Mack, Bendix work together on stability for concrete customers
January 1, 2006
I'm sitting in the passenger seat of a mixer truck, flying down a straightaway at about 30 mph. I see multiple objects lying in our path about 50 ft. in front of us, growing larger as we speed forward...
I’m sitting in the passenger seat of a mixer truck, flying down a straightaway at about 30 mph. I see multiple objects lying in our path about 50 ft. in front of us, growing larger as we speed forward. I look to the driver for some sign of easing off the throttle, but he just sits contentedly. Fifty feet quickly becomes five and I hold my breath and squeeze the edge of my seat, bracing for impact. At the last possible second, the driver jerks the steering wheel hard to the left and I close my eyes and wait for the mixer to tip.
A quarter second later the driver jerks the wheel quickly back to the right and I feel the chug-chug-chug of the brakes as we slow down and straighten out. I look in my passenger side mirror to check for damage. Not a single orange pylon is out of place as we calmly round the bend at the Las Vegas Motor Speedway and pull up beside a canopied tent. I hop out of the vehicle and I’m met by John Walsh, manager, trade relations of Mack Trucks.
“Well,” he asks me with a grin, “what did you think?”
“John,” I say with a sigh, “I think I’m a believer.”
I was one of the lucky few to test out the awesome power of the Mack Road Stability Advantage by Bendix (Mack RSA) at the recent World of Concrete exhibition (WOC) in Las Vegas, Nev. The new stability system is the first of its kind in the vocational market.
“We’re very proud to be the first heavy-duty truck manufacturer to offer this technology to vocational customers,” said Steve Ginter, Mack vocational products marketing manager. “Concrete customer demand for stability protection is strong because mixers, in general, are recognized to have a high center of gravity and carry dynamic loads.”
Ginter said he’s been working in the heavy-duty truck biz for about 28 years and has been able to see the evolution of stability technology, from the introduction of anti-lock braking systems in the late 70s up until the Mack RSA. While similar technology has been available in tractor-trailer applications for years now, the “next level of sophistication” for vocational vehicles was still in the works.
“I don’t think anyone has been waiting to do this, we’ve just been anxious to do this and now we’ve done it,” Ginter said. “We’ve accomplished something that’s really going to be an advantage for the driver.”
The technology for the Mack RSA can be broken up into three different stages: the identification of an issue, the decision-making process and the action taken.
In the identification process, the Mack RSA uses a number of sensors (including existing ABS wheel speed sensors, along with steering, yaw and lateral acceleration inputs) to determine what the driver is trying to do and where the vehicle is trying to go. The sensors detect everything from the amount of load on the vehicle to the amount of pressure being applied by the driver on the foot brake. It is in this stage where there is the first indication as to whether the driver could potentially have a dangerous event.
In the decision-making stage, the system performs a number of cross-checks between the sensors to determine whether the data from each sensor matches up and if the event (such as a rollover) might actually occur. Many factors are taken into account during this stage, especially since each individual vehicle will react differently in different situations.
“We go through a really good tuning process with each one of the vehicle configurations because each one of the vehicles is going to operate a little differently depending on its wheel base, the thickness of the suspension, the steering ratio and how it’s set up,” said Bendix’s Kevin Romanchok, product line director, electronics. “We make sure that all of those work together so that the driver has a good experience and the vehicle is optimized properly.”
In the final “action” stage, the actual application of the brake takes place. The system controls how much pressure on the brake is given on each side on the truck, depending on which direction the vehicle leans, allowing for a combination of brakes in order to execute the maneuver. Steady braking is the key with most avoidance maneuvers and applying full brakes can often be the worst thing a driver can do, depending on the situation.
“Air brakes are nice, but not when the brakes are up in the air,” Romanchok said. “We try to optimize the amount of braking power we apply in order to give the best stability margin.”
The entire process – from identification to action – takes about eight milliseconds, so it reacts much faster than the human mind can in almost any situation. Speaking as a passenger who drove through a number of rollover tests, I can tell you that 90% of the time I didn’t even realize we were rolling over until we’d already started tipping, making the Mack RSA invaluable.
The beauty of the new system, according to Romanchok, is that it works for both vocational and tractor-trailer applications, despite their differing stability thresholds.
“Compared to some of the other systems that are out and available, the nice thing about (the Mack RSA) is that it’s a full stability system – it handles both rollover situations and but also assesses jackknife situations with tractor-trailers or in the case of the vocational when you’re sliding out of line.”
Another key feature of the Mack RSA is driver control. The driver is able to apply brakes as usual and is capable of making a full stop even when the system is on. The system can even be used when the driver is running double and triple loads.
The Mack Granite Axle Back showcased at the event is slated to be available mid-2006, with other chassis in the pipeline for different wheel-based configurations to cover the rest of the applications.