A while back I was making some large LEGO vehicle of sorts, and I was faced with the choice of gearing down my motor or dedicating a whole extra motor to controlling a gearbox.
I chose to do neither, and build an automatic one. The ones I found where to big and relied on friction and differentials. After a few email exchanges and iterations, I arrived at this compact 2-gear automatic gearbox.
The gear has 2 sides, one with a 1:1 ratio, the other with a 12:20 slowdown.
When no torque is applied, the front lever is pressed onto the 1:1 chain by a rubber band, causing it to turn faster than the 12:20 side, and thus pushing the rear lever up.
When torque is applied, the front lever is pushed up by the force, and starts to slip, making the 12:20 chain turn faster, causing the rear lever to fall back into position.
I found some lost and forgotten Lego building lessons. I think you’ll love them.
Over at Lugnet, in an old thread, someone asked for tips and tricks about studless building(using smooth beams rather than the classic Lego bricks). Someone linked him to the “LEGO TECHNIC Design School”, which sounded really good, but unfortunately, the links where dead.
I searched, and searched, but LEGO just seems to have removed them. Are they to good for this world? Finally, I found them using the Wayback Machine. Enjoy!