Twin Sprockets

Discussion in 'Motorized Bicycle General Discussion' started by TexasDav, Jan 5, 2009.

  1. TexasDav

    TexasDav New Member

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    Has anyone done this; my brother had an old AMF Harley trail bike. It used two sprockets on the rear and a spring tensioner. You had to switch the gear manually. I was thinking that would work for these bikes. Have a 44 tooth sprocket and a spacer then a 36 tooth sprocket. The chain tensioner would need to be a bit wider and with lots of swing to allow the switching of gears. Windy days 44, calm and flat roads 36.
     
  2. mechanickid

    mechanickid New Member

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    i've actually tried this and i couldn't get it to work (a welder would have helped though) you have to bend your frame to make room for the extra sprocket, and the difference in the chain length (from a 50 tooth to a 38) was so large that i had to try to reverse the chain tensioner to push the slack down instead of up. to keep it from rubbing itself on the high gear. do u have any picture of the harley setup? dont try this without a spoke guard!
     
  3. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Those, and the early Honda 90's had two sprockets, one fit over the other. When you wanted to go to the other sprocket, you would remove the masterlink, remove (or add) the section of chain, pull (or push depending on which one you wanted to use) the other sprocket out of the way (it was on pins if I remember right) and re-install the master link.
     
  4. Creative Engineering

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    That makes sense.

    I was thinking the same thing that mechanickid pointed out, and wondered how it was done.

    Jim
     
  5. mechanickid

    mechanickid New Member

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    i think it could be done if the sprocket size wasn't very big and you had a well adjusted tensioner/derailleur.

    one of the reasons i gave up was because it would legally be a motorcycle if it worked, same with the shifter kit (much better way to go im my opinion)
     
  6. TexasDav

    TexasDav New Member

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    I don't think on the harley you took the master link out, But it might have to have a derailer type tension wheels to take up the slack
     
  7. 2door

    2door Moderator
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    I've been toying with this very concept for several weeks. My problem is frame width too. I've already built a sliding chain tensioner that would (manually) guide the chain from one sprocket to the other. I couldn't keep the chain from hitting the chainstay on the outer sprocket and I didn't want to skin up the paint with an experiment. I'm going over to a guys house this afternoon to look at his collection of old bikes. If I can find what I'm looking for, an old cruiser with fat tires, I'll buy it, if it has a wide stance in the chainstay area. My bike is just too skinny, like its owner, for the double sprocket idea. Maybe a fatter bike. I'll keep you posted.
    Tom
     
  8. TexasDav

    TexasDav New Member

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    Thanks, even if you had to take out a master link, it seems a cheap way of making your bike more versatile. If you could aford the 7 speed hub and jack shaft set-up, then thats a whole lot better.
     
  9. NEAT TIMES

    NEAT TIMES New Member

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    Would You Need A Front Derailer When You Use The Out Of Line Rear Sprocket. I`m About To Install My Sbp Shifter Kit On A "barnes" Schwinn Cruiser Style Frame. It Has A 5 Speed Rear Cassette. Are The Shift Kits Needing To Use A Front Derailer?? I Will Soon Find Out. Anybody Heard Of "barnes" ?? It Has A Decal Head Badge, Barnes Accross The Top And A Couple Of Lions Below, "bicycle Pedal'r" On The Bottom.i Would Post Pics, But They Are Too Large. Steel Frame. Tire Size UP To 26 X 2.125
     
  10. Dan

    Dan Staff
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    Cool thought Dav. Been wondering for a wile if a bicycle style derailleur could be used. #41 sized and the reverse of the rear, right side bike derailler. Be big time $ to have one made but great if it could be done! Can spread the dropouts and chainstays....
     
  11. Dan

    Dan Staff
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    Maybe a forward derailler upside down mounted to the chainstay?
     
  12. mechanickid

    mechanickid New Member

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    i tried reversing the bike derailleur, it got pretty complicated.
     
  13. toytime

    toytime New Member

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    "Neat Times", the front derailer would not be used with the SBP jackshaft kit. It would be impossible because both chains stay in place, one to peddle/start the bike and the other is always hooked to the jackshaft.
     
  14. mechanickid

    mechanickid New Member

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    sorry to sound corrective, but its not impossible. someone already made a thread on here with pictures of it working. i'll see if i can find it
     
  15. NEAT TIMES

    NEAT TIMES New Member

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    HI TOYTIME. THANKS FOR YOUR INPUT. I MEANT THE FRONT DERAILER TO BE USED ON THE SHIFT KIT ONLY TO KEEP CHAIN ON THE SPROCKET AS IT MOVES UP AND DOWN THE REAR CASSETTE AND GETS OUT OF LINE WITH THE FRONT FREE WHEEL SPROCKET. APPARENTLY IT HAS NOT BEEN A PROBLEM. I THINK ABOUT 200 KITS ARE IN USE. I HAVE NOT INSTALLED MINE YET. RON.bld.
     
  16. toytime

    toytime New Member

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    Oh, I get it. I'm just waiting for my kit and can't wait to start getting this thing together. I've got a brand new motor sitting in the box just waiting... My order number is above 300 if that is any indication of kits sold.
     
  17. NEAT TIMES

    NEAT TIMES New Member

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    TOYTIME, I THINK IT IS ALSO THE KIT NUMBER. DON`T LAUGH NOW!! MY KIT IS #36!!! STILL IN THE BOX. A NICE QUAILTY KIT AND A BARGAIN. I MOVE CAUTIOUSLY!!laff.bld. I DON`T WANT TO MAKE ANY MISTAKES!!! YOU MAY HAVE TO BUY THEIR CRANK BRGS ADAPTER. I THINK THERE IS 3 CRANK HEAD SIZES. CK WITH SBP. dnut
     
    #17 NEAT TIMES, Jan 6, 2009
    Last edited: Jan 6, 2009

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