another friction drive bike

hi guys,

here is something im working on.

this bike was once an electric and the battery gave out and i didnt wanna drop another $300+ on another battery, so its getting a gas engine on it.

this is what it looked like before:

it had a 350w brushed motor on 37v li-ion battery. top speed was around 30mph until the batteries went on it...lol

here is what im working with now:

here is a close up of the motor and driveline

its a homelite bandit 25cc motor thats been retimed to run in reverse which is powering a shimano 333 hub thats set up for neutral-1st gear-2nd gear. i have a 10 tooth sprocket on the motor and 18 tooth on the hub so it equates out to the "spindle" being a little bigger than 1 inch. the whole mount is made out of 3/4 inch square tubing. i had it out today and im having issues with tuning it. but it does work. its still a work in progress since its my winter project.
here is the first start up of it


i know LeeK did something like this with a 3-speed hub and a 4-stroke Robin-Subaru engine. i wanted to give it a shot and put a unique spin on it.

 

[SunkyWorks]

Great work Def, keep us posted on how this works out.

Chainsaw motors run CW on the clutch side and are sized down to 32cc.
Many have tapered shafts, that might be a problem to mount a sprocket.

A scissor lift clutch could give you 3 speeds:
Another Friction Drive, Last One I Swear!!
http://motorbicycling.com/showthread.php?t=31318


Lee_K
Build of 3 Speed Friction Drive
http://www.motoredbikes.com/showthread.php?39382-Build-of-3-Speed-Friction-Drive

 

[HeadSmess]

agreed , a saw motor is far superior in this application

except for the starter...hmms. freewheel prevents clutch starts, dangnamit!

at least with the "quick change" sprockets, playing with ratios is easy im thinking 24 is the biggest i got in my collection.

why only 2 speeds but? it is a 3 speed hub, isnt it?

 

[wheelbender6]

I never get tired of seeing DIY friction drive bikes. Many ways to do it and most work.
I no longer have loyalty to gas or electric assist. I used whichever one that is best suited
for my commuting route to work or the park-n-ride.

 

[def215]

thanks for the comments guys.

Lee_K
Build of 3 Speed Friction Drive
http://www.motoredbikes.com/showthread.php?39382-Build-of-3-Speed-Friction-Drive

his build is the reason i wanted to do this but i didnt want to copy his exactly. i had the idea a little while back to do this, but an electric version of it. but that would be more than i want to spend.

agreed , a saw motor is far superior in this application

except for the starter...hmms. freewheel prevents clutch starts, dangnamit!

at least with the "quick change" sprockets, playing with ratios is easy im thinking 24 is the biggest i got in my collection.

why only 2 speeds but? it is a 3 speed hub, isnt it?

yes, it is a 3-speed hub. i disengaged 1st gear so i can have a neutral so i can start it. it would be nice to have 3 speeds but i rather not add a clutch system to it and complicate it more than it actually is. plus, that would be one more thing to manage along with the "suicide" shifter

yeah, a chainsaw motor wouldve been nice, but this homelite bandit motor practically landed in my lap. because of that, this engine will be my test mule which will allow me to tinker with/modify a 2-stroke engine. if i destroy it in that process of doing mods, i wont be so upset. i have my full suspension cag-powered mountain bike also, but i would never use it as a test mule like im doing to this project.
but if anyone wants to let a chainsaw engine land in my lap, i wouldnt mind.

i had it out yesterday and it actually worked. but it does feel like its geared a bit tall with the 10 tooth sprocket on the motor, so i fabbed up a 9 tooth and bolted it on there.

it started life as a washer from home depot and now its a sprocket. i know that is the 10tooth, but the same process was used to make that 9tooth i have on the bike at the moment. chopping it out with an angle grinder and fine-tuning it with a dremel. a 9tooth sprocket on the motor should equate out to a 1 inch spindle in 1st gear.

now im just waiting for a day when im free and/or the weather is nice to test it out and get a video of it running.

 

[SunkyWorks]

I would try the following mod before gear change:

http://www.arboristsite.com/communi...ery-pleased-with-performance-increase.241457/

I split the seam on the muffler, ripped out the catalytic mesh, opened up the baffle,added a 3rd outlet louver and welded it back together. After a quick carb tuning it was like a completely different machine.


I have been able to buy 14" chainsaws 32cc to 36cc for $15, with the problem mostly being rotted fuel lines.
I bet if you had used a 36cc the gearing would have been ok.

 

[Lee_K]

Congrats on some really clever ideas. On the one I built I had to add a jackshaft to get the correct rotation direction on the left side to drive the hub. But what's really clever is disabling one gear to get a neutral. On my bike I have to kill the motor whenever I come to a stop. My pedal start system is nice, but it would be better with a neutral gear.

 

[def215]

thanks Lee_K. i was hoping to get some input from you since you were the first one ive seen do the 3-speed hub friction drive setup. your build inspired me to do this project.

but here is a ride video i did earlier today taking it through its paces.


top speed i saw on my speedometer was only 22.5mph. i calculated it to hit about 27mph the way its setup at the moment. the chain also stretched, but i am using bmx bike chain to power the hub. i might tear down the motor to do some port work when i tear down the mount for some paint. i feel like it could use a bit more power.

 

[Lee_K]

It's tough getting a chain to hold up when it's so short an running so fast. Make sure the tips of your sprocket are chamfered enough so they slide between the chains side plates without catching and trying to lift the chain. On the bike in my avatar I used a cheap single speed chain between the first and second jackshafts, it failed after about 30 miles. I replaced it with a KMC HL710 BMX chain which is still going with over 2000 miles. And it's a half link chain so you can cut to 1/2 inch increments. Check it out on eBay.

I am not real familiar with the insides of the Shimano hub but I do know it has 3 planet gears vs the Sturmey Archer which has four, so I expect the SA to be a bit stronger. I like the Shimano push rod vs the SA pull-chain, I also like the Shimano's smaller hub diameter for a friction drive. In these applications the gears are going to be plenty strong enough, I believe the weakness will be wear at the pins that the planet gears ride on, these gears will be spinning much faster than they would in the intended use. Of course in the middle gear the gears are bypassed so no wear except in high gear.

I have only ridden this bike about 30 miles, I built to develop a system that could be concealed. It works good, but like my other bike better. Anyway keep working on it.

 

[TREK820]

Work of art!!!

I love the design, very smart idea. The only qualm (not that my opinion matters) is that it would look even beter with a clean !