ENGINE No. 87. 



Single-valve cross compound, 15" and 23" x 15". Speed, 

 260 revolutions per minute. 



This engine has unpacked piston valves, one for each cylin- 

 der, with a shaft governor operating on the high-pressure valve. 



These diagrams are given to show the effect of a break in 

 the casting of the high-pressure steam-chest, which allowed 

 steam to pass directly into the low-pressure chest without going 

 through the high-pressure cylinder. The two cylinders and the 

 chest were all made in one casting. Diagrams No. Sl(t and 

 Sib were taken with a load of 7i>.5 I. H. P., and No. Sic and 

 Sid with a load of 131.1, I. H. P. In the former the low- 

 pressure cylinder developed 155.2 H. P., and in the latter 141.3 

 H. P. In the former the high-pressure cylinder produced a 

 resistance or negative power equivalent to 75.7 horse-power, 

 while in the latter this was reduced to 10.2 horse-power. The 

 difference in these quantities gives the respect i\<- horse-powers 

 as stated. In diagram Sid the upper line, which ordinarily 

 is the steam and expansion line, is here the compression line, 

 and the lower line is the one thai is made during the admission, 

 expansion, and release. The boiler pressure here is 7"> Ihs.. and 

 the compression of the exhaust carries the hack pressure up 

 to 120 Ibs. The point of cut-off takes place at the very begin- 

 ning of the stroke, and evidently there is no steam admitted 

 save that which comes from the compression of the exhaust. 



Diagrams S7< and 87/ were taken from an engine of the 

 same size and make, in which there was no defect such as that 

 mentioned : and a comparison with these will show the effect 

 produced by the disordered condition. In these diagrams the 

 high-pressure cylinder developed 71.4 I. H. P., and the low- 

 pressure 53.3, making a total for the engine of 124.7 I. H. P. 

 This is about the same power as that shown by diagrams 87c? 

 and 87(7. 



These diagrams are all from the crank ends. 



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