Protective frame figures

Figures C-1 through C-3 show illustrative tractor protective frames and the directions of test loads used to evaluate them. They provide a visual example of a tractor with a typical protective frame (Figure C-1), a side-load application (Figure C-2), and a rear-load application (Figure C-3).

• Use these illustrations to understand where test forces are applied on a protective frame during side and rear load tests.
• These figures are part of Appendix B to Subpart C of Part 1928 and are intended to clarify the test orientations referenced for protective frames under the agriculture standards.

See also OSHA's ROPS discussion in 1928 for the regulatory context.

Instantaneous deflection is measured as the immediate movement of the protective frame at a specified point where the load is applied, as shown in Figure C-4.

• Figure C-4 illustrates placing measurement points on the protective frame and recording the peak deflection that occurs right at the time of loading.
• Use the exact measurement points and timing shown in the figure to ensure repeatable, comparable deflection readings during testing or inspection.

Reference: Appendix B to Subpart C of Part 1928.

A typical L–D diagram plots applied load (L) versus deflection (D) to show how a protective frame deforms under increasing load, as illustrated in Figure C-5.

• Use the L–D curve to determine the stiffness and yielding behavior of the frame: the slope shows stiffness and sudden drops or plateaus indicate yielding or failure points.
• Compare measured L–D data from a tested frame to the expected or allowable performance to judge whether the frame meets performance criteria.

See Appendix B to Subpart C of Part 1928 for the illustrative diagram and context.

The pendulum test represents a controlled impact used to simulate a heavy object striking the protective frame; Figures C-6 and C-7 show the pendulum setup and a table relating impact energy to pendulum lift height for a 4,410 lb (2,000 kg) mass.

• Figure C-6 depicts the pendulum geometry and striking face orientation.
• Figure C-7 provides the relationship between the pendulum lift height and the resulting impact energy for a 4,410 lb (2,000 kg) test mass, which helps you set the pendulum height to achieve a desired impact energy.

Reference: Appendix B to Subpart C of Part 1928.

The side and rear impact illustrations show where and in what direction test forces or impacts should be applied to a protective frame to simulate realistic overturn or collision scenarios.

• Figures C-8 and C-9 show typical rear and side impact locations and angles.
• Figures C-15 and C-16 show additional rear impact applications and orientations for different protective enclosure configurations.
• Correctly orienting the test load is essential because protective frames may perform differently depending on the direction of force; follow the figure orientations to reproduce the test conditions the design intends to resist.

See Appendix B to Subpart C of Part 1928 for the drawings and intended load directions.

Yes — Figure C-10 shows the recommended bank and ramp geometry and tractor positioning for conducting a side-overturn test.

• Use the bank and ramp dimensions and the tractor orientation shown in Figure C-10 to set up the test so the tractor will roll over onto the protective frame in the intended manner.
• Proper setup ensures the protective frame is loaded in a repeatable way that represents a real side-overturn event.

Reference: Appendix B to Subpart C of Part 1928 and the tractor protective-frame guidance in 1928.

Figure C-12 shows a tractor fitted with a typical protective enclosure (cab) and highlights that enclosed cabs can be tested using similar impact and load orientations as open protective frames but attention must be paid to attachment points and enclosure structure.

• When a protective enclosure is present, follow the enclosure-specific load points and orientations shown in Figures C-12–C-16 to ensure the cab and its mounting are tested appropriately.
• Treat the enclosure and its supports as part of the protective structure during testing and inspection.

See Appendix B to Subpart C of Part 1928 for the enclosure figures and test orientations.

Orient the load so it contacts the protective frame at the point and in the direction shown in Figure C-13, applying force laterally (perpendicular to the tractor's longitudinal axis) at the illustrated height and location.

• Follow the figure's point of application and force direction to reproduce the intended side-loading condition.
• Ensure measurement points and deflection gauges are placed as shown so instantaneous deflection and L–D behavior can be recorded accurately.

Reference: Appendix B to Subpart C of Part 1928.

