3.18.

EQUIPMENT

What equipment do you need to put stringlining into actual practice in the field? To mark off the stations

and measure the ordinates, you need a tape at least 31 feet long, graduated in feet. Any such tape will do,

provided the same tape is used to measure all the stations on a curve. You also need a strong string, 62 feet long

or longer, marked at the 62-foot point. A ruler, graduated in inches and eighths of an inch, is required for

measuring ordinates. One graduated in inches and tenths will do, if a similar rule is used for all lining of a

particular curve. However, in this discussion, all ordinates are expressed in eighths of an inch. You also need a

notebook, a pencil, and a heavy crayon. A pair of wooden blocks, 1 by 1 by 2 inches, known as offset blocks, are

helpful. To mark the distance the track is to be moved, you need wooden stakes, surveyor's tacks, and a ruler or

tape.

3.19.

MARKING OFF STATIONS

The first step in stringlining is to divide the entire curve into 31-foot

lengths. This is known as marking off the stations. You start at some point on

the tangent, marking it with a heavy crayon on the web of the outside rail, as

shown in the sketch. Then you measure 31 feet toward the curve with the tape

and mark this point in the same way. Each of the points you mark is known as a

station, and you number them consecutively from the first point to the end of the

curve, as shown in the sketch.

Let us assume that you marked two

stations the first time you stretched the tape; the

first is numbered station 0 or Sta. 0, and the second

Sta. 1. Mark their numbers on the web at the

station marks, and enter them in a column in the left margin of your notebook. Now measure 31 feet beyond Sta.

1, and mark and record Sta. 2. Continue this all around the curve, until you are out on the other tangent. In

practice, it is a good idea to start far enough down the tangent to have 10 or 15 stations on the tangent, and to have

10 or 15 more beyond the curve on the other tangent. Why? Because the straight track at the approaches to a

curve is likely to be disturbed by the passage of trains around the curve, and its lining should be checked.