Bissel truck

Invented in 1857 by Levi Bissell [de][1] and usually then known as a pony truck, it is a very simple and common means of designing a carrying wheel.

The Bissel truck also helps stabilize a train in a turn, where centrifugal force causes a locomotive to lean away from the track.

It features a pair of inclined planes which mate with an opposing set on the engine's frame where the two join.

As the truck pivots sideways the outside of the locomotive is elevated, a practical modification used right to the end of the steam era.

John P. Laird was the first to attempt to equalize the pony truck with the drivers in 1857; he received a patent on the concept in 1866.

A more successful scheme for equalizing the pony truck to the drivers was invented by William S. Hudson, superintendent of the Rogers Locomotive and Machine Works, and patented in 1864.

Some older electric locomotives have Bissell trucks, if the driving axles are located in the main frame rather than the now usual bogies.