2. The layshaft is the other geared shaft (Fig. 24). Its primary function is to provide a means of changing ratios, or shaft speed. It also has one gear which can be slid back and forth to engage the gears on either side of it.
3. The sliding gears and sliding dog are moved back and forth by shifting forks. (Fig. 25). There are three of these in the gearbox, two on the mainshaft and one on the layshaft. The shifting forks fit into machined grooves on the sliding gears and sliding dog. These grooves allow the gear or dog to rotate while being held in place by the forks. The shifting forks slide back and forth on the shifter fork shaft.
4. The shifting forks are actuated by the shifting drum (Fig. 26). The shifting forks have a small round peg machined on each one of them. These pegs fit into grooves cut into the surface of the shift drum. Each shifting fork has its own groove. When the shifting drum is rotated, the grooves move the forks back and forth, engaging the correct gears. The drum is cut so that only one fork moves at a time, and only one gear or shifting dog is engaged at a time.