Compact Automatic Transmission using a Differential Planetary Gear

Hello, this is another idea of mine that I have no use for but I figured someone else could benefit from. Special thanks to 254D and “dontworryaboutit” for the general concept on how to create a automatic transmission like this. (Original post:




So a few nights ago, I thought up a way to create a differential, and what it turned out to be a planetary gear set except the output is driven as the input. This causes either the outer ring to turn or all 4 of the sprockets to turn, depending which has the least friction. The outer gear is linked together with a 2 speed transmission which then lead to the wheel. The sprockets are chained to 2 axles, each containing a worm gear, and are geared to spin in opposite directions. Those worm gears move flat gear racks (presumably on cut up linear sliders not shown in the CAD). Now looking at dontworryaboutit’s post, we can put some metal to push the axle that changes the gear ratio similar to how it was drawn up. As one gear rack is pushed forward, that pushes the axle with the gear-changer forward, changing the gear. That peice of metal would have a rubber band on it that would change how easily the gear ratios would change (more rubber bands mean it would require more force to change gear ratios)

I have yet to test this in real life, but I think it would work pretty well.

I posted a larger picture in the gallery since the ones in the post seemed really small and hard to look at

Very Cool Looking Transmission…

Are you going to try to actually Build It???

I started to build it today but I’m not sure if I have enough parts at home, so it might have to wait until the school year starts up again. It sounds like 1615 will have 2 teams this year, so I might be able to get the “b” team to try to build it for their robot.

Either way, it seems to be a quick build for anyone who wants to try it out. I managed to get the diff. planetary, 2-speed transmission and output mostly done in less then an hour. The tough part is getting the linear sliders fit in correctly with the worm gears.

Sorry to bring up such an old thread… Did you ever manage to finish the transmission? I’m really intrigued by it.

Haha aw man, I forget all about this. I never got to finish it, doubt it would have any chance of working either (never mind how crazily inefficient it would be). Feel free to mess around with the idea if you want :stuck_out_tongue:

Thanks man. I’ll see what I can come up with.


My first reaction to this was WHAT?

My second was THAT WOULD BE CRAZY INEFFICIENT. That is pretty cool, though. you could have something using a similar concept that powers two things depending on the direction of the motor.