1969 Triumph T120R 650 Motorcycle
Gearbox Animation and Gear Reference
Rear view looking forward
Click thumbnails at left to display photos and animation of the gear cluster in all four gears and neutral.
The animation shows the gear cluster shifting up and then down through the gears in an endless loop. Until you computer has downloaded the entire animated .GIFF (1.75mb) there may be delays. After the first time through, the gears will shift every 3-4 seconds.
Feel free to provide your own sound effects.
While the animation is running you can freeze any gear to examine the position of the gears, the camplate, and the selector forks, as well as how power is transfered, and the part numbers and specs for gears. Just click on the thumbnail in the scrolling menu to the left that corresponds to the gear you want to view as it comes up in the animation.
The green and red dots on the camplate (rear view only) represent the positions of the gear selector fork pins in the camplate's groove as they slide the selector forks back and forth, engaging and disengaging gears.
The mainshaft gear selector fork's pin/roller are green, and the layshaft's are red.
The pear-shape of the camplate's groove around it's center is what controls timing and direction of movement of the gear selector forks.
Even as the camplate turns, no movement is made by a peg or its selector fork while the peg glides within the constant radius of the circular part of the camplate's groove. While a peg is in this position, its selector fork is disengaging the dogs of both sliding gears on it's respective shaft.
A pin must be engaged by the elongated portion of the camplate before it begins moving and slides its gear selector fork.
Note that dogs only ever engage on one shaft at a time. While one gear selector fork engages either one of the two sets of dogs on its shaft, the other selector fork disengages both dog sets on its shaft. So while one peg is being moved by the camplate, the other peg is captured, unmoving, within the circular part of the camplate groove.
Note: The positionings of the gears shown here are somewhat theoretical. For example, to make it easier to see the dogs engaged, I placed them ever so slightly apart. Even so, these representations accurately show how the gearcluster, shifter forks, and camplate work in the real world.
More Gear Stuff...
Switch to the Front View Gearbox Animation
To see the animation and photos as seen from the front looking back, click here
Illustrations and photos depicting three different methods to index the gear selection camplate and quadrant in a Triumph Unit 650 Gearbox
Photos of a Triumph 650's gearbox components in various poses. Have a look...