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Truckee River Bridges

Truckee River Bridges

Postby Solomani » Sat Nov 21, 2009 3:21 pm

Hi everyone,

I apologize for this not being narrow gauge but it is early California/Nevada railroad history. I have been collecting info on the Howe Truss/Burr Arch bridges that the Central Pacific made to cross the Truckee river. My intent is to make a model of the Wadsworth covered bridge. Largely for sentimental reasons as I grew up in Wadsworth.

I have been looking over the Bridgeport California covered bridge and while it is a roadway bridge and not a rail way bridge it is likely of similar plan. What it does not have and I am curious about is the white "T" shaped patterns in the arch as shown in this photo. Any ideas what they might be?

-John
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h0279 Fourth Crossingof the truckee river 147 miles from sacramento.jpg
Fourth Crossing of the Truckee River
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Re: Truckee River Bridges

Postby Andrew Brandon » Sat Nov 21, 2009 4:27 pm

John,

Have you checked the technical drawings in the CSRM's library for a drawing?

http://66.129.110.33/SearchDrawingsBasic.htm
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Re: Truckee River Bridges

Postby Solomani » Sat Nov 21, 2009 9:04 pm

Andrew,

Thank you for the suggestion. I had not tried that resource. I did find a couple of later bridges but nothing from the earlier era. There may not be anything (I hope that is not true) as I understand an awful lot of plans when up in smoke in the Great San Francisco quake and fire.

-John
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Re: Truckee River Bridges

Postby Solomani » Mon Nov 23, 2009 7:30 pm

I had to go down to Beale AFB to pick up some uniforms and realized that my trip would take me almost right by the Bridgeport Bridge. I took the detour and spent about an hour looking over the bridge. It is of lighter construction, being a roadway bridge, but it was really neat to check out an "operating" 1862 bridge. The bridge uses square section rods for the tension rods and laminated 3x16 planks for the top and bottom chords.

The detail I found interesting that was for the joins in the arch there was a bolt run through vertically where the join was with plates top and bottom. I assume this is to support the joint as well as reduce checking in the wood.

I am wondering if the white sections in the photo above were some type of premade "join" for the arches.

best regards,
John
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Re: Truckee River Bridges

Postby Andrew Brandon » Mon Nov 23, 2009 8:18 pm

John,

If you ever need any detail information or photos of Bridgeport in the future I can grab them for you as I live in Grass Valley. I am about 10 minutes away. :)

I cannot remember how it is constructed off the top of my head but there is another covered bridge up Highway 49 at Oregon Creek.
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Re: Truckee River Bridges

Postby Solomani » Tue Nov 24, 2009 12:19 pm

Thank you Andrew I may just have to take you up on that.

My internet research seems to be leading me to believe that these bridges were of a type called "improved Howe truss." I found an article in "Elementary Principles Carpentry" by searching for "improved Howe Truss."
Section-X-Wooden-Bridges-Viaducts-Etc-264.jpg




Also found an article about a bridge using this system in the " Civil Engineer and Architects Journal." They did not seem to think much of it as a design. Their comment was that the Burr truss was superior or could be made superior.

The folks at UtahRails.net http://utahrails.net/articles/ambrose.php have an article called "the sins of Stephen Ambrose" and noted:
27th photo page, photo caption:

"This is a Howe truss bridge across river at Eagle Gap."

This is another of A. A. Hart's original photographs (#274) which was originally captioned "Bridge at Eagle Gap". The bridge is more accurately described as an "Improved Howe truss bridge" because of the heavy arches connected to the lower chord. All bridge spans over fifty feet were built on the Howe plan. The only bridges built with a supporting arch as used on the Central Pacific were with spans over 204 feet and known as the "Improved Howe truss" as patented by William Howe in 1852.




I have not been able to find the Howe patent though on either Google patents or on USPO. I did see a patent by Howe that showed an attachment of rods from the truss but they were not vertical rods but rather are 90 degrees from the point at where they attached to the arch. This was from figure 1879 in the book "Spons' Dictionary of engineering, civil, mechanical, military, and ..., Volume 4" By Edward Spon http://books.google.com/books?id=4kcOAA ... 22&f=false
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Re: Truckee River Bridges

Postby Andrew Brandon » Tue Nov 24, 2009 9:32 pm

John,

Long ago my father and his family lived at the farm there at Bridgeport, they were one of the last toll collectors for the bridge while it was still in use. Trips down there are always a pleasure so I wouldn't mind you asking in the future.

Interesting find on the Improved Howe, if I find any information that might be of use I will pass it on.

Andrew
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Re: Truckee River Bridges

Postby Solomani » Mon May 24, 2010 9:22 pm

I finally found some time to start working on my drawings. For the Truss portion I have a copy of the blue prints from the D&RG resident engineers office dated March 10th 1890 for a 202 foot Rio Grande Southern bridge (I don't know which one.) Since these are actual blueprints copies I expect that they are a pretty good source. I did run across something curious though and was wondering if anyone had an idea why they might have done it.

Here is the curiosity: the distance between the truss rods is 3/8 of an inch different between the top and the bottom chords. The top is 12' 3/8" between centers and the bottom chord is 12' even.

This bridge is pretty small by modern standard gauge designs (of 1890) but seems to be about spot on from what I can measure from the photos I can find.

Anyone know what the loading gauge might be for the CP in 1870? From the photos the bridges seem to be about 11' between truss's and 17 feet high for clearance.

-John
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Re: Truckee River Bridges

Postby Solomani » Sat Jun 05, 2010 3:34 am

Here is my current progress. In this pic we are roughly the same angle as Hart stereograph #279 "Fourth Crossing of the Truckee river. This design is a 204' clearspan with the overall truss length of 226 feet.

John
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Improved Howe Truss Sketchup drawing.jpg
Last edited by Solomani on Sat Jun 05, 2010 1:40 pm, edited 2 times in total.
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Re: Truckee River Bridges

Postby Solomani » Sat Jun 05, 2010 3:43 am

One more.
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204 foot clearspan.jpg
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