A Brown truss is a type of bridge

Bridge

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

 truss

Truss

In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

, used in covered bridges. It is noted for its economical use of materials and is named after the inventor, Josiah Brown Jr., of Buffalo

Buffalo, New York

Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...

, New York

New York

New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

, who patent

Patent

A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

ed it July 7, 1857 as US patent

United States Patent and Trademark Office

The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...

 17,722.

Description

The Brown truss is a box truss

Box truss

A box truss is a structure composed of three or more chords connected by transverse and/or diagonal structural elements.-Application:Box trusses are commonly used in certain types of aircraft fuselages, electric power pylons, large radio antennas, and many bridge structures...

 that is a through truss (as contrasted with a deck truss) and consists of diagonal cross compression member

Compression member

A compression member is a general class of structural elements of which a column is the most common specific example.-Description:For a compression member, such as a column, the principal stress comes mainly from axial forces, that is forces that fall along one line, usually the centerline.The...

s connected to horizontal top and bottom stringers. There may be vertical or almost vertical tension 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

Covered bridge

A covered bridge is a bridge with enclosed sides and a roof, often accommodating only a single lane of traffic. Most covered bridges are wooden; some newer ones are concrete or metal with glass sides...

, 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.

Patent

Brown's patent claims did not actually address the economy afforded by lack of vertical members ("braces"). Instead he focused on the improved strength over previous trusses that had members ("braces" in his terminology) come to the horizontal chord near to each other but not exactly together (at "gains" in his terminology), by having several members come together in the same place. From the patent text:

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

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.

History

The Brown truss enjoyed a brief period of favor in the 1860s, and is known to have been used in 4 covered bridges in Michigan, the Ada Covered Bridge

Ada Covered Bridge

The Ada Covered Bridge is a span Brown truss covered bridge erected in 1867 in Ada, Michigan, United States. Carrying Bronson Street across the Thornapple River, it is located just south of where the Thornapple enters the Grand River, in turn just south of M-21...

, the Fallasburg Bridge

Fallasburg Bridge

Fallasburg Bridge is a span Brown truss covered bridge, erected in 1871 in Vergennes Township, Michigan, United States, north of Lowell on the Flat River. Carrying Covered Bridge Road across the Flat, it is located in the Fallasburg Historical District south of Whites Bridge and Smyrna...

, Whites Bridge

Whites Bridge

Whites Bridge is a 120-foot span Brown truss covered bridge, erected in 1869 in Keene Township, Michigan, United States, near Smyrna on the Flat River. Carrying Whites Bridge Road across the Flat, it is located north of the Fallasburg Bridge and south of Smyrna...

 and one other. The design did not appear to gain wide acceptance as modern bridges tend to be Howe, Pratt, Bowstring or Warren trusses.