Compact and Comfortable

IAV subsidiary TRE GmbH specializes in chassis development. Its experts now demonstrate how to combine ride comfort, driving dynamics and compact design with their innovative package-economizing rear axle. This is particularly important in hybrid and electric vehicles where the battery's a space-guzzler.

Hybrid and electric vehicles pose a wide range of unresolved problems. One of them being: Where to put the bulky batteries? Before losing valuable space for passengers or baggage, somewhere else must be found for the energy-storage systems. This is why developers are hard at work reducing the size of vehicle components – axles, for example, that save as much space as possible. This can also benefit other alternative drives because ethanol or LPG also come with a lower energy density than diesel or gasoline which means they need more space for the tank that hold them.

Reason enough for IAV subsidiary, TRE GmbH from Neustadt an der Weinstrasse in the German state of Rhineland Palatinate, to team up with IAV and develop an extremely compact rear axle that takes up little space despite putting on excellent performance. This is where the engineers set store by innovative components, such as a rotational shock absorber instead of the conventional telescopic type.

Space minimizer and excellent performer – the space-saving axle from TRE

Innovative Technology: The Rotational Shock Absorber

"For the rotational shock absorber, we use a rotor to displace the oil", says TRE's Managing Director Eckardt Döhrer explaining the concept that was developed by ZF Sachs. "This saves no end of space and does not come at the expense of performance either." The space-saving axle also combines rotational shock absorbers with torsion-bar springs that also go easy on space and package. And, finally, the chassis specialists have also managed to eliminate and move down the upper strut level – this saves additional space too. Hence, all that is needed at the top of the wheel is space for the tire plot.

In 2008, the developers from TRE joined forces with IAV to install the new space-saving axle into an Audi A3 as a means of demonstrating the concept's practical efficiency. The A3 is predestined for the new component: "The space-saving axle only makes sense in high-end cars, such as in sports cars or coupes with special space requirements, e.g. for energy storage systems", Döhrer says. "Or in smaller-type, high-end segment vehicles, like the Audi A3 for instance." Because the new technology comes at a price: Although it is still hard to put a figure on the costs in mass production, Döhrer is expecting something in the region of the costs for multilink suspension systems. On top of this comes the rotational shock absorber – this forming the heart of the space-saving axle and in future also remaining somewhat more costly than the conventional telescopic shock absorber.

Sophisticated Driving Dynamics and High Utility Value

The extra cost for the space-saving axle, however, is certainly worth every penny because it provides the ideal basis for combining sophisticated driving dynamics with high utility value – sparing the motorist any compromise on performance. "There are, of course, other space-saving axles around, such as rigid axles or twist-beam axles", Döhrer says. "But this is where paring down on space clearly comes as the expense of ride comfort and driving dynamics. This is not the case with our space-saving axle." A patent is meanwhile pending for the new concept.

In developing the new axle, TRE was responsible for the layout and kinematics, with the mule being designed and set up in collaboration with IAV. IAV and TRE intend to use this in-house development to demonstrate their expertise in chassis development. "Our aim is not necessarily to sell the space-saving axle – for us it is more important to show we have what it takes to develop a completely new concept and also put it into practice", says Döhrer. "This is where the prototype in the Audi A3 is an excellent tool for attracting new business because we can use it to let OEMs know exactly what expertise we have."

Just how well the developers from southern Germany do their job is illustrated by their motor-racing activities. The abbreviation "TR" stands for "Team Rosberg" set up in 1994 by former Formula-1 world champion Keke Rosberg. Initially a wholly owned subsidiary of the team, TRE has been specializing in chassis development, lightweight construction and fiber composite materials since 1997. TRE is currently using its expertise to support "Team Rosberg" as Audi's official works team in the German Touring Car Championship (DTM). "Although most of our development work nowadays focuses on mass production, we utilize the synergies from motor racing wherever it makes sense", Döhrer stresses. "This is how it led to us carrying out an initial joint project with IAV back in 2001. An E-Lupo was equipped with four wheel-hub motors. TRE supplied the entire rear-axle module." Following several joint projects and a cooperation agreement, last year saw the "TR Engineering powered by IAV GmbH" (TRE) joint venture being hived off, with IAV holding the majority stake.