A new way of driving an off-road vehicle: MONROE ADVENTURE(TM) - Freedom, safety and comfort
Brussels (ots)
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INTRODUCTION
Thirteen years after the launch of the Monroe Gas-Magnum 4x4(r) shock absorbers, Tenneco Automotive - a world leading manufacturer of ride control systems - introduces a range of innovative shock absorbers for off-road vehicles, the Monroe Adventure(TM), designed to meet the needs of a rapidly growing off road car park.
In studies of the off-road market, Monroe found out that only 10% of these vehicles are driven off road, while the majority (90%) are actually driven on road. Suspension therefore, originally designed with a high rigidity in off road vehicles for absorbing the impact of rough terrain, would have to provide increased comfort for on road driving.
In designing its new 4x4 shock absorber, Monroe has tried to find innovative solutions to combine safety and comfort both on and off road into a single all-purpose shock absorber. The result is the new Monroe Adventure(tm), a monotube shock absorber which ensures the driver's safety and comfort on different road surfaces and various driving conditions, and whose high performance remains unaltered throughout its entire life.
TECHNOLOGY
But why choose a monotube shock absorber? The monotube design exposes the shock body to maximum airflow, lowering the operating temperature of the internal components and fluid, thereby extending the life of the shock absorber. In addition, this particular design allows for a corresponding larger piston (46 mm in diameter instead of the 34.9 mm of a twin-tube shock) therefore allowing higher sensitivity to wheel motions.
Inside the shock absorber, the nitrogen gas (which unlike air, does not change temperature when compressed) is separated from the superior grade oil by a specially designed, close tolerance, floating piston. This provides a constant pressure of 360 psi (20 bars) against the hydraulic fluid, absolutely eliminating any contact between gas and oil and the performance loss that is common to conventional twin-tube shocks, as the emulsion provoked by overheating creates micro-cavities (the emulsion/cavitation phenomenon) which prevent the smooth operation of valves.
The total elimination of foaming results in uninterrupted damping for even the smallest wheel deflections (2 mm): performance which no other type of shock can match.
SPECIFICATIONS
The self-adjusting working piston (46 mm in diameter), with spring-steel valving discs, precisely regulates oil flow for optimum compression and rebound control. There are no check valves or springs to wear out.
A high-viscosity superior grade oil guarantees uninterrupted and optimal damping at different temperatures ranging from -40°C to +120°C. When driving an off-road vehicle in particularly dry areas, the shocks temperature can even reach 100°C.
The piston rod, with a diameter of 14 mm (unlike the conventional models currently available on the market, which have a diameter of 11 mm) is hard-chromed uniformly without intermediate layers, and is the strongest in the industry. The self-lubricating rod guide and end seal insures longevity and prevents leakage, as well as corrosion and dust penetration.
The tube wall has a thickness of 2 mm (against the 1.27 mm of conventional twin-tube models), therefore the damage provoked by stones or external blows is drastically reduced.
These unique design features function in unison to allow Monroe Adventure(TM) shocks to operate at peak performance levels for life.
ADVANTAGES
The Monroe Adventure(TM) shock absorbers ensure five innovative advantages:
* Better heat dissipation
A shock is an energy converter. Spring energy has to be converted into thermal energy and the resulting heat has to be dissipated as quickly as possible.
A shock absorber's effectiveness is directly proportional to its ability to dissipate heat, since a "hot" shock quickly loses its damping ability.
In conventional twin-tube shocks, the heat must pass through two tubes. New Monroe Adventure(TM) monotube design results in a cooler running, more efficient and durable shock.
* Innovative piston design
The greater piston area - as a result, among other things, of the larger space available in monotube shocks - provides greater sensitivity for small piston movements to achieve effective damping at wheel motions as small as 2mm.
* Lighter weight
The reduced "unsprung mass" allows wheels and tyres to respond more readily to surface irregularities for improved control. Additionally, by reducing the unsprung mass, wear and tear on suspension and steering components is reduced.
* High-pressure gas
The permanent pressure exerted on the oil by the gas ensures instantaneous response as well as a smoother operation of piston valves. In addition, the gas pressure eliminates cavitation and foaming phenomena which could compromise the shock function, in particular under severe driving conditions.
