The Howe Truss
William Howe patented a wood and iron rod truss in 1840 and extended the patent with improvements in 1850. The truss was the first to be designed using mathematical stress analysis. The Howe truss, suitable for heavy duty bridge spans, was adopted by the railroad industry and became one of the most widely used trusses for railroad bridges.
The truss consists of wooden upper and lower chords, the chords linked together with sets of dual iron rods and wooden braces and counter braces. The braces and counter braces are butted against the chords on angle blocks. The rods are adjusted with nuts.
Of the four Howe truss bridges in Vermont, three are highway bridges. The Gold Brook Bridge in Stowe, built in 1844, is the oldest and is a miniature of the other three. The retired Rutland Rail Road Bridge in Shoreham is the last of Vermont's Howe truss railroad spans. The Connecticut River bridges in Lunenburg and Lemington, both Howe Truss highway bridges, are constructed with identical components, both having been built by the same company. The iron rods are one-and-three-quarter-inches in diameter, the braces measure seven by nine inches, and the counterbraces are six by six inches. The angle blocks are wood.
William Howe, born in 1803 in Spenser Massachusetts, came from a family of inventors. Tyler Howe invented a spring bed and Elias Howe was the inventor of the sewing machine.
For more on the Howe Truss and William Howe see Yankee Science in the Making, by Dirk J. Struik
From Spanning Time Vermont’s Covered Bridges, by Joseph C. Nelson