Part 1 (1/2)

Introduction of the Locomotive Safety Truck

by John H White

_Pioneer railroading was dangerous With increased speed and density of traffic came an increase in catastrophic wrecks that forced operators to take heed for the safety of their passengers and freight This safety was painfully achieved through the slow process of i such spectacular post-Civil War advances as the steel rail, automatic coupler, and airbrake, was the invention of the safety truck for loco locoh track of the early roads, it did much to reduce the all too numerous derailments that were a major cause of accidents_

The Author: _John H White, is associate curator, in charge of land transportation, in the Sy, United States National Museum_

American railroads of the early 19th century were cheaply and hastily built They were characterized by inferior roadbeds, steep grades, sharp curves, and rough track In spring, poor drainage and lack of ballast y roadbed and produced an unstable path In winter this sa pave stock was pounded to pieces

In those pioneering times the demand for new roads left little capital to i lines; therefore equip operating conditions

The first locoland Designed for well-ballasted track with large-radius curves and gentle gradients, they all too frequently left the rails, and the unsuitability of the essentially rigid British design soon becae posed by the American roadbed was met by American mechanics By the mid-1830's a distinctive Aht best be described by the word ”flexible” The basic features of its running gear were a bar fra levers to provide vertical relief and a leading truck to provide lateral relief

Of these devices the truck was probably the most iuished the Aear from that used by the British before 1860

[Illustration: FIGURE 1--Design drawing showing the 4-wheel leading truck, developed in 1831 by John B Jervis, applied to the _Brother Jonathan_ This loco truck, was built in June 1832 by the West Point Foundry association for the Mohawk and Hudson Rail Road The truck is attached to the locoht of the locomotive is carried by a roller which bears on the frame of the truck

(_Smithsonian photo 36716-a_)]

It was John B Jervis who is generally credited with first applying the truck to the locoure 1, was developed in 1831-32 Its merits quickly becanized in this country The truck successfully led the locomotive around sharp curves, the resultant 3-point suspension enabled the ether, the design did far less daid, iines[1]

The truck fras, was attached to the locoht rotate At first the weight was received by rollers or chafing pads mounted on the side bea surfaces and their location at a considerable distance from the center pin combined to restrict the free move was transferred to the center plate, producing a truck that turned more freely[2]

[Illustration: FIGURE 2--The 4-wheel Bissell truck as shown in the drawing for British patent 1273, issued May 5, 1857]

[Illustration:

A--Truck fra lever C--Loco device_) E--Truck bolster F--Swivel pin (_Pivot point_) _Drawn by J H White June, 1960_

FIGURE 3--Typical 4-wheel Bissell Safety truck of 1860 This drawing is based on plate 69 of Alexander L Holley's, _American and European Railway Practice in the Economical Generation of Steam_, New York, 1861

(_Sines this simple form of truck was entirely satisfactory, but it proved less satisfactory for 4- and 6-coupled machines Also, as train speeds increased, so did the number of derailments Many of these could be traced to the inability of the engine to negotiate curves at speed Levi Bissell, a New York inventor who investigated this problem in the 1850's, correctly analyzed the difficulty He observed that when the engine was proceeding on straight tracks the leading truck tended to oscillate and chatter about the center pin, and he noted that it was this action that i motion to the locomotive at speed The derailine entered a curve

This action can be more easily understood froure 2 For exaine, fitted with a center-swing truck, enters a right-hand curve The left truck wheels bear hard against the left rail The drivers jaht front and left rear wheels grinding into the rails As a result, the locomotive tends to leave the track in the direction of the arron on the figure (botto) It will be noted that the truck center pintle is in fact the fulcrue Under such strain the truck wheels are particularly likely to leave the rails when they encounter an obstruction Once derailed, the truck would then spin around on the deadly center pin, throwing the locomotive over

In effect, then, the center pin of the conventional truck extended the rigid wheelbase of the engine, and caused the truck to act idly to the engine fra wheels Bissell proposed to correct the faults of the conventional truck by fitting the locomotives with his invention, the first practical safety truck to be patented Since the priht angles to the rails whether on a straight or curved track, and to allow the driving axles to remain parallel, or nearly so, to the radial line of the curve, he moved the center pin to a point behind the truck and just in front of the forward driving axle This shortened the wheelbase of the engine and re as a fulcru them to assume a comfortable position on a curve

[Illustration: FIGURE 4--A 4-wheel safety truck fitted with A F

S device Built by the Hinkley Locomotive Works Fro and Railway Mechanism_, New York, 1871, pl 88]

Since the truck could assu curves, it was claimed in the patent specification that, unless all four wheels were simultaneously lifted off the track, the truck could pass over ”quite a considerable obstruction”[3] Bissell further claiht or curved track one of the truck wheels often breaks off, and the truck swivels around on its center pin in consequence, and throws the engine off the track, but with my device one wheel, or even the theels on the opposite sides diagonally of the truck ht break off and still the truck would not run off, because its position is set and it has no axis of