ebike11 said:
GlowInTheDarkNinja said:
ebike11 said:
From the selection of chainrings that Cyclone has, what tooth option would be best for top speed along with my Shimano 7 speed freewheel cassette in the rear??
Looking for the fastest possible speed combination
Thanks
You want a 48T option on your chainring. Just think about your existing chainring; more teeth on the chainring translates to more wheel RPM and less torque. Less teeth give you better torque, more teeth give you a higher top speed.
Also be aware that more teeth is a larger diameter and therefore you will have a lower clearance on your bike before you grind those teeth off.
Also I think a 44/48/##T chainring should give you a little extra speed as the motor will spin the outer 48T ring 'faster' than at 44T that is driven by the motor. Mathematically you wont go more than 8% faster, top speed, than with a 44/44/##T chainring.
Actually i have 3 chainring set from cyclone
Which position should i put the 48 tooth sprocket in?
At the moment I have the sprockets in this order
48 44 32 48 is the innermost chainring
Should I switch the 48 tooth chainring to a better position for top speed? Thx
I'll have to work this out to give a good answer so bare with me.
Lets say the motor spins at 100 RPM. I cant remember exactly how many teeth are on the motor freewheel so lets go with 14T.
That's 1400Teeth per minute from the motor.
1400/48= 29.2RPM on the chain ring. And that translates to 29.2*44=1280Teeth per min
1280TPM on a high gear of 13T, for example, is 99RPM on the back wheel.
99RPM * tire circumference will give you a speed, but the rear wheel RPM is sufficient for us to figure out which will give you a better top speed.
Now lets figure out a 44/48/32T
1400tpm from motor
1400/44= 32rpm on chainring
32*48=1536tpm
In high gear, in this example 13T, = 118RPM on the back wheel
Finally lets try 32/48/44T
1400TPM from motor
1400/32= 44rpm on chainring
48*44= 2100TPM
With a 13T high gear, = 162RPM on the back wheel.
So you want your motor's free wheel to be large, and the chainring it's linked to should be small.
And then you want to do the same thing from your chainring to your cassette. Chain should ride on a large chainring, to a small chainring on the cassette. This will should give you a high theoretical top speed. However, I'm not entirely sure how to calculate what would actually be best for you because at some point the motor may not have enough torque to keep pushing faster than a certain speed.
Thanks for asking this though, it was fun for me to work out. I've ran these numbers before but I was looking to maximize my torque rather than my top speed. With the 72V battery im planning to build, Top speed shouldnt be much of an issue anyways.
One last note, Ive noticed that on my bike, which is without motor or battery at the moment. I have a hard time pedalling uphill when my chainring is in high gear. My high gear is a 44T in front, and my low in the back is something like a 34T. So if you have a lot of hills you may want to consider keeping the 32T available for when you need to climb a hill, rather than using it for more speed.
I think I did everything here correctly. Hope it helps!
Brake pads I am getting around 4k miles out of the fronts, and chains I am getting around 5k miles per cassette chain, I yet have to replace my drivechain at 7k miles. 
