hi im a first time kid in autodesign!!!
can anyone tell how to relate the centre distance
of two chain wheel ,the diameter of the chain wheel
and the reduction obtained
thanks
You are probably best to draw it out full size and measure it. But that isn't the answer you wanted!
Decide on your chain link length. Decide what gear ratio you want (R). Choose appropriate number of teeth for small diameter chainwheel (at least 11). The large one will have R times as many teeth . work out their diameters (=no. of teeth*link length/pi). The distance between the wheels has no effect on the ratio, but if they are too close then you won't get enough wrap on the small cog.