2 Speed Transmission

Discussion in 'Performance Mods' started by andyinchville1, Dec 1, 2007.

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  1. Hi All,

    Just doing a little searching online and came across this 40 CC gas scooter with a 2 speed transmission (Stand on Goped Style not the large sit on ones)...Hard to tell from the pic but being that it is sooo small it must be able to fit easily on our bikes....Is this the solution?...Anybody have any idea how they make it work?...Here is the link to the page I looked at: http://www.trendtimes.com/evo-gas-scooter.html
    I wonder if this setup can be bump started?

  2. Alaskavan

    Alaskavan Guest

  3. Thanks Alaska....I looked at the manual but my brain still cant figure out how it works...I think it must work like the 2 speed jackshaft in another post on this board but even then i'm
    not sure how how that one works either....Thanks for the post tho. This one looks like
    it can't bump start but would probably help those of us who have recoil start and need a 2 speed.
  4. It is the exact same concept as the 2 speed jackshaft, except it is all belt driven instead of chains, which would make it a lot quieter. It would also be a nice, fully contained system. The problem with this set up (besides mating it to your engine, which may or may not be easy, I don't know) is that you would have to have 2 belts going from the transmission to your rear wheel.

    Heres how the concept works described in words only. A picture would be better. I'm good mechanically and at drawing, but scanning/downloading/computers in general are frustrating (I already deleted this whole post once). Here goes:

    1. The transmission (or jackshaft from the other thread) has a main shaft with three pulleys attached to it (sprockets in the case of the jackshaft).
    2. Pulley #1 is run by a belt from the engine, this is what turns the main shaft.
    3. Pulley #2 is attached to the main shaft with a freewheel type mechanism. If the shaft is turning then pulley #2 HAS to turn. Pulley #2 runs a belt goes to a pulley on the rear wheel and drives the rear wheel. Typical type drive system so far, except the freewheel.
    4. Here's the interesting part, pulley #3 is attached to the main shaft with a centrifugal clutch type mechanism. This allows the main shaft to spin WITH OUT turning pulley #3. At this point #2 is the only thing driving the rear wheel. However, as the RPM's of the main shaft increase, it reaches a point at which the centrifugal clutch engages and pulley #3 becomes powered up by the main shaft.
    5. Pulley #3 has a larger diameter than pulley #2 (more teeth in the case of the jackshaft) and is attached to the rear wheel with its own belt (seperate from pulley #2, they each have their own belt going to the rear wheel). The larger diameter of pulley #3 causes the rear wheel to spin faster than #2 would drive it.
    6. At this point pulley #2 starts working as a freewheel and #3 is the pulley driving the rear wheel.

    That is as clear as I can describe it, hope it helps.
  5. Alaskavan

    Alaskavan Guest

    When I started reading the description, I got myself all ready to end up being clueless. Very well explained! I totally get it. What rpm do you figure the clutch is turning when it engages?
  6. Klox

    Klox Guest

    Thanx! You nailed this explaination (hope this word is spelled correctly, LOL!) very well! I wonder if this design could be developed to a three speed.....
  7. Wow...Thanks KeepOn!....I fully understand it now!....I really had no idea before but you really did a good job with the wording (I'll admit it I drew a pic based on your wording to help me visualize it).....Very tricky until it's all broken down.....unfortunately, as far as I can tell, this would still not allow a bump start since pulley/sprocket #2 is on a freewheel...Ofcourse if one could devise a method to selectively enable or disable the freewheel mechanism on sprocket #2 or....

