Brown truss: Difference between revisions

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A '''Brown truss''' is a type of [[bridge]] [[truss]], used in [[covered bridges]]. It is noted for its economical use of materials and is named after the inventor, Josiah Brown Jr., of [[Buffalo, New York|Buffalo]], [[New York (state)|New York]], who [[patent]]ed it [[July 7]], [[1857]], as [[United States Patent and Trademark Office|US patent]] 17,722.<ref name="wmta">{{cite web|url=http://www.wmta.org/coveredbridges/whites_bridges.html |title=White's Covered Bridge page |work=West Michigan Tourist Association |accessdate=December 27, 2006 |dateformatarchiveurl=mdyhttps://web.archive.org/web/20070428162245/http://www.wmta.org/coveredbridges/whites_bridges.html |archivedate=April 28, 2007 |url-status=dead }}</ref><ref name="google">{{cite web| publisher = [[Google]] | url= httphttps://wwwpatents.google.com/patents?vid=USPAT17722&id=xwRXAAAAEBAJ&printsec=abstract&zoom=4patent/US17722 |title= "TBUSS-BEIDGE JO SI AH BROWN" (sic) |work=[[Google Patent Search]] |accessdateaccess-date=December 28, 2006|dateformat=mdy}}</ref><ref name= "uspto">{{cite web| publisher = [[US Patent Office]] | url= http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F17722 |title=Patent 17,722|work= Full-Text and Image Database|accessdate=December 28, 2006|dateformatarchive-date=December mdy20, 2016|archive-url=https://web.archive.org/web/20161220125821/http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F17722|url-status=dead}}</ref>

The Brown truss is a [[box truss]] that is a [[Truss bridge#Truss types used in bridges|through truss]] (as contrasted with a [[Truss bridge#Truss types used in bridges|deck truss]]) and consists of diagonal cross [[compression member]]s connected to horizontal top and bottom stringers.<ref name="AdaMarker">{{cite web| publisher = Michigan.org | url= http://www.michigan.org/travel/detail.asp?m=2&p=B5658|title=[[Ada Covered Bridge]] marker detail page|work=Michigan historical markers|accessdate=October Oct 099, 2006|dateformaturl-status= mdydead|archiveurl=https://web.archive.org/web/20060928225956/http://www.michigan.org/travel/detail.asp?m=2&p=B5658|archivedate=2006-09-28}}</ref> There may be vertical or almost vertical [[Tensiontension (mechanics)|tensionmembers]] members (the diagram shows these members, while the patent application diagram does not) but there are no vertical members in compression. In practice, when used in a [[covered bridge]], the most common application, the truss is protected with outside sheathing.

The floor and roof are also trusses, but are horizontal and serve to give the truss rigidity. The bottoms of the diagonals tend to protrude below the sheathing. The Brown truss is noted for economy of materials as it can be built with very little metal.<ref name="michigan.org">{{cite web| publisher = Michigan.org |url= http://www.michigan.org/travel/detail.asp?m=2&p=B5668|title=[[Whites Bridge]] marker detail page|work=Michigan historical markers|accessdate=December 22, 2006|dateformatarchive-url=https://web.archive.org/web/20080214175040/http://www.michigan.org/travel/detail.asp?m=2&p=B5668|archive-date=2008-02-14|url-status=mdydead}}</ref>

<blockquote><p>I do not claim broadly furnishing the main or counter braces with gains and passing them between the timbers of the chords;</p>

<p>What I do claim as my invention, and desire to secure by letters Patent, is— Providing each of the main and counter braces with two gains at top and bottom, and each of the timbers of the chord with a gain at the point where the braces are applied corresponding with the gains in the braces, and the braces thus formed up between the timber, with the gains of the braces in such relation to the gains of the timbers that when the timbers of the chords are brought together they are combined and become, as it were, only one piece, no part of which can be operated upon or affected independently of the other by the downward and upward thrusts common to truss bridges, even if the bolt which passes laterally through and intersects each set of braces and the timbers of the chord were removed.<ref name="google2">{{cite web| publisher = [[Google]] | url= httphttps://wwwpatents.google.com/patents?vid=USPAT17722&id=xwRXAAAAEBAJ&printsec=abstract&zoom=4#PRA1-PA36,M1patent/US17722| title="TBUSS-BEIDGE JO SI AH BROWN" (sic) | pages = 2|work =[[Google Patents]] |accessdateaccess-date=December 28, 2006|dateformat= mdy}} [[Optical character recognition|OCR]]ed and hand corrected to match image.</ref></p>
</blockquote>

The Brown truss enjoyed a brief period of favor in the 1860s, and is known to have been used in 4four covered bridges in Michigan, the [[Ada Covered Bridge]], the [[Fallasburg Bridge]], [[Whites Bridge]] and one other. The design did not appear to gain wide acceptance as modern bridges tend to be [[Howe truss|Howe]], [[Pratt truss|Pratt]], [[Bowstringbowstring truss|Bowstringbowstring]] or [[Truss bridge#Warren (non-polar) truss|Warren]] trusses.

<gallery caption="Detail images from existing bridges">>

Image:FallasburgBridge InteriorFloorDetailDSCN9995.JPG|Bottom of diagonal truss members interlock with floor ('''Fallasburg Bridge''')

Image:FallasburgBridge InteriorSnowProtectionDSCN9996.JPG|The truss ends are special, additional material may be present for rigidity or to protect the structure from snow. ('''Fallasburg Bridge''')

[[Category:Truss bridges by type]]