Protective frames (roll-over protective structures, known as ROPS) for wheel-type agricultural and industrial tractors used in construction.
The purpose of this section is to set forth requirements for frames used to protect operators of wheel-type agricultural and industrial tractors that will minimize the possibility of operator injury resulting from accidental upsets during normal operation. With respect to agricultural and industrial tractors, the provisions of 29 CFR 1926.1001 and 1926.1003 for rubber-tired dozers and rubber-tired loaders may be used instead of the requirements of this section.
The protective frame that is the subject of this standard is a structure mounted to the tractor that extends above the operator's seat and conforms generally to Figure W-14.
When an overhead weather shield is attached to the protective frame, it may be in place during testing, provided that it does not contribute to the strength of the protective frame. When such an overhead weather shield is attached, it must meet the requirements of paragraph (i) of this section.
For overhead protection requirements, see 29 CFR 1926.1003.
The following provisions address requirements for protective enclosures.
When protective enclosures are used on wheel-type agricultural and industrial tractors, they shall meet the requirements of Society of Automotive Engineers (“SAE”) standard J168-1970 (“Protective enclosures—test procedures and performance requirements”), which is incorporated by reference. The incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.
SAE standard J168-1970 appears in the 1971 SAE Handbook, or it may be examined at: any OSHA Regional Office; the OSHA Docket Office, U.S. Department of Labor, 200 Constitution Avenue, NW., Room N-2625, Washington, DC 20210 (telephone: (202) 693-2350 (TTY number: (877) 889-5627)); or the National Archives and Records Administration (“NARA”). (For information on the availability of this material at NARA, telephone (202) 741-6030 or access the NARA Web site at www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.) Copies may be purchased from the Society of Automotive Engineers, 400 Commonwealth Drive, Warrendale, Pennsylvania 15096-0001.
The requirements of this section apply to wheel-type agricultural and industrial tractors used in construction work. See paragraph (j) of this section for definitions of agricultural tractors set forth in paragraph (i) of this section.
Either a laboratory test or a field test is required to determine the performance requirements set forth in paragraph (i) of this section.
A laboratory test may be either static or dynamic. The laboratory test must be under conditions of repeatable and controlled loading to permit analysis of the protective frame.
A field-upset test, when used, shall be conducted under reasonably controlled conditions, both rearward and sideways to verify the effectiveness of the protective frame under actual dynamic conditions.
The tractor used shall be the tractor with the greatest weight on which the protective frame is to be used.
A new protective frame and mounting connections of the same design shall be used for each test procedure.
Instantaneous and permanent frame deformation shall be measured and recorded for each segment of the test.
Dimensions relative to the seat shall be determined with the seat unloaded and adjusted to its highest and most rearward latched position provided for a seated operator.
When the seat is offset, the frame loading shall be on the side with the least space between the centerline of the seat and the upright.
The low-temperature impact strength of the material used in the protective structure shall be verified by suitable material tests or material certifications according to 29 CFR 1926.1001(f)(2)(iv).
Test procedure for vehicle overturn—
The weight of the tractor, for purposes of this section, includes the protective frame, all fuels, and other components required for normal use of the tractor. Ballast must be added when necessary to achieve a minimum total weight of 130 lb (59 kg) per maximum power-takeoff horsepower at the rated engine speed. The weight of the front end must be at least 33 lb (15 kg) per maximum power-takeoff horsepower. In case power-takeoff horsepower is unavailable, 95 percent of net engine flywheel horsepower shall be used.
Agricultural tractors shall be tested at the weight set forth in paragraph (e)(1) of this section.
Industrial tractors shall be tested with items of integral or mounted equipment and ballast that are sold as standard equipment or approved by the vehicle manufacturer for use with the vehicle when the protective frame is expected to provide protection for the operator with such equipment installed. The total vehicle weight and front-end weight as tested shall not be less than the weights established in paragraph (e)(1) of this section.
The following provisions address soil bank test conditions.
The test shall be conducted on a dry, firm soil bank as illustrated in Figure W-15. The soil in the impact area shall have an average cone index in the 0-in. to 6-in. (0-mm to 153-mm) layer not less than 150 according to American Society of Agricultural Engineers (“ASAE”) recommendation ASAE R313.1-1971 (“Soil cone penetrometer”), as reconfirmed in 1975, which is incorporated by reference. The incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. The path of vehicle travel shall be 12° ±2° to the top edge of the bank.
ASAE recommendation ASAE R313.1-1971, as reconfirmed in 1975, appears in the 1977 Agricultural Engineers Yearbook, or it may be examined at: any OSHA Regional Office; the OSHA Docket Office, U.S. Department of Labor, 200 Constitution Avenue, NW., Room N-2625, Washington, DC 20210 (telephone: (202) 693-2350 (TTY number: (877) 889-5627)); or the National Archives and Records Administration (“NARA”). (For information on the availability of this material at NARA, telephone (202) 741-6030 or access the NARA Web site at www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html). Copies may be purchased from the American Society of Agricultural Engineers 2950 Niles Road, St. Joseph, MI 49085.
