24
2.18. FIRST DIVISION NDT
The first step in determining the NDT for the first division is
to find the starting tractive effort of the locomotives you have.
a. Tractive effort. Table. I shows that the 0660, 127ton
dieselelectric locomotive has a starting tractive effort of 75, 700
pounds. The continuous tractive effort for this locomotive is 50
percent of its starting tractive effort, or 37,850 pounds. Your
second step is to find drawbar pull.
b. Drawbar pull. The locomotives weigh 127 short tons each.
Subtract 20 pounds per ton of total locomotive weight from the
continuous tractive effort and you have the drawbar pull of each
locomotive:
20 x 127 = 2,540
37,850 2,540 = 35,310 DBP
c. Gross trailing load. The third step is to find the gross
trailing load for the locomotives. To use the formula for GTL
presented in paragraph 2.10, you must find the values for each
unknown. You already have a value for DBP; therefore, concentrate on
weather, rolling resistance, grade resistance, and curve resistance.
The process for finding values for each of these follows in the order
mentioned.
(1) Weather. Using table III and the information given on the
first division, you find that the loss in hauling power between 0
and +15 F. is 10 percent; therefore, the value for the weather factor
(W) is 0.90.
(2) Rolling resistance. Since the track for the first division
is rated good to fair, table II shows that a value of 6 should be
used for rolling resistance (RR).
(3) Grade resistance. Multiply 20 pounds per ton of train by
the percent of ruling grade for this division (1.5) and you find that
the value for grade resistance (GR) is 30.
(4) Curve resistance. The ruling curve for this division is
2.5, which must be multiplied by 0.8 pounds per ton of train to get
the value for curve resistance (CR) of 2.
Previous Page
