The new Mercedes-Benz Actros: Chassis and safety - Driving dynamics, comfort and safety systems at the highest level
A tough truck wouldn't be complete without brilliant underpinnings. The new Actros is equipped with a dynamic chassis based on a torsionally stiff frame with wide track. It integrates an intelligent concept which improves ride comfort and helps for a sensitive and firm steering for added fuel economy. The assistance systems provide extra safety and relieve stress when the truck is stuck in traffic. In the future, the range will be extended as the chassis was developed to properly fit new and additional wheelbase lengths.
Criteria such as handling and safety are becoming increasingly important in long-distance transport. The new Mercedes-Benz Actros takes account of this, ushering in a new era of driving dynamics for heavy-duty trucks. No other premium-category truck feels as poised, assured or safe on the road, largely thanks to a new frame and an extensively modified chassis. The new truck's exemplary ride comfort is at the same high level. A Mercedes-Benz is always extremely well prepared should the worst come to the worst: the already outstanding safety level has been further enhanced by extended functions. Last but not least, a perfected modular system means that the new Actros is available with a wide choice of wheelbase and frame variants. Plus it offers exceptional body-mounting ability.
Complete chassis and ride-comfort concept
Major plus points of the new Actros include its driving dynamics, handling and comfort, largely thanks to a complete chassis and ride-comfort concept, from the frame and the chassis through to the cab suspension and the driver's seat. A wealth of innovations in this field means that the new Actros conveys a safer driving feel than any other truck in its class.
Torsionally stiff frame with wide track
A new frame, uncompromisingly designed for on-road vehicles, forms the backbone of the new Actros. It is exceptionally torsionally stiff and has a wide track of 834 mm (previously 744 mm). Both factors together form the basis for excellent handling stability – the Actros hugs the road with an assured feel.
Tried-and-tested axles and a dynamic, new chassis
The core design of the tried-and-tested axles is the same as for the predecessor model; however, the developers have completely redesigned the control and the suspension to enhance driving safety and ride comfort.
New features include the location system for the Mercedes-Benz HL6 hypoid rear axle, based on optimised rear-axle location with new geometry and lines of action that now intersect behind the axle. Four-bellows air suspension, which responds precisely to road unevenness, is now responsible for the ride comfort. This is a symmetrical air suspension system (i.e. the bellows are of the same size). The spring track is wider than previously. Another advantage is the fact that four bellows operate faster and can lift higher loads than two bellows.
The tried-and-tested offset front axles are available with either steel or air suspension and with a choice of tonnages. The number of spring layers varies depending on the permissible axle load. The weight of the steel springs has been reduced thanks to an aluminium front spring bracket. New features include weight-optimised suspension with single-leaf parabolic springs on the front axle.
The chassis for the new Actros impresses with its high levels of directional stability, outstanding understeer/oversteer characteristics and high precision. Ride comfort has also been further enhanced.
Three cab mounting variants
The cab mounting is a major component in the driving-dynamics concept. There is a choice of three variants for the new Actros: Standard cab mounting, Comfort cab mounting (standard for cabs with a flat floor) and the exceptionally comfortable air suspension.
Sensitive and firm steering even saves fuel
One of the key factors behind the new Actros' excellent handling is the steering system, which impresses on account of its precision, thanks to a re-tuned steering gear, and conveys excellent road feel. The ratio is more direct whilst the kinematics have been improved and the controlled power steering pump saves fuel.
Powerful new engine brake and highly effective retarder
In 1996, the forerunner to the new Actros revolutionised the truck world on account of its four-disc brake system with a high-pressure system and electronic control. The new Actros takes this exceptional brake system a stage further. A new, optionally available high-performance engine brake sets new standards once again. The three-stage engine brake achieves an immense braking power of up to 400 kW (544 hp) on Euro VI models. Another new feature is the optionally available water secondary retarder with a braking torque of up to 3500 Nm or up to 750 kW. As well as being more powerful, the new retarder is lighter, weighing in at just 65 kg instead of 100 kg as previously.
