Manufacturing
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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