Experimental DIY Friction setup

Discussion in 'Friction Drive' started by Tinker1980, Oct 3, 2009.

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  1. Tinker1980

    Tinker1980 Guest

    Boredom and spare engines are the blame for this. I found, around springtime, three vertical shaft engines - one is a tecumseh (with an electric starter!!) and refuses to run right, the other two are B&S engines, both did run after some carb cleaning, but one was missing parts from it's recoil starter, so it became spare parts. This left me with an older style Briggs engine with the ball-bearing style recoil starter. I removed the crankcase cover (The entire bottom of the crankcase) from my vertical engine, and the crankcase cover from a horizontal B&S engine I had. Also removed shrouds, to see the flywheels better. I learned some things:

    1.) The only difference, internally, is the dipper on the con-rod of the horizontal engine. The vertical engine uses a gear driven spinning device. One can put the dipper on the con-rod of the vertical engine, and it will work.

    2.) At least with the engines I had in front of me, the flywheels were the same weight. I removed both of them, and they weighed the same amount, so I know the vertical engine will idle without a blade on it.

    Why use a vertical shaft engine at all, if I have a horizontal one to compare it to? Mounting. I wanted to try a friction drive rack mount setup. A horizontal engine has it's mounts on the bottom, , so you'd have to build some kind of L-Shaped setup off the side of your rack mount. (Or use a HF 2.5 engine, which has mounts on the bottom AND the side)

    The lawnmower engine has a three bolt pattern on it, and I intend to make a t-shaped part that will reach all three bolts, but miss the crank itself.

    I can't use commonly available rollers for my design, since a 1.5" roller at 3600 rpm gives me a speed of around 16 MPH. I got lucky in that respect, my brother brought me a piece of scrap from where he works. It's the very end of a piece of 7000 aluminum round bar that is 2.75" diameter, about 2.5" thick. I wanted a roller that was 2.25"-2.5" diameter, but for free I won't complain. It goes to the machine shop for a .875 hole soon.

    Thoughts on this setup? I have pictures but nothing has been assembled yet. The part you see on the bicycle will have angle mounted to it for the motor mounts.


    Attached Files:

  2. professor

    professor Active Member

    Issues I see-
    you will be putting a side load on the wheel but the main stregnth in the wheel is vertical.
    There will always be some scuffing of the roller drive, since the width of the roller will engage different diameters on the tire.

    Engines with the heavy flywheel will operate fine without the blade attached.

    If you use a jackshaft, you can center the engine properly - use a 90 degree twisted belt and convert the drive to horizontal.
  3. give me vtec

    give me vtec Active Member

    good advice...
  4. Tinker1980

    Tinker1980 Guest

    Lol I wasn't clear, I guess. The vertical shaft engine has been modified to run On It's Side. I've run two tanks of gas through it on a test stand, with the shaft horizontal. I won't need a twisted belt.

  5. srdavo

    srdavo Active Member

    I'm watching this one... i dig the home-brew bikes!!

    Do you plan on a way to disengage the roller from the wheel?

    wondering how fast an aluminum drive roller will wear down. The hardened steel rollers do wear down over time.

    keep us posted on your progress.
  6. Tinker1980

    Tinker1980 Guest

    It looks like there will be a change of engines. The wife asked me exactly how big the HF engine is, (she is helping quite a bit with this project) not the displacement but how large, outside. I had been thinking it was close to the size of a 3.5 HP engine like the one I had ready to use, but I really didn't know. So we went across Tulsa to the harbor freight and actually *looked* at one, and it's so much smaller than I thought. I will use that engine instead, especially since it has mounts on the side and bottom. It will be easier to add a larger fuel tank too, since the carb isn't part of the tank.

    For the roller, after I have the hole in it, I will try coating the outside with a mixture of epoxy and sandblaster sand. No idea how this will hold up, but it may get me more traction.

  7. loquin

    loquin Active Member

    Maybe you could sleeve it with a short chunk of pipe. If you size the aluminum so that it is just a few thousandths too big to go inside the pipe, you could put it in the freezer and make it fit. (Aluminum has a much greater thermal expansion coefficient, so it would shrink more when cold) And/Or, drill a couple of holes through the pipe into the Aluminum, then thread them & use screws to lock things down.
  8. floridaboy

    floridaboy Member

    You might like to check out a vedio that was on MySpace called Motorized Bike Walkthrough Video by Vernon. It showed a vert. engine mount that looked good and easy.
    Last edited: Oct 13, 2009
  9. augidog

    augidog New Member

    ok, i'm the culprit here...i posted an idea i had in another friction topic, not aware of this one, & Tinker1980 showed me this link to the walkthrough video...now it's where it belongs:
    i haven't let him off the hook about his welds, but i still want to see pics...only kidding, mark...my welds are solid enuff, but pretty is for flowers :jester:
    Last edited: Oct 13, 2009
  10. seanhan

    seanhan Member

    Man 3.5 HP !!!!

