Until now air suspension has mainly been a comfort for drivers of on-road vehicles, due to its poor ground clearance. But then some engineers at Volvo Trucks decided to turn their new air suspension upside down – combining the ground clearance of leaf suspension with the comfort and efficiency of air suspension.
In a construction environment there is little tolerance for spring members and air bellows that hang below the axle. They simply interfere with precious ground clearance. “So we’ve placed these things on top of the drive axle where they are less vulnerable,” says product planner Bosse Franzon. “This results in at least 300 millimetres of ground clearance and the suspension is no longer in the line of fire for rocks and stones.”
Forgiving yet firm
Improved stabilisers also play an important role in the new air suspension. Turned upwards and located centrally between axles, these now convey the forces of the road and the trailer into the stiffest part of the frame to improve roll stability.
“The air suspension has an intelligent control system that makes sure the load distribution between the axles is optimised for maximum tipping stability,” adds strategic planner, Peter Frleta. “Anyone who thinks all air suspended tippers are swampy is in for a surprise.”
No longer in the line of fire for rocks and stones
Who needs comfort to deliver gravel?
Having experienced the washboard effect when driving on pitted quarry roads, Peter Frleta believes this is where air suspension is most justified: “The vibrations go from the chassis, to the cab and into the driver. It feels like you’re getting shaken to pieces.” He pauses for a moment. “It’s no wonder the drivers who tested the new air suspension were happy to carry on testing – they didn’t want to go back to the fatigue of driving a conventional truck again.”
The truck is better off, too, as there is less vibration damage, which ultimately increases uptime. On top of this, a higher pace improves productivity. “We saw an increase of 5 to 10 km/h – that’s just a consequence of the comfort,’’ adds Peter Frleta.
The new suspension design leaves nothing behind the rear axle to interfere with tipping. One of the benefits of this is being able to tip directly into an asphalt paver. “You can have the tipping axle very close to the rear wheel for a very short overhang. It has so many benefits, but then it is the first purpose designed air suspension for construction,” says Bosse Franzon.
Across the range
The new air suspension is now available with almost all axle configurations, including trucks with a driven front axle (4×4, 6×6, 8×6 and 10×6). The maximum load capacity is high – 26 tonnes with a tandem bogie and 36 tonnes with the tridem – which makes for a total load capacity of 46 tonnes for a four-axle truck such as an 8×4.
Best of the best
The Volvo FMX with an extra high chassis for construction can be specified with rear air suspension in combination with either drum brakes or disc brakes. Together with the Tridem configurations, Bosse Franzon sees this as the key to fantastic manoeuvrability. “The fact that you can choose disc brakes means you can also have Volvo Dynamic Steering. And with the best suspension, the best brakes and the best steering, the truck takes on a completely new character.”
Peter Frleta reminds him of I-Shift. “In that case I want mine with the best transmission, too.”
Read more about the rear air suspension for construction trucks