. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . them, having one linevertical, were pasted on the web of the rail. A camera wasfocused on the rail about 10 feet away. An initial exposurewas taken of the unloaded rail. Then, without disturbanceof the camera, the desired train load was run over the trackat the desired speed. When the train (or locomotive) was atthe desired point, it closed an electric circuit which operated rT- --I- FiG. 222.—DepressioN Plug. §543.
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . them, having one linevertical, were pasted on the web of the rail. A camera wasfocused on the rail about 10 feet away. An initial exposurewas taken of the unloaded rail. Then, without disturbanceof the camera, the desired train load was run over the trackat the desired speed. When the train (or locomotive) was atthe desired point, it closed an electric circuit which operated rT- --I- FiG. 222.—DepressioN Plug. §543. STEESSES IN TRACK. 605 the shutter for a .001 second exposure. The resultant photo-graph showed for each cross a double cross with one verticaland two horizontal lines whose distance apart represented, aftersuitable reduction, the depression of the rail. Using a magnify-ing micrometer microscope, and a computed constant multiplier,it was possible to measure from the photographic plate theactual deflection of the rail with a precision of about Pressure transmitted from tie to ballast. This subjectwas investigated both theoretically and experimentally. The. 30 27 24 21 18 15 12 9 6 3 0 3 6 9 12 15 18 21 24 27 Distance from Center Line of Middle Tie-InchesFigures within diagram indicate percentages Fig. 223.—Lines of Equal Vebtical Pkessure in Ballast fob EqualLoads on Ties, Spaced 21 experimental work included not only track tests but also anextensive series of laboratory tests using sand ballast, pebbles,and broken stone. If ballast consists of absolutely clean spheresof perfectly elastic material, whose mutual actions and reactionsare only pressure without friction, a definite theoretical solutionas to distribution of pressure is possible, although equation of pressure is a logarithmic equation which ischiefly useful in interpreting experimental results. Both theoryand experimental tests demonstrate that: (a) The bearing pressure of the
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
