WAC 296-155-960 Protective
frame (ROPS) test procedures and performance requirements for wheel-type
agricultural and industrial tractors used in construction.
(1) Definitions applicable to this section.
(a) SAE J333a, Operator Protection for Wheel-Type Agricultural and
Industrial Tractors (July 1970) 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 chapter applies only to construction
work, the following definition of “agricultural tractor” is adopted
for purposes of this part: “Agricultural tractor” means a wheel-type
vehicle of more than 20 engine horsepower, used in construction work,
which is designed to furnish the power to pull, propel, or drive implements.
(b) “Industrial tractor” means that class of wheeled
type tractor of more than 20 engine horsepower (other than rubber-tired
loaders and dozers described in WAC
296-155-955), used in operations such as landscaping, construction
services, loading, digging, grounds keeping, and highway maintenance.
(c) The following symbols, terms, and explanations apply to this section:
Eis = Energy input to be absorbed during side loading.
Eis = 723 + 0.4 W ft.-lb. (E'is = 100 + 0.12
W', m. - kg).
Eir = Energy input to be absorbed during rear loading.
Eir = 0.47 W ft. - lb. (E'ir = 0.14 W', m. - kg).
W = Tractor weight as prescribed in WAC
296-155-960 (5)(a) and (5)(c) in lb. (W', kg).
L = Static load, lb. (kg.).
D = Deflection under L, in. (mm.).
L - D = Static load-deflection diagram.
Lm - Dm = Modified static load-deflection diagram (Figure V-20).To
`account for increase in strength due to increase in strain rate,
raise L in plastic range to L x 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, if higher carbon or other material is used, K must be determined
in the laboratory. Refer to Charles H. Norris, et al., Structural
Design for Dynamic Loads (1959), p. 3.
Lmax = Maximum observed static load.
Load limit = Point on L-D curve where observed static load is 0.8
Lmax (refer to Figure V-19).
Eu = Strain energy absorbed by the frame, ft.-lb. (m.
- kg) area under Lm-Dm curve.
FER = Factor of energy ratio, FER = Eu/Eis; also = Eu/Eir.
Pb = Maximum observed force in mounting connection under static load,
L, lb. (kg.).
FSB = Design margin for mounting connection FSB = (Pu/Pb)-1.
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 or (H' = 125 = 0.107 W') (Figure V-14).
FIGURE V-14
Impact energy and corresponding lift height of 4,410
lb. (2,000 kg.) weight.
(d) Source of standard. The standard in this section is derived from,
and restates, Society of Automotive Engineers Standard J334a (July
1970), Protective Frame Test Procedures and Performance Requirements.
This standard must be used in the event that questions of interpretation
arise. The standard appears in the 1971 SAE Handbook.
(2) General.
(a) The purpose of this section is to set forth requirements
for frames for the protection of operators of wheel type agricultural
and industrial tractors to minimize the possibility of operator
injury resulting from accidental upsets during normal operation.
With respect to agricultural and industrial tractors, the provisions
of WAC
296-155-955 and 296-155-965
for rubber-tired dozers and rubber-tired loaders may be
utilized in lieu of the requirements of this section.
(b) The protective frame which 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 V-15.
FIGURE V-15
Typical frame configuration.
(c) If an overhead weather shield is attached to the protective frame,
it may be in place during tests: Provided, That it does not contribute
to the strength of the protective frame. If such an overhead weather
shield is attached, it must meet the requirements of subsection (10)
of this section.
(d) For overhead protection requirements, see WAC
296-155-965.
(e) If protective enclosures are used on wheel-type agricultural and
industrial tractors, they shall meet the requirements of Society of
Automotive Engineers Standard J168 (July 1970), Protective Enclosures,
Test Procedures, and performance requirements.
(3) Applicability. The requirements of this section apply to wheel-type
agricultural tractors use in construction work and to wheel-type industrial
tractors used in construction work. See subsection (1) of this section
for definitions of agricultural tractors and industrial tractors.
(4) Performance requirements.
(a) Either a laboratory test or a field test is required in order to
determine the performance requirements set forth in subsection (10)
of this section.
(b) A laboratory test may be either static or dynamic. The laboratory
test must be under conditions of repeatable and controlled loading in
order to permit analysis of the protective frame.
(c) A field upset test, if used, shall be conducted under reasonably
controlled conditions, both rearward and sideways, to verify the effectiveness
of the protective frame under actual dynamic conditions.
