Let's say I've got a trestle on a 2% grade. Is the grade all in the upper storey (with all the girts horizontal), or is it in the lower storey (with the upper girts on the grade), or is it in the foundation (with all of the girts on the grade)?
I figure you do what you want. 2% is modest enough, you might not even notice. The Indiana Gulch trestle is built on a 2% grade. I built all the bents in a jig, and adjusted the bottom elevation of each bent slightly upward. The trestle is about two feet long, and it rises about 1/4" over the length.
I'm not sure about the C&S, but RGS engineering drawings c 1910-20 show that for framed trestles on grades, all upper story bents were identical in height. The lowest story bents varied in height to produce the grade or conform to the topography under the trestle. So the girts between bents, in my view, would always be parallel to the stringers that the bents supported (at least that's how they appear on the drawings).
This thread does beg the question though: Did the C&S narrow gauge have any frame trestles of greater than one story?
I can't think of any, even the Gold Pan trestle had only one story, no girts between the bents. Ditto for the tall trestle at Kokomo, that crossed over the D&RG grade.
In the prior Union Pacific years, management was pretty compulsive about replacing trestles with fills, and most larger bridges were iron or one-two span straining beam wood truss bridges, like just east of Pine, Eastabrook and the crossing of Chalk Creek south of Buena Vista.
The straining truss wood bridge at Eastabrook (No. 1077) still survives (as of the summer of 2015) as a private bridge to a home, but there wasn't a way for me to get close to it for photos, as it is on private property. There are a series of photographs by Richard Boulware here: http://www.narrowgauge.org/EOC/html/estabrook-bridge.html
Can anyone think of a tall wooden trestle of 2 or more stories anywhere on the C&S at any time?
In many respects the DSP&P was better engineered than the D&RGW, as is evidenced by the fact that the road bed survives in relatively good shape since abandonment circa 1940, compared with Marshall Pass, which is in far less good shape and was abandoned about 18 years later.
If only they would have stuck to the north side of Ten Mile and Chalk Creek!
In any case, the number of high trestles is limited.
Speaking of trestles and wood straining-truss bridges, this photo is in the Klingers' Platte Canon Memories . . . , page 115:
Richard B. Jackson Photo, c1936. California State RR Museum
The original two span wood straining truss bridge was at the east end of Pine Valley, just west of the iron bridge at Buffalo. The bridge rests on the original cut stone abutments and center pier, but has been strengthened, probably in the 1920s to accommodate the big B-4-F engines from the DB&W.
The right hand span has been reinforced with extra stingers, resting on short trestle bents next to the abutment and center pier. The left hand span has been reinforced with two trestle bents, directly supporting the iron I-beams under the upper bridge stingers. Another oddity that makes the C&S narrow gauge way cool !!!
As of the summer of 2015, the two stone abutments still survive in a fenced pasture, visible from the road from Buffalo to Pine:
The bridge abutments and center pier are much taller than at Pine Valley. But both bridges have those pyramid shaped capstones on either side of the tracks on the abutments and pier, much like the small bridge at Hancock, near the Hancock tank:
I discovered the South Park when I spotted the grade running off toward
Weston from Trout Creek Pass while driving from Buena Vista to Denver
in 1977. I stopped and looked it over and was taken/puzzled by the small
scale of the ties and berm. It looked like some sort of toy railroad, but clearly
wasn't. I began trying to figure out just what I had been looking at when I
got home and the charm of the little railroad that could just kept growing
with every little bit I learned.
It is such a shame the C&S did not survive the war. I suspect a lot more
would have been saved had it made it into the post-war railfan era. Any NG
is cool, but the South Park was such a rag-tag, cinderella story kind of operation,
their way of making ancient stuff work makes the modernized Rio Grande