When Ferrara Bros. Building Materials Corp. needed some new mixer trucks last year, Bob Gartman, vp-maintenance, knew some changes needed to be made to boost vehicle performance.
For starters, the Flushing, NY-based fleet switched to a four-axle setup for its mixers, including a steerable 20,000-lb. drop axle that gives the vehicle more maneuverability and payload capacity.
Gartman also decided to drop the manual gearbox Ferrara had long used in favor of Allison Transmission's 6-sp. automatic, making its new T800 Kenworth mixers easier to drive, without skimping on transmission reliability and durability.
That's critical in the rough-and-tumble world of concrete hauling operations. “A steady flow of concrete is important…and we depend on our trucks to deliver the concrete on time,” he notes. “We can't afford any unscheduled downtime.”
Changes in axle and transmission specs are also part of the fleet's effort to lighten the vehicle chassis to increase payload capacity, a big factor in boosting vehicle performance. “Starting with our 1999 model-year trucks, we've changed the engineering specs to lighten our trucks. If loaded properly, we can carry up to 12 yards of concrete on our trucks legally,” Gartman explains. “That allows us to deliver up to an extra one-and-a-half cubic yards per load, more than most other operators.”
But that improvement can't come at the expense of safety, which is why Ferrara retained the Chalmers suspension package for its rear axles. “Mixer trucks have a high center of gravity,” Gartman explains. “But the Chalmers keeps the chassis rail straight to prevent a rollover when the weight of the concrete inside the barrel is unevenly distributed.”
Ferrara Bros. is not alone in its decision to use automatic transmissions. According to Charlie Allen, national service manager for ArvinMeritor, there is a strong trend toward automatics among vocational fleets because automatics give them several performance advantages, including ease of use by drivers, plus constant torque and power.
“While transmission cost is still an issue, driver skill level is an even bigger one,” Allen says. “An automatic takes the driver out of powertrain management, so they don't need that shifting skill. This increases the pool of available drivers and also makes the job more attractive since they don't have to shift.”
Constant power and torque is another key performance advantage of automatic transmissions, Allen points out. And it's one that automated transmissions, which are built on a manual platform, can't provide, he adds. “Automated transmissions are great on hard ground, such as in OTR applications, [but] on softer ground they become a problem,” says Allen. “Automated transmissions, like manuals, interrupt torque when shifting. So if the truck gets stuck, it becomes difficult to rock the vehicle back and forth since there's no power during the shift. An automatic, however, gives you that power. That rocking capability is the performance key.”
According to Lou Gilbert, Allison Transmission's director-North American marketing, “The importance of uptime, productivity and driver retention has turned the vocational market toward fully automatics over the past five or six years.
“Price is always a factor, no matter what the application. But fleet managers understand the complexities of initial price versus overall life cycle value. In the stop-and-go duty cycle a construction truck lives in, the transmission is one of the most critical components,” he adds.
“After all, in a week's worth of work, there will be thousands of up and downshifts, with all types of terrain, loads and driver styles,” continues Gilbert. “The transmission must perform reliably for many years in this environment. Downtime, clutch-adjustments and replacements, driver training and retention, productivity plus other maintenance items must be part of the purchasing decision.”
FUEL ECONOMY, TOO
Although fuel economy has not traditionally been a top concern in terms of transmission performance, it has been gaining steam of late in the vocational market, says Stephanie Bell, product planning manager-fleet for Eaton Corp.'s heavy duty transmission division.
“With the recent fuel spikes, fuel savings are getting more important…[although] it's a challenge to drive fuel savings with the transmission alone because it's but one component within the drivetrain,” Bell says. “Improvements from the transmission are usually limited to a small percentage of the total fuel savings calculation, but it's a performance metric fleets are trying to achieve nonetheless.”
Eaton is tuning its UltraShift automated transmission line to address specific vocational markets. According to Mark Thurman, gm, heavy duty fleet and automated transmission line, Eaton has extended its current UltraShift technology to transmissions designed for use in mixers, dumps and severe-service trucks, with releases scheduled in mid-2008.
“Automatic and automated transmissions help them hire and retain drivers, because all drivers become as good as the best driver on the fleet with this technology,” he said. “If the price-value ratio is there for customers, it helps the bottom line with driver retention and savings.”
“Every fleet is different and requires its own unique specs…climate, terrain, employee requirements and safety are just a few factors that come into play,” adds Allison's Gilbert.
