is minus. Compute and record for each station the sum of errors at that station and at all previous stations. To do

this, add each station's error to the sum of errors at the previous station. The sum of errors for the last station

must be zero. Compute the necessary half throw for each station by adding the sum of errors and the half throw at

the previous station. The half throw at the last station must be zero. If necessary, change ordinates to adjust the

curve and recompute. Double the half throw at each station to find the full throw. Adjust the proposed ordinates

if the final throw is other than zero and if restricted clearances, a bridge, or a turnout makes it impossible to move

the track.

Section V. Lining an Actual Curve

3.27.

GENERAL

For a long distance on tangent or straight track, a foreman with an "experienced eye" can sight kinks

readily and have them corrected. But on curved track where his view is shortened to only a few feet and where he

can see only outstanding kinks and discrepancies that need to be corrected, he would do well to forget about

trying to line the curve by sighting and stick to a more reliable method. He should use either his track gage along

with the centerline stakes placed by the engineers laying out the tracks or the stringline method discussed in

section IV. To bring the track back into line, he will direct his gang to use their lining bars, or, if available, a

track liner. This section discusses precautions that the track supervisor should heed, the computations of an actual

curve, the marking and the throwing of the track, and the re-dressing of the ballast.

3.28.

PRECAUTIONS

When making stringline computations, heed two important precautions: calculate accurately and keep

throws short. Remembering these precautions will make the computations simpler and the work on the track

itself easier.

a. Accurate calculations. When you make stringline calculations, be very careful of your arithmetic.

Check your results every time you can. An error in addition or subtraction at any point will make your figures

wrong from there on. It is often harder to find and correct a mistake than it is to make the whole computation in

the first place.

b. Size of throws. Keep the throws as small as possible when men are to move the track with lining

bars. Since the entire