|A USMRR trestle on the City point line built with |
the usual design of vertical posts under the rail stringers.
Both bridges show similar construction techniques. They use finished lumber instead of raw logs. The ties are relatively thin boards and not normal thickness ties.
The bridges include a curious feature- sections of timber under the stringers where piers rest. The timber sections do not form a complete stringer and I wonder what purpose they serve. Since they appear on both bridges, I assume they are intentional design items and not field changes perhaps added to raise the grade to allow standard bents to be used in a slightly deeper location. These extra pieces are not included in Haupt's drawing.
With all the variation in field installations, following a standard drawing is probably not the best way to get an accurate model. Ideally a modeler would follow a prototype example when building a model trestle. If you pick a spot where no photo documentation exists, like I did at Clairborne trestle, then following the standard drawing is a reasonable fall back approach, but just about anything could be possible.
|The Culleaoka Trestle. Note the details in the lower left showing the piers and bracing at the ground. Also|
note that the piers are finished lumber and not raw logs. In spite of Haupt's text, this trestle
has X bracing on most of the visible bents.
|The Harris Trestle shows similar construction details as the Culleaoka Trestle above. This bridge is|
closer to Haupt's drawing, but it has the curious cut timbers between the
piers and stringers.
I will offer the guess that the "short stringers" functioned as splices. The length of them would allow for green wood shrinkage.ReplyDelete
It seems that these blocks were common on trestles on the Ohio River and Western (last narrow-gauge in Ohio), and I chatted about it with the main historian in the FB group dedicated to it. He believes that they were there to spread the load on the trestle cap, since each stringer could only bear on half the cap. He also said that they were on each trestle that he knew of. That road had over five miles of trestle, or about four per cent of its mainline.Delete