FARM MACHINERY 



191 



or babbitt. When made of different materials there is less 

 tendency for the surface to become rough and abraded. 



Roller and Ball Bearings. Roller and 

 ball bearings substitute rolling friction for 

 sliding friction. Such bearings are usually 

 much more expensive than plain bearings, 

 but in many places the extra expense is 

 justified. Roller bearings furnish a very 

 satisfactory means of holding a supply of the lubricant and 

 prevent binding and heating, due largely to misalignment. 



Fig. 102. A ball 

 bearing-. 



Fig. 103. A roller bearing- for wagons. The hub of the wheel fits over 



the rollers shown. 



Ring Oiling Bearings. A ring oiling bearing has a 

 reservoir of oil underneath the shaft, or journal, into which a 

 ring resting on the upper side of the shaft is allowed to dip, 

 and as the shaft rotates the oil is carried up onto the shaft, 



where it spreads out to 

 each side, thoroughly lu- 

 bricating the bearing. 

 Such a bearing is very 

 desirable for a machine in 

 continuous service. 

 Inclosed Wheel Boxes. It is customary on the best 

 machines that are to be subjected to much dust, to enclose 

 the outer end of the wheel boxes and provide a collar at the 

 inside end of such a construction as to practically exclude all 

 dust. The lubricant is usually "hard oil" or heavy grease, 



Fig. 104. A ring oiling bearing. 