(5) Test procedure-General.
(a) The tractor used shall be the tractor with the greatest weight
on which the protective frame is to be used.
(b) A new protective frame and mounting connections of the same design
shall be used for each test procedure.
(c) Instantaneous and permanent frame deformation shall be measured
and recorded for each segment of the test.
(d) 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.
(e) If 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.
(f) The low temperature impact strength of the material used in the
protective structure shall be verified by suitable material
tests or material certifications in accordance with WAC
296-155-955 (7)(b)(iv).
(6) Test procedure for vehicle overturn.
(a) Vehicle weight. 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 if necessary
to achieve a minimum total weight of 130 lb. (59 kg.) per maximum power
takeoff horsepower at 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.
(b) Agricultural tractors shall be tested at the weight set forth in
subdivision (a) of this subsection.
(c) 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 where 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 subdivision (a) of this
subsection.
(d) The test shall be conducted on a dry, firm soil bank as illustrated
in Figure V-16. The soil in the impact area shall have an average cone
index in the 0.6 in. (153 mm.) layer not less than 150 according to
American Society of Agricultural Engineers Recommendations ASAE R313,
Soil Cone Penetrometer. The path of travel of the vehicle shall be 12°
± 2° to the top edge of the bank.
(e) The upper edge of the bank shall be equipped with an 18 in. (457
mm.) high ramp as described in Figure V-16 to assist in tipping the
vehicle.
(f) The front and rear wheel tread settings, where adjustable, shall
be at the position nearest to halfway between the minimum and maximum
settings obtainable on the vehicle. Where only two settings are obtainable,
the minimum setting shall be used.
(g) Vehicle overturn test-Sideways and rearward.
(i) The tractor shall be driven under its own power along the specified
path of travel at a minimum speed of 10 m.p.h. (16 km./hr.) or maximum
vehicle speed if under 10 m.p.h. (16 km./hr.) up the ramp as described
in subdivision (e) of this subsection to induce sideways overturn.
(ii) Rear upset shall be induced by engine power with the tractor
operating in gear to obtain 3-5 m.p.h. (4.8-8 km./hr.) at maximum
governed engine r.p.m. 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.
FIGURE V-16
(7) 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 subsection (8) or (9) of this section, shall be made.
(8) Static test.
(a) Test conditions.
(i) The laboratory mounting base shall include that part of the tractor
chassis to which the protective frame is attached including the mounting
parts.
(ii) 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 V-17, V-18, and V-19.
FIGURE V-17
Side load application
FIGURE V-18
Rear load application.
FIGURE V-19
Method of measuring instantaneous deflection.
(iii) 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 subsection (1)(c) of this
section). The gauges shall be placed on mounting connections before
the installation load is applied.
(b) Test procedure.
(i) 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 V-17 “L” and
“D” shall be recorded simultaneously. The test shall be stopped when:
(a) The strain energy absorbed by the frame is equal to the required
input energy(Eis) or
(b) Deflection of the frame exceeds the allowable deflection, or
(c) The frame load limit occurs before the allowable deflection is
reached in the side load.
(ii) The L-D diagram, as shown by means of a typical example in Figure
V-20, shall be constructed, using the data obtained in accordance
with item (i) of this subdivision.
(iii) The modified Lm-Dm diagram shall be constructed according to
item (ii) of this subdivision and according to Figure V-21.The strain
energy absorbed by the frame (Eu) shall than be determined.
(iv) Eis, FER and FSB shall be calculated.
FIGURE V-20
Typical L-D diagram.
FIGURE V-21
Typical modified Lm-Dm diagram.
(v) The test procedure shall be repeated on the same frame utilizing
L (rear input; see Figure V-19) and Eir. Rear load application shall
be uniformly distributed 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 which is midway between the
centerline of the seat and the inside of the frame upright.
(9) Dynamic test.
(a) Test conditions.
(i) The protective frame and tractor shall meet the requirements
of subsection (6)(b) or (c) of this section, as appropriate.
(ii) The dynamic loading shall be produced by use of a 4,410 lb.
