File:The Street railway journal (1901) (14571946459).jpg

Identifier: streetrailwayjo181901newy (find matches)
Title: The Street railway journal
Year: 1884 (1880s)
Authors:
Subjects: Street-railroads Electric railroads Transportation
Publisher: New York : McGraw Pub. Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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e sills at CC, wherea second crossing is placed.The whole longitudinalstrength of the structure isinconsiderable, depending,as it does, entirely on theside sills. Compare thiswith tlie platform of asteam coach or a Pullman,in which case the structureis its own load. In spile ofthe fact that it is only anenlarged step, it can lesistthe impact of a ioo,ooo-lb.locomotive when coupling. The electric car platformis supported by platformtimbers, often called knees,of the general shape shownin Fig. 7. These are canti-levers, which are hung neartlieir centers from the endsills, with their inner endsresting against a cross tim-ber. LTsually there are twoat the center of the i)iat-form and one on each side. As the load is dis-tributed along the outer ends of these cantilevers, thewhole of the strain, amounting usually to twice the load,is taken liy the end sill and end of the car. When theinboard and oullxiard ends of the cantilever are enu d, the 254 STREET RAILWAY JOURNAL. (Vol. XVIIL No. io.
Text Appearing After Image:
FIG. II.—PLAN AND CROSS SECTION OF PLATFORM OF 25-FT. BOX CAR ILLUSTRATED IN FIG. 10 September 7, 1901.) STREET RAILWAY JOURNAL. 255 upward thrust against the crossing is equal to that of theload. This arrangement is comparatively favorable, but,unfortunately, this condition of things can not always beobtained. The outer arm is often prolonged, and the innerarm shortened until the strain on the end sill may be three,or even four, times the load, while the crossing gets anupward thrust of from one and a half to three times asmuch. The tie-rods on each side of the door, the door-posts and the whole end frame of the car are called intoservice in sustaining the strains of the platform load. Fig.8 shows a platform timber cut oft at the bearing. Theload is carried by the angle-iron, and the cut shows the un-favorable conditions of support sometimes necessary. It is the fact that the leverage is in favor of the loadagainst the framing that makes heavy controllers, sand-boxes and the like,

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