It's one of the most important product premieres at ZF's booth at the 2015 Busworld Kortrijk: The technology company presents for the first time the official successor of the worldwide well-established AV 132 – the AV 133 rear low-floor axle for city buses. The trailblazing axle generation is basically designed for both modern traffic concepts like Bus Rapid Transit (BRT) and new vehicle generations. Thus, the AV 133 comes with the best efficiency, weight, and noise level.
The requirements for modern public transport systems are continuously increasing – currently, they encompass extensive eco-friendliness and higher comfort, lower cycle times and BRT concepts as well as a more efficient operation with higher passenger volumes at the same time. High-performance technology is needed to ensure that the means of transport are able to meet these requirements. A city bus chassis enabling a very low floor height and a consistently level passenger area are the basic prerequisites in this context. "Because of this and of many other sought-after features, our established AV/AVN 132 model range has become the worldwide most successful low-floor rear axle for city buses," says Andreas Moser, Senior Vice President of Axle & Transmission Systems for Buses & Coaches at ZF Friedrichshafen AG. "We will continue this success story with the technically optimized successor AV 133 that will enter volume production in 2016."
Higher performance, less weight
Even the AV 133 basic version scores with integrated functions for panels and screw connections. Compared to the predecessor system, it offers higher performance with unchanged installation dimensions. Nevertheless, its weight amounts to no more than 983 kg including its spring carriers made of spheroidal cast iron, air springs, dampers, and control arms. Furthermore, ZF developed optional lightweight spring carriers made of aluminum for the AV 133 lowering the axle weight by another 45 kg, i.e. five percent. In this way, the low-floor portal axle compensates for a large part of the additional vehicle weight that is and/or will be generated by the additional components required for the new emission standards or for driveline electrification.
For efficiency and acoustics reasons, the ZF engineers placed further emphasis on the portal drive and the oil supply. They improved the surface stress of the bevel gearsets and extended their diameter by ten millimeters. Similarly, the portal gearing for the AV 133 was optimized with regard to noise emissions and stability and got a newly designed input gear. A look into the inside of the axle differential discloses an advanced bearing concept and an improved lubricating system. With these effective detailed measures, the AV 133 will surely attract attention in public transport operation: The noise level is up to three decibel lower than with the current AV 132 – which feels like half of the loudness level.
Oil change not before 240 000 km
In addition, ZF offers an optional efficiency package for the AV 133 which contains further innovations apart from the aluminum spring carriers: an innovative bleed system integrated into the axle with oil and water-repellent filter membrane, for instance. This ZF solution which is independent from the corresponding bus OEM contributes to reducing the number of interfaces to the vehicle. The low-floor bus axle is filled with a special, semi-synthetic lubricant at the plant that extends the AV 133's oil change intervals from 180 000 to 240 000 km.
RL 82 EC independent front suspension for higher axle loads
The new RL 82 EC low-floor independent front suspension which also offers numerous benefits is the ideal supplement to the AV 133 rear axle system. Taking the RL 75 EC as basis, its design was adapted to the ever-increasing bus weight featuring high-tensile steel. As a consequence, the load on the front axle increases by up to 700 kg to a maximum of 8.2 tons. On the other hand, the installation space and the wheel and tire sizes remain unchanged for the RL 82 EC.