Hello all, first post on here. My fathers friend recently died of cancer and he was the person we used to turn to for this question, I've been racking my brain and searching the net for info, found this link (http://www.schsm.org/html/gear_ratio_calculations.html) and have got the ratio down to 6 and 17/18ths.Not much use. I have an "escape wheel" on a turret clock. The "escape wheel" has 9 teeth on it and it meshes with a wheel with 145 teeth. The 145 needs to turn at 1/2 rev per min exactly. What I am looking for is a motor speed and gear ratio to drive the "escape wheel" to give the desired output, preferably not stepped if at all possible. There are several motor speeds that are stock from the supplier, 5, 6, 8, 10, 12 and 15 rev per minute, but I have no idea how to factor these in to the ratio.