2,6 AXLE-ARM CH. Ill 



advantages. The fancy of some builders or owners 

 for having a Collinge axle with a sham plate and 

 three bolt-heads, put on over the cap, cannot be 

 commended, since one of the objections to the mail 

 axle is the ugliness of the plate, especially on a 

 private coach. 



The present fashion certainly is to have Collinge 

 axles on private coaches and mail axles on public- 

 coaches, and there seems to be no objection to it 

 as a proper distinction ; but the more the coach is 

 used for long drives and fast work, the more reason 

 is there for adopting the mail axle. The fact that 

 a public-coach, running at a high speed, a number 

 of miles every day, with heavy loads, requires a 

 much more frequent inspection in all its parts than 

 does a private drag, makes the trouble of frequent 

 oiling of relatively less importance. 



It is a mistake to have the axle-arm too small ; a 

 somewhat large hub is not out of place on a heavy 

 vehicle, and the best practice in modern machinery 

 tends toward large rubbing surfaces on all journals, 

 although the resistance to the turning of the wheel 

 due to friction is directly as the diameter of the axle. 

 The value of the oil as a lubricant depends upon its 

 particles remaining in good condition between the 

 rubbing surfaces, and on small surfaces, with heavy 

 pressures, this condition is rapidly destroyed. Jn 

 any question as to the dimensions of an axle-arm, 

 therefore, the designer should lean toward a large 

 size, both on account of its superior strength and 



