Callender-Hamilton Bridges
The Callender-Hamilton bridge is a modular portable pre-fabricated Warren truss bridge, designed for both temporary and permanent applications. Assembly takes much longer than for the Bailey Bridge as it uses individual lengths of steel sections connected by numerous bolts, rather than pin-jointed panels.
The system was designed by the New Zealand engineer, Archibald Milne Hamilton, and patented by him in 1935. Bridges on this system are currently fabricated by Painter Brothers, Hereford, operating within the Balfour Beatty Power Networks Division.
The above information is condensed from the Wikipedia entry.
1937 Description of tests made by the Royal Engineer Experimental Bridging Establishment, Christchurch, Hants, on a 140-ft. double-truss bridge made on the Callender-Hamilton unit construction System.[1]