bottom bracket jackshaft

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by jazz2561, Nov 11, 2014.

  1. jazz2561

    jazz2561 New Member

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    Does anyone know how to make a stock bottom bracket work as a jackshaft? Any particular bearing size?
     
  2. Imthegrt1

    Imthegrt1 New Member

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    That's what I'm working on at the moment. I've seen one done on a bike but never could get any info from the guy on how he did it.
     
  3. jazz2561

    jazz2561 New Member

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    what size bearings are you using?
     
  4. BarelyAWake

    BarelyAWake New Member

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    Keeping in mind not all bottom brackets are the same - I used 499502HNR sealed bearings w/snap rings (5/8" ID x 1-3/8" OD, same as the shift kits) & after lightly honing down the threads in the BB they pressed right in. Add a 5/8" keyed shaft, "BMX" freewheel, threaded freewheel adapter, lock collars & 5/8" keyed sprockets of your choice;

    pedal driven: http://youtu.be/U10xLqTekOw
    engine driven: http://youtu.be/_GTS0xG8BPM

    [​IMG] [​IMG] [​IMG] [​IMG]
     
  5. FFV8

    FFV8 New Member

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  6. jazz2561

    jazz2561 New Member

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    FFV8 is that a custom frame with a custom bottom bracket
     
  7. curtisfox

    curtisfox Well-Known Member

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    FFV8 love your idea. Here is another Goldy did ..............Curt


    http://motorbicycling.com/showthread.php?t=28747
    http://motorbicycling.com/showthread.php?t=28747&page=14


    The band might not be necessary if your clutch drum sticks out past the hub far enough (about 1/8")
    There was a hole already in my clutch hub that I simply tapped 1/4 UNF to fit the pawl screw...upon final installation, I peened the end of the screw over to prevent it from unscrewing and falling out. The roll pin prevents the heavy side of the pawl from contacting the drum when running and also provides a point to fasten the return spring. I use a rare earth magnet to hold the pawl in the disengaged position when pedaling , or pushing it around. Also the heavy end of the pawl rests on the central part of the clutch hub when in the engaged position, I figured this would give it some extra strength and take some of the strain off the drum.
     
  8. FFV8

    FFV8 New Member

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    Actually it is an off the shelf Silver State frame with a standard bottom bracket. I started with his most basic frame kit to build that bike.

    .
     
  9. Mr.B.

    Mr.B. Well-Known Member

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    Sportscarpat sells a nice bolt on unit that’s tough & adjustable...

    About 2/3rds down the parts bikes/page- http://www.sportsmanflyer.com
     
    #9 Mr.B., Nov 12, 2014
    Last edited: Nov 12, 2014
  10. Imthegrt1

    Imthegrt1 New Member

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    So were did you get the shaft and bearing from looks real good.
     
  11. BarelyAWake

    BarelyAWake New Member

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    Thank you :) The shaft & bearings I picked up at a local hardware store, it's pretty common stuff ;)
     
  12. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    Bottom bracket jack shaft.......easy with a tandem

    [​IMG]

    [​IMG]

    You can use it with or without the stoker cranks with an SBP BB and their shift kit parts....
     

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