Jackshaft (locomotive)
This problem can be solved by mounting the jackshaft on unsprung bearings and using side-rods or (in some early examples) chain drives.
In the early 20th century, large numbers of jackshaft-driven electric locomotives were built for heavy mainline service.
These locomotives used step-up gearing to achieve a reasonable running speed using small diameter driving wheels.
"[2] In his 1837 patent for what became known as the crab class of locomotives, Ross Winans referred to his jackshaft as "a pinion wheel shaft", or "third axle.
Phineas Davis's first B&O Grasshopper tested on the B&O in 1831 was in this class, as was the Stockton and Darlington Railway's Swift from 1836, where the crankshaft was directly between the driving axles.
In the latter case, the reason inferred for using a crankshaft distinct from the driven axles was "to take the shocks of working away from the power shaft.
Ross Winans designed a series of 0-8-0 locomotives starting in 1842, launching what became the B&O Mud Digger class of engines.
[7] In 1880, the Fowler Steam Plough Works of Leeds England received a patent on a similar 0-4-0 locomotive design with vertical side rods between the crankshaft and rear axle.
[11][12] Once these problems were understood, jackshafts emerged as one alternative for linking the output gearbox of the turbine to the driving wheels.
In Europe, Oerlikon and Brown, Boveri pioneered a variety of jackshaft designs, while in the United States, Westinghouse was dominant.
Examples include the PRR DD1 and FF1 electric locomotives, as well as the Swiss Class Ce 6/8 Crocodile and its narrow-gauge cousin, the Rhaetian Railway Ge 6/6 I.
When Baldwin first began building internal combustion locomotives in the first decades of the 20th century, they used a 2-speed transmission from the gasoline engine to a jackshaft.
The heavy engine is carried over the drive wheels for adhesive weight, but the relatively lightweight gearbox can be mounted at one end, beyond the coupled wheelbase.
The Swedish D-lok of 1925 did use it, with two motors geared to a single jackshaft with short rods between two driving axles of a 1-C-1 layout.
This carried a sliding crankpin journal for the centre axle, and bearings for the long coupling rods to the unevenly-spaced pairs of drivers ahead and behind.
To maximise the length of its drive rod and reduce its angulation, this was connected near to the furthest driven axle.
This arrangement is simple and robust, but does not give a perfect geometry and so is known for its creaking noises and rough running, particularly if the rod bearings become worn.
