Being a Timber Framer has me hold a special appreciation for certain carpentry-centric truss types. Specifically, Longs and Paddlefords, this not solely for their connection to New Hampshire, but for their solving structural truss required needs with advanced carpentry and not Iron. This just appeals to something in me, which is more than a simple appreciation for the cleverness exemplified by how their developer chose to make them work. But yes, something of the carpenter in me, just plain appreciates a carpenters solution.
So I must admit being a little surprised at how much fun it was I found in pre-tensioning the Pratt Trusses in the Chester Bridge. I fully expected that tuning the angled tension rods to easily change the geometry in each panel. It was just how responsive that seemingly modest additions in tension were, in dialing in a desired modest 1 inch camber in each truss. This Hyper-finetunableness – I failed to foresee.
I’m used to iron in bridges, but its use is seldom fun. This was, and with an appreciation unanticipated. Like that one holds for a new tool which is both well designed, and just also functions particularly ably.
This sent me on a differing quest, with a desire to look with new eyes, at truss types with angled Tension Rods in their Panels. This happily seems to coincide with this running series of Blog entries on New Hampshire truss types…
I opened the Patent folder to Childs Patent No. 4963, (patents can be readily accessed though the Patent office or Google Patents) and that of Concord engineer J.C. Briggs and his first patent No. 22,106, both have such Rods in their designs. Another reason to again read, what are dry, but seldom better, seldom more direct, in the mans own words kinda way, source materials, was a welcome one.
Besides the tensile Counter Rods, and being contemporaries and living none so far from one another, John and Horace share another sad commonality. This that, despite their prolific success, and with both doing much Railroad work, no example of either of their trusses, (2 for JC), built here in their home range still exists.
This had me then looking at what are seen as the living embodiment of existing Childs Trusses, and I came across this welcome oddity. Always love ads placed by bridgewrights. This one has me scratching my head a bit….
He offers to build Howe’s, Burr’s, or Sherman’s – No mention of Childs.
Despite the fact that every bridge attributed to the man is held up as a Childs. Here’s where the what-if wonderment kicks in. Everett holds but one patent, No. 191,552, a very short span iron pony – Yet here in his advertisement he lists a “Sherman” under a heading of “Covered Wood Bridges” and holds up his “truss” as being “30 to 50 percent stronger than any iron bridge”.
Putting aside for a moment, just how right he was, that time proves his postulation that a wooden bridge, provided that it’s cladding is properly maintained and remains weather tight, can and will have a far longer service life than one built of iron or steel…
It does seem more than likely, if not probable, that he was appending his own name to his own much modified iteration of a Childs. Which in truth, do not use either of Horace’s “claims to invention”, those aspects of his design, which he saw as unique and new and and therefore deserving of a patent, nor do the Sherman bridges have the double rods or double posts.
Turning up some contract documents for a still existing bridge will answer one of the obvious questions this opens.
Are the Ohio spans something other than that which they are held up as?
Did Everett ever call them Childs Trusses? Or something else all-together?