Numbers as Great as They Now are Few

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.

The Old Russell Bridge of Wilton New Hampshire is sometimes also known as The Livermore

The Russell Hill carried traffic until recent years and is in all likelihood this was the last Boxed Pony Truss Bridge to have done so

The Russell Hill is a Town Lattice Truss – The Pilaster (and the concrete pad which supports them) seen lower right was added to take up load inboard of the compromised Chord ends to keep the bridge in service – The decayed Chords are likely a result of unchecked leaf litter building up between the Back walls and the Truss ends which slowly decomposed into a soil like matter holding moisture borne of rainfall against the Chord lamanie for weeks and months until they likewise decomposed – This an entirly preventable set of circumstance

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.

The B&M built Moose Brook Bridge seen here while still in service nineteen years prior to its loss to arson – This photo was taken by Joseph D. Conwill – Joseph over a period of decades has visited every wooden bridge in North America, many such as The Moose Brook no longer exist

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.

An As-Built drawing of The Moose Brook created by the Historic American Engineering Record – Seen here as a courtesy of NPS-HEAR and the Library of Congress

10 X 16 X 48 Chord Lams laid down on edge to allow for the cutting of clearance cuts for the Moose Brooks massive Truss Rods

Angle Block Abutments and a bird’s eye view of the Truss Rod clearance Cuts – Though a Howe truss differs from most other types in that Iron parts join those of wood this is still necessarily done with the high levels of tolerance required for Truss Framing to sustain intended geometry under the massive loads they are designed to bear

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

The Reynolds Covered Bridge stood on Blue Ball Road in Cecil County Maryland until 1949 – This Queen Post Pony was built by Joseph G. Johnson the same year he built the Gilpin’s Falls – This Image is seen here as a courtesy of Jim Smedley and mdcoveredbridges.com

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.

This image of the Colvin Covered Bridge of Schellsburg Pennsylvania is seen here as a courtesy of Carolyn Williams – I find The Colvin a particularly clever and visually appealing MKP Pony and should you find yourself in need of a short span bridge I’d love to build you a copy

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