Centrifugal clutch on jackshafts?

Discussion in 'Performance Mods' started by 5-7HEAVEN, Sep 2, 2007.

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  1. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Hi. i'm involved in a twin-engined project for my next cruiser bike. i need to control both engines independently in starting/accelerating/idling/clutching/shutdown.first, i was gonna use 3 10-tooth sprockets(one-to-one ratio), backed by a 36-tooth rear sprocket. the clutch levers would control engine functions.
    now i'm curious about COMET jackshafts with centrifugal clutches. in what little info i could find, it seems to be one to shift gears at speed.
    not really what i need it for.
    anyone know anything about these centrifugal clutches on jackshafts?


  2. CVT on a Jack Shaft

    (I Think) Dual engines could work on this setup. Left & right side drive motors? One side CVT & the other more direct chain drive Bigger displacement.....

    Picture 005.jpg

    Picture 006.jpg

    JAX runs really well, pretty even throughout CVT range. No replacement for displacement... a 4 HP Tanaka could Rock this.
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    :confused:Zomby, both engines drive through the left side 36-tooth sprocket.
    actually, i'm having second thoughts about this jackshaft clutch idea. i've searched a lot for more information, but haven't found much. maybe i should stick to the simplest connection, which is one jackshaft and three 10-tooth sprockets. the ratio would remain the same as the chinese engine to rear sprocket. if i want to shift my power range, i can just replace the drivetrain sprocket to 8t, 9t or 11t for 4.5,4.0 or 3.27 gear ratio.
    are your pictures of pocket bike engines in tandem? you would think that dual engines would outpower a 4HP TANAKA.
    personally, i'm not worried if my twins don't produce much more power than one 80cc engine. they're mainly for eye candy and ear candy...sights and sounds.:grin:
    Last edited by a moderator: Sep 3, 2007
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    :confused:still looking for the correct centrifugal clutch to control my rear drive sprocket. if i can locate that part, i can fabricate a pullstart mechanism like SlicerDicer is working on (or install kickstart assembly on the left-side engine as a last resort). that way, my engines can be individually started and controlled, idle at the stoplight and pull away from a dead stop.the clutch levers can be relocated to the downtube, because they'll just be needed to separate the engines during startup, or when one engine needs to be disconnected from the drive for whatever reason.
    i contacted COMET dealer, no response yet.

    Last edited by a moderator: Sep 12, 2007
  5. iRide Customs

    iRide Customs Member

  6. 5-7HEAVEN

    5-7HEAVEN Guest

    :confused:nope, nothing i could use there.

    i believe what i need will slide onto the shaft towards the middle.they're probably available with a belt pulley. i don't want to use that pulley, because i'd need a SECOND jackshaft to convert to gear sprocket.

    maybe the last resort would be a one-direction sprocket, to use as #3 sprocket on the jackshaft.

    still looking.

  7. vintagebiker

    vintagebiker Guest

    I tried to use a centrifugal clutch on a jackshaft.
    It didn't work because I had the jackshaft spinning slower than the motor RPM (gear reduction) so the clutch would not hook up, not enough centrifugal force to engage the clutch properly. I even tried weaker springs but had to abandon the idea and put the clutch back on the motor.

    I wanted to take the clutch off of the motor and move it to the jackshaft so the motor would be more narrow, not for a twin engines set up.
  8. 5-7HEAVEN

    5-7HEAVEN Guest

    Bernie, you are so correct!

    :cool:Jesus H. Christ, Bernie!

    you're absolutely correct!

    since the engine has a 4.15:1 gear reduction and a centrifugal clutch generally opens at 2000rpm, the engine would have to rev to 8,300rpm to actuate the clutch on the jackshaft!:shock:

    in other words, the rear wheel sprocket would NEVER ever spin!

    THANKS! for your insight. it saved me time, $$ and effort. i was so close to buying two COMET jackshaft clutches on ebay.($100+)

    okay, no centrifugal clutch for my twin engine project, but i need to work on my pullstart mechanism instead.

    i WAS gonna relocate both clutch levers to the downpost if i could utilize the centrifugal clutches. now they need to stay on the handlebars.

  9. Alaskavan

    Alaskavan Guest

    Hi 5-7. This is off topic and I'll try to keep it short. I've been studying gear ratios, jack shafts, torque converter's etc. I've read a bunch of your posts. I think the germ of an idea is starting to emerge. This may be way cool, but I'm going to let it ferment a bit before sharing. Anyway, thanks for your knowledge.
    Aw. To heck with it. I'll post it in general so people can tell me why it won't work.
  10. Old Dude

    Old Dude Guest

    Newbie, 1st post.

    I have been pondering an idea that would ideally allow driving the pedal crank with the motor, and still retain full pedal function with the motor off. One could still use the pedals as a foot rest while motoring. Also allow a geared rear wheel hub to function.

    I stumbled across another forum where a forum member made a vague reference to driving thru the crank. It turned out to be a jackshaft arrangement. Looked like it would work but not the solution I was hoping for.

