Chapter 22. -DIESEL AND GASOLINE ENGINES 



Note that in figure 22-38, which shows the 

 mechanism more clearly, the gears are set for 

 reverse rotation, and the brake band is clamped 

 to the drum. The parts which are shaded are held 

 stationary by the brake band, and the remaining 

 internal parts, which are not shaded, rotate. (The 

 rotation of the engine shaft and engine sleeve is 

 transmitted directly to the cone clutch and the 

 short pinions. The cone clutch rotates freely out 

 of contact with the stationary front cover. The 

 short pinions drive the long pinions, which drive 

 the propeller drive sleeve. The latter unit is 

 keyed to and drives the reduction gear shaft, 

 which rotates opposite to the engine shaft.) 



The reduction gear unit is bolted to the 

 reverse gear housing, as shown in figure 22- 

 31. It consists merely of an external gear, 

 mounted on the reduction gear shaft, and in mesh 

 with a larger internal gear, mounted on the pro- 

 peller shaft. Power is transferred, at a reduced 

 speed, from the smaller drive gear to the larger 

 internal gear. 



Lubrication of the clutch and reverse gear 

 mechanism is accomplished by means of a 

 drilled passage in the crankshaft which supplies 

 oil, as a spray, to the gears and other moving 

 parts. This oil returns to the engine sump by 

 gravity. 



Lubrication of the reduction gear unit is 

 accomplished by an external line from the 

 engine's main oil gallery. Oil is sprayed over 

 the gears and moving parts to lubricate and 

 cool them. Excess oil either drains back to the 

 engine sump by gravity, or, where the unit is 



below the engine, returns to the sump by means 

 of a scavenging pump. 



Airflex Clutch and Gear Assembly.— On the 

 larger diesel-propelled ships, the clutch, re- 

 verse and reduction gear unit has to transmit an 

 enormous amount of power. To maintain the 

 weight and size of the mechanism as low as 

 possible, special clutches have been designed 

 for large diesel installations. One of these is 

 the airflex clutch and gear assembly used with 

 some General Motors engines on LST's. 



A typical airflex clutch and gear assembly, 

 for ahead and astern rotation, is shown infigure 

 22-32. There are two clutches, one for forward 

 rotation and one for reverse rotation. The 

 clutches are bolted to the engine flywheel by 

 means of a steel spacer, so that they both rotate 

 with the engine at all times, and at engine speed. 

 Each clutch has a flexible tire (or gland) on the 

 inner side of a steel shell. Before the tires are 

 inflated, they will rotate out of contact with the 

 drums, which are keyed to the forward and 

 reverse drive shafts. When air under pressure 

 (100 psi) is sent into one of the tires, the inside 

 diameter of the clutch decreases. This causes 

 the friction blocks on the inner tire surface to 

 come in contact with the clutch drum, locking 

 the drive shaft with the engine. 



The parts of the airflex clutch which give 

 the propeller ahead rotation are illustrated in 

 the upper view of figure 22-32. The clutch tire 

 nearest the engine (forward clutch) is inflated 

 to contact and drive the forward drum with the 

 engine. The forward drum is keyed to the forward 



TOGGLE PLUNGER BRAKE MECHANISM 



ASSEMBLY -^^^^>i^ /r BRAKE BAND 



LONG PINION 



DRUM 



SHORT PINION 



REDUCTION 

 COLLAR GEAR SHAFT 



AND YOKE 



PROPELLER 

 DRIVE SLEEVE 



ENGINE SLEEVE 

 ENGINE SHAFT 



75.255 



Figure 22-38.— Schematic diagram of Joe's reverse gear assembly. 



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