(2,000 kg.) weight acting as a pendulum. The impact face of the weight
shall be 27 plus or minus 1 in. by 27 plus or minus 1 in. (686 + or
- 25 mm.) and shall be constructed so that its center of gravity is
within 1 in. (25.4 mm.) of its geometric center. The weight shall
be suspended from a pivot point 18-22 ft. (5.5-6.7 m.) above the point
of impact on the frame and shall be conveniently and safely adjustable
for height. (See Figure V-22.)
FIGURE V-22
Pendulum.
(iii) For each phase of testing, the tractor shall be restrained
from moving when the dynamic load is applied. The restraining members
shall be of 0.5-0.63 in. (12.5-16 mm.) steel cable and points of attaching
restraining members shall be located an appropriate distance behind
the rear axle and in front of the front axle to provide a 15°-30°
angle between a restraining cable and the horizontal. The restraining
member shall either be in the plane in which the center gravity of
the pendulum will swing or more than one restraining cable shall give
a resultant force in this plane. (See Figure V-23.)
FIGURE V-23
Method of impact from rear.
(iv) The wheel tread setting shall comply with the requirements of
subsection (6)(f) 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 specified tire inflation, the restraining
cables shall be tightened to provide tire deflection of 6-8 percent
of nominal tire section width. After the vehicle is properly restrained,
a wooden beam 6 x 6 in. (15 x 15 cm.) 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 the
operator's station and shall be secured to the floor so that it is
held tightly against the wheel rim during impact. The length of this
beam shall be chosen so that when it is positioned against the wheel
rim it is at an angle of 25 -40° to the horizontal. It shall have
a length 20-25 times its depth and a width two to three times its
depth. (See Figures V-23 and V-24.)
FIGURE V-24
Method of impact from side.
(v) Means shall be provided indicating the maximum instantaneous
deflection along the line of impact. A simple friction device is illustrated
in Figure V-24.
(vi) No repair or adjustments may be carried out during the test.
(vii) If any cables, props, or blocking shift or break during the
test, the test shall be repeated.
(b) Test procedure.
(i) General. The frame shall be evaluated by imposing dynamic loading
to rear followed by a load to the side on the same frame. The pendulum
dropped from the height (see definition “H” in subsection (1)(c) 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, if used,
shall not influence the attitude of the block.
(ii) Impact at rear. The tractor shall be properly restrained according
to subdivisions (a)(iii) and (iv) of this section. The tractor shall
be positioned with respect to the pivot point of the pendulum such
that the pendulum is 20° from the vertical prior to impact, as shown
in Figure V-23. The impact shall be applied to the upper extremity
of the frame at the point which is midway between the centerline of
the seat and the inside of the frame upright of a new frame.
(iii) Impact at side. The block and restraining shall conform to
subdivisions (a)(iii) and (iv) of this subsection. The 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.
(10) Performance requirements.
(a) General.
(i) The frame, overhead weather shield, fenders, or other parts in
the operator area may be deformed but shall not shatter or leave sharp
edges exposed to the operator, or violate dimensions as shown in Figures
V-17 and V-18 as follows:
D= 2 in. (51 mm.) inside of frame upright to vertical centerline
of seat.
E= 30 in. (762 mm.).
F= Not less than 0 in. and not more than 12 in. (305 mm.), measured
at centerline front of seat backrest to crossbar along the line
of load application as shown in Figure V-17.
G= 24 in. (610 mm.).
(ii) The material and design combination used in the protective structure
must be such that the structure can meet all prescribed performance
tests at zero degrees Fahrenheit in accordance with
WAC 296-155-955 (7)(b)(iv).
(b) Vehicle overturn performance requirements. The requirements of
this subsection (10) must be met in both side and rear overturns.
(c) Static test performance requirements. Design factors shall be incorporated
in each design to withstand an overturn test as prescribed in this subsection
(10). The structural requirements will be generally met if FER is greater
than 1 and FSB is greater than K-1 in both side and rear loadings.
(d) Dynamic test performance requirements. Design factors shall be
incorporated in each design to withstand the overturn test prescribed
in this subsection (10). The structural requirements will be generally
met if the dimensions in this subsection (10) are adhered to in both
side and rear loads.
WAC 296-155-965 Overhead
protection for operators of agricultural and industrial tractors.
(1) General.
(a) Purpose. When overhead protection is provided on wheel-type agricultural
and industrial tractors, the overhead protection shall be designed
and installed according to the requirements contained in this
section. The provisions of WAC
296-155-955 for rubber-tired dozers and rubber-tired loaders
may be used in lieu of the standards contained in this section.
