Caterpillar Performance Handbook, January 2017, SEBD0351-47

Tables

CURVE SUPERELEVATION IN PERCENT GRADE,TO PROVIDE NO LATERALTIRE FORCE

Superelevated turns present a danger when slippery. For this reason, curves superelevated over 10% should be used with caution. Unless the proper speed is main- tained, matching the elevation of the curve, a vehicle may slide off of the lower edge of the roadway. Superelevated curves should be maintained in good tractive conditions.

Negotiating curves can generate high lateral tire forces. These forces contribute to high tire wear and ply sepa- ration. Superelevating the curve helps eliminate these forces. The amount of superelevation depends on the curve’s radius and the speed at which it is negotiated. The following table is a guide for providing the super- elevation necessary to eliminate lateral forces.

Speed Speed 16 km/h 24 km/h 32 km/h 40 km/h 48 km/h 56 km/h 64 km/h 72 km/h Speed Speed Speed Speed Speed Speed

TURN RADIUS

m ft

10 mph

15 mph

20 mph

25 mph

30 mph

35 mph

40 mph

45 mph

15.2 30.5 45.7 61.0 91.5 152.4 213.4 304.9

13% 7% 4% 3% 2% 1% 1% 1%

30% 15% 10%

—

— —

— — —

— — — —

— — — — —

— — — — —

50

27% 18% 13%

100 150 200 300 500 700 1000

28% 21% 14%

8% 5% 3% 2% 2%

30% 20% 12%

9% 5% 4% 3%

27% 16% 12%

8% 6% 4%

21% 15% 11%

27% 19% 14%

9% 6%

8%

MAXIMUM SPEED ON CURVES FORVARIOUS SUPERELEVATION GRADES WITH A 0.20 LATERAL COEFFICIENT OFTRACTION

30

Another approach to superelevated curves is to deter- mine the safe speed for negotiating a turn at a certain lateral tire force. In general, a 20% lateral coefficient of traction is conservative for all but ice and slippery condi- tions, making table values safe to use for most applica- tions. The following table shows maximum speed with various superelevations to maintain a 0.20 lateral coef- ficient of traction. A transition section may be necessary at higher speeds when entering or departing from a superelevated turn.

5% Super- elevation

10% Super- elevation

TURN RADIUS m ft

Flat Curve

km/h mph km/h mph km/h mph

7.6

14 20 28 34 39 48 62 74

16 22 31 38 44 54 70 —

17 24 34 42 48 59 76 —

25 50

9

10 14 19 24 27 34 43 —

11 15 21 26 30 37 47 —

15.2 30.5 45.7 61.0 91.5 152 .5 213 .5

12 17 21 24 30 39 46

100 150 200 300 500 700

Edition 47 30-5