8. 4th Gear. To shift from 3rd to 4th gear, the gearshift is again
lifted upward, causing the selector shaft to rotate. This moves the selector
pawl upward, rotating the shifting drum clockwise. This draws gear 1 to
the left, disengaging it from gear H, and returning it to a neutral position.
The sliding dog, K, then moves to the left, engaging into gear D. The transmission
is now in 4th gear, as illustrated in Fig. 36. The power flows along the
mainshaft to the sliding dog, which is locked to the mainshaft, and to
gear D, into which it is engaged. Gear D then drives gear G, and because
G is locked to the mainshaft, the shaft turns along with gear F. F then
turns E, causing the sprocket to rotate.
To calculate the 4th gear ratio, divide the number of teeth on gear
G by the number on gear D. Divide the number of teeth on gear E by the
number on gear F. Multiply the two answers together to obtain the ratio
of 4th gear.