A new shift concept for the engineers....

Discussion in 'Motorized Bicycle General Discussion' started by ferball, Jul 26, 2010.

  1. Kevlarr

    Kevlarr New Member

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    It goes on the little gas scooter I posted a picture of. Already know it would handle our motors since it runs off a 49cc and it looks teeny.

    I was thinking there should be room behind the seat tube on most bikes (think jackshaft kit) and on a stretch...well where couldn't you put it? laff

    Just replace the clutch bell and output pulley with a 10T sprockets, fab up a mount and you're golden. :D
     
  2. Goat Herder

    Goat Herder Gutter Rider

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    Well no one can come up with a hub that is left side drive with gears that will hold up. I hope Jim's works out! I really do! I have my self compaired j shaft to direct drive you always loose power going that route. That magical hub is gotta be out there some where.

    The best part to this game is trying to get the torque transferred directly to the pavement, and not lost in a contraption.:(
     
  3. ferball

    ferball New Member

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    I finally got my bike back together and one of the things I have noticed when I try to switch between my 44t sproket and my 50 is that there is way to much chain to slack out. the tensioner for a left side hub is the real key, because you are working with much bigger sprockets, the amount of chain that needs to be tensioned is huge, and because the drive sprocket is above the chain stay you are limited to where you can "store" the chain. But I will endeavor to persevere.
     
  4. silverbear

    silverbear The Boy Who Never Grew Up

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    Do you think it would make much of a difference if the two were 44 and say 48 in size? Not so much of a jump, so less chain to tension? What about two tensioners, spring loaded? Even 44 to 48 would make a big difference in gearing. I so much want this to work. Thanks for sharing your efforts. Pictures of the problem?
    SB
     
  5. bairdco

    bairdco a guy who makes cool bikes

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    they do make left side drive hubs with left side drive freewheels and fixed gears. BMX'ers have been doing it for awhile. just Google "left side drive BMX."

    as far as the gears go, this guy: Circle A Cycles — Custom freewheel might be able to make a two-speed for ya...
     
  6. ferball

    ferball New Member

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    I think that a two tensioner set up would be needed to take up enough slack.

    I believe that a smaller jump in sprocket size would help, but Jim is working on a three gear system with a 4 tooth difference between each, a total of 8 teeth, this seems practical and doable, so if I solve the problem for a 6t difference then 8t should be doable with the same set up.
     
  7. Goat Herder

    Goat Herder Gutter Rider

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    Yeah but Ferball is already there? Still looking at needing a derailleur. Whut good is single speed. The guy doesn't list big enough sprockets. Everything I see so far is absolute junk..

    Even if a so called BMX was used the free wheel is too small and under built.


    Need to have an internally geared set up at this point.


    Someone with a machine shop of sorts would be able to make a triple spring action derailleur that could by some miracle be universallaff
     
    #127 Goat Herder, Aug 13, 2010
    Last edited: Aug 13, 2010
  8. bairdco

    bairdco a guy who makes cool bikes

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    sorry, i run a 30tooth...;)

    finding two sprockets and welding them to a left hand drive fixie cog should be pretty easy.

    while i'm interested in this experiment, i'm pretty confident that a multi-speed system, based on a derailleur bicycle system, will fail.

    there's too much torque, problems with chain alignment, and chain tension.

    i think the only way it would be functional would be to completely re-build a bicycle system on a grand scale. i don't think any derailleur made today will work, otherwise you would've seen one on a moped. i'm sure every old moped manufacturer has tried, tested, and failed this idea 40 years ago.

    bicycle derailleurs are fragile objects. just talk to any hardcore Mountain biker or roadie and they'll tell you. mountain bikers have problems with "chain slap" and other related drive train problems on a routine basis.

    it's just asking too much from what we're working with.

    the only thing i think will work is an internal hub, or an external, bolt on transmission.

    all that being said, i'm still interested in the final outcome of this.

    but, even if it more or less worked, i don't think i'd wanna shift gears at 40+mph. it might work at low speeds for climbing hills, but i don't think it would work for speeders...
     
  9. ferball

    ferball New Member

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    The left side sprockets I think are the easy part, the derailer and tensioner is the problem area. Conventional rear derailer/tensionar is no good, because the drive chain is above the chain stay. Conventional MB spring loaded tensioners solutions I don't believe will work, because the amount chain slack/play needed to allow switching between such large sprockets. So from where I sit these are two fairly simple problems to solve if we don't focus on trying to reapply what is already out there, I mean we can use existing hardware, but it will have to be in a completely different manner than intended and that to me is the fun of tinkering on my Motor Bike
     
  10. ferball

    ferball New Member

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    I agree Baird when we solve this the first generation will not be intended for speeders, but once the concept is proven, it is just a matter of time before it is improved upon.
     