The purpose of the standard is to minimize the possibility of
operator injury resulting from overhead hazards such as flying
and falling objects, and at the same time to minimize the possibility
of operator injury from the cover itself in the event of accidental
upset.
(b) Applicability. This section applies to wheel-type agricultural
tractors used in construction work and to wheel-type industrial
tractors used in construction work. See WAC
296-155-960 (1) and (3). In the case of machines to which
WAC
296-155-625 (relating to site clearing) also applies, the
overhead protection may be either the type of protection provided
in WAC
296-155-625 or the type of protection provided by this section.
(2) Overhead protection. When overhead protection is installed on wheel-type
agricultural or industrial tractors used in construction work, it shall
meet the requirements of this subsection. The overhead protection may
be constructed of a solid material. If grid or mesh is used, the largest
permissible opening shall be such that the maximum circle which can be
inscribed between the elements of the grid or mesh is 1.5 in. (38 mm.)
in diameter. The overhead protection shall not be installed in such a
way as to become a hazard in the case of upset.
(3) Test procedures-General.
(a) The requirements of WAC
296-155-960 (5), (6) and (7) shall be met.
(b) Static and dynamic rear load application shall be uniformly distributed
along a maximum projected dimension of 27 in. (686 mm.) and a maximum
area of 160 in.2 (1,032 cm.2) normal direction of load application.
The load shall be applied to the upper extremity of the frame at the
point which is midway between the centerline of the seat and the inside
of the frame upright.
(c) The static and dynamic side load application shall be uniformly
distributed along a maximum projected dimension of 27 in. (686
mm.) and a maximum area of 160 in.2 (1,032 cm.2) normal to the
direction of load application. The direction of load application
is the same as in
WAC 296-155-960 (8) and (9). To simulate the characteristics
of the structure during an upset, the center of load application
may be located from a point 24 in. (610 mm.) (K) forward to
12 in. (305 mm.) (K) forward to 12 in. (305 mm.) (L) rearward
of the front of the seat backrest to best utilize the structural
strength. See Figure V-25.
FIGURE V-25
Location for side load.
(4) Drop test procedures.
(a) The same frame shall be subjected to the drop test following either
the static or dynamic test.
(b) A solid steel sphere or material of equivalent spherical dimension
weighing 100 lb.
(45.4 kg.) shall be dropped once from a height 10 ft. (3,048 mm.) above
the overhead cover.
(c) The point of impact shall be on the overhead cover at a point within
the zone of protection as shown in Figure V-26, which is furthest removed
from major structural members.
FIGURE V-26
Zone of protection for drop test.
(5) Crush test procedure.
(a) The same frame shall be subjected to the crush test following the
drop test and static or dynamic test.
(b) The test load shall be applied as shown in Figure V-27
with the seat positioned as specified in WAC
296-155-960 (5)(d). Loading cylinders shall be pivotally
mounted at both ends. Loads applied by each cylinder shall be
equal within 2 percent, and the sum of the loads of the two
cylinders shall be two times the tractor weight as set forth
in WAC
296-155-960 (6)(a). The maximum width of the beam illustrated
in Figure V-27 shall be 6 in. (152 mm.).
FIGURE V-27
Method of load application for crush test.
(6) Performance requirements.
(a) General. The performance requirements set forth in WAC
296-155-960 (10)(b), (c) and (d) shall be met.
(b) Drop test performance requirements.
(i) Instantaneous deformation due to impact of the sphere shall not
enter the protected zone as illustrated in Figures V-25, V-26, and
V-28.
FIGURE V-28
Protected zone during crush and drop tests.
(ii) In addition to the dimensions set forth in WAC
296-155-960(10)(a)(i) the following dimensions apply to
Figure V-28:
H = 17.5 in. (444 mm.).
J = 2 in. (50.8 mm.) measured from the outer periphery of the steering
wheel.
(c) Crush test performance requirements. The protected zone as described
in Figure V-28 must not be violated.
(7) Source of standard. This standard is derived from, and restates,
the portions of Society of Automotive Engineers Standard J167 which pertain
to overhead protection requirements. The full title of the SAE standard
is: Protective Frame with Overhead Protection-Test Procedures and performance
requirements. The SAE standard shall be resorted to in the event that
questions of interpretation arise. The SAE standard appears in the 1971
SAE Handbook.
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