. The elements of railroad engineering . thetrack of equal length. The top of the crib should be fixedexactly at grade, so that trains may pass from the embank-ment to the trestle, and vice vcrsa^ without any frequently vary ^ inch in thickness, so that theactual elevation of the top of the crib may vary 1 or 2 inchesfrom the calculated one. This discrepancy may be readilyremedied by shims, if the top of the crib is too low,and by notching down the stringer, if the top is toohigh. It is well to have the stringers extend back fromthe face of the crib several feet. The bottoms of
. The elements of railroad engineering . thetrack of equal length. The top of the crib should be fixedexactly at grade, so that trains may pass from the embank-ment to the trestle, and vice vcrsa^ without any frequently vary ^ inch in thickness, so that theactual elevation of the top of the crib may vary 1 or 2 inchesfrom the calculated one. This discrepancy may be readilyremedied by shims, if the top of the crib is too low,and by notching down the stringer, if the top is toohigh. It is well to have the stringers extend back fromthe face of the crib several feet. The bottoms of thestringers should be kept from coming in contact withthe earth of the embankment. This may be preventedby spiking planks to the crib timbers underneath thestringers. The stringers should be drift-bolted to thecrib timbers. Such a connection between embankment 1 -io^ RAILROAD STRUCTURES. and trestle as we have just described is shown in Fig.(;17. ^=^^s^^ ^^„^^^„r 1—TT [ ^ • i - i \iy41\ [\ J I 3 Plank •1- ^ _] - < V o a r. Fir,. 617. Connection between the embankment and the trestlemay be made by means of a l?aul bent, either of piles orframed. This construction is more favored than the cribform previously described. It consists of a strong frame orpile bent built into the slope at the end of the embani:mentfor the support of the stringers. If piles are used, the bentshould contain four piles deeply driven into the embank-ment, so tliat they will not only safely carry the train load,but will sustain the pressure of the back filling, which is RAILROAD STRUCTURES. l--*(iii carried up to the base of the stringers. To hold this pilingin place, the back of the bent is close planked with 3-inchor 4-inch plank. When the bank bent is of considerableheight, struts of 8-in. by 8-in. stuflf should extend fromthe bank bent to the timbers of the first trestle bent, toinsure its stability. When the bank bent is of framed tim-ber, special pains should be taken to insure a safe
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
