sprocket diameters made easy

[diceman2004]

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 .

 

[azbill]

yup, thats the size of my 72

 

[Randog707]

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.

 

[azbill]

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)

 

[diceman2004]

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 )