This is my gearbox whitch consists of a 2 sets of gears.Motion comes from the top shaft which has the gears casted on it. upper 2 gears are connected with the lower ones and are continiously transfering motion.The lower gears are mounted on bearings and then on the other shaft,,, (these gears are spinning freely when in neutral). in the middle of the two geras there is a clutch which is controled by a lever. if we mode the shaft on the one side, it connects with the gear and transfers the motion to the shaft and finally we get the output power...This gearbox acts as a reducer with the first combination (z1=60 m=1 z2=100 m=1)and as an icreaser with the second combination (z3=45 m=2 z4=35 m=2)