Set up the rear-overturn test so the tractor's rear contacts the bank or ramp as shown in Figure C-11, allowing the tractor to tip rearward onto the protective frame in the illustrated manner.

• Use the bank geometry and tractor positioning in Figure C-11 to guide where the tractor's center of mass will shift and where the protective frame will bear load.
• Verify measurement points and the direction of applied forces follow the figure to record accurate deflections and loads during the overturn event.

See Appendix B to Subpart C of Part 1928 for the drawing and setup guidance.

Figure C-4 suggests placing a deflection gauge at the specified measurement point on the protective frame and recording the immediate peak movement when a controlled load is applied.

• Practical steps:
  • Identify the measurement point shown in Figure C-4 and attach a displacement gauge or dial indicator.
  • Apply the test load in the direction shown (use an approved test method or calibrated loading device).
  • Record the instantaneous peak deflection and compare it to allowable or expected values from the frame's design or test records.

Reference: Appendix B to Subpart C of Part 1928.

Yes — OSHA will accept a ROPS that meets the performance requirements of SAE J2194 or ISO test standards as functionally equivalent, provided the ROPS also satisfies SAE material/temperature and seat belt requirements.

• The OSHA Letter of Interpretation of July 8, 1997 (https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0) states OSHA would accept ISO test standards as equivalent per SAE J2194 when the SAE conditions are met.
• However, OSHA does not independently validate each manufacturer's test report; the employer is responsible for ensuring the equipment meets the applicable performance requirements and for maintaining documentation of compliance.

See 1928 and the July 8, 1997 Letter of Interpretation at https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0 for details.

Figure C-7 uses a 4,410 lb (2,000 kg) test mass to illustrate impact energy and the corresponding pendulum lift heights.

• The figure provides a direct relationship so you can select a pendulum height to produce a desired impact energy when using that 2,000 kg mass.
• Use those tabulated values to set up pendulum impact tests consistent with the illustrations in Appendix B.

Reference: Appendix B to Subpart C of Part 1928.

Figures C-14 and C-15 illustrate rear-load applications for protective enclosures and show that rear-loads may be applied at different contact points or angles compared with open frames, reflecting differences in enclosure geometry and attachment.

• When testing enclosures, apply loads to the enclosure and its mounting in the positions and directions shown in the figures, since enclosures transfer loads differently than open ROPS tubes.
• Ensure that fixtures and load surfaces match the figure details so test results reflect the enclosure's true performance.

See Appendix B to Subpart C of Part 1928 for the rear-load application drawings.

The employer (or equipment owner) is responsible for ensuring and documenting that a protective frame meets the applicable OSHA requirements or an equivalent standard.

• The July 8, 1997 Letter of Interpretation (https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0) states OSHA can accept SAE/ISO equivalency, but OSHA cannot independently verify every manufacturer's test results — responsibility for compliance rests with the employer.
• Keep test reports, manufacturer certificates, and installation records on file to demonstrate equivalency during inspections.

See 1928 and the LOI at https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0.

Figures C-2 (side-load application for an open frame) and C-13 (side-load application for an enclosure) show similar lateral force directions but differ in the exact contact points and heights because enclosures have panels and mounting structures that alter load paths.

• For open frames follow the tube contact points and heights in Figure C-2.
• For enclosed cabs use Figure C-13 which shows loads applied to the enclosure shell and its mounting structure at points that reflect enclosure geometry.
• Testing and inspection should respect those differences so loads are applied where the structure actually receives impact in service.

Reference: Appendix B to Subpart C of Part 1928.

No — the figures in Appendix B are illustrative guides for test orientations and measurement methods, but they are not a substitute for documented performance testing and certification showing the protective structure meets required performance criteria.

• Use the figures to set up and interpret tests, but maintain formal test reports, engineering calculations, or third‑party certification showing compliance.
• OSHA accepts performance-based equivalence (see the July 8, 1997 Letter of Interpretation at https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0), but the employer must retain evidence that the protective frame meets the applicable performance standard.

See Appendix B to Subpart C of Part 1928 and the LOI at https://www.osha.gov/laws-regs/standardinterpretations/1997-07-08-0.