Equipment Type

Bendix: 2nd Connector Could Improve Tractor-Trailer Communications

Use of a second electrical line between tractors and trailers might become common as a need for electronic communications

March 27, 2017

Use of a second electrical line between tractors and trailers might become common as a need for electronic communications, say brake-performance specialists. The second wire–something already in use on certain trailers–would carry signals that ensure optimum timing and balance among the brakes and shorten stopping distances in the future.

So said Fred Andersky, of Bendix Commercial Vehicle Systems, and Keith McComsey, director of marketing and customer solutions at Bendix Spicer Foundation Brake, who briefed reporters at the Mid-America Trucking Show in Louisville, Ky., last week.

Photo above: The seven circuits in the common single electrical connector (between the red and blue air lines) is almost at capacity, Bendix experts say. So a second connector line might be needed to ensure precise, balanced brake operation between tractors and trailers in the future.
Below: Some trailers already use a second connector to the trailer for operation of accessories. This Fontaine flat’s power-slide tarping system gets power from the second cord (right).

They were discussing the superior stopping power of air disc brakes and how the slow but steady adoption of ADBs among North American fleets would enable greater highway safety through shorter stopping distances. A federal mandate for stability control systems on certain heavy vehicles this August adds to the communications burden.

Stopping distances could be even shorter and stability better with more precise signaling between tractors and trailers, Andersky, said. But the current seven-way power cord is almost at capacity, and a second cord could increase signaling capability.

“It’s got to happen if a trailer is to become an integrated part of a combination vehicle,” which federal safety authorities are talking about, he said. “But retrofitting the extra cable on existing trailers could be a problem.”

Using a wireless local area network (LAN) would be easier; communications boxes could be installed on each vehicle, then talk to each other over the air. But wireless signals are subject to interference and hacking, “and you don’t want someone hacking into your braking system.”

The extra cable could securely perform the signaling function until LANs are protected against interference to the same level as a wire.

Air disc brakes are now on 27 percent of tractors and 20 percent of trailers, McComsey said. ADBs not only help combination vehicles stop quicker, but also are better balanced side-to-side. That aids stability.

But disc brakes make an excellent business case in maintenance alone, he said. Pads wear longer than the drum-brakes’ linings, and are much easier and quicker to change, saving labor costs.

“The return on investment with cumulative maintenance steadily increases with time,” he said. “And that doesn’t include (greater) safety and reduction in fines and CSA scores” for out-of-adjustment drum brakes. ADBs are inherently self-adjusting, and maladjusted drum brakes adversely affect drivers’ and companies’ scores in the federal Compliance, Safety, Accountability program

Bendix is “bundling” disc and drum brakes for use on tractors – discs on steer axles and drums on drive axles – which seems to be the way the industry is heading toward further adoption of discs, Andersky said. But he and others would like to see more use of ADBs on trailers.

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