A Crewe Tractor in Road Trim.
A Crewe Tractor as Light-Railway Engine on Active Service.
[To face p. 130.
At first sight the casual observer might reasonably have been excused for puzzling his brain as to the exact nature of the contrivance, curious if compact, and neatly secured on the familiar Ford chassis. But on closer inspection, the salient features would resolve themselves into a fairly obvious entity; nor should a due meed of praise be withheld from the draughtsmen and engineers responsible for the successful evolution of the tractors on a sound and practical basis.
At the outset, considerations such as height of centre of gravity contingent upon the loads likely to be carried over an uneven, narrow and diminutive track measuring but 1 foot 11-5/8 inches wide, length of wheel-base and corresponding ability to safely negotiate sharp curves, available tractive effort depending upon a coefficient of sliding friction between tyre and rail, all these appeared as obstacles not altogether easily surmountable.
Official cynicism, too, coupled with an amount of adverse criticism, had, perhaps not unnaturally, to be faced and met. How for instance could a "flimsy" Ford chassis be expected to withstand loads and stresses for which evidently it had never been designed? Unlike that Government, however, which "foresaw nothing and only discovered difficulties when brought to a standstill by them," Mr. Cooke, with a quiet assurance bred of innate knowledge and experience, could well afford to go ahead "on his own"; official disdain should wait and see. Probably but few were aware for example that, whereas in regular locomotive practice a tensile strength of twenty-eight tons per square inch is considered ample margin for special axle steel, the "flimsy" Ford is built up of Vanadium steel, having a tensile or breaking strength of no less than seventy-five tons per square inch!