Figure 20. Feedwateb pump ol the Pioneer. (Smithsonian ph 



sliort and the plunger is in less rapid motion, the 

 present eccentric arrangement is more complex but 

 less prone to disorder than the simpler but Faster 

 crosshead pump. 



The check valves are placed slightly below the 

 centerline of the boiler (fig. 18). These valves are 

 an unfinished bronze casting and appear to be of a 

 hi cut pattern, probably dating from the 1901 renova- 

 tion. At the time the engine was built, it was usual 

 to house these valves in an 0rn.m1ent.1l spun-brass 

 1 In- smokestack is of the bonnet type com- 

 monly used on wood-burning locomotives in this 

 country between about 1845 and 187(1. The exhaust 

 steam from the cylinders is directed up the straight 

 stack (shown in phantom in fig. 27) by the blast pipe. 

 This creates a partial vacuum in the smokebox th.it 

 draws the fire, gases, ash, and smoke through the 

 boiler tubes from the firebox. 1 he force of the 

 exhausting steam blows them out the stack. At the 

 top of the straight stack is a deflecting cone which slows 

 the velocity of the exhaust and changes its direction 

 causing it to go down into the funnel-shaped outei 

 casing of the stack. Here, the heavy embers and 



PAPER 42: THE 'T'lONKI-.R" 1 >F ISM 



cinders are collected and prevented from directly 

 discharging into tin- countryside as dangerous fire- 

 brands. Wire netting is stretched overtop of the 

 deflecting cone to catch the lighter, more volatile 

 embers which may defy the action of the cone. 

 The term "bonnet stack" results from the fact that this 

 netting is similar in shape to a lady's bonnet. The 

 cinders thus accumulated in the stack's hopper could 

 be emptied by opening a pluu.it 1 he base of the stack. 

 While the deflecting cone was regarded highly 

 as a sp.nk .in ester and used practically to the exclusion 

 other arrangement, it had the basic defect 

 ol keeping the smoke low and close to the train. This 

 was .1 great nuisance to passengers, as the low trailing 

 smoke blew into the ears. If the exhaust had been 

 allowed to blast straight out the stack high into the 

 air. most i«l iIk' sp.nks would have burned out before 

 touching the ground. 



I R \M1 



The frame of the Pioi exact classification 



but it more closely resembles the riveted- or sandwich- 



261 