    That ought to burn your tire up real quick !!!!
    But will be interesting ..... " MORE POWER " !!!!!!
  11. Tinker1980

    Tinker1980 Guest

    It will be different than a bitty two stroke on a friction roller, that's for sure. My huge 2 3/4" (69.9mm) roller will allow me to run just about 30 mph at the governed speed of 3600 RPM. I've heard from more than one source that the little HF engine can handle 4200+ with no problems. Another nice part about the large roller is better grip due to more area in contact with the tire.

    Right now the roller and the engine are down at the machine shop, the roller is being drilled for the engine's crank. More to come soon!

  12. Tinker1980

    Tinker1980 Guest

    Got to start my new motor earlier, with the roller mounted to it. Not on the bike yet, just mounted to a test stand. It's much quieter and smoother than I thought it would be, and it's leaps and bounds smoother than the HT setup it will replace. I'm getting batteries for the camera so I can post pics of the build.

  13. professor

    professor Active Member

    Very good, these engines are REAL available but some will not run without the heavy flywheel. I nearly broke my hand trying to start one that had a loose blade I didn't know about, It would backfire and rip the rope back- just would not run, until I fixed the blade mount ( broken washer).
  14. Tinker1980

    Tinker1980 Guest

    The Beast Lives!

    Took it on it's maiden voyage to Quiktrip and back. (about 3 miles round trip) It does not, as yet, accelerate as quick as my HT did, BUT it runs considerably smoother and quieter, and will reach speeds I can only describe as terrifying. On a 35 mph stretch I had a car that couldn't make up it's mind to pass me, I throttled up (With the governor) and pulled away from the car. At it's top governed speed it gives me the heebie-jeebies and I manfully whimped out after about 10 seconds of the scenery coming at me too fast. If you hold the governor around the 1/4 setting it putt-putts along at a nice 25mph-ish speed. I had to help it up a fairly steep hill, the engine slowed down to the point I thought it would stall. The roller didn't slip at all, but ate up my 15 year old Panracer MTB tire. I think a smoother tire would help a lot. I also need to cut out part of the mount, so the bolt that holds on the roller doesn't rub.

    An interesting note, the engine is easily bump-started. I wasn't expecting that.


    Attached Files:

    Last edited by a moderator: Oct 17, 2009
  15. Tinker1980

    Tinker1980 Guest

    Slight problem I'm having... When I throttle the engine up, it just dies. if I'm rolling, then the engine starts back up after a few seconds. Does the HF 2.5 engine have problems accelerating normally, is it supposed to be only one speed?

  16. Tinker1980

    Tinker1980 Guest

    Took the machine on a decent ride today, about 5 miles. It's so much smoother and quieter than the HT than I thought was even possible. It seems like the top speed is right around 28 MPH, this is using the governor, not applying the throttle directly. The best way to run the engine seems to be by simply shutting it off when you want to stop, instead of disengaging it from the tire. When you want to start, you begin pedaling, the engine starts at around 6-8 MPH and starts to pull you along. At low speeds the front tire nearly leaves the ground during the power stroke. Roller slippage is a non-issue, but I haven't ridden it with a wet tire yet. It will be ready to take me to work in a week.

  17. Pirate88179

    Pirate88179 Member


    Nice work! I really like that HF engine too. How did you handle installing a clutch? And yes, you really need like cruiser type tires for that. The BMP guy I got my kit from told me that mountain bike tires will get chewed up in no time at all.

    I want to build something next time with an engine like that but I can't figure out the clutch part yet. I saw a Youtube video of a guy riding a trike that had a lever to engage/disengage but it looked really dangerous if one needed to stop real fast, no time to grab the lever. But, he showed that when at idle, he was doing over 8 mph, and no loss due to clutch. So, I am very curious as to how you rigged a clutch up to this.

    Best of luck with your MB

  18. jcchappy

    jcchappy New Member

    ok it was aways back but a side shaft engine with the dipper repositioned will oil everything just fine on its side(horizontal)? awesome setup you have there.
  19. Tinker1980

    Tinker1980 Guest

    Actaully... I don't have a clutch. I originally set it up this way to just see if the engine had the power to move the bike with such a large roller. I pedal the bike to start the engine, around walking speed it will start to pull me along. I keep pedaling up to about 8 MPH and than apply throttle, and it pulls me away! I normally run it right around 25-27 MPH, the engine seems to like that speed. It will run 30 with no problems, and my top speed on the flats is about 37 mph which is really way too fast. When stopping, I have a kill switch wired up to the handlebars, and I stop the engine just as the bike gets down to walking speed.

    The friction drive doesn't really work too well for the large of an engine. There is too much torque, it will slip the roller fairly easy, and there is quite a bit of tension on the roller. The least bit of a puddle and it slips. I think I will use this engine on a chain drive, I'm going to use an old 7 speed rear wheel cassette and axle for a jackshaft, and put the entire thing over the back wheel.

  20. Tinker1980

    Tinker1980 Guest

    Thanks for the compliment. :) Yes, the vertical shaft engine will oil itself just fine if you first put a oil dipper from a side shaft engine in it. The rest of the parts (For the briggs and stratton engines) are the same. The only problem you might have is the flywheel, some of the vertical shaft flywheels aren't as heavy as the side shaft flywheels. The engine will still run with the light flywheel, but be prepared to have the starting cord snatched from your hand occasionally when starting.