FIG. 33

on the right end of gear E. When the layshaft turns, the power flows along it to gear F, which then turns gear E, and the drive sprocket now turns. Another vital part of understanding gearbox operation is knowing how to calculate gearbox ratios. As a final step after each gearchange, the method for determining the ratio for that gear will be pointed out.

EXAMPLE: If gear A has 18 teeth, and gear J has 28, divide 18 into 28. 28 -- 18 = 1.55. If gear E has 24 teeth, and gear F has 16, divide 16 into 24. 24 - 16 = 1.5. Multiply 1.55 x 1.5, and the answer is 2.325, or the 1st gear ratio.

In 1st gear, the power is transmitted from the mainshaft to the layshaft from gear A to gear J, and from the layshaft back up to the mainshaft from gear F to gear E. Therefore, count the number of teeth on gear J and divide it by the number of teeth on A. Write down the result, then divide the number of teeth on gear E by the number on F. Write that figure down. Now multiply the two figures together, and the answer you get is the ratio for 1st gear, or the number of times the clutch must turn in order to make the drive sprocket turn once.

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