GearBob, a LEGO Mindstorm NXT orbital gearbox

Hi Everyone!

I've been willing to do an automatic LEGO-style Gearbox since a long time, but I never managed to do it because i could only think of a linear one ( like those in european cars), and it 's quite difficult to do a LEGO one. Then I learned that there was another type of gearboxes : the orbital one(like in the automatic cars)! In LEGO geometry, it' s often easier to do orbital stuff ( which means "round" stuff) than linear mechanisms.

The principle of the gearbox is simple : whith the same motor, you have to make the wheels turn at different speeds, by changing the gearing. You may wonder why not to choose the fastest at the beginning, and it' s because the car doesn't have enough torque(=strenght) to move : the faster you go, the weaker you go. The car is able to move at high speed if it' s already moving, thanks to the phenomenon of inertia.

There is not much other things to say about gearboxes ( at least lego ones, because a real car gearbox is much more complicated). Still, the difficulty is to make a stable speed-changing mechanism, because the gears have the tendancy to say goodbye to each other, and to make the wheels move, you must absolutely stick them together.

Even if it' s not very complicated, it' s always fun to play with gears, and the gearing is quite beautiful, it makes me think of a watch mechanism :).




Bobly yours.