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 railroads. 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 manufacturers 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 remarkably high and very nearly approached that of the best
wrought-iron plate.
The cylinders are cast iron with an 8-1/2-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 deg. 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 extensively used on
mid-19th-century American locomotives 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 approaching 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 rationalization 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 or 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).
[Illustration: Figure 27.--"PIONEER" LOCOMOTIVE. (1) Air chamber, (2)
reversing lever, (3) counterweight, (4) reversing shaft, (5) link
hanger, (6) rocker, (7) feedwater line to boiler, (8) link block, (9)
link, (10) eccentric, (11) pump plunger, (12) pump steamheater line,
(13) feedwater pump, (14) wire netting [bonnet], (15) deflecting cone,
(16) stack, (17) stack hopper. (Drawing by J. H. White.)]
[Illustration: Figure 28.--REAR ELEVATION of _Pioneer_ and detail of
valve shifter; valve face and valve. (Drawing by J. H. White.)]
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 the rear cylinder head and supported in the rear by a
yoke. The yoke is one of the more finished and better made pieces on the
entire engine (fig. 27). The main rod is of the old pattern, round in
cross section, and only 1-1/2 inches in diameter at the largest point.