128 SCIENCE OF SUCCESSFUL, THRESHING 



emergencies, the hub of the left traction wheel is made so 

 that a pin can be inserted and both wheels locked to the 

 axle. This, of course, makes both traction wheels revolve 

 together, and prevents the differential gear from working. 

 The engine must be steered straight when the lock-pin is 

 used, or broken gearing is liable to result. 



Oiling the Differential. There are several moving 

 parts within the differential gear which should be oiled 

 occasionally. The bevel-pinions revolve about their 

 shafts. An oil-hole is drilled through the center of each 

 of these shafts to provide for oiling them, as shown in Fig. 

 40. The center wheel turns on the hub of the left-hand 

 or inside bevel-gear, when the differential-gear works, and 

 accordingly it should be oiled occasionally through the hole 

 provided for this purpose in the bevel-gear hub, as shown 

 in Fig. 40, which applies to all except the no horse-power 

 engine. The oil passes into a chamber, then along the 

 groove and out through the radial holes to the journal. 

 The oil also works farther along the groove and oils right- 

 hand countershaft pinion where it turns on the shaft. On 

 the no horse-power engine, there is no oil groove in the 

 shaft. The oil holes in the hub of the inside bevel gear 

 carry the oil direct to the bearing of the center wheel, and 

 the right-hand countershaft pinion is provided with holes 

 in its hub for oiling the shaft. The hub of the left-hand 

 traction wheel turns upon the axle in turning corners, and 

 therefore should be oiled occasionally. This is done by 

 removing the cap-screws in the hub of the traction wheel. 



