Dreadnaught wheel

A dreadnaught wheel is a wheel with articulated rails attached at the rim to provide a firm footing for the wheel to roll over. It has also been known as endless railway wheels when fitted to road locomotives, and were commonly fitted to steam traction engines. They are very similar to pedrail wheels, differing primarily in that they are not connected to the wheel directly, but articulated to each other.

Prior to wide adoption of continuous track on vehicles, traction engines were cumbersome and not suited to crossing soft ground or the rough roads and farm tracks of the time. The "endless rails" were flat boards or steel plates loosely attached around the outer circumference of the wheel which spread the weight of the vehicle over a larger surface and hence were less likely to get bogged by sinking into soft ground or skidding on slippery tracks.

An early version was patented by James Boydell in August 1846 and February 1854. Boydell worked with the British steam traction engine manufacturer Charles Burrell & Sons to produce road haulage engines from 1856 that used his continuous track design. Burrell later patented refinements of Boydell's design.

Boydell's design saw service with the British Army in the Crimean War where it was known as "The Megatherium war horse". A number of horse-drawn wagons, carts and gun carriages were successfully deployed in the Crimean War, waged between October 1853 and February 1856, the Royal Arsenal at Woolwich manufacturing dreadnaught wheels. A letter of recommendation was signed by Sir William Codrington, the General commanding the troops at Sebastapol.

An Australian blacksmith and engineer, Frank Bottrill (1871-1953), after a failed endeavour using wheeled traction engines in outback Australia, and becoming aware of the Boydell wheel, decided to improve the design. In 1907 he patented an "improved road wheel for travelling, useful for traction engines". Bottrill's design used two rows of overlapping rails fastened to the rim with cables to smooth the transition from rail to rail.

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