another friction drive bike

Discussion in 'Photos & Bicycle Builds' started by def215, Dec 14, 2013.

  1. def215

    def215 Member

    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

    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. :devilish: its still a work in progress since its my winter project. :cool:
    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. :idea:
    Last edited by a moderator: Dec 15, 2015

  2. SunkyWorks

    SunkyWorks Member

  3. HeadSmess

    HeadSmess Well-Known Member

    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?
  4. wheelbender6

    wheelbender6 Well-Known Member

    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.
  5. def215

    def215 Member

    thanks for the comments guys.

    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.:thinking:

    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. :devilish:

    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.:cool:
  6. SunkyWorks

    SunkyWorks Member

    I would try the following mod before gear change:

    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.
  7. Lee_K

    Lee_K Member

    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.
  8. def215

    def215 Member

    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. :D

    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. :devilish:
    Last edited by a moderator: Dec 15, 2015
  9. Lee_K

    Lee_K Member

    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.
  10. TREK820

    TREK820 New Member

    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 ! :)
  11. def215

    def215 Member

    i had some KMC 410 bmx chain and i swapped my old chain out for it. about a mile in to the ride, the chain seized. so im running the bell bmx chain at the moment and its been holding up. im gonna get new chain for it and ill keep the KMC 710 in mind.

    i had my shimano hub seize on me last month when i had it out making test runs. luckily i had a spare shimano hub laying around so i swapped in. i want to crack the old seized hub open and rebuild it so i have a spare one, but i cant get it open.

    i also went with a bigger sprocket on the hub, so i have a 9 tooth on the motor sprocket and a 22 tooth sprocket on the hub. so far ive got it up to 25 mph. its no speed demon, but it sure is something different compared to my cag-powered MTB.

    im still tweaking it and getting it dialed in to run correctly, and all this snow and below freezing temperature doesnt really help. but then again, it is

    thanks! i dont think of it as needing a clean or a paintjob, i think of it more as "theft deterrent." but even with my bikes being dirty, grease-covered, and chipped paint, it still attracts
  12. def215

    def215 Member


    ive been playing with this thing recently since the snow has cleared up a bit and ive had it out. im trying to get my fuel tank situated and i decided to go a little bit different with this one:
    i have it mounted under the bottom bracket so i can have it out of the way and a bit more "hidden." i also put the fan shroud on the motor for the looks and safety.:D i like how it looks like a weedeater just hanging out back there and i wont have a flywheel spinning at 7k rpm directly behind

    it seems to work at the moment. it starts up and idles, but i wanna take it on the road and see how it will handle me actually riding it. i havent seen a gas tank mounted this far away from a walbro pumper-style carb before. if anyone can give me any input on this will be greatly appreciated.:grin5:

    but heres a quick video of it running with the new fuel tank setup
    Last edited by a moderator: Dec 15, 2015
  13. HeadSmess

    HeadSmess Well-Known Member

    while its a fair lift up hill, pumpers are usually good for that. used to mount my tanks anywhere but near the engine, mostly on the handlebars.

    only issue i ran across was the tanks themselves and fuel lines... most tanks didnt have the requisite 3 lines. that thin fuel tube is expensive from the mower shop! so i used to have a wee lil baby "surge tank" mounted up next to the engine... only needed one long line from the tank, any return from the primer etc just went back to the lil surger...
  14. def215

    def215 Member

    thanks for the input headsmess. i was a bit skeptical on the capabilities of the pumper carb with my fuel tank placement, but its good to get confirmation that it can handle what i need it to do.:D right now im itching for good weather to take it out. :devilish:
  15. def215

    def215 Member

    update on this project

    so, this project has been fun and ive had some unreliability with it, especially with the reverse-rotation homelite bandit motor, and the shimano hub locking up on me a few times. but its nothing i couldnt fix.:grin5: well until the motor broke.:veryangry:

    as i mentioned, this is a reverse-rotating homelite bandit motor. but i had a rollpin in the shaft to hold everything on the output shaft of the motor. i took it out one day and the rollpin sheared and the flywheel backed out and ruined the keyway on the crank and the flywheel. so that motor was completely trash to me. it was fun while it lasted and was a good experimental motor for me.

    because that motor got buggered, i decided to up my game a bit and get this:
    its a factory refurbished homelite 42cc chainsaw.

    so this motor was put in place of the old motor:

    im hoping this will keep the cars at a :evilgrin:

    i am using the chainsaws clutch with my custom-made sprockets welded to the bell. it slips a bit but once it fully engages, it works great.

    but here is a ride video of it:

    sorry guys, i know its in portrait mode because it was in my shirt pocket. i needed my hand free to shift. :goofy:

    this chainsaw is supposedly rated for 2hp. and it definitely seems like it. its tearing up the friction material on my drive roller
    maybe its a bit too much

    but i did a top speed run on it the other day and this is what i got:
    the top speed is in the upper right-hand corner. not too bad for what it is. this bike closely matches my cag-powered MTB which goes 38 mph.

    but on my first ride out with the motor, the manifold ripped on the chainsaw engine, since its made out of rubber, literally. im now seeing why this chainsaw was getting bad reviews. im making a "real" manifold for this thing that will be made of steel.
    Last edited by a moderator: Dec 15, 2015
  16. motor7

    motor7 New Member

    great progress!