Hey everybody.....look at me.....I'm a monkey!!!

Discussion in 'Friction Drive' started by VinnyVanVin, Oct 3, 2013.

  1. VinnyVanVin

    VinnyVanVin New Member

    To All,

    Now that I've got your attention to read my post I, like everyone else on here, need some advice (or personal opinions :cool:) on my first build. Before that hello to all! About me......215LBS, and looking to setup a friction bike with a 46CC McCulloch 4-18 MX chainsaw. Looking for good overall top speed with decent pull on hills.
    My questions:

    1. I want to use the centrifugal clutch so that I can idle. Besides the pricey aftermarket setups (straton, etc) what ideas have been used in the past for mounting a roller directly onto the clutch? A clutch bell?

    2. I want to be able to idle at higher speeds, basically coast without having to shut off the engine. How can I do this without tearing up the clutch or worrying about internal engine problems?

    3. If I leave the roller pressed into the tire at all times, like when I'm ridding the bike like normal, will it affect my engine even if it's not running? I guess I'm just looking for a permanent mount I don't have to adjust.

    I have done some research but haven't found any answers that really "push me over the edge" in the direction I should go. Thanks for your time and any help / beatings for ignorance you throw my way!


  2. IbedaYank

    IbedaYank Member

    you get what you pay for in terms of quality.
    If you have the tools and skills you can build one very cheaply.. aka a lathe/mill
    Do some research on here on what others have built.
  3. HeadSmess

    HeadSmess Well-Known Member

    1/2" bearings and mounts. 1/2" hi ten bolt. 1/2" starwashers. coupla other washers, some scrap steel, a welder and an imagination.

    9/16" may work just as well.

    keeping the roller permanent engaged wont hurt the engine...as long as the roller is supported at both ends.

    just hard to pedal.
  4. keatonx

    keatonx Member

    Yep, you can probably just weld a roller to the clutch bell, and have a bearing on the other end of the roller that also applies downforce (to stop the bearing in the clutch bell from being twisted). I've only torn apart 1 chainsaw, and it had a needle bearing in the clutch(good) rather than the brass bushings in weed wacker clutches. I don't think a bushing would last too long, as I've had them wear out lots of times without even any side-loading, but a needle bearing should be fine for a looong time
  5. IbedaYank

    IbedaYank Member

    welding=heat=warped clutch drum..
    tapped 76mm clutch drums are 10 0r 8mm thread Staton does not sell the 3/8s 24 thread anymore
    bearings used are 1 3/8s O.D. 5/8s I.D.

    you must support the roller on both sides or the clutch will never disengage
    These are the bearings used.. Note the snap ring that keeps them in place


    might be nice if some really did know how things are built
  6. keatonx

    keatonx Member

    I've welded on clutch bells tons of times and I didn't notice any warping. And they worked fine. Anyways in this case it would only be welded to the chain sprocket (if it's outward facing, if it isn't then you might not be able to use the clutch), where warping would be very minimal
  7. HeadSmess

    HeadSmess Well-Known Member

    most chainsaws ive encountered have m8 or m10 LEFT hand threads, use caged needle bearings, usually in the 12ID to 15OD size, and are pretty darn good. they also dont have standard sized clutches. 76mm is meaningless in chainsaws. keaton said it all...

    inboard sprocket may be unuseable, and the bearing on most chainsaws is good enough to use as a roller support directly.

    what you want is one with a removable, outboard sprocket.

    braze/tack weld. either heat the whole thing up evenly or make the welds small, opposing and it wont warp. clamp it first and weld completely. drill holes and plug weld from the back. plenty of ways to prevent it warping if you have a brain ;)

    to be specific on a particular saw cant be done. you need a big box of bits and pieces to work out what clutches will swap over etc etc etc. 10 million makes and models and every single one is different!

    hardest bit on a saw is mounting.

    said it before elsewhere...pick a saw with a seperate motor to everything else. remove everything, starter and clutch. they have solid mounts, unlike just about every other engine available.

    extend one shaft as "roller". seriously, use star washers as a roller, theyre cheap, hardened, easily replaced and last a lot longer than a knurled piece of bar.

    remember, a bearing at EACH END. either side of the wheel. use "self centring" flange or bracket mounts to save on being accurate. sealed bearings, considering the location.

    setting up a "clutch" isnt terribly difficult, especially when you think of overcentre locking mechanisms...

    such as these...


    some lock in both directions, but normally... have them set so it locks when driving.
    Last edited: Oct 9, 2013