Chapter 22. -DIESEL AND GASOLINE ENGINES 



FORWARD ROTATION 



IDLER GEAR 



75.252 

 Figure 22-36. — Forward and reverse gear trains 

 for Gray Marine engines. 



The clutch operating lever moves the throw- 

 out fork, which in turn shifts the sliding sleeve 

 lengthwise along the forward shaft. When the 

 operating lever is placed forward, the sliding 

 sleeve is forced backward. In this position the 

 linkages of the spring-loaded mechanism pull 

 the floating pressure plate against the forward 

 disk, and cause forward rotation. When the op- 

 erating lever is pulled back as far as it can go, 

 the sliding sleeve is pushed forward. In this 

 position, the floating pressure plate engages the 

 reverse disk and back plate for reverse rota- 

 tion. 



The clutch has a positive neutral which is 

 set by placing the operating lever in a middle 

 position. Then the sliding sleeve is also in a 

 middle position, and the floating plate rotates 

 freely between the two clutch disks. (The only 

 control that the operator has is to cause the 

 floating plate to bear heavily against either the 

 forward disk or the reverse disk, or to put the 

 floating plate in the positive neutral position 



so that it rotates freely between the two 

 disks.) 



The reversing gear unit is lubricated sepa- 

 rately from the engine by its own splash system. 

 The oil level of the gear housing should never 

 be kept over the high mark because too much 

 oil will cause overheating of the gear unit. The 

 oil is cooled by air which is blown through the 

 baffled top cover by the rotating clutch. Grease 

 fittings are installed for bearings not lubricated 

 by the oil. 



JOE'S DOUBLE CLUTCH REVERSE GEAR.- 

 A gear mechanism found on many power boats 

 is Joe's double clutch reverse gear. The in- 

 stallation of a typical Joe's reverse gear and 

 clutch assembly for the Navy type DC engine 

 is shown in figure 22-37. The drive from the 

 engine crankshaft is taken into the clutch and 

 reverse gear housing by an extension of the 

 crankshaft drive gear. The crankshaft rotation 

 is transmitted to the reduction gear shaft through 

 the clutch and the reverse gear unit. 



If one could open the clutch and reverse gear 

 housing and watch the reverse gear drum and 

 the reduction gear shaft while the engine is run- 

 ning, the following operation would be observed: 



When the operating lever is thrown forward, 

 the drum and reduction gear shaft rotate in the 

 same direction as the engine crankshaft. This 

 causes forward rotation of the propeller. 



In the intermediate position of the operating 

 lever, the drum rotates but the reduction gear 

 shaft remains stationary. This is the neutral 

 setting. 



Forward rotation is obtained by dual clutch 

 action while reverse rotation is obtained through 

 the operation of the planetary gears. The unit 

 consists of a housing enclosing a split conical 

 clutch and a multi-plate friction clutch and 

 gearing. Additional components include the col- 

 lar and yoke and an outer brake band with an 

 operating toggle mechanism. Movement of the 

 sliding collar selects the direction of rotation. 



When the operating lever is placed in the 

 forward position, the linkage between the lever 

 and the collar and yoke assembly slides the 

 collar lengthwise to the left along the reduction 

 gear shaft. This motion operates the toggle 

 assembly which, in turn, drives the three 

 plungers to the right, pressing them hard against 

 the disk clutch. 



When the plungers are driven hard against 

 the disk clutch, the disks are locked together 

 by friction. This locks the drum housing to the 



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