Divided drive (locomotive)

A divided drive locomotive is a steam locomotive that divides the driving force on its wheels by using different cylinders to power different pairs of driving wheels in order to give better weight distribution and reduce "hammer blow" which can be damaging to the track, or else to enable the wider spacing of the driving wheels to accommodate a larger firebox.

The system of dividing drive was originally developed by Anatole Mallet in the 1870s on a number of rigid-wheelbase compound locomotives, and then during the 1880s, on Mallet articulated locomotives.

Mallet's ideas inspired Francis Webb in Britain who introduced 2-(2-2)-0, 2-(2-2)-2, 2-2-2-2T, 2-2-(4-0)T divided drive locomotives between 1882 and 1903.

Alfred de Glehn introduced a successful divided drive 2-(2-2)-0 compound based on Webb's ideas,.

Dugald Drummond of the London and South Western Railway used divided drive (not very successfully) in his simple expansion T7 and E10 Classes of 4-2-2-0. In the latter two instances the divided drive was adopted to allow the driving wheels to be spaced more widely than normal without the need for long coupling rods. This enabled an extra-long firebox.

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