Howe truss patentIn 1840, William Howe was issued a U.S. patent (No. 1,711) for a Truss Bridge. It differed from his earlier patent (10 Jul 1840, No. 1685) because - importantly - he replaced the wooden post members in his frame with vertical iron rods, furnished with screw nuts, to effect tensioning. He described “straining up, and cambering” by tightening the screws. The frame had top and bottom horizontal members, and crossed diagonal braces and counter-braces. Although these were originally envisioned using timber, the Howe Truss was later used in steel bridges. It was popular as a railroad bridge because it had good strength over long spans. Timber truss covered bridges were also built as road bridges. Wooden walls and roof were added to protect the frame from weathering. A few remaining examples have been conserved.«[Image: detail of part of frame, showing vertical iron rods and wooden members.] |
