Manufacturing

ROPS

Duys Designed & Manufactured Roll-over Protection Units (ROP’s)

Engineering Design The product was primarily developed due to a safety drive initiative taken up by BHP Billiton involving the need to prevent human driver fatalities on their open cast mines. Computational methods, confirm by the physical drop testing of the structures,has proven that the roll-over structures will protect the driver as well as passengers in the vehicles in the event of a roll-over situation. Simply put, the ROP prevents any section of the cab from collapsing that could cause serious head or neck injury by transferring the impact energy to the structure. Much attention has also been given to the operational needs of the driver/operator by providing numerous tie-down points and bolt down points for custom toolboxes as an example. Tie points are also provided around the bin perimeter (drop side models) for a cargo net cover if required, as well as for oxy-acetylene bottles for easy loading and safe transportation. Various areas on the structures have been prepared for the application of reflective tape or company identification livery. A fire extinguisher is also positioned for easy access for effective fire control. All models released are SABS approved for manufacture and fitment to the particular intended vehicle by a NATIS registration number. Materials The ROP’s boast a variety of steel in the structure to maximize strength and minimize weight. Keeping the mass of the designs to a minimum is a critical parameter since the payload ability of the vehicle must be kept to a maximum for the benefit of the driver, not to mention fuel consumption. Certain grades of Docol®, Domex® and Gr300WA SABS1431 steel are used in the structure, where Docol and Domex exhibit superior material properties to commercial hot-rolled steel. Manufacture All ROP structures are manufactured at the DUYS New Germany site in Durban in a dedicated facility intended for ROP manufacture by layout, using a team of coded welders, skilled assemblers, and quality personnel under the production supervisor. Specialized jigs and fixtures have also been designed and made in-house to ensure conformance to manufacturing standards set by the engineering team. Installation Fitment of the roll-over protection structures are performed by DUYS employees trained specifically to fit the intended model. An untrained person may not fit the structure to the vehicle. LS DYNA Simulated Roll-Overs Where linear simulations can only indicate levels of stress and where the structure can be expected to yield or fail, non-linear capabilities render actual deformation of the structure based on material property inputs, even taking into account strain hardening due to the previous moments in time yielding of the material. Any design changes could be made to give satisfactory results. This theory coupled with physical drop tests conducted on site guarantees the protection of vehicle occupants. US standards require that 1.5 times the vehicles mass is supported by no more than 125mm, using 'energy absorbed' theory where Work or energy absorbed (E) = Force (F) X Deflection (s). DV Experts International has, however, found through a number of tests and simulations, that for effective roll-over protection, the structure must withstand up to 4 to 6 times the vehicle mass. The various distances from which the structures are dropped in the simulations are calculated to give the equivalent effect of this requirement. Actual rolling simulations were also performed.

Roll-Over Propensity The propensity for roll-over is commonly calculated using a formula relating the front wheel track width and the height of the centre of gravity to obtain a ratio of T/2H. Intuitively, the higher your centre of gravity, the higher the propensity for roll-over. Hence, the smaller the ratio, the more prone the vehicle will be to rolling over; and the opposite is also true. It must also be realized that more occupants and payload in the vehicle can shift the centre of gravity higher, resulting in a higher likelihood of rolling over during an abrupt swerve or corrective steering action. Swerving and tripping on an obstacle or steep roll pitch roads are the most common cause of rollover accidents, especially on dirt roads. A large number of fatalities are recorded every year due to rollover accidents. Many countries, including the US, still do not have stringent requirements for vehicle manufacturers to test roll-over propensity of their vehicles. Because of the high accident rate, car manufacturers have developed roll prevention control systems available in high priced models. The most common cases of rollover accidents occur in SUVs and pick-ups due to higher than normal ground clearances and higher payloads. Fitting the ROP structures increases the height of the centre of gravity slightly due to the location of the additional mass. Although the effect on the CG is not significant, the driver should be aware at all times of the additional mass attached to the bin or bin section.

Contact Details

1 Progress Road Pinetown New Germany Kwazulu Natal South Africa T: (031) 713 1722 F: (031) 713 1727 enquiries@duys.co.za