saving bearings in weed eater FD?

Discussion in 'Friction Drive' started by keatonx, Jan 1, 2011.

  1. keatonx

    keatonx Member

    A few years ago I built a FD ELECTRIC scooter with a drill motor. After a few
    weeks the motor bearings were so worn the shaft wiggled a few milimetres.
    How can I prevent this in my weed eater bike i'm making? oiling? The weed eater i'm using has tons of compression, and has a 3/4" spindle. This should make pedal-starting a big problem without extra spindle tension, ruining my bearings even faster. So far I have roughened the spindlewith a flap-wheel, and cut a few grooves in it with a dremel. That should help, but not much. Any ideas?

    P.S. Does the ryobi 31cc or 30cc have lots of compression too?. My MTD 31cc has an identical carb, and engine shape.
    Last edited: Jan 2, 2011

  2. adb140275

    adb140275 Member

    yeah the 31cc ryobis have a higher compression ratio than the weedeaters and they make a ton more power
  3. GearNut

    GearNut Active Member

    Most of the friction drives that I have seen or read about have the friction roller resting on it's own set of bearings, separate from the engine or motor's bearings.
  4. a/c man

    a/c man Member

    I have a 31 cc ryobi friction drive set up.
    If you are attaching the friction roller directly to the motor
    you will be putting too much stress on the end of the shaft, which is actually
    the motor crankshaft.
    It's only a skinny little 1/2 " shaft .
    The length of the roller added to the length of the shaft puts too much pressure,or leverage on the shaft and motor bearing when you get enough downward force onto the tire to get a good bite.
    Usually it will bend or eventually break the shaft.
    The bearing is not designed to hold up to the task either.
    You need a set up that isolates the engine from the roller, thus taking the stress off of the shaft end.
    Here's the link to the set up I duplicated from a former member and I'll also show you links to my build.

    Original link to Johnyboys build:

    My build:

    Finished product:
    Last edited: Jan 2, 2011
  5. keatonx

    keatonx Member

    Since i don't have access to any metal sheeting, maybe I could put some skateboard bearings on the OTHER side of the drive roller, then pull down on that end of the roller, too. So basically, one end is on the crank, and the other is on the skateboard bearings. How much would that help?
    Last edited: Jan 2, 2011
  6. keatonx

    keatonx Member

    I'm also planning on sand-blasting my spindle for grip.
  7. a/c man

    a/c man Member

    I think if you could rig up some kind of bearing on the far end of the roller
    it would have to help some for sure.

    Assuming you could apply equal downward pressure on both ends I don't see why not.
    I'd go for it!

    Necessity is the mother of invention.

    I'm not sure sandblasting will give you enough of a rough surface on the roller though. Mine is pretty heavily grooved and even they wear down.
    Some guys have welded little blobs of welding rod, or even used some kind of grit epoxied to the roller.
    Have you watched any you tube videos on weed wacker bicycles?
    also some ryobi friction bike vids, not real good but may give you some ideas

    Keep building and good luck
  8. keatonx

    keatonx Member

    I'll try it. But also, is there some type of lube made for these bearings? I've done so many mods to this engine, so i don't plan on breaking it.