One of four trussed beam models

One of four trussed beam models, unsigned, United Kingdom, 1855-1876. Probably used experimentally for testing the strength of different methods of trussing beams.

These models were probably made by the company of Boulton, Watt & Co. when designing beams for their steam engines, as there is evidence that at first the engine beams gave trouble through their insufficient strength and rigidity. The smaller beams have parallel top and bottom booms, with diagonal timber struts inclined at 60 deg.; in one case the tie bolts are inclined, and run axially through the timber struts, while in the other vertical iron tie bolts are used. In the latter case the model has been loaded to destruction. The two larger beams consist each of a lower timber beam with a built-up truss above, the chief difference between them being that in one all the members are in duplicate. They have gudgeons and hooks or staples attached by which their strengths could be experimentally determined. From their trussing it is evident that these beams were designed for single-acting engines.