pic: 4WD Concept

[asid61]

Originally Posted by AdamHeard

For 1:1 ratios, the math becomes dead simple. For Chain, the c-c must be a multiple of the chain pitch (.25 for #25, .375 for #35). It can be a multiple of the half pitch if you're willing to use a half link.

For belt, it must be a multiple of the half pitch (BUT don't assume all belts are sold!). Required toothcount on the belt (B) is;

B = T + 2*C-C/P

T = Pulley toothcount
C-C = Center to center (in same units as P!!!)
P = Pitch (in same units as C-C).

For both chain and belt there are arguments for adding a fudge factor to the c-c. I generally don't for shorter distances, but will more commonly do so for longer distances (or for small pitch belts).

If you have multiple sizes or want to save time, you can just use a chain length calculator: https://www.rbracing-rsr.com/chainlength.html