I'll try to give you an answer, although it's just my speculation from being in the hobby for several (19+) years. I've never tried to bend my own gear. My way of thinking says the number of coils would depend on the weight of the model. Look through some of the online retailers and compare available gear sets to determine a pattern to the number of coils. Another thought I'm having (and yes it sometimes hurts), is whether or not the metal would need to be heat treated after the coil is formed to make it less brittle?