STEAM ENGINES 217 



Newly Fitted Bearings. The bearings of new engines are 

 particularly liable to heat, as the wearing surfaces of the 

 brasses and journal have just been machined and hence are 

 comparatively rough. The conditions just mentioned also 

 exist with new brasses and the journals of an old engine. If 

 a new engine or one with new brasses is run moderately, in 

 regard to both speed and load, and with rather loose brasses, 

 there will be little danger of hot bearings, provided proper 

 attention is given to adjustment and lubrication. This is 

 what is familiarly termed wearing dawn the bearings. 



Brasses Too Tight. When the brasses of an engine bearing 

 are set up too tight, heating is inevitable. It is often the 

 case that an attempt is made to stop a pound in an engine by 

 setting up the brasses when the thump should be stopped in 

 some other way. The brasses should be slacked off as soon 

 as possible. As a matter of fact, hot bearings should never 

 occur from this cause. 



Brasses Too Loose. Bearings may heat because the brasses 

 are too loose. The heating is caused by the hammering of the 

 journal against the brasses when the crankpin is passing the 

 dead centers. The derangement is easily remedied, however, 

 by setting up the cap nuts or the key. Most engineers have 

 their own views regarding the setting up of bearings. One 

 method is to set up the cap nuts or key nearly solid and then 

 slack them back half way; if the brasses are still too loose, they 

 are set up again and slacked back less than before, repeating 

 this operation until there is neither thumping nor heating. 



Another method of setting up journal brasses is to fill up 

 the spaces between the brasses with thin metal liners, from 

 18 to 22 Birmingham wire gauge in thickness, and a few paper 

 liners for fine adjustment. Enough of these should be put 

 in to cause the brasses to set rather loosely on the journal 

 when the cap nuts or keys are set up solid. The engine should 

 be run for a while in that condition; then a pair of the liners 

 should be removed and the brasses set up solid again. This 

 operation should be repeated until there is neither thumping 

 nor heating. It may require a week or more, and with a large 

 engine longer, to reach the desired point. If this system is 

 carefully carried out, there will be very little danger of heating. 



