Lego Technic Sliding worm 3-speed automatic gearbox

This gearbox design just came to me last night while fiddling with gears. It uses a worm gear's tendency to slide along axles to create a compact 3-speed automatic gearbox. There is essentially a long axle with a worm gear and several springs from Lego shocks (two soft and one hard). On each side of this axle are longitudinal beams with 8T gears sandwiched between them, which mesh with the worm gear. If the worm is to the motor side of the axle, it directly drives the output through an 8T gear, if the worm is in the middle, it runs a different 8T gear, which drives a 16T gear, which drives a 28T gear, which drives the output, and if the worm is on the far side of the axle, it drives the output through two stages of 16:28 gearing. Half of the 8T gears are actually idlers, and only function to press the worm into the 8T on the opposite side. The shifting happens when the worm gear "decides" that it is easier to not run the output (because it is stressed), and instead inches down the axle against the springs, causing it to mesh with a different gear, at a slower ratio.

The video may help you understand how it works.

The gearbox is fully functional, but somewhat clunky. It could be expanded to have more speeds, but this would require an axle longer than a 12 (I have ordered a 16L and a 32L, but they aren't here yet), but there might not be much practical benefit, since gears get exponentially lower, and complexity and size increase. It would be interesting to try this relatively compact gearbox in a car, but its space efficiency might be annulled by its mechanical inefficiency, what with the worm gear and all.

[dannypipewrench]

This is a really clever concept. It would be very practical for high torque applications, perhaps large dump trucks.

[carlbModels]

try making it with just 2speeds, to prove the concept more thoroughly. Cap the end to stop end float of the axle, and maybe you have made a super compact 2 speed transmission. The worm gear idea is interesting and you could develop it further 👍🍺

[mojolotz]

Really neat idea. I can definitely see it struggling already, so a lot of works needs doing on it to make it stable enough i assume... really interesting though.

[Silverdev]

this doesn’t seem the best but i think ot has a lot of potential

[weskridge]

Sthidding gearbox nerd! But tbh smart at like a cvt