Measurements | Accuracy |
Deflection of the frame, in. (mm) | ±5 percent of the deflection measured. |
Vertical weight, lb (kg) | ±5 percent of the weight measured. |
Force applied to the frame, 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 frame in ft-lb (J); area under the L-D curve;
FER = Factor of energy ratio;
FERis = EuEis;
FERir = EuEir;
Pb = Maximum observed force in mounting connection under a static load, L lbf (N);
Pu = Ultimate force capacity of a mounting connection, lbf (N);
FSB = Design margin for a mounting connection; and
FSB = Pu/Pb
d = 2 in. (51 mm) inside of the frame upright to the vertical centerline of the seat;
e = 30 in. (762 mm) at the longitudinal centerline;
f = Not greater than 4 in. (102 mm) to the rear edge of the crossbar, measured forward of the seat-reference point ("SRP");
g = 24 in. (610 mm) minimum; and
m = Not greater than 12 in. (305 mm), measured from the seat-reference point to the forward edge of the crossbar.
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 frame. 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. §1928.52