This is a fiddly project and you should be prepared to adjust and tweak as you go. I did not go into a ton of detail as this would become a 100 slide instructable. I will however add little tips that helped me.
I made it at the TechShop in San Jose CA.
Step 1: Templates
I went with a planetary gearset design. I bought the template from here: http://www.mkdrafting.com/buyropeplans.html
Print out the templates and spray mount them on your 3/4 stock.