430 ELECTRICAL MACHINERY 



are kept free from the dust and moisture with which the 

 car truck gets covered.) If it is not possible to use an 

 enclosed type of machine, the attendant must exercise 

 special care in keeping the commutator clean and must 

 blow the dust out of the windings by means of a bellows 

 whenever the machine is shut down. 



138. Precautions in Starting a Machine. After a machine 

 has been properly installed a thorough inspection must be 

 given before the machine is started. The operator must look 

 over the machine very carefully to see that there are no 

 mechanical or electrical faults which would injure the 

 machine as soon as started. 



The machine should be thoroughly blown out by a 

 bellows, so that any dust, dirt, chips, etc. which may have 

 collected in the interstices of the windings and various 

 parts, may be cleaned out. 



Tightening of Parts, etc. All parts of the machine 

 should be thoroughly tightened; a pole may pull loose 

 from the yoke very soon if its fastening bolts are not drawn 

 up snug; the same precaution holds with respect to the 

 pole shoes and any other parts held together by bolts. 

 Care must be observed to see that there is nothing in 

 the air gap; a small nut, nail, etc., in the air gap may 

 cut the armature winding badly when the machine is 

 started. 



Bearings. The machine must turn freely in its bearings 

 and the oil-rings must be picking up the proper amount of 

 oil. This latter point is extremely important; oil-ring 

 bearings operate so reliably in general that they receive 

 less attention from the operator than they really require. 

 The oil used in the bearing should be the best grade of 

 machine oil; if too thick, it will not flow freely through the 

 oil ducts in the bearing and if too thin it runs out too 

 quickly and there is not a sufficient layer of oil between 

 the shaft and bearings for proper lubrication. The bearings 

 must be thoroughly cleaned from dirt, grit, etc, 



