AXLES. 67 



ment. The fore part of the under-carriage is attached to the 

 back section by means of two semicircular plates, one bearing 

 and turning over the other and secured by a perch bolt pass- 

 ing through the centre. 



AXLES. 



The axle-trees comprise the most important part of the 

 under-carriage. The light axle-trees are made of a single 

 solid shaft of iron ; but for heavier vehicles this part is com- 

 posed of numerous bands of "scrap" iron firmly "fagoted" 

 or welded together. An axle-tree is technically divided into 

 three parts : the two arms and the bed, or that portion which 

 connects the arms together. The axle-tree arms are usually 

 conical, but in some patterns they are made cylindrical. On 

 the upper surface a groove is cut to receive the oil and the 

 ends are threaded to fit the nuts which keep the wheel in 

 place. The common axle (see Fig. 36) is the only kind that 

 can be employed where lightness is sought, but for heavier 

 vehicles it is inferior in some respects to the Collinge and 

 Mail axles. 



THE COLLINGE AXLE. 



The Collinge axle consists of a cylindrical arm with a 

 flanged collar at the shoulder. A short distance from the 

 collar the diameter of the arm gradually diminishes and then 

 continues in cylindrical shape, with an oil groove on the upper 

 surface, until within a few inches of the end ; here it is ab- 

 ruptly reduced in diameter. The diminished part is made 

 flat on top to receive the "D" slide or collet that is 

 pressed against the thick portion of the axle box. Beyond 

 this part which takes the " D " slide the axle arm is further 

 reduced and threaded the width of a nut. At the end of 



