covers, indicate that a steam dome or manhole was 

 located at this point. It is possible that this was the 

 original location of the steam dome since many build- 

 ers in the early 1850's preferred to mount the dome 

 forward of the firebox. This was done in the belief 

 that there was less danger of priming because the 

 water was less agitated forward of the firebox. 



The firebox is as narrow as the boiler shell and fits 

 easily between the frame. It is a deep and narrow 

 box, measuring 27 inches by 28 inches by about 40 

 inches deep, and is well suited to burning wood. A 

 deep firebox was necessary because a wide, shallow 

 box suitable for coal burning, allowed the fuel to burn 

 so quickly it was difficult to fire the engine effectively. 

 With the deep, narrow firebox, wood was filled up to 

 the level of the fire door. In this way, the fire did not 

 burn so furiously and did not keep ahead of the fire- 

 man; at the same time, since it burned so freely, a 

 good fire was always on hand. The Pioneer burned 

 oak and hickory. 14 For the firebox fi' 6 -inch thick sheet 

 was used, for heavier sheet would have blistered and 

 flaked off because of the intense heat of the fire and 

 the fibrous quality of wrought-iron sheet of the period. 

 Sheet iron was fabricated from many small strips of 

 iron rolled together while hot. These strips were 

 ideally welded into a homogeneous sheet, but in prac- 

 tice it was found the thicker the sheet the less sure the 

 weld. 



The fire grates are cast iron and set just a few 

 inches above the bottom of the water space so that 

 the water below the grates remains less turbulent and 

 mud or other impurities in the water settle here. 

 Four bronze mud plugs and a blowoff cock are 

 fitted to the base of the firebox so that the sediment 

 thus collected can be removed (figs. 17, 18). 



The front of the boiler is attached to the frame by 

 the smokebox, which is a cylinder, bolted on a light, 

 cast-iron saddle (not part of the cylinder castings 

 nor attached to them, but bolted directly to the top 

 rail of the frame; it may be a hastily made repair 

 put on at the shops of the C.Y.R.R.). The rear of 

 the boiler is attached to the frame by two large cast- 

 iron brackets, one on each side of the firebox (fig. 18). 

 These are bolted to the top rail of the frame but the 

 holes in the brackets are undoubtedly slotted, so that 

 they may slide since the boiler will expand about 

 ', inch when heated. In addition to the crown 

 bars, which strengthen the crown sheet, the boiler 

 is further strengthened by stay bolts and braces 



M Annual Report, C.V.R.R., 1853. 



located in the wagon top over the firebox, where the 

 boiler had been weakened by the large hole necessary 

 for the steam dome. This boiler is a remarkably 

 light, strong, and compact structure. 



BOILER FITTINGS 



Few boiler fittings are found on the Pioneer and it 

 appears that little was done to update the engine 

 with more modern devices during its many years of 

 service. With the exception of the steam gauge, it 

 has no more boiler fitting than when it left the 

 builder's shop in 1851. 



The throttle valve is a simple slide valve and must 

 have been primitive for the time, for the balance- 

 poppet throttle valve was in use in this country- 

 previous to 1851. It is located directly below the 

 steam dome even though it was common practice to 

 place the throttle valve at the front of the boiler in 

 the smokebox. Considering the cramped condition 

 inside the smokebox, there would seem to be little 

 space for the addition of the throttle valve: hence its 

 present location. The dry pipe projects up into the 

 steam dome to gather the hottest, driest steam for the 

 cylinders. The inverted, funnel-like cap on the top 

 of the dry pipe is to prevent priming, as drops of water 

 may travel up the sides of the pipe and then to the 

 cylinders, with the possibility of great damage. After 

 the steam enters the throttle valve it passes through 

 the front end of the valve, through the top of the 

 boiler via the dry pipe (fig. 18), through the front 

 tube sheet, and then to the cylinders via the petticoat 

 pipes. The throttle lever is a simple arrangement 

 readily understood from the drawings. It has no 

 latch and the throttle lever is held in any desired 

 setting by the wingnut and quadrant shown in figure 

 18. The water level in the boiler is indicated by the 

 three brass cocks located on the backhead. Xo gauge 

 glass is used; they were not employed in this country 

 until the 1870's, although they were commonly used 

 in England at the time the Pioneer was built. 



While two safety valves were commonly required, 

 only one was used on the Pioneer. The safety valve 

 is located on top of the steam dome. Pressure is 

 exerted on the lever by a spring balance, fixed at the 

 forward end by a knife-blade bearing. The pressure 

 can be adjusted by the thumbscrew on the balance. 

 The graduated scale on the balance gave a general 

 but uncertain indication of the boiler pressure. The 

 valve itself is a poppet held against the face of the 

 valve seat by a second knife blade attached to the 



258 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



