Category Archives: Maryland

As it Was

Those from among my longtime readership will recognize that my ofttimes mention of Maryland’s Gilpin’s Falls Bridge, go all the way back to a description of its system of un-nailed flooring, and how it came to be returned to this long neglected Burr in my maiden voyage entry. That first of frequent mentions having to do with the return of The Gilpin’s to its original fastener free flooring system, and the connection of that system to many early Bridgewrights, and Wooden Truss patent holder Col. Stephen Harriman Long who described it in his Set of Directions to Bridge Builders.

The Floor and the Truss Framing as viewed looking towards the north Portal

The Floor and the Truss Framing as viewed looking towards the north Portal

While recently back in the area involved in a non bridge related timberframe Preservation effort, I stopped back in at The Gilpin’s to check on how both the replacement timber, and the once common and now uniquely applied flooring, was seasoning in, in the three years which have now passed since the bridges celebrated and awarded restoration saw completion.

The North Portal

The North Portal

I was happy to see a second return of tradition and methodology to the Gilpin’s. One that like other aspects of followups in Bridgewrighting, ( See August ’12 entry – Less Than Hardwired for Hardware – for example of other similar seasoning driven followups ) and how a full understanding of the materials used, demand and require a return to the bridge for simple maintenance as timbers in these bridges, and their claddings and other wooden elements of finish and enclosure necessitate. To use the terminology of the day through the words of Col. Long – After seasoning and shrinkage of the Flooring, the “Binders” had been taken up, the un-nailed Flooring had been moved to remove the gaps left by seasoning, and every eight or ten feet along the bridges length – A new piece of Flooring had been added to cancel out the aggregate of those 3/16” gaps. A dozen or so pieces in total along the bridges length.

The added pieces obvious both for their coloration and for the lack of this mysterious red chalk line just adjacent to the “Binders” – Note also the Arches seen in this image descending past the Flooring and the nearby Chords

The work we were following on the restoration of The Gilpin's, was that of Cecil County Bridgewright Joseph Johnson - Photo courtesy of Mike Dixon & Window on Cecil County's Past

The work we were following on the restoration of The Gilpin’s, was that of this fine gentleman, Cecil County Bridgewright Joseph Johnson – Photo courtesy of Mike Dixon & Window on Cecil County’s Past

The full return of this system of Flooring, has with these added pieces of Flooring, now been returned to our Nations Covered Spans. On Sunday the 28th of the coming month, The National Society for the Preservation of Covered Bridges will hold one of its Summer meetings at The Gilpin’s. My longtime associate Tim Andrews, the fellow Bridgewright I subcontracted to on this restoration effort, will discuss challenges, victories and aspects of the effort both structural and logistic. As well as this now revived system of Flooring.

As it was, at least for this piece of Maryland history, is for the foreseeable future, as it will be…

Less than Hardwired for Hardware

If I were to define what it is I do, the description I see as mayhaps that one most accurately describing it, with both eloquence and in as few words as is possible, is simply to suggest that “I join timber”

My work is to take one of our planets greatest blessings, Trees. And to take their only modestly converted stems, (With variation, but in essence with only four sapwood slabs removed) and then join this blessing into useful configurations. Be it, houses, barns, or bridges.

In most such efforts joining timber, I find myself working to wholly avoid the use of large metal fasteners – This is almost one of the sub-definitions of what it is to be a Timberframer. Wood to wood is what we do.

Bridgewrighting, as allied a trade as it is, is a bit different. Even those Truss types without iron in them – Longs, Paddlefords, Burrs and Towns, still are often peppered with a smattering of bolts…

Many Truss types, share iron as almost an equal partner, equal in effort if not proportion of material used. A Symbiont of sorts, necessary to allow a largely wooden truss, to do what is asked of it.

Pratt’s are one of these “types” – So, echoed in the lyrics of one of my favored songs, with The First Day in August, last years local Timber Framers Guild project – The Wason Pond Bridge marked the passing of its first year, (see July / August ’11 archives) and I recently found myself willingly engaged in a once common bridgewrighting chore – A first of several, wrench in hand scheduled visits, to tighten Truss Rods and assorted Bolts to compensate for expected and predictable shrinkage as the Timber in the Through Truss seasons.

