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Bridges and Grades Scenery and structures
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Prolific poster 1,515 posts dkaustin Prolific poster 1,515 posts
dkaustin

Just curious about this topic.  I live in NW Louisiana where it is flat compared to Colorado so there is not much to compare to. I know that railroads tried to avoid grades as much as possible. My question is when the route was in a continuous steady grade and a bridge was required was the bridge set to meet the same grade or was it set level to cross the terrain? I have read some opinions that prototype bridges were set level because heavy braking on a downhill grade on a bridge would cause damage to the bridge structure and foundation.  Is there any truth to this?

I am building a layout that will have mountains and many bridges.  There will be a steady continuous grade throughout the layout using the Woodland Scenics risers.  To me it makes sense that on the "model layout" it would be a best practice to not break the grade as uncoupling could become problematic with the truck mount couplers.  Would setting my bridges to match the grade be a glaring error?  What have other modelers done?

Any and all advice would be appreciated.

Thanks!

Dennis

 

n1910(1).jpg 

     Dennis Austin located in NW Louisiana


 
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DKRickman Prolific poster 3,069 posts
DKRickman

Bridges can be on a grade

I can personally attest to the fact that some bridges are on grades!  I would think that it would be far better to have a continuous grade than a level bridge.  Changes in grade can cause nightmares for train crews trying to keep a train together.  We have a spot in Danville, VA where the track (on a 1% grade) crosses over a short bridge over a road.  Even though the grade is more or less continuous there, the slight variation caused by the transition from ballasted track to deck girder bridge has been enough to break many knuckles.  I can only imagine what it would be like if they had actually tried to level the bridge.

Ken Rickman

Danville & Western HO modeler and web historian

http://southern-railway.railfan.net/dw/
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DKRickman Prolific poster 3,069 posts
DKRickman

Another thought on the subject

At least around here (Piedmont area of NC/VA), a bridge of any size is usually over a stream, and a stream is usually at the bottom of a valley.  Thus the tracks go down to the bridge, level over it, and up the other side.  The only bridges on grades, for the most part, are short ones over roads and the like.

I would imagine that in other parts of the country, where a bridge might cross an arm of a valley as the track clings to the side, the bridge would definitely be on a grade.  Still, I think anything more than a short (50' or less) bridge on a grade would be unusual, if not quite rare.

Ken Rickman

Danville & Western HO modeler and web historian

http://southern-railway.railfan.net/dw/
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Geared Frequent poster 840 posts
Geared

Bridge Grades

Here on Vancouver Island on a line in my area the trestles are built to the grade of the roadbed. When I walked the grade this past summer it was quite noticeable over the longer trestles. In mountainous areas like BC, these grades can often be seen from the road as the line progresses up along the side of a mountain.

Roy

Roy

Geared is the way to tight radii and steep grades. Ghost River Rwy. "The Wet Coast Loggers"

 
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dreesthomas Regular poster 495 posts
dreesthomas

extreme example

I was just leafing through Ken Drushka's "Working in the Woods" and came across a photo (p 157) of Comox Logging's bridge at Haslam Creek.  What reminded me of this thread was the line in the caption: "The bridge was 196 feet high and 546 feet long, and had a five percent grade."

Of course loggers could get away with just about anything.

DRT
David Rees-Thomas
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