“So, what were you doing in Ohio last week?” asked a friend of mine. “Thrashing big trucks around on a skidpad,” I enthusiastically replied. “You should have been there – we did these J-turns at 45 mph…” By now my friend was rolling his eyes with that ‘whatever floats your boat’ look. Some people just don’t get it.
Actually, my visit to the Transportation Research Center in East Liberty was a blast, but there was a practical purpose behind the fun. Bendix Commercial Vehicle Systems was demonstrating two potentially lifesaving technologies that may soon find their way onto heavy trucks in North America.
Much like high-end passenger car systems, the company’s Electronic Stability Program (ESP) automatically applies brakes at individual wheel ends to restore stability to a truck or combination vehicle that’s losing control or headed for a jackknife on dry or slippery surfaces. It also provides roll stability by engaging brakes on all axles to reduce a vehicle’s speed when it exceeds a roll threshold on dry surfaces. ESP can be triggered, for example, by taking an exit ramp too fast or – as I learned from behind the wheel – making an emergency lane change at even moderate speeds.
Bendix’ ESP package is built entirely on its ABS platform, and does not involve electronically controlled braking (ECBS, EBS or brake-by-wire). Additional components are added to the ABS, such as yaw and steering-angle sensors, but the system retains familiar components and service procedures, according to Kevin Romanchok, product line director, electronics. “We think this is the most cost-effective solution for North America,” he says. “It provides all the benefits of ECBS – except for the slight improvement in service-brake response time, and friction material wear control – with less cost and complexity.”
The TRC demos included several moderate-speed (30-45 mph) J-turns and lane changes with ESP turned off, then on. The switched-off runs were wheels-in-the-air exciting, with the test rig saved from rollover only by wheeled outriggers on the trailer. The switched-on runs were boring by comparison, with stability maintained and speed reduced, despite the best efforts of yours truly and the other drivers to “lose it.”
Given enough speed and enough steering input, says Romanchok, the laws of physics will eventually outmuscle ESP, and you could still be looking at a costly accident. Fortunately, out on the road, no one tries to lose it, even though it happens every day. Romanchok cautions that ESP is not a cure-all, but, coupled with prudent driving, it can provide a substantial safety margin.
The second technology demonstrated was Bendix’ latest version of its air disc brake. The demos showed what most of us already know. Discs stop better than drums, especially after repeated hard stops and under wet conditions – which cause drum brakes to fade and lose effectiveness.
Air discs, says Bendix, could prove to be the best way for trucks to meet the National Highway Traffic Safety Administration’s proposed 248-foot-from-60-mph stopping requirement. We watched as the Bendix product did it in 202 feet with discs all around, and 224 to 236 feet with discs on the front axle only, while an identically loaded vehicle with standard drums all around took from 260 to 292 feet.
Moreover, the shortcomings of earlier designs have been addressed, according to Ron Plantan, engineering manager, air disc brakes. Apply/release hysteresis has been reduced from up to 30 percent to around 9 percent; the external auto slack has been replaced with an internal, sealed, clearance-sensing mechanism; and there have been great strides in rotor design and friction materials that the company hopes will eliminate longevity and drum compatibility concerns.
The only drawback is the estimated 20 percent initial cost premium, which Bendix says will be offset by reduced maintenance costs. And prices will no doubt come down as sales increase, which will stimulate further sales, further price reductions, and so on.
That’s a cycle I’d like to see get kick-started soon.