Joints again fully seated, camber re-tuned. All went as hoped for and expected, with but one small exception. The washers on some of the smaller Bolts sunk into the now dry White Pine wood grain as an attempt was made to re-tighten. I chose to replace these. My first thought was to go to the cast Ogee’s found so commonly in this application. Their cost and limited availability saw me turn to the second most common washer type found on Wooden Bridge Bolts – Large Square Flats.

As such explorations often do, I went looking for contemporaneous Rules of Thumb in what was seen as a norm for such hardware. In AJ DuBois’ – The Strains in Framed Structures – We find these not only crunched number, but period proven suggestions in his list of specifications.

As always, I like to point out how White Pine was and is, the favored Species for the framing of Wooden Bridges – Also from the DuBois List – Section VIII

In Jacoby’s – Structural Details or Elements of Design in Timber Framing – A wealth of information is found on the seemingly mundane subject of washers, as they are related to Timber Work.

The restoration of Maryland’s Gilpins Falls, is the only time we’ve worked with “Special Countersunk Washers” and their funky headed friction dependent Bolts. This bolt & cast washer type was also that chosen and used by Nichols Powers in The Blenheim.

The Wason Pond Bridge is fitted with a number of “Malleable Iron Washers” on both the smaller section Truss Rods at Mid-Span, and at the Tie Beam Bolts.

And like many other wooden spans, it is now home to a large handful of Squares.

Lost to Evermore

Those of you who occasionally click in on my twitter feed might recognize this image as its background. (click to enlarge) I’d meant to only someday post a blog entry about it. Someday, when I’d moved on from New Hampshire’s historic connection to wooden bridge building. The recent floods however have moved up someday.

Irene’s aftermath will long be memorable, perhaps in part for video caught as the Bartonsville slipped into the storm swollen Williams River. We still don’t know the full number of bridges lost or damaged, but we do know this image has several things in common with what is perhaps the greatest loss. There is no question that it was the largest lost, and arguably, (and silly, my dog’s better’n your dog, arguments were ongoing) among the very last of the giants, that being New York’s Old Blenheim.

The image is, for a number of reasons, one of my favorites. In part because it shows one of history’s giants. Many are not aware that such wooden giants existed, because they have long since been replaced, usually because they crossed at all too important, high traffic areas. As often, the piers they were built on were far more expensive and time consuming to construct than the bridge they carried, and they were wanted to carry a new span which could carry a higher volume of traffic.

This bridge circa 1866, stood just upstream from the confluence of the Susquehanna with the Chesapeake Bay. It was a fourteen span Howe – Thirteen of 250′ and a Draw Span of 175′, for a total length of 3,500′. It carried the rail traffic it was designed for until the 1906. And then was re-purposed in 1910 for vehicular use, and continued to serve another couple of decades until its removal sometime in the late 30’s. Its Piers still sit idle next to the yet operational Iron Railroad Bridge.

Another reason it’s a favorite, is because, though as photographic technology of the time demanded it is obviously posed, all the same, it captures the actual circumstance of that moment in time. Drawn from a photograph prior to the existence of affordable ways to print photographic images on newsprint, a common technique of the day. It shows us not only the Falsework still in place under the near span, and how that Falsework is designed to interact with the masonary in the piers, and how the seeming ornamentation in the masonry was designed with two-fold purpose to receive that Falsework. We also see crews at work, and various aspects of the bridge still under construction.

The Bottom Chords of the Double Barreled Blenheim

It also pictures two men at the images center. Though only a theory of mine, I don’t see it as much of a stretch. The one in the top hat is George A. Parker, engineer and designer of this bridge built for the Philadelphia, Wilmington and Baltimore Railroad. The man next to him with the cane, is undoubtedly his clerk of the works hand picked lead framer, and Master Bridgewright, Nichols Powers.

Parker and Powers, in building this span, on this stretch of the Susquehanna, which like the nearby Schuylkill, stood host to many of these early giant spans, quite literally joined the ranks of bridgewrighting’s giants. Palmer, Wernwag and Burr.

