Heavy Duty Trucking

DEC 2014

The Fleet Business Authority

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38 HDT • DECEMBER 2014 www.truckinginfo.com behind the front bumper. That's the shortest in the truck-building busi- ness, we were told, so the long wheel- bases needed in many bridge-formula states are easy to attain. Minimum specified distances between axles and axle groups gain the maximum allow- able weights and payloads under laws in such states. Think western "super dumps" and "bridgemaster" mixers and you get the picture. Our test truck was neither; it was basically a 10-wheeler with a single, small-wheeled lift axle ahead of the tandem. Zingre said the Bibeau steel dump box carried 15 tons of sand. Add the truck's tare weight of about 26,000 pounds and we were at 56,000 pounds gross, so the pusher axle stayed in the air. A forward-set steer axle limits wheel cut left or right, especially with wide wheels and tires, so a driver has to immediately begin spinning the steering wheel in the desired direction while starting a 90-degree turn — something I had to quickly relearn. Anticipating a right turn at the first public intersection, I had angled the truck to the right, but Zingre said no, we turn left here. I couldn't do it in one swing, so backed up to correct. After that I was OK. That limited turnability also requires more room on tight jobsites, something regular drivers know and take in stride. Helping in such fore-and-aft maneuvers is an automatic transmis- sion, specifically Cat's own CX31 on this particular truck. It's not a cheap option, but half the buyers of CT660s have been taking it, our hosts said. (Cat also offers Eaton manual and UltraShift automated gearboxes, but no Allison automatics.) CX means on-highway and 31 is the diameter of its internal clutches in centimeters, by the way. It's based on a powershift transmission developed years ago for a Cat off-road articulated dump truck. It has six forward ratios that move a truck from a dead stop to 65 mph or more on the highway. With a 4.63 ratio in our truck's rear differentials, 70 mph was about it. The CX in this dumper was test drive SPECIFICATIONS TRUCK Caterpillar CT681, conventional-cab 6x4 straight truck, BBC 114 in., BA (bumper-to-front axle) 28 in., 12.25-in.-high frame rails w/ 120,000- lb yield strength ENGINE Cat CT13 (Navistar N13), 12.4 liters (758 cu. in.), double turbocharged, intercooled and aftercooled, 430 hp at 1,700 rpm (governed at 2,100), 1,550 lb-ft at 1,000 rpm, with urea injection and engine brake TRANSMISSION Caterpillar CX31 full automatic, locking torque converter, 6-speed w/ overdrive 5th and 6th FRONT AXLE 18,000-lb. Meritor FL-941 on 18,000- lb parabolic leafs LIFT AXLE 8,000-lb. Watson & Chalin SL-0890 steerable, air-sprung, w/ 17.5-in. wheels & tires TANDEM 40,000-lb. Meritor MT-40-14X-4DCR w/ 4.63 ratio and driver-controlled Locking differentials, on 40,000-lb. Hendrickson HaulMaxx rubber-spring walking beam WHEELBASE 246 in. TIRES & WHEELS Continental 385/65R22.5 front, 11R22.5 rear, on Alcoa Durabright polished aluminum discs FUEL CAPACITY: 100 gallons BODY: 17.5-ft., 21-cu-yd. Bibeau BFL-S AR450/AR550 steel dump unfailingly smooth and positive in its shifting. Earlier CX31s I drove would occasionally thump during an up- or downshift, but not this one, and I gave it plenty of opportunities to hiccup. After making a couple of 30- to 40-mph circuits amid clouds of dust on the test course, I repeat- edly stopped and started the truck on The 430-hp Cat CT13 (aka Navistar N13) diesel is painted Cat yellow, and works well with the optional Cat CX31 automatic transmission.

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