Integrated cooling system one of key enhancements to new generation articulated dump truck.

When an equipment manufacturer develops a new generation of a flagship product, many of the enhancements it incorporates to the new model can be plainly seen and felt. But some of the most significant changes are subtle enough to escape immediate notice.

Such is the case for Bell Equipment,

Many of the changes from the B series models, such as higher horsepower engines, a new Allison transmission, improved suspension and better ergonomics in operator's compartment, are plainly apparent to the user. But others, notably the integrated cooling system developed for the vehicles by Karmazin Products Corp., play an instrumental role in the improved performance and durability of the trucks, which are often operated in hot and dusty climates.

Bell, Richards Bay, South Africa, is one of the world's leading manufacturers of articulated haulers, and is in the midst of a major effort to expand into North America. Bell was looking for a U.S. supplier in part because they're looking for greater penetration into the U.S. market, said Lance Jenkins, director of sales for the Wyandotte, Mich.-based Karmazin. We worked in the development process with them back and forth for about three months before they made their decision.

It was also significant for us because Bell was also looking at some very big competition and we were able to get the business. And while we're on a lot of equipment in those types of environments, this is our initial voyage into the articulated truck market.

The Karmazin integrated cooling system consists of a severe-duty, steel radiator, aluminum charge-air cooler and steel transmission oil cooler, which replaces previous copper core components. The expansion tank is also incorporated into the radiator assembly, simplifying the cooling package.

The radiator utilizes the company's nested fin tube design, with an 8 fins per in. and a total core size of 1190 sq.in. The aluminum charge-air cooler, which utilizes a purchased core also incorporates an 8 fins per inch design. "They liked that fin spacing because these trucks work in areas where it's very dusty and they don't want it clogging up," said Jenkins. "They can also clean it out more easily."

The steel transmission cooler is a two-pass unit, mounted below the charge-air cooler, ahead of the engine radiator. "The transmission cooler was very important, because this is one of Allison's first applications with that transmission in an articulated truck," said Jenkins. "They were very concerned about cooling, because that determines whether the transmission lives or dies.

"We had their engineers here for the cooling tests and they went very well. They're very confident."

The engines used in the new ADTs are in-line, six-cylinder direct injection Mercedes-Benz OM366 diesels manufactured under license by ADE of Capetown, South Africa. Engine horsepower had been increased in two of the three new units. The engine in the B17C truck is rated 174 gross hp, an 8 percent increase from the B version. The B20C truck has the same rating, 231 gross hp, as the previous model, while the B25C truck is also up 8 percent, to 248 gross hp. Torque ratings for the three engines ranges from 440 to 592 lb. ft.

All three trucks incorporate directly driven Allison MD 3560 World transmissions, which Bell said allows more engine power to reach the wheels, increasing machine performance by as much as 12 percent. The transmissions are operated through an electronic gear shift control unit made for Allison by Arens Controls. The control unit has a digital display screen and selector buttons for drive (forward gear range), neutral and reverse. A mode button allows selection of performance and economy operating modes.

The transmission drives a remote-mounted, Bell manufactured transfer case that integrates a three helical gear drop box; a lightweight, cast aluminum housing; a planetary inter-axle differential with 33/67 front/rear torque proportioning; and a lockable differential with dog-clutch for engagement.

The drive axles incorporate ZF limited slip differentials and Bell-built final drives. The final drives have a 7 percent deeper ratio to reduce the loading on the differential and side shafts. The gear tooth profiles have been optimized and the ring gear diameter has been increased.

Brakes are conventional dry-disc type with full hydraulic actuation as opposed to the air-over-hydraulic system previously used. The parking brake is a spring-applied, hydraulic released unit.

The hydraulic system, used to operate the dump body, steering and braking, is driven by a Rexroth load-sensing pump. Flow rates range from 36.5 to 41 gpm. A priority valve provides priority flow for the Eaton series 20 SCU steering unit with Q-Amp system. The Eaton system provides variable steering, dependent on the input rpm of the steering wheel, which results in more positive control and less of the jerkiness typically associated with articulated vehicles. The steering system also includes a ground driven, load-sensing emergency steering pump which assists the main pump at low engine speeds.

Other features targeting enhanced durability include the use of Deutsch and Packard sealed connectors; braided woven sleeving for the wiring harnesses; and O-ring face soft-seal connectors on all hydraulic couplings.

The sound insulated, ROPS/FOPS cab has been redesigned, with a fully adjustable, tilt-telescoping steering column, air suspension seat and new digital display that replaces the previous analog gauges. The MFA 10 unit, manufactured by Motometer, a division of the Bosch, features a modular design with separate clip-on switch/display, warning light and speedometer units, which are individually replaceable. In the event of engine or transmission malfunction, the control unit sounds a warning and displays the appropriate error. The display unit also incorporates a diagnostic feature which monitors the engine and allows for recording and retrieval of fault information.

For more information on the Bell C series articulated trucks, contact: Bell Equipment North America, 2843 Hwy. 80 W, Garden City, GA 31408. Telephone: (912) 966-2615; Fax: (912) 964-1594.