STEAM ENGINES 221 



bearings sooner or later. Hot clinkers and ashes should be 

 sprinkled, and the fireroom door should be closed while the 

 ashes and clinkers are being hauled or wet down or while the 

 fires are being cleaned or hauled. As an additional precaution, 

 all open oil holes should be plugged with wooden plugs or 

 bits of clean cotton waste as soon as possible after the engine 

 is stopped, and should be kept closed until ready to oil the 

 engine again preparatory to starting up. Plaited hemp or 

 cotton gaskets should also be laid over the crevices between 

 the ends of the brasses and the collars of the journals of every 

 bearing on the engine and kept there while the engine is stand- 

 ing still. 



Overloading of Engine. The effect produced by overloading 

 an engine is this: the pressure on the brasses is increased to- 

 a point beyond that for which they were designed, the friction 

 exceeds the practical limit, and the bearing heats. In case 

 an engine is run at or near its limit of endurance, or if the 

 journals are too small, it would be a wise and economical 

 precaution to have a complete set of spare brasses on hand 

 ready to slip in when the necessity arises. 



Engine Out of Line. If an engine is not in line, the brasses 

 do not bear fairly upon the journals. This will reduce the 

 area of the bearing surfaces in contact to such an extent as to 

 cause heating. If the engine is not very much out of line, 

 matters may be considerably improved by refitting the brasses 

 by filing and scraping down the parts of those which bear 

 most heavily on the journal. If this does not answer, the heat- 

 ing will continue until the engine is lined up. 



The crosshead guides of an engine out of line are apt to heat, 

 and they will continue to give trouble until the defect is rem- 

 edied. The guides may also heat from other causes; for instance, 

 the gibs may be set up too much. The danger of hot guides 

 may be very much lessened by chipping zigzag oil grooves 

 in their wearing surfaces and by attaching to the crosshead 

 oil wipers made of cotton lamp wicking arranged so as to dip 

 into oil reservoirs at each end of the guides if they are hori- 

 zontal, and at the lower end if they are vertical. These 

 wipers will spread a film of oil over the guides at every stroke 

 of the crosshead. 

 16 



