SHORT STOPS AND SLIPPERY TRUCKS

November 22, 2006 Vol. 2, No. 24

In a period that you might think would be rather slow in terms of significant product-oriented news, the reverse is actually true. In fact, I won’t be able to pack it all in here. That’s actually far from uncommon, so much so that I sometimes wonder just how many engineers are out there striving to make Product A better or to get New Product B ready for testing. The number is nearly unfathomable. Just think of the engineering activity this one industry – albeit a big one – must generate every single day.

So my hat’s off to the men and women who create the stuff that makes trucks easier to drive and manage, cheaper to operate and maintain, and more able to mesh with stupid four-wheelers as safely as they do. People sometimes tell me they’re amazed by a writer’s ability to organize thoughts and put them down on paper – virtual paper, I guess – in a more or less coherent fashion. Well, maybe in the same way I’m always astonished to look at a thing as complex as a big diesel engine or a disc brake and realize that a group of engineers nailed it. How can they go from blank sheet to real product? How do they take the first step? How can they possibly manage all the tiny details and come up with a functioning whole? It’s beyond me.

In any case, let me follow on from that disc brake example and then I’ll move to aerodynamics.

This past Monday I joined a small group of other journalists in a web-based conference call – slides on my computer screen, phone to my ear — with some brake experts from Meritor Braking Systems and Meritor WABCO Vehicle Control Systems. The object was an update on the new stopping-distance regulations we’ll see next year, likely in March, according to ArvinMeritor brake chief Paul Johnston.

The original National Highway Traffic Safety Administration proposal called for a stopping distance reduction of 20-30% for three-axle highway tractors. Johnston says they’re betting on 30% in the final rule (copy this URL into your browser for the full text of the original rule-making proposal in the U.S. Federal Register — http://a257.g.akamaitech.net/7/257/2422/01jan20051800/edocket.access.gpo.gov/2005/05-24070.htm). The likely
implementation date is 2009, he added, and probably 2011 for what are called “specially configured” tractors – meaning anything other than the basic three-axle vehicle that makes up 80% of what’s produced.

So what does a 30% reduction mean? The present rule demands that an air-braked three-axle tractor pulling an unbraked trailer (more on that in a minute) be able to stop in 355 ft from 60 mph. In fact, truck makers test to stop at about 280 ft. Assuming a 30% reduction, as of 2009 that same tractor will have to stop in 249 ft with a 10% compliance margin. In practice, OEMs will aim for – and reach – 220 ft, which is getting very near to car
territory.

How will they do it? By adding brake torque, possibly even on the steer axle alone. That could simply mean bigger cam brakes, maybe a combination of cam and disc brakes, or possibly disc brakes all round. Johnston says you can gain 20% brake torque with bigger cam brakes, 28% with discs up
front and S-cams out back, or 38% with air discs at all wheel positions.

All of those options will cost more, he admits, and there may be a small weight penalty, but regardless of which combination you spec, you’ll see significantly longer brake life to offset the downsides. And he means 25% to as much as 100%.

Will there be balance problems if big braking capability is sitting ahead of an ordinary cam-braked trailer? Possibly, and this is an issue being addressed, but they would only appear in panic stops. Given that the vast majority of braking applications are at 25 psi or less, most drivers will never know the difference because in those circumstances the brakes will feel and act as they always have.

And as far as trailers are concerned, I asked Johnston if it makes sense to test tractors only and to demand nothing in particular of a trailer’s braking capability.

“From an engineering point of view,” he said, “it makes no sense. But from a regulatory standpoint it does.”
And it hs the virtue of being repeatable. In any case, he added, that’s what the FMVSS 121 regulation demands – tractors only, and from 60 mph whereas it would probably make more sense these days to test at 75 mph.

In fact, the Meritor and Meritor WABCO folks said that several aspects of the NHTSA brake-testing procedures need an overhaul, and they suggested some specific changes in their response to the rulemaking.

The bottom line here is that you won’t necessarily need to spec air disc brakes on your 2009 and later tractors because a high-performance S-cam will quite possibly meet the standard. Every application is different, of course, so there will be some learning to do.

I’ll follow up on all of this in a coming issue of Today’s Trucking.

Elsewhere on the hardware front, there was an interesting display of prototype aerodynamic advances recently on display in Washington, DC.

International, Freightliner, Mack and Volvo showed the results of research done during a two-year partnership that also involved trailer-maker Great Dane and the U.S. Department of Energy to develop more aerodynamic heavy trucks.

International says it’s developed systems and devices that reduce the aerodynamic drag of class 8 tractor-trailer applications by 14%, substantially increasing fuel efficiency and potentially saving millions of gallons of diesel fuel.

“The Energy Department estimates that class 8 trucks consume as much as 12% of the U.S. petroleum supply and half of that is spent overcoming aerodynamic drag at highway speeds,” said Patrick Charbonneau, International’s vice president, government relations. “The industry must continue to squeeze as much performance as possible from these heavy trucks while also limiting the drain on natural resources and, ultimately, the cost to
customers. That’s what this initiative is all about.”

During the development program, managed by the Truck Manufacturers Association on behalf of the Department of Energy, International partnered with Great Dane to develop a full-scale experimental aerodynamic trailer for Wal-Mart.

They focused on the three major sources of aerodynamic drag in the typical tractor-trailer: the tractor-trailer gap, trailer sides, and trailer wake.

Freightliner, owning the only full-scale wind tunnel on the continent, produced specific design guidelines that will benefit all existing and future heavy-duty trucks. Research shows that even small improvements in a truck’s aerodynamic design can save millions of gallons of fuel when applied to fleets across the country, the company says. It paid particular attention to mirror and mirror-mounting systems.

Engineers selected different mirror head configurations, shapes, and support systems and outfitted a Freightliner Century Class S/T tractor with each one to analyze how much each mirror style affected the truck’s overall aerodynamic drag. Believe it or not, Freightliner learned that even today’s best-designed mirrors can affect vehicle aerodynamics by as much as 6% or more. It’s not just a matter of the mirror shape, but its placement on the
truck and even the shape of the truck in the vicinity of the mirror.

I’ll dive further into this subject as well in a future issue of Today’s Trucking. For now, I’m out of room.

But one last note about the individual products I mention in this e-newsletter, as in the magazine. By and large I don’t – I can’t – test them, so by writing about them I’m not endorsing them in any way. Rather I’m pointing out those that seem newsworthy to me, those that seem likely to interest you. I’m just reporting. I cut out the hyperbole and the exaggerations, but in the end it’s up to you to decide what sounds right and what’s worthy of
further investigation.

And that’s no weasel clause. Just reality.

This newsletter is published every two weeks. It’s a heads-up notice about what’s going on with trucking technology as well as what you can see at www.todaystrucking.com where you’ll find in-detail coverage of nearly everything that’s new. Plus interesting products that may not have had the ‘air play’ they deserved within the last few months. Subscribe today!

If you have comments of whatever sort, please contact me at rlockwood@newcom.ca.