Can someone explain how this transmission works?

[slmechanis]

Googling around I came across this r/c car transmission:

http://www.gtbracing.com/?p=671

It appears to be 3 sets of gears with different ratios all engaged with one another. the small gears go to a clutch to the motor, but the bigger gears are more interesting
I can't figure out how it works, I think that one of the bearings is a one way bearing, but I can't see how it wouldn't bind up without at least two.

In my mind I'm imagining the lowest gear ratio beginning to turn, once a higher ratio has enough torque to overrun the lower gear, it does so and the lower gear freespins on its one way bearing, but then what happens when the next stage takes over and there is no one way bearing (assuming?)

 

[SwinnyGG]

They use a combination of one way bearings and centrifugal clutches.

The input shaft is connected to the engine through a centrifugal clutch, so the engine can idle without the car moving

Once the car is off idle, this clutch locks and the input shaft turns, turning all three gears mounted to the input shaft, in turn turning the 3 gears on the layshaft.

First gear uses a one-way bearing- so if the layshaft can spin faster than the first output gear, but not slower.

Second gear uses a centrifugal clutch. So as engine speed in first gear increases, this centrifugal clutch locks, engaging second gear as the drive gear. Since any further acceleration will cause the layshaft to overspeed first gear, the one-way bearing for first gear unlocks, allowing it to spin at a different speed than the layshaft.

The relationship between second and third is the same as between first and second- second gear has a one-way bearing in addition to its centrifugal clutch. So at high enough output shaft speed, third gear's clutch engages, second gear's one-way bearing disengages, and second gear rotates independently of the layshaft.

Typically, the engagement points of the 2nd and 3rd gear clutches are tuneable, so they can be adjusted to match the engine being used.

 

[slmechanis]

Neat, thanks for the clear explanation!