The upper edge of the bank shall be equipped with an 18-in. (457-mm) high ramp as described in Figure W-15 to assist in tipping the vehicle.
The front and rear wheel-tread settings, when adjustable, shall be at the position nearest to halfway between the minimum and maximum settings obtainable on the vehicle. When only two settings are obtainable, the minimum setting shall be used.
Vehicle overturn test—sideways and rearward.
The tractor shall be driven under its own power along the specified path of travel at a minimum speed of 10 mph (16 kph), or maximum vehicle speed when under 10 mph (16 kph), up the ramp as described in paragraph (d)(5) of this section to induce sideways overturn.
Rear upset shall be induced by engine power with the tractor operating in gear to obtain 3 to 5 mph (4.8 to 8 kph) at maximum governed engine rpm, preferably by driving forward directly up a minimum slope of two vertical to one horizontal. The engine clutch may be used to aid in inducing the upset.
Other test procedures.
When the field-upset test is not used to determine ROPS performance, either the static test or the dynamic test, contained in paragraph (g) or (h) of this section, shall be made.
The laboratory mounting base shall include that part of the tractor chassis to which the protective frame is attached, including the mounting parts.
The protective frame shall be instrumented with the necessary equipment to obtain the required load-deflection data at the locations and directions specified in Figures W-16, W-17, and W-18.
The protective frame and mounting connections shall be instrumented with the necessary recording equipment to obtain the required load-deflection data to be used in calculating FSB (see paragraph (j)(3) of this section). The gauges shall be placed on mounting connections before the installation load is applied.
The side-load application shall be at the upper extremity of the frame upright at a 90° angle to the centerline of the vehicle. The side load L shall be applied according to Figure W-16. L and D shall be recorded simultaneously. The test shall be stopped when:
The strain energy absorbed by the frame is equal to the required input energy (E
Deflection of the frame exceeds the allowable deflection; or
The frame load limit occurs before the allowable deflection is reached in the side load.
The L-D diagram (see Figure W-19 for an example) shall be constructed using the data obtained according to paragraph (g)(2)(i) of this section.
The modified L
m diagram shall be constructed according to paragraph (g)(2)(ii) and Figure W-20 of this section. The strain energy absorbed by the frame (E
u) shall then be determined.
is, FER, and FSB shall be calculated.
The test procedure shall be repeated on the same frame using L (rear input; see Figure W-18) and E
ir. Rear-load application shall be distributed uniformly along a maximum projected dimension of 27 in. (686 mm) and a maximum area of 160 sq. in. (1,032 sq. cm) normal to the direction of load application. The load shall be applied to the upper extremity of the frame at the point that is midway between the centerline of the seat and the inside of the frame upright.
The protective frame and tractor shall meet the requirements of paragraphs (e)(2) or (3) of this section, as appropriate.
The dynamic loading shall be produced by using a 4,410-lb (2,000-kg) weight acting as a pendulum. The impact face of the weight shall be 27 ± 1 in. by 27 ± 1 in. (686 ± 25 mm by 686 ± 25 mm), and shall be constructed so that its center of gravity is within 1.0 in. (25.4 mm) of its geometric center. The weight shall be suspended from a pivot point 18 to 22 ft (5.5 to 6.7 m) above the point of impact on the frame, and shall be conveniently and safely adjustable for height (see Figure W-21).
For each phase of testing, the tractor shall be restrained from moving when the dynamic load is applied. The restraining members shall be 0.50- to 0.63-in. (12.5- to 16.0-mm) steel cable, and points for attaching restraining members shall be located an appropriate distance behind the rear axle and in front of the front axle to provide a 15° to 30° angle between the restraining cable and the horizontal. The restraining cables shall either be in the plane in which the center of gravity of the pendulum will swing, or more than one restraining cable shall give a resultant force in this plane (see Figure W-22).
The wheel-tread setting shall comply with the requirements of paragraph (e)(6) of this section. The tires shall have no liquid ballast, and shall be inflated to the maximum operating pressure recommended by the tire manufacturer. With the specified tire inflation, the restraining cables shall be tightened to provide tire deflection of 6 to 8 percent of the nominal tire-section width. After the vehicle is restrained properly, a wooden beam that is 6-in. × 6-in. (150 mm × 150 mm) shall be driven tightly against the appropriate wheels and clamped. For the test to the side, an additional wooden beam shall be placed as a prop against the wheel nearest to the operator's station, and shall be secured to the floor so that when it is positioned against the wheel rim, it is at an angle of 25° to 40° to the horizontal. It shall have a length 20 to 25 times its depth, and a width two to three times its depth (see Figures W-22 and W-23).
Means shall be provided for indicating the maximum instantaneous deflection along the line of impact. A simple friction device is illustrated in Figure W-18.
No repair or adjustments may be carried out during the test.
When any cables, props, or blocking shift or break during the test, the test shall be repeated.
The frame shall be evaluated by imposing dynamic loading to the rear, followed by a load to the side on the same frame. The pendulum dropped from the height (see the definition of “H” in paragraph (j)(3) of this section) imposes the dynamic load. The position of the pendulum shall be so selected that the initial point of impact on the frame shall be in line with the arc of travel of the center of gravity of the pendulum. A quick-release mechanism should be used but, when used, it shall not influence the attitude of the block.
