The success of Bissell’s invention prompted others to perfect safety trucks for locomotives. Alba F. Smith came forward in 1862 with the simple substitution of swing links ([fig. 4]) for the incline planes.[11] A swing-bolster truck had been developed 20 years earlier for use on railroad cars,[12] and while Smith recognized this in his patent, he based his claim on the specific application of the idea to locomotive trucks. That the swing links succeeded the incline planes as a centering device was mainly because they [p125] were cheaper and simpler to construct, and not, as has been claimed, that the V’s wore out quickly.[13]

Figure 7.—Bissell’s 2-wheel truck of 1858 as shown by the drawing for British patent 2751, issued December 1, 1858.

Smith’s swing-bolster truck, with the heart pendant link, a later refinement, became the dominating form of centering devices and was used well into this century. It was to be superseded in more recent years by the constant resistance and gear roller centering devices which, like Bissell’s invention, depended on the double incline plane principle.

The British-born engineer William S. Hudson, superintendent of the Rogers Works and an early proponent of the Bissell truck, in 1864 obtained a patent[14] for improving Bissell’s safety truck. Hudson contended that since the Bissell arrangement had a fixed pivot point it could traverse only one given radius accurately. He proposed to replace the fixed pivot with a radius bar (see [fig. 5]) one end of which was attached to the locomotive under the smoke-box and the other to rear of the truck frame, at the same point of attachment as in the Bissell plan. Thus, according to Hudson, the pivot point could move laterally so that the truck might more easily accommodate itself to a curve of any radius. He further claimed that a better distribution of weight was effected and that the use of the radius bar relieved the center bearing casting of much of the strain of propelling the truck.

[p126]

Figure 8.—A 2-wheel Bissell truck installed on the Pennsylvania Railroad’s No. 91. This engine originally an 0-8-0 Winans Camel built in February 1854, was rebuilt by John P. Laird in 1867, at which time the Bissell truck was added. Note that Hudson equalizing lever was not used. (Smithsonian photo 46806-k)

The British journal Engineering, in an article otherwise friendly to the inventor, expressed some skepticism as to the real merit of Hudson’s invention.[15]