For some time I wanted to make my own remote-controlled reliable gearbox with more than 2 speeds. I've seen some nice designs, like Sariel's aeroshift and Sheepo's 7+R gearbox, for which I've had the honour to make building-instructions.
There were a number of important aspect:
- Reliable drivetrain
- Preferably 4-speeds
- Being able to switch gears with a single motor
- No pneumatics
- Like in Sariel's design, the transmissions consists of identical modules, where each module has 1 driving-ring and adds 1 gear. All the gear-ratios are identical: 5/3 from 1st to second, 5/3 from 2nd to 3rd and 5/3 from 3rd to 4th. The total amount of gear-reduction is about 4,63. By using the 24-8-tooth gear combinations (instead of 12-20), ratio's of 3/1 can be achieved.
For effeciency-reasons, the gearbox only reduces speed, the highest gear is actually neutral (same speed coming out as is coming in). Also for the efficiency, the module(s) with gear-reduction are located nearest to the input. This way the dead gears have less effect.
The switching systems was inspired by Sheepo's gearbox, but I wanted to use the ridged axle-joiners insted of the smooth ones Sheepo used. This way the driving-rings would stay in place better, contributing to a more reliable drivetrain.
This gearbox will be used in my new supercar, with which some succesful driving tests have been done.
I plan to expand the desing with some kind of stepped motor to improve the swithing-system, but for now it works quite nicely.
I've made complete step-by-step building instructions so you can include this gearbox in your own designs. You can download them on the instructions-page.