* More safety
All these characteristics ensure safer driving conditions both on road and off road, as well as higher comfort.
"The tyre to road contact is increased under any driving condition, both on road and off road" says Jean-Pierre Dolait, Vice President of Tenneco Automotive Europe's Aftermarket Sales and Marketing division. "In the case of an emergency stop, the braking distance is strongly reduced. A safer journey is also guaranteed under diverse weather conditions such as rain, wind, snow and ice. The new Monroe Adventure(TM) shocks - concludes Dolait - indeed allow for better vehicle control on the road as well as in extreme situations."
"The new shock absorbers designed for off-road use - underline Tenneco engineers - protect all the fundamental components of the vehicle, tyres included, against early and hazardous wearing."
WORKING PRINCIPLE
Monroe Adventure(TM) does not need manual adjustment to compensate for wear or for varying road surfaces. The shock responds instantaneously to the speed of suspension movement to provide the exact damping characteristics required for maximum control, safety and performance. But, how has been possible to achieve all this?
A piston fixed to the car body by the piston rod slides into oil filled cylinder that moves together with the wheel. During that movement calibrated openings in the piston allow the oil to pass between the upper and lower chamber of the cylinder, so damping the oscillation of the spring. The monotube shock absorber contains at one end a small quantity of an inert gas (nitrogen) under high pressure (20 to 25 bars). A floating piston separates this gas from the oil.
During the compression stroke, the rod changes the volume available for the oil, which compresses the nitrogen. During the rebound stroke, the rod moves out again, and the gas pushes the floating piston back to its original place.
The force generated by the damper during its rebound or compression stroke must be variable in function of the vehicle speed and of the road surface. The reaction forces must be able to control the car body movements on motorway at high speed as well as the fast movement on a bad road at low speed and still providing the best compromise between comfort and road holding.
THE VALVING
The Monroe Adventure(TM) shocks have 3 stage valves to provide the ideal damping under all circumstances. The first stage corresponds to the low piston speeds (motorways), the 2nd stage to the medium speeds (standard or dirt roads) and the 3rd stage to the high speeds (off-road tracks).
The monotube valving functions as follows:
1st stage (low piston speed): When for instance the shock absorber is slowly extended, the piston and the rod move upwards and force oil to flow from the upper chamber to the lower chamber through the piston valve. It flows successively through the holes in the piston and through the constant orifices (bleeds) shaped in the discs at the bottom of the piston. Due to the very small size of the bleeds, the flow resistance of the oil increases rapidly with the piston speed.
2nd stage (medium piston speed): When the piston speed increases, the pressure is high enough to lift the discs The damping characteristic is now linear.
3rd stage (high piston speed): When the piston moves very quickly into the cylinder, it is necessary for the damping force to increase rapidly as well to prevent topping. So, at that moment the discs are completely open and their limited opening now form a restriction that builds up a higher resistance for the oil flow.
The permanent pressure exerted on the oil by the gas guarantees an instantaneous response as well as quieter operation of the piston valves.
COVERAGE
Monroe has always invested a large part of its resources in offering the best coverage in the industry.
Hard work of research, market analysis and new vehicles identification are the key for Monroe to offer 96% coverage for 4x4 vehicles.
REPLACEMENT
Generally speaking, shock substitution frequency depends on the use of the vehicle and the conditions of the road surface. On average, shock absorbers should be replaced every 50,000 kms, and checked every 20,000 kms. Drivers are recommended to replace all the shocks fitted on the same axle at the same time, similarly to brake disks and tyres, because for increased safety, the shock absorbers on the same axle must ensure identical performance.
Tenneco Automotive headquartered in Lake Forest, USA is the world's largest producer of ride control and emission control products under the Monroe(R) and Walker(R) brand names. With 23,000 employees and a turnover of USD 3.5 billion, the company has over 100 facilities in 22 countries in North and South America, Europe, Africa, Australia and the Far East.
Contact:
Simonetta Esposito
Communications Manager
Tenneco Automotive Europe
Tel. +322 706 9147
Fax +322 706 9199
E-mail: Simonetta.Esposito@eu.Tenneco-Automotive.com