In trying to figure out just what I want this blogging adventure to be, I feel a need to somehow intertwine real historical information around the logic of preservation, and the capitol P Preservation community, and at the same time keep it lively, so that membership in one of the geekdom subcultures of bridges, or preservation, or being a historian maybe needn’t be requisite for interest in reading on…
So maybe I’m missing my own mark, that it might not be possible to keep all those balls in the air. But I can’t know unless I try. And I’ve decided that lively and the history can’t, don’t and maybe even shouldn’t part ways.
So, I still see, a next logical step might be an extension of the last entry. And have decided to do a short series, (in number, not necessarily in a time frame all that short) on New Hampshiremen (yes, this is the historical term of choice for someone who hails from here – political correctness be damned) who influenced the development of wooden bridge construction in the 19th Century.
Though for this entry, just because I keep finding more and more information on the good Colonel, I’ll continue with a reflection on his writings, wrapped ever so slightly around our experiences at the Gilpin’s.
I’ve alluded to how the Gilpin’s had its guts ripped out in a failed attempt to increase its capacity, that Floor Beams and Flooring were changed out for Hardwood species in the all too commonly mistaken notion that stronger wood always makes for a stronger construction.
The Gilpin’s was proof positive evidence that this is not the case. Tens of thousands of pounds of added weight in a “stronger floor” did not strengthen the bridge. But, because those who did this, did not take the time to understand the materials they were working with, or the bridge as a unified structural system, one comprised of multiple systems, They in fact weakened it. The weight they added directly resulted in the failure of every Bottom Chord “splice” in the bridge, so severe were these failures, that the bridge did not see another decade of service.
So, how does a man distracted by a life so busy and so storied. A life so much so, that his multiple bridge patents, do not even register as a minor blip on his research radar. A life of academic achievement, military service, continental exploration, railroad surveys and silkworms. A man who likely never even once watched a shaving roll up off the end of a chisel he was himself pushing, (he was not a timberframer) how does such a man understand these things?
Somehow he did.
In Long’s “Description” in the prologue to “Directions” he cites –
“The timber best adapted to a frame bridge, is White Pine. The qualities which entitle it to to this distinction, are its lightness, stiffness (strength to weight ratio in modern engineering-ese) and exemption of the ravages of worms, insects, &c. – In all cases, the material of which it is made should be the lightest attainable. The exterior covering, should it be applied, ought also be constructed of the lightest materials.“
So granted, his vast travel is part of this understanding. Even if he had not seen the several examples of Palmer’s trussed arches in New England at this time, he had certainly seen both his “Permanent Bridge” and Wernwag’s “Colussus” in Philly while a resident there. (Home town of his 1819 bride Martha Hodgkins) His exceptionally wide travel for his time would certainly have afforded him the opportunity to see many many bridges in the rivers and streams he crossed. Those crossed by fording or ferry might well have had him wondering after a better way. All this coupled with his very creative mechanical mind explains how a non-timberframer might design a timberframed bridge…
All the same, how does a non-carpenter come to the specific carpenterly related conclusions he had?
Was it just that people of his time were more in tune with the materials that made up their world? Is it his aptitude for over-achievement, or his obvious scary-smart intellect?
I’m not sure we can know –
I do know a mistake he seemingly almost innately avoided, one which was exemplified at the Gilpin’s eighty long years ago, is somehow, and for the same lack of understanding, and failure to properly and fully explore all aspects of the bridges engineering, about to be repeated.
And this none so far away. The Rudolph & Arthur, just over the state line from the Gilpin’s, in Chester County (Perhaps the healthiest most original and intact Burr I have ever visited) is about to be rehab’ed, The plan calls for the Floor Beams, (most of them original and problem free) Sleepers and Flooring to be replaced with Bongossi. A rare African rot resistant (this the siding & roofings purpose and an unnecessary redundancy?) species of hardwood, which is incredibly dense and beyond amazingly heavy.
To para-phrase Yogi Berra – Isn’t this just like Déjà Vu all over again?