Measurements | Accuracy |
Deflection of the enclosure, in. (mm) | ±5 percent of the deflection measured. |
Vertical weight, pounds (kg) | ±5 percent of the weight measured. |
Force applied to the enclosure, pounds force (newtons) | ±5 percent of the force measured. |
Dimensions of the critical zone, in. (mm) | ±0.5 in. (12.5 mm). |
W = Tractor weight (see 29 CFR 1928.51(a) ) in lb (W" in kg);
Eis = Energy input to be absorbed during side loading in ft-lb (E"is in J [joules]);
Eis = 723 + 0.4 W (E"is = 100 + 0.12 W");
Eir = Energy input to be absorbed during rear loading in ft-lb (E"ir in J);
Eir = 0.47 W (E"ir = 0.14 W");
L = Static load, lbf [pounds force], (N) [newtons];
D = Deflection under L, in. (mm);
L-D = Static load-deflection diagram;
Lmax = Maximum observed static load;
Load Limit = Point on a continuous L-D curve where the observed static load is 0.8 Lmax on the down slope of the curve (see Figure C-5);
Eu = Strain energy absorbed by the protective enclosure in ft-lbs (J); area under the L-D curve;
FER = Factor of energy ratio;
FERis = Eu/Eis; and
FERir = Eu/Eir.
d = 2 in. (51 mm) inside of the protective structure to the vertical centerline of the seat;
e = 30 in. (762 mm) at the longitudinal centerline;
f = Not greater than 4 in. (102 mm) measured forward of the seat-reference point ("SRP") at the longitudinal centerline as shown in Figure C-14;
g = 24 in. (610 mm) minimum;
h = 17.5 in. (445 mm) minimum; and
j = 2.0 in. (51 mm) measured from the outer periphery of the steering wheel.
10-mm * 10-mm (0.394-in. * 0.394-in.) specimen: 8.0 ft-lb (10.8 J) at -20 °F (-30 °C);
10-mm * 7.5-mm (0.394-in. * 0.296-in.) specimen: 7.0 ft-lb (9.5 J) at -20 °F (-30 °C);
10-mm * 5-mm (0.394-in. * 0.197-in.) specimen: 5.5 ft-lb (7.5 J) at -20 °F (-30 °C); or
10-mm * 2.5-mm (0.394-in. * 0.098-in.) specimen: 4.0 ft-lb (5.5 J) at -20 °F (-30 °C).
Specimens shall be longitudinal and taken from flat stock, tubular, or structural sections before forming or welding for use in the protective enclosure. Specimens from tubular or structural sections shall be taken from the middle of the side of greatest dimension, not to include welds.
29 C.F.R. §1928.53