“In general, fleets want to decrease the cost per mile to operate their vehicles. We believe a fully-automatic transmission can contribute to this reduction by using a TES-295 synthetic transmission fluid to extend maintenance intervals. A torque converter and full-power shifts provide superior vehicle acceleration and overall performance, which increases productivity and higher average speeds, ultimately running more miles in the same amount of time versus other types of transmissions. Fleets with fully automatic equipped trucks will also reduce time and money invested in driver training, putting a truck and operator in revenue service quicker, thus improving performance.”
AXLE ENDS
Down at the axles, improving performance can be much more challenging in some ways within the harsh vocational arena.
Steve Slesinski, Dana Corp.'s director of product planning for axles, says more and more vocational fleets are looking for tighter turning radius from their front axles to make their vehicles more maneuverable in tight urban areas and at the job site. They also want beefier construction, so the axles can carry heavier loads — boosting payload capacity and thus productivity — yet hold up over longer maintenance intervals.
“We're looking at stiffer axles with bigger drum or disc brakes to improve their lifecycle, as well as braking power,” explains Slesinski. “Handling heavier loads in a not-so-pleasant environment requires axles to last longer and perform better. Lubed-for-life axles in this case don't apply here because of the stress and strain the axles are exposed to. You need to be able to refresh the lubricant, and having something permanently sealed drives up repair time and cost if it fails.”
“Durability — having a product work day in and day out without failing — is a major performance characteristic of axles,” adds ArvinMeritor's Allen. “Vocational fleets expect their axles to live and work in a tough environment.”
But Allen stresses that axles can't be looked at in isolation from the rest of the driveline. Fleets have to recognize they are part of a system that must work together as a whole in many different driving applications. “The first thing the fleet needs to look at is, do they have a vehicle that's spec'd for the job? Can it operate off-road at a crawl over uneven and sloppy terrain, then get on road and roll down the highway smoothly at 60 mph?” he asks. “All of those factors affect overall vehicle performance.”
Dana's Slesinski notes that weight enters the picture as a performance metric at the rear axle, although it's a metric that must be treated carefully. “You can't sacrifice durability and reliability to get weight savings. That's a given in the vocational market,” he emphasizes. “You're not going to get payload increases or fuel savings worth a one or two pound change to the axle weights. First and foremost, those axles must perform every day in tough conditions.”
Rear axles in the vocational market must also be flexible as part of their performance matrix, able to incorporate wheel differential locks and electro-magnetic retarders into their design — devices used in the construction and refuse markets to improve off-road handling and braking performance, respectively, says Slesinski.
SALES & SERVICE
Post-sale service and support is another big factor affecting axle performance, albeit indirectly, as a truck down for unexpected repairs or waiting for a part to arrive means time away from performing revenue-generating work.
“You can't overlook this, for a concrete mixer down waiting on a part is money lost to the fleet, and that directly affects performance,” says ArvinMeritor's Allen. “It's also about being able to tap into a support network that will help get to the root cause of a problem, not just address the symptoms. If a component, be it a transmission or axle, doesn't live as expected, you have to find out why and make sure it doesn't happen again.”
“Being able to service these components easily is another performance factor,” says Slesinski. “In the vocational market, more vehicle maintenance is required simply because of the nature of the work environment. So minimizing maintenance time, expense and vehicle downtime due to these components is also critical to improving overall performance.”
Making mixers safer
Making trucks safer, both on- and off-road, is an important factor in a vocational fleet's performance calculations. One way of addressing this issue is to add electronic stability systems to vocational vehicles.
“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,” says Steve Ginter, vocational products marketing manager for Mack Trucks. Mack introduced its Road Stability Advantage (Mack RSA), in conjunction with Bendix Commercial Vehicle Systems' electronic stability program (ESP), on its Granite model truck last year.
Using the truck's existing ABS wheel speed sensors, along with steering, yaw and lateral acceleration sensors, the system deactivates the throttle and selectively applies the brakes in sharp curves, sudden lane changes, or obstacle avoidance maneuvers to reduce the potential of a rollover, explains Kenneth Koyan, application engineer with Bendix.
“We tailor our ESP product to specific vocational models, like concrete mixers, factoring in height, loaded and unloaded weight, center of gravity, wheelbase and type of suspension,” he says. “With the concrete drum turning, the potential for a rollover during a right turn is vastly increased, even at speeds as slow as 5 to 10 mph. While it doesn't prevent every rollover, ESP widens the safety zone, especially in mud, snow, and ice conditions.”
The engine, axles, suspension, and brakes all play a critical role in making ESP work, says Koyan. “When a driver goes to hit the brake, there's a time lag,” he explains. “With ESP, as soon as the sensors detect a potential rollover situation, the system activates — the brakes come on and the engine decelerates. Same as when the driver jerks the steering wheel in a panic maneuver. It's all about improving the truck's safety performance.”
