CHAPTER XXIV 

 TRANSMISSION OF POWER 



320. Methods of Transmitting Power. The power that 

 drives a machine is usually transmitted in one of three ways : 

 (1) from a fly-wheel in the power house to a pulley on a main 

 line of shafting in the shop and then to another pulley on a 

 small shaft over each machine, called a countershaft; (2) 

 directly from the pulley of an electric motor, located in the 

 shop where it drives the main line of shafting; or (3) by 

 means of gears from a separate electric motor attached to 

 each machine. The first two methods are called power trans- 

 mission by shafting, and the third is called power transmission 

 by separate motor or "individual drive. " 



321. Arrangement of Shafting. The transmission of 

 power by shafting is accomplished by means of pulleys and 

 belts, or ropes attached to the shafts, which in turn are sup- 

 ported by hangers. Shafting consists of cylindrical bars of 

 steel or wrought iron from 1J^ in. to 2J^ in. in diameter. 

 The different lengths of shafting are connected by a device 

 called a coupling. The shafting is supported by hangers 

 attached to the ceiling (Fig. 140) and revolves through an 

 opening in the hanger called a bearing. The part of the 

 shaft which rotates in the bearing is called the journal. The 

 bearing is encased in a soft metal called Babbitt metal, to 

 reduce the friction to a minimum. Babbitt metal is white 

 alloy of copper, tin, and antimony. The hardness of the 



283 



