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Yellowstone corkscrew bridge built to allow cars and horse buggies the ability to travel up and over Sylvan Pass.
https://diqn32j8nouaz.cloudfront.net...e_fullsize.jpg
https://diqn32j8nouaz.cloudfront.net...1_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...388#post154569
https://www.homemadetools.net/forum/...158#post134554
I am thinking, the first big rain that whole bridge is coming down from the water rushing down the gulley.
I don't see a corkscrew bridge. I see a curved bridge that functions as part of a corkscrew structure.
Am I reading that correct? Is "1698" the date???
Seems like it would have been nearly as simple just to go straight down the slope right there.
That date is in error. The same photo is show here with the caption "A Frost and Richard tour party returning from Yellowtone approx. 1915."
information here
The number '1698' is not for the date, January 6 1898, the way we might write it now.Quote:
Originally Posted by mlochala
It is a catalog reference number for the photo.
Since photography and multiple copies were so expensive then, the number and title would have been in the reference book for both the Park Service and Department of Interior and likely Library of Congress among other locations.
I don't know the original size of this but many of these photos were/are very large, like 20" by 30", so they had to be stored and handled carefully.
As far as the road in the pass, it's up in the 8000- 9000 foot elevation and at a very, very steep grade.
Going straight down was probably simpler; the stopping/braking and steering a wagon would have been the issue with any, up or down.
There is also the livestock problem. A horse or mule singly or in teams couldn't have made that grade safely if at all pulling a loaded wagon.
It appears from the photo the loop reduced the effort possibly as much as 3 fold. A guesstimate, yes.
Any civil engineers to elaborate on the picture?
I am not an engineer, but even animals (dogs, cats, cows, elk, buffalo, mountain goats, etc) do not try to travel straight up or down a mountain. They "traverse" the incline, making the journey longer, but much less steep.
This crude measurement shows this section of the road has about 6% grade. Very steep by todays standards.
Attachment 41971
How to determine pitch
Have seen a couple of these bridges - near Mt Rushmore. There are also quite a few switchbacks along that path.
I don't remember anything curently at Yellowstone.
