Jackshaft Hopeless gearing?

Discussion in 'Transmission / Drivetrain' started by Charles Laypool, Feb 5, 2016.

  1. Charles Laypool

    Charles Laypool Active Member

    Im just trying to figure out what gearing is best for me with a jackshaft kit

    If my motors Max rpm is 5500 and its internal gear reduction is 4.1 so my output sprockets rpm is 1341.4634146
    So 10t to 17t is 1.7:1
    (789.09612623 rpm)
    17t to 10t is 1.7
    (469.17419194 rpm)
    10t to 44t is 4.4444444444
    (105.49413453 rpm(at the pedals)
    44t to 36t is 1.2222222222 (86.313382798 rpm(to rear tire)
    Now if i calculate

    Axle teeth / Pedal teeth = gear ratio.

    Sprocket RPM / Gear Ratio = Wheel RPM (wRPM)

    Tire circumfrence in feet * wRPM = feet per minute.

    Feet per minute * 60 = feet per hour.

    Feet per hour / 5280 = miles per hour.

    1st----9mph
    2nd-10mph
    3rd-12mph
    4th-16mph
    5th-18mph
    6th-21mph
    7th-24mph
    8th-27mph

    Now i really hope im doing something wrong i ordered my shift kit im jus waiting to get it but i want to get best gearing and these results are crap someone enlighten me
     

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  2. bakaneko

    bakaneko Active Member

    What is going on here? You are going from 10T to 17T at 1:1.7 for 1341 to 789 RPM. And, then you are going from 17T back to 10T for 789 to 469 RPM. Wouldn't it be back to 1341 RPM? Also, there is a 10% power reduction when using a jackshaft apparently. Cheers
     
  3. Charles Laypool

    Charles Laypool Active Member

    Ooooo snap see i knew i was missing something. Thank u for the info
     
  4. bakaneko

    bakaneko Active Member

    No problem, m8. We all make mistakes. I suspect the new speed numbers would be much higher now. Have fun and stay safe! :cool:
     
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