Help with custom transmision and gear CAD.

[Nikhil Bajaj]

AndyMark now has a 4:1 high/low ratio option for their shifters, it's an optional gear set. It works very well once you have the original shifter (Super Shifter, or Gen 1) set up.

Our drive train uses the guts of the Super Shifter but one of our drive module plates is the same as the side plate of the Super Shifter (we CNCed it to match but also hold our wheel and tensioner shafts.) If you are really excited about building your own shifting transmission, that's awesome, and there are plenty of people on this site (myself included) who would be happy to offer feedback and help.

However, if you just want a drivetrain that has 28:1 low speed and 7:1 high speed, I'd recommend taking an AndyMark shifter with the optional gear set, and then finishing your ratio with some nice cheap sprockets, which would make it easy to get another 6/7 speed reduction on top of that, so you get 24:1*(7/6) = 28:1.

That said, building custom gearboxes is often very rewarding, and I'd say you can't really make a wrong decision going either way.