# Friction motorized bicycle

Discussion in 'Friction Drive' started by syfer, Sep 9, 2007.

1. ### syferGuest

Hello all.
I used my old Go-Ped's engine - "Zenoah Komatsu" 22.3cc, to make a motorized bicycle friction powered.
The original ratio between the axis pole and the rubber wheel in the Go-pad was 1:10 (1.5cm to 15cm).
I've made a new axis, size 6.5cm connected to 65cm bicycle wheel, (same ratio 1:10).
But it has no power to move the bicycle wheel, even when no rider on the bike and the bicycle is lifted from the ground.
I want to know if its a problem with the engine (like - no compresion) ?
or if the engine it to weak (to small) ?
or maybe the ratio is wrong?
or the axis is to big (6.5cm)
The engine is working well when not connected to the bike.
Thank you.

2. ### Large FilipinoGuest

It may well be too small of an engine. If you get it working with a small enough wheel you may go like 5 mph.

4. ### 5-7HEAVENGuest

it's all about gearing ratio, aka leverage.:shock:

as the ancient greek scientist Archimedes stated, "give me a big enough lever and a place to stand, and i can lift the world."(using just his own "man power")

your Zenoah 22.3cc engine has enough power to push your bike past 20mph, all parameters being optimum, such as total weight, gearing, etc.

i would venture to presume that a ratio between 15.00-18.75:1 would have you and your bike flying down the road.

a ratio of 10:1 is too high, in my opinion. your axis(friction roller, i presume) is too large.

try to reduce axis to a diameter between 7/8"-1 1/4"(.875"-1.25").

quoting David Staton's recommendations, at .875" roller size a 250lb man might fly up hills with 22mph on the flats.

at 1.125", a 200lb man has all around performance and max 28mph.

at 1.25" and 165lbs, less low end and 30+mph.

at 2.57" friction roller diameter, your bike has NO performance, using deductive reasoning.

the smaller the roller diameter, the more low-end produced. at 1.00, you'll be climbing hills easily. at 1.75", you have less low end and be flying on the top end.

with an axis of 6.5cm(65mm or 2.57"), your engine is WAY out of its power range. my 35cc ROBIN engine has a 1.125" roller, and i was very happy with its performance. unsure what its gear ratio was, but it worked for me and my 20" DAHON.

do you have a centrifugal clutch on your engine?

Last edited by a moderator: Sep 9, 2007
5. ### Large FilipinoGuest

So in theory does it even matter how big the wheel your motor's gonna roll on is? I mean that engine on the original go ped spins a much smaller wheel. But for every revolution the engine axle turns the go ped will go a set distance. So for the sake of argument,one revolution of the engine makes the go ped go 3 inches so the same friction drive on a 26" wheel should also go three inches?
So the drive wheel shouldn't be changed at all,right?
Then it should go as fast as your go ped if you don't change that drive wheel.
What am I missing here?

6. ### 5-7HEAVENGuest

como esta, Manong.

Mabuti, i hope.:grin:

my wife is Filipino. Visayan.

my Staton drive is 18.75:1, and my twin-engine project with stock engine sprockets, 1:1 jackshaft and 36-tooth rear sprocket will have 14.84:1 ratio.

the Staton drive is low-end gearing for hills and 20-something mph, comparable to happy time engine and 43-tooth rear sprocket.

happy time engine with 36-tooth rear sprocket has less low end and great top speed, maybe 30-something mph.

with 10:1 ratio, it'd be like happy time engine and 24-tooth rear sprocket.

someone here can probably calculate theoretical mph with 24t gears and 10:1 ratio.

7. ### syferGuest

Thank you all for your quick help.
My engine has no cluch, its connected to the wheel by a strong spring and I have the option to disconnect it at any time.
I will start by reducing the size of the friction roller to 1.125" and hope it will do the job.
Again, thank you for all the help.
Great forum, great site and most of all great people.
I will be writing back as soon as I make the changes.
Thanks.

8. ### gone_fishinGuest

wanna really thank 'em? go post in "introduce yourself"...

and read a bit about topic placement, too, if you'd like to show your gratitude to staff.

9. ### DougCGuest

You need to put the original diameter roller back on the go-ped engine, and use that. The diameter of the bicycle wheel doesn't matter--the drive ratio is set just by the roller diameter, and 1.5cm is the right size to get the engine at its best RPM's for power output.
~

10. ### dbigkahunnaGuest

All right. This is starting to make some sense. Scary. If I have a larger tire then the bike will travel faster. A 20 inch tire will not travel as far per engine revolution as a 26. So if I increase my tire diameter to 29 inch, the bike will travel further per revolution than with a 26. Pi and all that math stuff. So increase the size of the friction roller the roller is going to go further per revolution which makes the drive tire go further.

11. ### srdavoActive Member

pi & the math don't lie!!

on friction drive, the top speed is not affected by the tire size. only the amount of torque you'll have. (smaller tire = less torque)
yes....a larger friction wheel will give you more top speed....but there is a trade off. you'll have to pedal more to get up to speed.