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APPENDIX B

WITH 100,000 LBS. DRAWBAR FORCE

89 ft. CAR

& APPENDIX B

50 ft. CAR

15° CURVE

13° 28°

LATERAL COMPONENT REACTING
AT TRUCK CENTER

12,190 LBS.

E SHORT CAR

E LONG CAR

LATERAL COMPONENT REACTING
AT TRUCK CENTER

23,150 LBS.

Figure 12.

Table 3 shows the steady-state drawbar forces that will produce critical lateral forces for long short car combinations for various degrees of curvature for a car weight of 33.5 tons.

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40

60 80

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100 120 140 16°

N

300,000 lbs. 300,000 lbs. 300,000 lbs.
205,000
240,000

262,000
154,000
180,000

197,000
123,000
144,000

158,000
103,000
122,000

132,000
88,000
103,000

113,000
77,000
91,000

99,000
*Based upon the overturning characteristics of a rail
and neglecting the torsional resistance produced by a heavier
car both preceding and trailing the light car.

N

N

M

THOSE WHO ARE RESPONSIBLE FOR THE MAKE UP OF TRAINS
SHOULD BE AWARE THAT HIGH L/V RATIOS CAN BE DEVELOPED
W'H EN CARS OF 85 FEET OR LONGER ARE COUPLED WITH CARS OF
LESS THAN 50 FEET IN LENGTH.

3-7

Many railroads tend to limit the drawbar pull of the locomotive (s) to 250,000 lbs. or less by limiting the tractive effort in the locomotive consists.

Most of the very high drawbar forces are experienced when heavy trains are ascending or descending those ruling grades that limit the maximum train tonnage. The three principal factors that are involved in the problems associated with the make-up of long car short car combinations in the train are:

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The grade and degree of curvature are fixed characteristics of the particular route. The placement of long car short car combinations in a train should vary depending upon the trailing tonnage.

For the suggested maximum allowable tonnage to trail an empty long car, which may be used by terminal operating personnel to govern their train make-up procedures, see Table 4.

When considering the placement of long car - short car combinations ahead of helper engines, the tonnage and the effective grade under the cars preceding the helper must be considered. The allowable steady-state drawbar forces (buff) because of increased coupler angularity, are approximately 20% higher than draft forces in a given degree of curvature. See Table 5.

Tables 4 and 5 do not take into consideration speed or superelevation for trains negotiating curves. However, if the speed and superelevation are in equilibrium, or reasonably close, the guideline table can be effectively used. If speed is significantly different than the equilibrium speed, a further reduction in trailing tonnage for long car - short car combinations must be made.

APPENDIX B

100

TABLE 4 Guideline Tonnage to Trail An 85 Ft. Empty Car in Draft
Sharpness of Curve 40

60
80

120 140 160 Maximum Safe

250,000 | 190,000 140,000 Drawbar Force (lbs.)

110,000 90,000 77,500 67,000

Drawbar Steepness Force/ Of

Trailing Grade

Ton

0.2%

10.1

24,700

18,800

13,800

10,900

8,890

8,650

6,610

0.4%

14.1

17,700

13,300

9,790

7,700

6,290

5,420

4,690

0.6%

18.1

13,800

10,500

7,720

6,070

4,960

4,280

3,700

0.8%

22.1

11,300

8,590

6,330

4,970

4,070

3,500

3,030

1.0%

26.1

9,570

7,270

5,360

4,210

3,440

2,970

2,560

1.2%

30.1

8,300

6,310

4,650

3,650

2,990

2,570

2,220

1.4%

34.1

7,330

5,570

4,100

3,220

2,640

2,270

1,960

1.6%

38.1

6,560

4,980

3,680

2,890

2,360

2,030

1,760

1.8%

42.1

5,930

4,510

3,320

2,610

2,140

1,840

1,590

2.0%

46.1

5,420

4,120

3,040

2,390

1,950

1,680

1,450

2.2%

50.1

4,990

3,790

2,790

2,190

1,800

1,550

1,340

2.4%

54.1

4,620

3,510

2,590

2,030

1,660

1,430

1,240

2.6%

58.1

4,300

3,270

2,410

1,890

1,550

1,330

1,150

NOTE:

Above table based on the following criteria

Maximum Drawbar Force based upon Knuckle Strength

250,000 lbs.

Grade Resistance

20 lbs./ton/percent grade

Rolling Resistance

6.13 lbs./ton for 35 ton cars at 21 MPH

APPENDIX B

TABLE 5 Guideline Tonnage to Preceed an 85 Ft. Empty Car in Buff

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Maximum Safe Drawbar Force based upon 250,000 lb. Guideline Drawbar
Strength and 20% Increase in Coupler Angle when in Buff

Grade Resistance - 20 lbs./ton/percent grade

Rolling Resistance = 6.13 lbs.,/ton for 35 ton cars at 21 mph

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