    HEY I may have just thought of the solution.....OK I hope I can word my thoughts as well as you but to make it bump startable imagine that Pulley/sprocket # 2 has a hole in it (on its side all the way through it)...Now place another disc (Call it Disc 2A) and spline or or welded onto the same shaft as pulley/sprocket #2 (it always spins with the shaft) in between pulley/sprocket #2 and Pulley # 3 with the centrifical clutch mechanism (need not have teeth or grooves in it) BUT simply a hole through it....NOW to bump start the engine one can take a "pin" to go through the hole on pulley/sprocket #2 and Disc 2A
    and fire up the engine....(hold in temporarily w/ nut and bolt or a cotter type pin), then after engine fires, remove the bolt or whatever was used to lock Pulley/sprocket #3 to Disc 2A and motor away!.....As a side benefit, nobody cam motor away under engine power without the startup "pin".....
    Think that'd work?....as far as I can think I think it would but I may have overlooked something.....of course with recopil start the bump start of the added disc would not be needed.
  8. I like the idea of automatic and at least 2 speed.
    Now the key would be to use this same concept to build a smaller chain or gear(they are narrower than belts for the same HP) driven device based on the same theory using a centrifugal clutch to bridge the step from low(1st) to high(2nd); and small enough to fit below the chinese bicycle engine, but instead of both(the 1st and 2nd) connected to the rear wheel, to have them both connected to a jackshaft and from there to the rear wheel with only ONE chain.
    I am sure it could be designed as a 3 speed(using one more centrifugal clutch and gears or chain system), but it would begin to grow in size, weight and rotating mass.
    But again I am open to the idea. So far 2speeds would be relatively cheap to build and bullet proof compared to internal hubs I think.
    Last edited by a moderator: Dec 3, 2007
  9. Oh...Note: to pull the pin out separating pulley # 2 from Disc 2A in order to allow Pulley #2 to freewheel after starting the engine, the clutch has to be pulled in and the bike has to be motionless for obvious safety reasons.
  10. Andyinch, yes your idea might work. Somehow we have to start those butstart engines. I did'n think of that.
  11. Another solution is to use a very small starter motor with small RC NiH batteries; and also using a freewheel so that once the engine revs up the starter simply is left behind. To start the engine: Pull the clutch, press the starter bottom and ready to go.
    Some chinese engines have secondary coils for lights that could be used to recharge the batteries.
  12. Hmmm....electric start....I like that....I think somebody here also mentioned somehow trying to start the engine via a cordless electric drill.....Some RC car engines I think are started that way.....alternatives to the bump start could definitely help us in the quest for the multi speed tranny...

  13. Egor

    Egor Guest

    Andy - It would be fun to see if you could adapt it to one of our bikes. Actually the two belts don't go to the rear wheel they go to the counter shaft, you still have one drive to the rear wheel and it could be a chain. Also the first drive could be a chain to the main shaft Instead of a centrifugal clutch off there engine, you would use the clutch inside our engine. The drive from the happy engine would go to the position of the centrifugal clutch. You would remove the tooth belt drive and replace with a sprocket for the rear wheel. If you look it has a lever on the handle bars to engage the 2nd gear, as you let it out it engages the 2nd gear clutch and the 1st gear is over-ridden ( it has a sprag clutch ). Simple outfit, it has been used for a long time, but not with a hand clutch. Have fun, Dave
    PS: I am going to keep there PDF manual. It uses a unique method, and is compact. The one that came on the Tote Goat uses two Centrifugal clutches.
  14. Egor

    Egor Guest

    Take a look. This whole outfit could be used. Drive would go to where the clutch drum is. and Sprocket too the rear wheel would come off the lower left shaft. Remove the tooth drive on the left side, and replace with a sprocket. The housing carries the shafts and has the bearing bosses in it. You would still use the belts to the gears. The lever with the holes in it is the lever that engages the clutch inside High gear. Have fun, Dave
    PS: You would have to use the pull starter.

    Attached Files:

  15. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:JMO, bumpstart mechanisms could be fabricated and adapted from any of the engine's four shaft locations. Basically, a knurled or roughly-textured shaft would protrude through the engine covers. These would be wrapped with a pullstart rope to start the engine.

    The pullstart mechanism could also be attached wherever there was ample space to installed the knurled or textured surface onto the jackshaft. The jackshaft itself could be machined to accept the pullstart rope.

    Orrr, a starter pawl or bolt head protruding from the engine shaft or jackshaft could be cranked up by a cordless screwdriver drill. Some jackshafts have threaded ends and retaining nuts. Those nuts would be perfect starter pawls for the cordless drill.

  16. kevbo

    kevbo Guest

    If you could add or encorporate a reversed freewheel into the clutched gear, then you could bump start in high gear. You might be able to make this work like a coaster brake does, using parts of the clutch.
  17. Douglas65

    Douglas65 Guest

  18. Egor

    Egor Guest

    You are correct there is no freewheel in high gear, that would work. It will start in high gear. I think this outfit would fit behind the engine in front of the rear wheel nicely, I wonder what the unite would cost? Have fun Dave

    Attached Files:

  19. Hi Dave,

    It is true that there is no freewheel in high gear, BUT there is a centrifugal clutch on the high gear sprocket that would unfortunately prevent the bump start I believe (most likely the expanding shoes etc are attached to the shaft itself and the sprocket is attached to the driven hub so, I believe, no matter how fast you pedaled the bike all you would do is spin the clutch hub with no hope of engagement since the "expanding guts" of the system is attached to the shaft meant to be spun by the engine (if it were running)....If the shoes don't expand to touch the clutch hub there is no direct connection....I hope I worded that well enough to be understood...

  20. What if, instead of automatic shifting=centrifugal clutch, the high gear is engaged manualy with a second manual clutch and a shift lever. While running on low gear the second clutch is not engaged, only later to shift to high gear; this time by actuating the shift lever that releases the second clutch engaging the high gears(well sprockets & chain, or belts etc) and taking over while the transmission freewheel leaves low gear behind.

    This way we could still butstart on high.