It can be stated that Hudson's modification of the Bissell truck is of
unquestioned importance, for without the introduction of the equalizer
it is doubtful if the 2-wheel pony truck would have been a complete
success on American railroads. Bissell's 4-wheel truck was extensively
employed, but it did not enjoy the universal popularity of the 2-wheel
truck, and in the 1880's was eclipsed by other forms of 4-wheel safety
trucks. The Hudson-Bissell pony truck, however, survived in its basic
form to recent times, when, in the late 1940's and early 1950's, the
last steam locomotives were constructed in this country.
1. Three-point suspension in a 4-2-0 was easily gained--the center
plate of the truck and the two bearings of the driving wheel axle.
On a 4-4-0 the center plate served as one point, while the fulcrum
of each equalizing lever served as the other two points, thus
providing the desirable and highly stable 3-point suspension.