Nichols, eleven years earlier, also built the now lost Blenheim –

The Trait de Jupiter / Bolt 'o Lightning Bottom Chord Scarfs of Powers' Masterwork

Among other still existing bridges, he also built the Brown, near his home town of Clarendon Vermont. We are yet to hear how it fares in the aftermath of Irene.

Recent video imagery accompanied by particularly timely & poignant original music by Kevin Sullivan.

Eighty Beeves Driven in Close Gang & a Wish

An interesting find sparks one more Long post before we move on…

The Colonel in his own words, describing the construction of the Jackson Bridge in a letter accompanying the publication of his letters patent in the 1830 Journal of the Franklin Institute, Vol 5 It’s particularly interesting because it defines a timeline for us, and tells us the Jackson was the only existing example at the time of patent. This is curious because the short-line B&S RR and its three bridges are known to have been built between ’28 and ’31 – So we now know the three examples listed in the ad Moses’ placed, were built following or perhaps even as Stephen penned this letter, or as it sat waiting in the post, and then somewhere in the offices of the Institute for some editorial decision, and after some unknown turn of time and delay, publication.

He also describes the crew that built The Jackson, but sadly does not name even the lead…

I do wish he had put a name to at least the crew lead for the “six workmen”, I am sure these are people from whom he learned much, and used this learned information in his “Description”, and do find it regrettable that he did not share names, and this not simply out of some personal curiosity

This because I do now have some real sense of the man. He had by this point in his life, led expeditions deep into the then unknown vast western wilderness, where survival did quite literally depend on the skills and smarts of every handpicked person in your company. He had accomplished much. And he knew full well, that his own success was in part attributable to the accomplishment and abilities of those under his command.

119′ Clamps

Recently a cyber acquaintance visited the Gilpin’s Falls, a bridge I, as part of a team of three, helped restore for many long months back in ’09. His photographer’s eye for detail saw him notice and ask after the now unusual way the floor of this bridge is assembled…

It’s a good story, and I thought I’d elaborate here, and use it as a catalyst to finally kick this blogging thing off and up a notch.

The floor as constructed, exists because knowledgeable people found historic evidence, made a case and lobbied for a construction detail to be returned to the bridge. It also helped that this evidence did not fall on deaf ears.

The floor system on the Gilpin’s had been almost wholly replaced in the 20’s, the last decade the bridge carried traffic. This in a failed attempt to increase its load carrying capacity, all the Floor Beams but one, all the Sleepers, (longitudinal joists which run from Floor Beam to Floor Beam) and all the Flooring, had been switched out from softwood to mixed species hardwood. The Flooring had also been installed on a slight bias, (though so slight as to not lend any triangulation and bracing effect) and this proved to have been done simply to avoid any need to cut the material to length, it was simply laid down in the raw rough slightly random lengths provided by the sawmill.

Occasionally things fall together as they should, and as we disassembled the floor system, it became obvious that the hardwood replacements had suffered massive infestations of Powderpost Beetles and would again require replacement, this was fortuitous in that the huge increase in weight and dead load they introduced had been directly responsible for much of the distortions to the bridges framing.

As we dismantled the Floor we found long multiple panel / bay sleepers, with longitudinal rebates and unused bolt holes. The use of these “rabbits” had been long abandoned, but we found their intended original use obvious, having read about such systems, most notably in the very descriptive hand written proposal documents of Indiana bridgewright J.J. Daniels and in the writings of Col. Long.

They are part of a simple but ingenious flooring clamping system, which obviously once saw use over a wide geographic area. Its advantages are based in a simple understanding of the materials being used, the intent being both to allow the clamp to be loosened after the flooring seasons and shrinks, rows of flooring to be tightened up, and gaps filled by adding additional pieces. This system also avoids the damage and reduction to service life in Sleepers, which comes with the repeated spiking down of flooring as wear demands its repeated replacement.

We returned these pieces to their intended use, and it is possible, if not probable, that the Gilpin’s Falls Covered Bridge is the only existing example of this system in use today.

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