting.

By the way could you post the link to your belt built bike?

Thanks a lot and keep it up.
 
Well with 11 to 26 and the engine idle your jackshaft would be spinning at 740 rpm , so you need
a centrifugal clutch that ingages just higher then that.
 
As it sits:





The engine is pretty loud and it spits flames at high revs. Its very cool.
Killswitch is ok, so is the hand operated brake and throttle.
Only thing (main) left is the transmission.
Should I go with the arrangement drawn above?

Keep it up
 
Jackshaft 750rpm = 2000rpm
engine 1750rpm = 4600rpm

I think your engine max rpm is about 3600
The reason they make clutch ingage at 2000 is so it kicks in just higher than your engines idle(1750)
 
Your gearing ratio looks right, with your engine at max rpm (3600) and you go with the 44 tooth that puts
your back wheel at 380rpm. So with your back wheel having a circumfrence of 82.12 inchs that puts you at
29 mph, but you might want to put the clutch on the motor not the jack shaft so it starts before you run
out of rpms.
 
Yep!. that was the problem I was referring to earlier. The engine's shaft is conical, and not suited for the straight keyway on the clutch... Hence the need to place it on the jackshaft..
What do you think of the belt vs. chain arrangements? Besides the aestetics of both things.
Thanks for helping out.
 
Bro those vids are great!
That's a 2 stroker right?
Great fun.
Did you post your build anywhere? I'm curious about the way you fixed the 20" rim to the back wheel, and also how you built the lever (?) that allows the belt to engage. Or is it a cent clutch?
Thanks a lot.
 
I finished the bike last year. It's a 1954 Hawthorne, hand made springer front end. leather seat, with a 139cc 2 stroke out of
an old snow thrower. I sand blasted the frame then left it bare, The first belt between the motor and the jack shaft has a
spring loaded idler hooked to a brake lever. the second belt goes to a 20inch hoop bolted to the back wheel with 6 hand
made stainless steel brackets. sorry i don't have any pics of the build, I didn't know about this site at the time.
About your clutch maybe you could swap the springs. I bet you could find some to make it engage at w lower rpm,
If you get it to work at 1000rpm it would work on the jack shaft.
 
Hey there
Too bad you don't have pics. Maybe you could build another and document it :D
I'll go for the jackshaft, but I also like the looks of your belt drive. Could you post a close up pic of those stainless steel brackets attachin the loop?
My clutch has only one spring, a long one, that surrounds all of the 4 engaging parts (don't know the name). I can stretch it so it looses some strength, and then cut it to fit.
If it does not work, I'll try a 16'' or 18'' rim with a pulley, same look and more speed.
Will it work if I use a slightly larger belt that engages the pulleys with a tensioner lever / arm?
Thanks and keep it up.
 
Wanted to show you some better photos of my bike (rustbucket) so you could see how i set up the belts.
It works well enough, I might do it a little different if i did it over.
IMG_20120511_173738.jpg

IMG_20120511_173636.jpg

IMG_20120511_173342.jpg

IMG_20120511_173301.jpg

IMG_20120511_173859.jpg

The brackets for the hoop are " Y " shaped with the two top taps bent back and bolted to the 26" rim, and the
bottom tap bent forward and bolted to the 20" hoop.
I also Had to " Z " the lower wheel stays to make room for the hoop and belt.
 
Looks great!
I really like the looks of the belt. Its simpler and rattier.
Is that spring over the beer can, and also the bearings and lever ment to engage the belts?
What is that white pulley for, could'nt you drive it directly from the engine to the back wheel?
Thanks and keep it up.
 
The spring keeps tension on the idler pulley to keep the belts engaged until i pull it back with the left brake lever,
The white pulley is on left side of the jack shaft, With a 2 stroke I get much higher rpms (5000+) so i have to step it way down,
hence the need for the jack shaft. With a 4 stroke, say at 3000 rpm and a 4" pulley on the motor and a 24"pulley at the wheel
that gives you about 500 rpm at the back wheel, in other words 39 mph. As long as low end range insist to far off it might work.
I geared mine way low so i max out at 30 , but i can do burnouts! so it just depends what you going for.
 
Burnouts! Yeah..
I'd like some torque and speed, a balanced thing.
I'm gonna visit my machinist next week to find out if I can thread the engine«s shaft without taking it apart, so I can mount the cent clutch onto it.
Thanks for helping and checkout my RustyNail build.
 
Some sweat and almost some tears last night.
I could'nt get the spark plug to spark. A electrical problem could have been a serious setback if something was wrong with the magneto, for instance.
I redid all the wiring, cleaned all the contacts, checked the killswitch and wiring, and nothing.. no spark.
Luckly, I made the mistake of grabing another sparkplug that was nearby, instead of the one I was using and what a glow!
I had a bad sparkplug going :oops: :oops:
Mental note: don't be an A## and try simple things first!
 

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