ISMG

There are many Lego Technic built gearboxes all over the Internet,
from the simplest to the most complex gearboxes and transmissions.
But all theses require one driving ring for two different gear
changes while there is three clutch positions for each driving ring.
Conventionally, the central position is the neutral position but what a
waste if you build an 8 speed gearbox using 4 driving gears, still
one sliding clutch, eight driving gears and many other gears !
I told myself : “can we use the central position of the driving axle
to create three different gears per driving ring instead of two ?”

After a lot of brainstorming, testing and prototyping, I came up with
a variety of “one driving axle for three speeds gearboxes.
My best 3 speed gearbox is very compact (125 studs³ = 5x5x6) and modular,
it means that some gears are on the outside so you can change some gear
ratios easily.

My first idea, before coming up with 3 speeds gearboxes, was to create
a modular gearbox witch you can combine with the exact same copy of it
and connect them with a differential to create speed combinations.
It would work just like an analogical computer.

with two 3 speed gearboxes, you can create 9 combinations.
with three 3 speed gearboxes, you can create 27 combinations.
with four 3 speed gearboxes, you can create 81 combinations.
and so on…

In comparison with a 2 speed gearbox mash-up

with two 2 speed gearboxes, you can create 4 combinations.
With three 2 speed gearboxes, you can create 8 combinations.
With four 2 speed gearboxes, you can create 16 combinations.
and so on…

The 3 speed gearbox mash-up is much less space consuming !