The opposed-piston engine does not have cylinder valves; and since two other drives are provided to operate the accessories, the primary purpose of the camshaft drive is to transmit power for, and to time the operation of, the fuel-injection pumps. The camshafts are located in the upper crankshaft compartment (fig. 5-7). The shafts turn at the same rate of speed as the crankshaft.

CHAIN ASSEMBLY

The power required to operate the fuel-injection pumps at the proper instant during the cycle of operation is transmitted through the cam-shafts from the crankshaft by a chain drive

Figure 5-7.Location of drive mechanisms in an opposed-piston engine (Fairbanks-Morse 38D8 1/8).

(frequently called the timing mechanism). The names and arrangement of the components of the drive are shown in figure 5-8. The drive sprocket is attached to the upper crankshaft at the control end of the engine. A sprocket is attached to the end of each camshaft, and there are three other sprockets for timing and adjustment purposes. The chain conveys the rotation of the upper crankshaft to the camshaft sprockets by passing over the crankshaft sprocket, under the two timing sprockets, over the two camshaft drive sprockets, and under the tightener sprockets. The timing sprockets are mounted on an adjustable bracket or lever. By moving the lever, the timing of the two camshafts can be adjusted. The adjustable tightener sprocket is used to obtain and maintain the proper slack in the chain.