US323424A - Petee ii - Google Patents

Description

(No Model.) v

P. E. JACKSON.

METHOD OF UUTTING AND EMPLOYING WOODEN BEAMS AND GIRDERS.

No. 323,424. Patented Aug. 4, 1885.

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PETER H. JACKSON, OF SAN FRANCISCO, CALIFORNIA.

METHOD OF CUTTING AND EMPLOYING WOODEN BEAMS AND GlRDERS.

SZECIFICATION forming part of Letters Patent No. 323,424, dated August 4, 1885.

7 Application i'ilcd December 30, 1884. (No model.)

To M5 2071-0112, it may concern:

Be it known that 1, PETER H. JACKSON, of San Francisco, State of California, have invented an Improved Method of Cutting and Employing W'ooden Beams and Girders, by which an increased number of pieces can be obtained from the log; and I do declare the following to be a full, clear, and exact description thereof.

My invention relates to timber beams, with reference to the propertyin the various kinds of wood of greater resistance to compression than tension, together with the manner in which I employ them to sustain loads, the form given them admitting of a greater number of beams or girders being cut or sawed from alog or large piece of timber than in the common manner of doing, the said beam being still of equal strength to resist transverse strain as in the other, as will be more fully explained by reference to the accompanying drawings, in which Figure 1 is a cross-section of a log of wood marked to be out in this improved manner, showing how six beams or girders with tapering sides may be sawed. Fig. 2 also represents a crosssection of the same size log as Fig. 1, marked to be cut in the present manner of doing, from which but four beams or girders can be sawed. Fig. 3 is a crosssection of a large stick of timber marked to be cut in this improved manner into twelve beams or girders with tapering sides. Fig. 4. is a cross-- section of the same size stick of timber as in Fig. 3, marked to be cut in the present manner of doing, from which but eight beams or girders can be sawed of this size. Fig. 5 is a 'cross-seetion of one of these improved cut wooden beams or girders, taken from either Figs. 1 or 3, with tapering sides, and employed in the manner designed, the greatest width being across the top, to resist compression, in which most, if not all, timber has this property of resistance in the least, and the material in that part is increased to make up this deficiency, the dotted line a b representing the neutral axis. Fig. 6 is a cross-section of a beam or girder taken from either Fig. 2 or 4:, out rectangular in the ordinary manner of doing, the material outside of the dotted lines being so much useless material in resisting transverse strain, as will be hereinafter explained. Fig. 7 is a longitudinal section of a beam or girder of any material, W in all the figures representing the weight or load, which may be central or distributed. The arrows pointing toward each other on the top surface indicate that part is being compressed by the load, and the arrows at the bottom pointing in opposite directions indicate that part is in a state of tension or separation of the parts, the parts being compressed and extended the greater as the distance is increased in either direction from the neutral axis a. b. Fig. 8 is a cross-section of a castiron beam or girder with the bottom and top parts duly balanced in metal quantities in accord with the capacity of the material to resist compression and tension. Cast-iron, being weak in its resistance to separation, should have about six and a half times more material in the bottom than the top part to equilibrate the two forces. Fig. 9 is a cross-section of a wrought-iron beam or girder with the top and bottom parts duly balanced in metal quantities. \Vrought-iron, being the weakest in resisting compression, to equilibrate the two forces, should have about thirty-five per cent. more inaterialin the top, subject to compression, than in the bottom,subjected to tension or separation of the particles.

In the treatise on the resistance of materials by De Volson Wood the resistance to compression and tension per square inch of different timber is given as follows:

In the work entitled Mechanics Text- Book, by Thomas Kelt, is as follows:

Resists Resists tension or compression. separation. T n, i 2,028 lbs. 12,346 lbs. Red pine... 5,375 11,800 y ll pine 5,445 11,1535

Taken from the California Architect and Building News, December, 1884, issue:

Resists Resists tension or compression. separation. d d 5,908 lbs. 12,000 lbs. spruce 6,000 17,000

It will be seen by the table of reference that fir, oak, white, red, and yellow pine, redwood,

and spruce, from which beams and girders are usually made, have about twice the capacity to resist separation to that of compression, and these two forces being equal when the l e mm or girder is employed, the material, to be used economically, should have about twice the amount of material in the top part, subjected to compression, to that of thelower part, subjected to tension. Therefore wooden beams or girders sawed in the tapering shape shown and described, and employed with the wide part at the top, as in my device, have equal strength to the rectangular beams or girders, and from one-third to one-half more pieces can be obtained from a large piece of timber by the former than by the latter.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

A wooden beam or girder of suitable depth 20 PETER H. JACKSON.

Witnesses:

J AMES B. LANE, HENRY HAUSTEIN.

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