pic: Dual FisherPrice Gearbox

[Pat Roche]

Originally Posted by vivek16

I initially wanted to use the existing pinion and 32 pitch gears but I could not find gears thick enough for reasonable prices.

I understand your predicament with the hex shafts. A future consideration with gearboxes though, as your stages move closer to the motor their is clearly less torque transmitting through the gears. If you were to run your stress analysis on your gears in your first ratio I'm sure you'd find that you don't need a terribly thick gear for your ratio allowing you to use a 32 pitch gear. Usually in my transmission designs I start small and work my way up in size through the stages of your gearbox. This saves weight by using less steel, cast iron or bronze (depending on the application) in the transmission.
Disclaimer: Always check you stresses before you decide on a pitch size however, there is nothing worse than stripping teeth.