Hi I was wondering if anybody could help me figure out some gears I have to make. I have never worked with gears before and I am hopelessly stuck. I have attached a simple drawing to explain what I need. I am constructing a planetary gear where gear A will be the driving gear. Gear A needs to be turned 80 complete revolutions for gear D to do 1 complete revolution. http://postimg.org/image/oaeytu6wh/ Is it possible to do this just using A-B + C-D exchange? (C+D preferably in one part) Like I said, I have never worked with or learnt about gears, so I am completely lost with the math on this. Could anybody help me figure out the number of teeth + ratio between the exchanges? If it is not possible, adding another exchange might be possible. I really hope somebody could point me in the right direction with this.