Hedley's experimental model for testing adhesion.

Christopher Blackett, the proprietor of Wylam Colliery, had been looking for a new method to haul coal wagons the five miles between his colliery and the quayside of the River Tyne. Blackett had been using animal power to move his wagons, and wanted a more reliable and efficient method. William Hedley constructed this model to see if he could come up with a solution. There are four road wheels secured to axles, which are geared together and can be rotated by external handles. The results Hedley obtained from his model led to the construction of a full-sized version, worked by the men carried along with it so that all four wheels were available to maximise traction.