The drive mechanisms of an opposed-piston engine will obviously differ, to a degree, from those of single-acting engines because of design differences. Some of the differences are

Figure 5-5.Rear gear train of a 16-V 149 series Detroit diesel 2-stroke cycle engine.

Figure 5-6.Rear gear train timing marks on a 16-V 149 series Detroit diesel engine.

because (1) power is supplied by two crankshafts in an opposed-piston engine, instead of one, and (2) the camshaft drives of the engines we have discussed thus far supply power to one or more accessories as well as to the valve-actuating gear. This is not true of the camshaft in an opposed-piston engine since ports are used instead of valves for both intake and exhaust.

Regardless of differences in mechanisms, the basic types of drivesgear and chain are found in both single-acting and opposed-piston engines. While the two engines described in preceding sections had only gear-type drive mechanisms, the opposed-piston engine used as an example in this section has chain assemblies as well as gear trains incorporated in the mechanisms that supply power to engine parts and accessories.

The Fairbanks-Morse (FM) opposed-piston engine has three separate drive mechanisms. The drive that furnishes power to the camshaft and fuel-injection equipment is the chain type. The blower and the accessories are operated by gear-type drives. The location of each drive is shown in figure 5-7.