was thus subjected to the additional strain of the lo- 

 comotive's vibrations as it passed over the road. In 

 later years, as locomotives grew in size, this practice 

 was avoided and frames were made sufficiently strong 

 to hold the engine's machinery in line without using 

 the boiler shell. 



The front and rear frame beams are of flat iron 

 plate bolted to the frame. The rear beam had been 

 pushed in during an accident, and instead of its 

 being replaced, another plate was riveted on and bent 

 out in the opposite direction to form a pocket for the 

 rear coupling pin. Note that there is no drawbar and 

 that the coupler is merely bolted to the beams. Since 

 the engine only pulled light trains, the arrangement 

 was sufficiently strong. 



RUNNING GEAR 



The running gear is simply sprung with individual 

 leaf springs for each axle; it is not connected by 

 equalizing levers. To find an American locomotive 

 not equipped with equalizers is surprising since they 

 were almost a necessity to produce a reasonably 

 smooth ride on the rough tracks of American rail- 

 roads. Equalizers steadied the motion of the engine 

 by distributing the shock received by any one wheel 

 or axle to all the other wheels and axles so connected, 

 thus minimizing the effects of an uneven roadbed. 

 The author believes that the Pioneer is a hard-riding 

 engine. 



The springs of the main drives are mounted in the 

 usual fashion. The rear boiler bracket (fig. 18) is 

 slotted so that the spring hanger may pass through 

 for its connection with the frame. The spring of the 

 leading wheels is set at right angles to the frame (fig. 

 27) and bears on a beam, fabricated of iron plate, 

 which in turn bears on the journal boxes. The springs 

 of the trailing wheels are set parallel with the frame 

 and are mounted between the pedestal plates (fig. 18). 



The center of the driving wheel is cast iron and has 

 spokes of the old rib pattern, which is a T in cross 

 section, and was used previous to the adoption of the 

 hollow spoke wheel. In the mid-1830's Baldwin and 

 others used this rib-pattern style of wheel, except that 

 the rib faced inside. The present driving-wheel 

 centers are unquestionably original. The sister engine 

 Jenny Lind (fig. 22) was equipped with identical driving 

 wheels. The present tires are very thin and beyond 

 their last turning. They are wrought iron and shrunk 

 to fit the wheel centers. Flush rivets are used for 

 further security. The left wheel, shown in figure 17, 



is cracked at the hub and is fitted with an iron ring 

 to prevent its breaking. 



The truck wheels, of the hollow spoke pattern, are 

 cast iron with chilled treads. They were made by 

 Asa Whitney, one of the leading car-wheel manufac- 

 turer^ in this country, whose extensive plant was located 

 in Philadelphia. Made under Whitney's patent of 

 1866, these wheels may well have been added to the 

 Pioneer during the 1871 rebuilding. Railroad wheels 

 were not cast from ordinary cast iron, which was too 

 weak and brittle to stand the severe service for which 

 they were intended, but from a high-quality cast iron 

 similar to that used for cannons. Its tensile strength, 

 which ranged from 31,000 to 36,000 psi, was remark- 

 ably high and very nearly approached that of the 

 best wrought-iron plate. 



The cylinders are cast iron with an 8,^-inch bore 

 about half the size of the cylinders of a standard 

 8-wheel engine. The cylinders are bolted to the 

 frame but not to the saddle, and are set at a 9° 

 angle to clear the leading wheels and at the same 

 time to line up with the center of the driving-wheel 

 axle. The wood lagging is covered with a decorative 

 brass jacket. Ornamental brass jacketing was ex- 

 tensively used on mid- 19th-century American loco- 

 motives to cover not only the cylinders but steam 

 and sand boxes, check valves, and valve boxes. The 

 greater expense for brass (Russia iron or painted 

 sheet iron were a cheaper substitute) was justified by 

 the argument that brass lasted the life of the engine, 

 and could be reclaimed for scrap at a price approach- 

 ing the original cost; and also that when brightly 

 polished it reflected the heat, preventing loss by 

 radiation, and its bright surface could be seen a 

 great distance, thus helping to prevent accidents at 

 grade crossings. The reader should be careful not 

 to misconstrue the above arguments simply as ration- 

 alization on the part of master mechanics more 

 intent on highly decorative machines than on the 

 practical considerations involved. 



The valve box, a separate casting, is fastened to 

 the cylinder casting by six bolts. The side cover 

 plates when removed show only a small opening 

 suitable for inspection and adjustment of the valve. 

 The valve box must be removed to permit repair oi 

 removal of the valve. A better understanding of this 

 mechanism and the layout of the parts can be gained 

 from a study of figures 23-26, 28 (8, 8a, and 8b). 



Both crossheads were originally of cast iron but 

 one of these has been replaced and is of steel. They 

 run into steel guides, bolted at the forward end to 



264 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



