LEGO automated gear box

Januari 2005. This page is to show you another version of the automatic gearbox designed by Misha van Beek ( search Brickshelf for "Autotranny". ) The main difference is the addition of an adjustable load on the middle axis. The following picture gives the best view on all the separate parts. The input axis is at the bottom part of the picture and the output is at the top side of the picture. If the differentials don't turn, the transmision is 1:1. The differntials can be blocked or slown down by pulling the blue string. The axis at the left side of the picture drives a worm wheel. With this axis it is possible to control the amount of stretching of the string, and thus the amount of torque that is needed to make the string rotate with the middle axis. If there is some load on the output axis, because e.g. a car equipped with this gearbox rides uphill, the lower differential starts rotating. The upper differential will rotate with a speed that is reduced by a maximum factor three, if 24-tooth gear in the middle gets the same rotating speed as the upper differntial. This can be enforced by letting the gear at the rigth side of the picture rest freely in the ears in the middle. This is shown in the second picture. In this situation, the input axis can only rotate counter-clock-wise.



This box will automatically switch between 1:1 or 1:3 at a critical load on the output axis. This switching point can be chosen by pulling the string more or less. At high speeds, the freely resting 24-tooth gear will vibrate up and down, because it is pushed up by the difference in speed of the connecting gears. At low speeds it will be automatically pushed down. With carefull tuning of the load on the output it should be possible to get transmission ratio's with a value between 1:1 and 1:3.