  11. Goat Herder

    Goat Herder Gutter Rider

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    Ok so has any one had a good look at the whole lot of internally geared hubs internally?

    How can we get things in motion and have something re-engineered?

    Because left side drive is where its at. That is where it is needed. Somebody needs to get the gumption to invent one then. They are going to become very rich!!!!


    All the power is on the left side. Transferring the torque directly to the pavement is more power. Less chains to fig-it with. It is a very good and beautifully simple concept.
     
    #131 Goat Herder, Aug 13, 2010
    Last edited: Aug 13, 2010
  12. ferball

    ferball New Member

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    I have to admit that I have not looked into internally geared hubs, but honestly I want a bolt on system, so some day I can unbolt the parts and use the bike as it was originally intended....(I doubt that day will ever come, but just in case....)
     
  13. Goat Herder

    Goat Herder Gutter Rider

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    Then unbolt the wheel and put a normal one back on?

    One tensioner one chain.

    Or.....



    Also from what I understand attention to detail has to be subjected to shifting some of these internal hubs as well. They are not quit as on the fly as a N.V. hub
     
    #133 Goat Herder, Aug 13, 2010
    Last edited: Aug 13, 2010
  14. ferball

    ferball New Member

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    lol....got me there goat.
     
  15. corgi1

    corgi1 New Member

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    how 'bout a scuer lock like seat post size? too adjust the idler chain tention,and I've seen chains run under the chain stays,so if there was an under and over set of idler adjusters that moved at an angle as they moved for and aft ,looking like the regular derailers movement on the other side ,still manual switching but would be lot more of slack adjustment and the idlers would still be locked in position for starting the motor,,,,Tractor supply idler gears,
     
  16. Goat Herder

    Goat Herder Gutter Rider

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    #136 Goat Herder, Aug 14, 2010
    Last edited: Aug 14, 2010
  17. Tim_B_172

    Tim_B_172 New Member

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    When I built my first bike I had this very same idea. I even went as far as to bolt on a 44 and 48 tooth sprocket at the same time, sandwiched. Of course at the time I knew very little about motorized bikes. I ran the bike on the 48T for a while with a regular fixed tensioner just for break-in, plus I need the bigger sprocket because there are a lot of hills in my part of town. Later I got a spring tensioner hoping to prove that the bike would run just fine while using it so that I could come up with some kind of derailleur in the future. I worked OK for a while, but I ran into problems with chain length. When manually switching between the 48 and 44 tooth sprockets, my tensioner ran out of travel and the bottom and top halves of the chain were almost touching where the tensioner was pushing up (barely pushing). Due to a misalignment of my back wheel after I re-installed it following some maintenance I did experience one unexpected "shift". The bike sounded like a car or motorcycle shifting gears as you might expect. it accelerated briefly and then the chain jumped all the way off, so I stopped. The kicker came when (and this is important) I was coasting down a hill, I let off the clutch to accelerate for the next hill and I didn't time it right. The chain was still slack at the top because the tensioner spring had been pushed down as the wheel drove the chain rather than the engine driving the chain. When I let off the clutch, the slack chain slapped into the engine sprocket in such a way that it skipped a link and jammed in the engine. My engine stopped immediately and the back wheel locked up. I didn't crash, in fact it was remarkably smooth and controllable sliding on the tire at 30 mph. But I guess my point was that any derailleur based shifting system would be subject to the same chain slack problem that I experienced. That being said, I think that it would work with a freewheel on the left side, because a freewheel would not allow the chain to be pulled by the wheel.

    Also, I hate messing with rag-joints, so both sprockets are still on my bike. ;)
     
  18. ferball

    ferball New Member

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    I am not thinking the freewheel left side is the answer, I think the wheel driving the chain will be the best method for shifting, think front derailer on bike.
     
  19. Goat Herder

    Goat Herder Gutter Rider

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    Yeah shifting with the motor would lend to some interesting surprises.. Fo Sho
     
  20. Tim_B_172

    Tim_B_172 New Member

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    Then might I suggest having two spring tensioners, one for the top and one for the bottom. That way, there will be tension on the chain no matter how it's being driven.
     

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