. 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 . higher level thanthat through the mortise, so that the cap will be drawn downtight when the pin is driven. Occasionally iron dowels (aniron pin about 1| in diameter and about 8 long) are insertedpartly in the cap and partly in the pile. The use of drift-bolts,shown in Fig. 68 (6), is cheaper in first cost, but renders repairsand renewals very troublesome and expensive. Split caps,shown in Fig. 68 (c), are formed by b
. 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 . higher level thanthat through the mortise, so that the cap will be drawn downtight when the pin is driven. Occasionally iron dowels (aniron pin about 1| in diameter and about 8 long) are insertedpartly in the cap and partly in the pile. The use of drift-bolts,shown in Fig. 68 (6), is cheaper in first cost, but renders repairsand renewals very troublesome and expensive. Split caps,shown in Fig. 68 (c), are formed by bolting two half-size stripson each side of on top of the pile. Repairs are veryeasily and cheaply made without interference with the trafficand without injuring other pieces of the bent. The smallerpieces are more easily obtainable in a sound condition; the § 161. TRESTLESo 197 decay of one does not affect the other, and the first cost is butHttle if any greater than the method of using a single piece. Forfurther discussion, see § 170. For very hght traffic and for a height of about 5 feet threevertical piles will suffice, as shown in Fig. 68 (a). Up to a height. \wi iW Fig. 68. *m !w^ of 8 or 10 feet four piles may be used without sway-bracing, asin Fig. 68 (6), if the piles have a good bearing. For heightsgreater than 10 feet sway-bracing is generally necessary. Theoutside piles are frequently driven with a batter varying from1 : 12 to 1 : 4. Piles are made, if possible, from timber obtained in thovicinity of the work. Durability is the great requisite ratherthan strength, for almost any timber is strong enough (exceptas noted below) and will be suitable if it will resist rapid following list is quoted as being in the order of preferenceon account of durability- 1. Red cedar 5. White pine 9. White oak 12. Black oak 2. Red cypress 6. Redwood 10. Post-oak 13. Hemlock 3. Pitch-pine 7. Elm 11. Red. oak 14. Tamarac 4. Yellow pine 8. Spruce Red-cedar piles are s
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
