New Electronic Controlled Brake System Eventually May Bring S-cam Brake Use to Halt

A new brake system is in the works - one that promises to change the nature and feel of truck braking in the not-so-distant future. The components involved are electronic controlled braking systems (ECBS) and air disc brakes. Combined, they may bring the curtain down on the S-cam brake in the North American truck market.

During a one-day session arranged by The Maintenance Council of the American Trucking Associations, leading proponents of ECBS and air disc brake technology talked about the advantages - and limitations - of this approach.

Dick Radlinski, a former engineer for the National Highway Traffic Safety Administration and president of consulting firm Radlinski & Associates, said the primary advantage of ECBS is faster brake actuation. "With ECBS, electronic controls replace pneumatic or air controls," Radlinski said. "That's critical because pneumatic signals travel at the speed of sound, while electronic signals travel at the speed of light."

However, truckers won't experience significantly faster brake times unless ECBS and air disc brakes are used on both the tractor and trailer. Meritor WABCO illustrated this by publishing results of stopping distance tests it has conducted. At 60 miles per hour, fully loaded, an all-drum-brake-equipped tractor-trailer needed 3,330 feet to stop completely. With air disc brakes on just the tractor, the vehicle stopped in 234 feet.

However, with ECBS and air disc brakes on both tractor and trailer, the vehicle stopped in 189 feet - a shorter distance than the average passenger car, which requires 194 feet.

Potential economic advantages to ECBS exist as well, according to Radlinski. Electronic control would allow the brakes to conduct self-diagnostics making maintenance easier. Electronic controls may also balance the brakes better, allowing for more even wear and longer brake life. ECBS could also help truck drivers get a better "feel" for the brake pedal, so there would be no need to use the brakes differently when pulling loaded and unloaded trailers, Radlinski said.

However, he said adding ECBS may mean more complex technical work for the mechanic, and the combination of air discs and ECBS weighs more than S-cam brakes.

Although Radlinski thinks ECBS is the brake system for the future, he added that it may take 10 years before ECBS arrives on a significant number of trucks.

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