sprocket diameters made easy

Discussion in 'Motorized Bicycle General Discussion' started by diceman2004, Feb 9, 2010.

  1. diceman2004

    diceman2004 New Member

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    for anyone who needs to figure out the diameter of any given sprocket

    simply multiply the pitch of the chain , by the number of teeth on the sprocket
    then divide by 3.14

    Number 35 Chain: Pitch = 3/8" | Roller diameter = 3/16" | Roller width = 3/16" | Pin diameter = 1/8" | Tensile = 2,100

    Number 41 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 1/4" | Pin diameter = 1/8" | Tensile = 2,000

    Number 40 Chain: Pitch = 1/2" | Roller diameter = 5/16" | Roller width = 5/16" | Pin diameter = 5/32" | Tensile = 3,700

    eg: - whats the diameter of a 72 tooth sprocket , that uses number 41 chain ?
    Number 41 Chain: Pitch = 1/2"
    .500 x 72 = 36
    36 / 3.14 = 11.464 diameter

    NOTE : This is the diameter at the center of the chain roller , so you can also use this number accurately in calculations .

    The outside diameter of the actual sprocket will be roughly 3/8 - 1/2 bigger at the tips of the spurs .
     
  2. azbill

    azbill Active Member

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    yup, thats the size of my 72 ;):)
     
  3. Randog707

    Randog707 New Member

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    Hey Bill,hows the 72t sprocket working out? probely pulls real heard but hows the top end speed,are you looking at the low 20mph mark? I was thinking of buying one so that I can pull my kids around.Randy P.S when I asked about the top speed its not that I want to ride real fast with my kids,its just when I'm not toting my kids around,I would like to be able to at least hit 20mph.Thanks agin.
     
  4. azbill

    azbill Active Member

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    pulls the girls from a stop with my feet on the ground and just a blip of the throttle (^)
    I was expecting a top end of 25, but had it at 27 with 1/3 throttle left ;)

    the little Hua Sheng is a really nice engine :)
    (the EZM Q-Matic is a sweet gearbox as well)
     
  5. diceman2004

    diceman2004 New Member

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    i have a 72 also , my final gear ratio is 16 - 1 , you could probably pull tree stumps outta the ground , i only get 20 mph , i like that pulling power , ideally i want to build a 3 speed trany 3-1 , 2-1 , 1-1 ( no not a 3 speed hub that will break ) i want the final ratios to work out to 18-1 , 12-1 , 6-1 , that should give me a final top speed of around 50 mph ( bit too fast for a bicycle for me , but ide be able to just chug along at low idle if i wanted ) either that or i,m thinking a good quality cvt ( cvt is probable better , as the gear trany will class it as a motorcycle )
     

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