Among the earliest troubles of the young engineer and his employer, Robert L. Stevens, was the fact that as there were only four wheels under the engines, they were derailed frequently in going around curves; so it was necessary to provide an appliance to prevent this.
THE FIRST PILOT.
The first pilot was planned, 1832, by Robert L. Stevens. A frame made of oak, eight by four feet, pinned together at the corners, was made. Under one end of it a pair of wheels twenty-six inches in diameter were placed in boxes, and the other end was fastened to an extension of the axle outside of the forward driving wheels, it having been found by experience that a play of about one inch on each side on the pedestals of the front wheels of the pilot or engine was necessary in order to get around the curves then in the tracks. For years afterward there was very little change in constructing the pilots from that originally applied to the “John Bull.”
The spiral spring, which held the front wheels of the pilot in place, acted substantially as the center pin of a truck. The turntables in use on the road were so short that it was necessary to unconnect and take off these pilots before turning the engine. After the pilot was adopted the forward large wheel on right of the engine was made loose on the shaft in order to afford additional play in going around curves. Other changes and additions were also made in the locomotive.
[Footnote 6: Changes in the locomotive
“John Bull” since date of
Steam dome changed from rear of boiler
forward to a part over what
was called the “man-hole,” and throttle valve placed therein.
Steam pipes changed to outside of boiler,
connecting new dome with
smoke box, entering it on each side.
In the beginning the reverse gear was changed from one single eccentric rod on each side to two on each side, connecting on to the same eccentric wheel, and the lifting rod, in pulling back, lifted the forward gear hook off the rocker arm, and the back motion hook then connecting on the rocker arm reversed the engine.
Side rods were never used.
Driver spring was changed from a bearing
under the pedestal boxes
to a point over the boxes.
The pilot was attached in this manner:
Right forward wheel being loose, forward axle extended eight inches beyond box on each side; to this was attached the beam of the pilot, having play of about one inch between box and pedestal plate to act while going around curves. The weight of forward part of engine rested upon a cross brace of the two-wheel pilot, which took bearing by a screw pin surrounded by a spring, by turning which pin the weight on the drivers could be adjusted.
A brace used as a hand rail was added
on top of the frame, bracing
frame and acting as a guide to the driving springs.