    Having a lot less life ahead of me than behind me Ive come to the conclusion that there arn't to many original ideas out there. If you can think of it, odds are someone somewhere already has. So I'm going to share my idea in hopes someone on the forum will have heard of or seen it done....or do it and share with the group.

    Basic parts: 3pc crank, main shaft modified are retooled to accept a sprag clutch/bearing on one end and a bearing of the same OD on the other end.
    (Because of load torque it may prove necessary to use two sprag's and omit the bearing)

    This assembly is inserted in to a hollow outer shaft. Each end of this outer
    shaft is fitted with a bearing. This whole assembly is inserted into
    the existing bike crank cylinder. (about 2" ID) The "drive sprockets" left motor, and
    right wheel, go on the outer hollow shaft and the pedals on the inner crank
    shaft. (Where they were originally) It will help to draw this as you visualize it in your mind. Also google "Sprag" clutch if your unfamilar with them.

    I have no doubt this scheme will work, but fitting it into the existing crank cylinder might be impossible. Kinda like 10lbs of stuff in a 5lb bag.
    A new larger crank cylinder could be fitted to the bike in place of the original.

    The rights to this idea (If it is original) belong to this forum and its members, to refine, expand, improve or change for the use and sharing of all on the forum.

    Their are some clever guys on this forum, so hash it out guys.

    BernieP, the "Old Dude"
    Last edited by a moderator: Sep 17, 2007
  11. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Alaska, see you in "General Discussion".
  12. Egor

    Egor Guest

    The drive you are thinking about was used on the 1903 Indian. Works well and is a good idea. Have fun, Dave
  13. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Egor, i nixed the centrifugal clutch on the jackshaft because the happy time engines' gear reduction would not allow the clutch to activate(theoretically). besides, i don't think one clutch would be able to handle twin engines' torque.

    my handlebars would be less busy if i could utilize the centrifugal clutch. right now i've got twin throttles, twin clutch levers and front brake lever on the bars. i could've relocated the clutchers onto the frame itself.

    so my jackshaft will just accommodate three 10-tooth sprockets and homemade pullstart mechanism.

    and maybe an alternator pulley.:grin:
  14. Egor

    Egor Guest

    You should not try and use so many control's. Go to Honda and get a throttle cable for any 60's twin, you will see how they split for two carb's. You can use the centrifugal clutch out on the counter shaft but it must be spinning at correct speed. Whizzer uses two clutches in there two speed clutch, you would have to see it apart to get the vision. I was going to try and build a twin engine I think it would be cool. I was looking to move the front engine close enough to engage the large gear to the crankshaft gear of the second engine. This way you would only need the clutch on the second engine, you could leave all the extra parts off the first. If you modified the cases on the two engines I think you could seal them up with silver sealer and you would not tell. The intake and exhaust would need extensive mods to stay out of the way and good motor mounts to keep the gears meshed. That could be a plate that would pick up all the cover screws and then place the covers over that with them trimmed down. OK all solved lets get two engines and have some fun. Lets call Duane and get two of his sale engine kits. Have fun, Dave
    PS: Have you seen the twin engine Whizzer? I think he is going 90MPH now.
  15. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Egor, thanks for input.

    i chose the simplest, cheapest route. aside from multiple controls, it is also the most accommodating. the engines are mounted side-by-side, never contacting each other. they will be bolted onto individual mounts, then onto a 1/8" metal plate. each engine can be separately adjusted for chain adjustment towards the jackshaft. the 1/8" plate also mounts the jackshaft; this plate is bolted onto a 3rd plate, which is welded to the bike's frame. the 1/8" plate has sliding adjustment, so the jackshaft-to-rear sprocket can be tightened.(of course, there is some chain adjustment at the rear dropout, but it also affects the primary chain on the right side.)

    each engine has entirely separate controls. at rest, each clutch lever is pinned, so the bike is freewheeling. one lever is unpinned, then one engine is bumpstarted(or pullstarted at the jackshaft with the rear tire off the ground). with the 2nd engine primed and ready to fire, its clutch lever pin is released. the running engine will bumpstart the 2nd engine. now both engines are warming up, with the rear tire off the ground. when ready. both levers are pinned, and rear tire is placed on the ground. the rider pedals a short way and engages one or both engines.

    if one engine falters, or whenever the rider chooses to, either engine's clutch lever can be pinned to remove the engine from the drivetrain. if one engine dies, disengagement will allow the rider to drive home under power.

    the builder could also choose an 80cc engine for torque, and a 48cc engine for rpm and better gas mileage. at any given speed, the 80cc engine could be disconnected, and the smaller engine can wind to higher rpm or attain better gas mileage.

    with so much low-end torque and more clutch area on tap, one MIGHT be able to pull away from a standing start. however, it would be prudent if the driver pedals a few feet before engaging one or both engines.

    centrifugal clutches would definitely be advantageous and convenient, especially at startup and while idling. personally, i just want to finish the project and enjoy the ride.

    Last edited by a moderator: Oct 8, 2007