Attempt at a two speed automatic

This one doesnt work very well. The worm gear tends to bind up as it transitions between the two speed settings. Im only posting the pictures because some people asked to see them.

I got the idea from a construct similar to this one where a worm gear slides back and forth to select a diffrent output shaft depending on the direction that the input shaft turns.

In the transmission on this page, the wormgear drive shaft only turns one way, but the worm gear is still slid back and forth to select a different gear ratio. For example, when the final output shaft of the transmission is stalled, the power from the motor forces the worm gear to walk to the end of its travel in its cage, which disengages from the high speed gear to engage the low speed gear. When the output shaft has little or no load, the wheel with the slipping belts exerts enough back pressure on the worm gear to walk it back up into the high gear position.

Anyway, it didnt work very well. Because the two 8 tooth gears in the cage are turning at different rates, the worm gear often doesnt line up correctly with the gear teeth as it slides into them, and that jams up the whole works.

If you have any luck making a sliding worm gear automatic transmission work, I'd love to hear about it!


Copyright 2004, Jeff Jahr < >

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!