The power to drive the blower is transmitted from the upper crankshaft, through a gear train (fig. 5-7). The train consists of a drive gear, a pinion gear, and the two timing (impeller) gears of the blower.

The drive gear is the flexible type (fig. 5-7). The principal parts of the FLEXIBLE DRIVE GEAR are a spider drive hub (which is keyed to the crankshaft), a gear (within which spring spacers are bolted), and springs (which absorb torsional oscillations transmitted by the crankshaft). A view of the flexible drive gear with end plate removed and the spider drive hub is shown in figure 5-9.

The flexible drive gear meshes with the drive pinion (fig. 5-7). The pinion is keyed to the lower impeller shaft and held in place by a locknut. The lower impeller driving (timing) gear meshes with the upper impeller driven gear (fig. 5-7).

ACCESSORY DRIVE MECHANISM

The majority of the accessories for the FM 38D are driven by a gear mechanism that receives power from the lower crankshaft at the control end of the engine (fig. 5-7). A more detailed view of the accessory drive is shown in figure 5-10. Referring to both these figures as you read the following description will help you become familiar with the components of the drive and with the way that power is transmitted to the driven units.

The accessory drive transmits power to the water pumps, the fuel oil pump, the lubricating oil pump, and the governor. The drive gear (fig. 5-7) of the mechanism is bolted to a flange on the crankshaft. The drive gear is the flexible type; therefore, engine shocks transmitted by the crankshaft are absorbed by the drive springs of the gear.

The water pump drive gears mesh directly with the flexible drive gear. The fuel pump drive gear

Figure 5-8.Camshaft drive and timing mechanism (Fairbanks-Morse 38D8 1/8).

Figure 5-9.Blower flexible drive gear (Fairbanks-Morse 38D8 1/8).

Figure 5-10.Accessory drive (Fairbanks-Morse 38D8 1/8).

(attached to the flexible drive gear) transmits power to the fuel pump driven gear through an idler. (See the fuel pump driven gear on the mounting plate in fig. 5-10.) The lubricating oil pump drive gear meshes directly with the flexible drive gear. Power is transmitted to the pump through a shaft and an internal gear coupling the lubricating oil pump drive. The shaft of the lubricating oil pump drive also transmits power to the governor. A gear on the shaft meshes with a mating gear on the governor drive gear shaft. This shaft drives the governor coupling shaft which, in turn, drives the governor, through a beveled gear drive (fig. 5-7).