Pony Truss Traditional Cache
fog: The approach to the cache is now taken over by poison ivy and the truss itself is about to collapse from rot, so I'm archiving this, my first hide.
peace - love - fog
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Parking area for Mass Central Rail Trail is on Thomas Street, just 100 feet south of State Rt 140 at Oakdale. Cache is small tube. The immediate area of the cache is very overgrown.
The original ammo box was pilfered by some local kids June 2006. I have replaced it with a micro. The Micro went missing Summer 2010 and I have replaced it with another micro. I have also raised the terrain rating from 1.5 to 2 because the overgrowth is much thicker now and includes pointy sharpy things. 5/13/2014 update: Terrain rating downgraded due to some work with a chain saw. Bring your own pen.
Bring bikes as there is an open area for biking adjacent to the cache where kids can go crazy while you go crazy trying to find this cache. In winter, this is a very popular starting point for Nordic skiing.
Dogs OK, as cache is on West Boylston town property, but dogs must be kept on lease. Please respect DCR (watershed) property rules to the south of the trail.
What we have here is a rare relic from a bygone era; the remnants of a wood Howe Pony Truss bridge. This type of bridge represents a transitional type between all wood and all steel bridges. William Howe patented this design in 1840 and it is distinguished by the use of wrought iron rods for the tension members (posts) and wood for the bulkier compression members and top and bottom chords.
Because steel is good at dealing with tensile forces and wood is good at dealing with compressive forces, it was a very clever design indeed, but for some reason, not too many bridges of this type were fabricated. My guess is that wood bridge fabricators probably preferred all wood designs and the steel bridge fabricators probably preferred all steel designs. Given their druthers, the former would have made the rails of wood and the latter would have stoked the steamers with pig iron.
"Pony" comes from the fact that the height of the trusses are lower than those of through-truss type bridges. Through-truss bridges have overhead re-enforcing sections. Most of New England's old covered bridges are of the through-truss type, which could be made of thinner and lighter materials, but the trusses had to be made high enough so the trains could clear the overhead sections, adding to the overall material burden. With a pony truss design, the roof is eliminated, and the superstructure is made smaller, stronger and bulkier to provide the equivalent carrying capacity. This used less material overall and had the side effect of longevity as well.
The bridge now found in parts at this cache was originally placed at the junction of Hartwell Street and the Boston & Maine RR in West Boylston at N42 20.507 W071 46.207. It was moved to its current location around 1999. The only other working example of this bridge type I have found is at Hermosa, CO on the Durango to Silverton narrow guage line near N37 50.029 W107 50.029.
Wachusett Greenways (the local rail trail group) and the town attempted to preserve the bridge so it could be re-used on a trail somewhere. To move it, the town had to cut the bridge up, but they only cut the horizontal members, keeping the truss sections intact. Unfortunately, Wachusett Greenways' engineer deemed the trusses too rotted even for pedestrian traffic. A close look at the top of the south westerly most top chord might lead you to the same conclusion, too, but only if you were a structural engineer I suppose.
We hope you enjoy this, our family's first cache.
Additional Hints
(Decrypt)
rlr-yriry
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
Loading Treasures