Assistance systems to enhance comfort and relieve stress when stuck in traffic
The previous model series also set milestones with its safety and assistance systems. Whether it be adaptive cruise control, Lane Keeping Assist, Stability Control Assist or the revolutionary Active Brake Assist with autonomous emergency braking when stationary obstacles or moving obstacles ahead are detected, the Actros has always led the way for others to follow.
The new Actros builds on this lead. Stability Control Assist is now fitted as standard on both the semitrailer tractor and the chassis version, while the unique Proximity Control Assist system with stop-and-go function now even controls moving off and stopping in traffic automatically – making the driver's job much easier when driving through cities or in stop-and-go traffic. What's more, the Proximity Control Assist is no longer automatically linked to the retarder. The sensed fifth wheel coupling informs the driver of its lock status via a display in the cab. The exterior mirror with manoeuvring function on the co-driver's side extends the range of vision when manoeuvring by automatically adjusting outwards by ten degrees when reverse gear is engaged.
Standard equipment for all Actros models includes automatic activation of the hazard warning lights following an emergency stop so as to warn following traffic and help prevent rear-end collisions. The optional rain and light sensor activates the windscreen wipers and dipped beam when required, while the likewise optionally available tyre pressure monitoring system for the tractor and trailer is primarily aimed at enhancing safety: burst tyres as a result of insufficient inflation pressure are just as much of a safety risk as flat tyres. Furthermore, insufficient tyre inflation pressure increases the tyre's flex and, therefore, fuel consumption as well as reducing service life – a key factor when it comes to economy.
Attractively priced safety packages
Ready-made safety packages available at attractive prices encourage the inclusion of safety technology. The “Basic Safety Pack” comprises Proximity Control Assist, Lane Keeping Assist and a driver's airbag, while the Classic Safety Pack includes all of these as well as Active Brake Assist and roll control for dropsiders. Meanwhile, the Top Safety Pack features all of the above plus a retarder.
Range extended to include new and additional wheelbase lengths
The new Actros is a bespoke premium truck with an even larger range of models available than its predecessor. It can be ordered as a two- or three-axle version with trailing or leading axle and with a choice of three frame heights: standard, low and lowliner. Mercedes‑Benz has also further extended the range of wheelbase lengths by narrowing the gap between each version. Hence the two-axle semitrailer tractor is now available with a choice of four wheelbase lengths – 3550, 3700, 3850 or 4000 mm – while the two-axle chassis with cab gives customers a whopping eleven wheelbase lengths to choose from, ranging from 3600 to 6600 mm in steps of 300 mm.
Low-frame and lowliner models now have a slightly lower coupling point height, while the dropsider frame is also noticeably lower, making it easier to mount bodies.
Good body-mounting ability prioritised
The new Actros chassis already offers exceptionally good body-mounting ability as it is. The 50 mm hole pattern throughout in the frame side members, including the area of the axles, gives bodybuilders a great deal of freedom, as does the absence of rivets aft of the rear axle. Frame overhangs can be selected in steps of 300 mm, while the end crossmember can be relocated in 50 mm steps.
Although the exhaust system takes up more space on the frame due to the Euro VI requirements, optimised exhaust outlets make the bodybuilder's job easier. If required, space can be left within the frame – for demountable-platform vehicles, for example. In this case, there is no need to relocate the tank subsequently. Standardised fastenings, brackets and fixing bolts facilitate body mounting. All of which saves costs and shortens delivery times.
New chassis with new tanks
The wider frame, the in-line engines and the more complex exhaust gas aftertreatment system for Euro VI require a modified chassis design. The developers have taken this opportunity to introduce a new fuel tank concept among other things. Four tank cross-sections give a fuel supply volume of 290 to 1300 litres. The tanks are flexibly inter-combinable for individual solutions, and there are no conversion costs. Even the AdBlue tanks are available in a choice of sizes: 60 or 75 litres.
The main fuel tank and the AdBlue tank are mounted on the left-hand side of the vehicle. There is space for an additional tank on the right-hand side. The full vehicle width of 2.55 metres can be used to optimise the tank volume. There is also a combination tank with two chambers for diesel fuel and AdBlue available for semitrailer tractors.
Source: Daimler AG
Copyright © 2011, Mercedes-Benz-Blog. All rights reserved.