[Mark McLeod]

Here's the basic math. The center distance sprocket-to-sprocket for a tight chain is determined by:

• c = sprocket center-to-center distance in inches
• L = chain length in pitches (# of links)
• P = pitch of chain or length of a chain link [in inches] (.250" for #25 chain and .375" for #35 chain)
• N = number of teeth in large sprocket
• n = number of teeth in small sprocket

c = P/8 * (2*L - N - n + sqrt((2*L - N - n)^2 - 0.81 * (N - n)^2))

Begin with a chain length approximately the distance you are looking for and solve for it, then pick the nearest even whole number for "L" to get the final distance "c". Using an even number just means you avoid having to use a half-link.


P.S. This is from Machinery's Handbook