This is a set of dis-assembly pictures that I took of a nine-speed locking differential transmission that I designed. Like the Mechanical Three Speed Automatic Lego Transmission, it uses ratchets and differential gears to route power through different gear trains, but instead of a single locking diff, it uses two of them. They are ganged together so that one feeds into the other. I wrote a computer program to search for a set of gears for the two stages of the transmission such that there would be no overlapping gear ratios. It really does have nine unique speeds!
It is not easy to tell from these pictures just how the thing works. It has two three-position shifter bars, one at the front and one at the back. They work by blocking the rotaion of the spinning lever arms that are attached to each side of the differential gears. Power goes from the motor directly to the front diff gear body using a length of lego chain.
One problem with this particular design is that because of the spinning lever arms, it is both wide and unbalanced. The thing would shake quite a bit as it whirled down the road. Someday I might try to build this one up again, but in a smaller form factor. I want to try using a pair of the center-mounted gear locking systems that I cooked up for the automatic so that I can get rid of the twirling and shaking of the lever arms.
If you have any success with locking diffential transmissions, let me know!
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I've been helping run The Last Outpost since '91. If you need a break from playing with Lego and want to play a fun, free, online multiplayer game, click the banner link below to go to the game's home page and learn how to play!