A different shake of the box this go, no external wonder over maddening happenstance. This time a glimpse of history and not from my typical perspective, this go we will look at what was, simply because it is so little looked at, and with that somewhat under-realized.
We are about to look at wooden Pony Truss bridges and in the doing, we will explore what was with photographs in numbers greater than is typical of our explorations. Though unlike the allusion of our chosen title, which speaks to how common Wooden Ponies once were and how remarkably those numbers have dwindled, dwindled to a point just short of totality, from untold hundreds if not thousands, to a count which depending on how you categorize the type, which can arguably be seen as countable on one hand.
Pony Trusses were a common solution for short span situations bridging waterways of twenty to sixty feet. In essence a Pony is a Truss short in stature, of a height less than that which is typical of a “Through Truss” – Perhaps the most common approach to weatherproofing Ponies was to “Box” them in, to simply board in both sides of both trusses and to put a little Roof-ette over each of them individually.
This is almost certainly why the landscape is now almost devoid of “Boxed Ponies” – This approach left the Flooring and the Floor Beams exposed to the ravages of the sun and rain and the oxidation and decay such exposure encourages. My educated guess is that long ago replacements were about the need for the regular maintenance wood exposed to the elements requires. With the maintenance regime such exposure demands, Boxed Ponies were in time replaced with Creosoted timber stringer and bent piling bridges and concrete box culverts.
New Hampshire through a collection of happenstance, climate, Yankee thrift, and the sheer numbers in late examples built by the Boston & Maine Railroad stands as home to most of the Boxed Ponies still standing. One of these was lost to arson in 2004, several years later I helped Barns & Bridges of New England, The National Society for the Preservation of Covered Bridges and NPS-HAER in the replication of its trusses with salvaged iron Rods and Angle Blocks from the original. These were used as full-scale models at Case Western Reserve University in an engineering study and have now returned to NH and are in search of a future home.
This video, though a bit grainy, does drive home the tolerance of fit strived for in wooden bridge framing. Here, Tim Andrews of Barns & Bridges of New England guides a Truss Terminus Angle Block into place as I lower it with hydraulic assistance
Not all Ponies were Boxed, sometimes the choice was to protect the Trusses from the weather by adding a “House” as opposed to Boxing the Trusses independently, whether this choice was made to provide protection to the Floor Beams and the flooring they carried or if this was seen as money better spent, and a more affordable alternative over the service life of a bridge is something the record has yet to suggest.
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