Impact at rear.
The tractor shall be restrained properly according to paragraphs (h)(1)(iii) and (h)(1)(iv) of this section. The tractor shall be positioned with respect to the pivot point of the pendulum so that the pendulum is 20° from the vertical prior to impact as shown in Figure W-22. The impact shall be applied to the upper extremity of the frame at the point that is midway between the centerline of the frame and the inside of the frame upright of a new frame.
Impact at side.
The blocking and restraining shall conform to paragraphs (h)(1)(iii) and (h)(1)(iv) of this section. The center point of impact shall be that structural member of the protective frame likely to hit the ground first in a sideways accidental upset. The side impact shall be applied to the side opposite that used for rear impact.
The frame, overhead weather shield, fenders, or other parts in the operator area may be deformed in these tests, but shall not shatter or leave sharp edges exposed to the operator, or violate the dimensions shown in Figures W-16 and W-17, and specified as follows:
D = 2 in. (51 mm) inside of the frame upright to the vertical centerline of the seat;
E = 30 in. (762 mm);
F = Not less than 0 in. (0 mm) and not more than 12 in. (305 mm), measured at the centerline of the seat backrest to the crossbar along the line of load application as shown in Figure W-17; and
G = 24 in. (610 mm).
The material and design combination used in the protective structure must be such that the structure can meet all prescribed performance tests at 0 °F (−18 °C) according to 29 CFR 1926.1001(f)(2)(iv).
Vehicle overturn performance requirements.
The requirements of this paragraph (i) must be met in both side and rear overturns.
Static test performance requirements.
Design factors shall be incorporated in each design to withstand an overturn test as specified by this paragraph (i). The structural requirements will be met generally when FER is greater than 1.0 and FSB is greater than K-1 in both side and rear loadings.
Dynamic test performance requirements.
Design factors shall be incorporated in each design to withstand the overturn test specified by this paragraph (i). The structural requirements will be met generally when the dimensions in this paragraph (i) are used during both side and rear loads.
Definitions applicable to this section.
“Agricultural tractor” means a wheel-type vehicle of more than 20 engine horsepower, used in construction work, that is designed to furnish the power to pull, propel, or drive implements. (SAE standard J333a-1970 (“Operator protection for wheel-type agricultural and industrial tractors”) defines “agricultural tractor” as a “wheel-type vehicle of more than 20 engine horsepower designed to furnish the power to pull, carry, propel, or drive implements that are designed for agricultural usage.” Since this part 1926 applies only to construction work, the SAE definition of “agricultural tractor” is adopted for purposes of this subpart.)
“Industrial tractor” means that class of wheel-type tractors of more than 20 engine horsepower (other than rubber-tired loaders and dozers described in 29 CFR 1926.1001), used in operations such as landscaping, construction services, loading, digging, grounds keeping, and highway maintenance.
The following symbols, terms, and explanations apply to this section:
is = Energy input to be absorbed during side loading in ft-lb (E′is in J [joules]);
is = 723 0.4 W ft-lb (E′
is = 100 0.12 W′ , J);
ir = Energy input to be absorbed during rear loading in ft-lb (E′ ir in J);
ir = 0.47 W ft-lb (E′ ir = 0.14 W', J);
L = Static load, lb (kg);
D = Deflection under L, in. (mm);
L-D = Static load-deflection diagram;
m = Modified static load-deflection diagram (Figure W-20). To account for an increase in strength due to an increase in strain rate, raise L in the plastic range L × K;
K = Increase in yield strength induced by higher rate of loading (1.3 for hot, rolled, low-carbon steel 1010-1030). Low carbon is preferable; however, when higher carbon or other material is used, K must be determined in the laboratory. Refer to Norris, C.H., Hansen, R.J., Holley, M.J., Biggs, J.M., Namyet, S., and Minami, J.V., Structural Design for Dynamic Loads, McGraw-Hill, New York, 1959, p. 3;
max = Maximum observed static load;
Load Limit = Point on a continuous L-D curve at which the observed static load is 0.8 L
max (refer to Figure W-19);
u = Strain energy absorbed by the frame, ft-lb (J); area under the L
FER = Factor of energy ratio, FER = E
is; also, FER = E
b = Maximum observed force in mounting connection under a static load, L, lb (kg);
Pu = Ultimate force capacity of mounting connection, lb (kg);
FSB = Design margin for a mounting connection (P
H = Vertical height of lift of 4,410-lb (2,000-kg) weight, in. (H′, mm). The weight shall be pulled back so that the height of its center of gravity above the point of impact is defined as follows: H = 4.92 0.00190 W (H′ = 125 0.107 W′) (see Figure W-24).
Source of standard.
The standard in this section is derived from, and restates, in part, Society of Automotive Engineers (“SAE”) standard J334a-1970 (“Protective frame test procedures and performance requirements”). The SAE standard appears in the 1971 SAE Handbook, which may be examined at any OSHA regional office.