With the specification of the Freightliner Cascadia 126 36, the brand have brought a truck which is a genuine B-double prime mover with no compromises involved. Tim Giles takes one for a spin to see how it performs.
In the specification driven for this truck test, the Freightliner Cascadia 126 is fitted with the 36” XT sleeper cab and, correctly coupled, this prime mover can pull 34 pallet B-double curtainsider set and stay in side the 26 metre envelope.
Ever since the B-double allowance was extended from 25 to 26 metres, the makers of conventional trucks have spent a lot of time and research dollars trying to shoehorn their typical conventional prime movers, based on original design concepts from North America (where length is never an issue), into the space in front of a 34 palleter.
The 126 denomination is the 126 inches between the bumper and back of cab and just to make sure you remeber this, the number is written in letters a metre high down the side of the cab. The wheelbase is 4,925mm and has a factory fitted bullbar that keeps the dimensions inside the envelope.
Often this kind of exercise has led to compromises with cab interiors feeling cramped or just difficult to move around in, and for a driver trying to rest in the bunk. Some have been more successful than others, but none have come up with a truly suitable solution. That being said, this design of the Cascadia does get Freightliner a quite a bit further down the road to the perfect solution and there is plenty to commend this Cascadia.
The arguments for a conventional B-double prime mover have always been the same. With the driver sitting further back from the front wheels there is less of a tendency for the prime mover to ‘nod’ out on the highway when its under power and working hard. Conventional prime movers feel more stable, especially on rough road surfaces, and we have plenty of them in Australia.
Alongside precise dimensions, the other deciding factor in the choice of B-double prime mover is the power and torque available to the truck. Hauling up to 68 tonnes GCM does put a strain on a driveline. Also, for many operators, many tasks are moving cross to the use of A-doubles, occasionally or more regularly, this puts more pressure on the driveline at 85 tonnes GCM.
The engine at the heart of that driveline is the Detroit DD16 rated at 600hp and at 2050 ft lb of torque, right in the sweet spot many look for in this kind of application. Choices range down to 500hp and 1850 ft lb, but Freightliner are finding that the specification at 560hp and 2050 ft lb of torque is suiting many of the operators running these trucks in B-double applications. The 600hp versions are chosen by operations where the trucks are up on their weights most of the time.
Behind this is the Detroit DT12 AMT, but there is still an option for traditionalists of an Eaton 18-speed Roadranger. However the DT12 predominates, with the Roadranger chosen often in rural locations or for heavy haulage.
On the back end there’s the Meritor 46160 rear axles with a final drive ratio of 1:3.42, a common choice for a North American truck in Australia with the AMT, whereas the Roadranger is normally coupled with the 1:3.79 ratio.
Out on the highway in the DT12’s top gear, 100km/h sees the engine running at just over 1400rpm. At 1150rpm the engine reaches peak torque and maintains that torque up to 1600rpm. This means that the engine is producing maximum torque most of the time while out on the road.
This driveline uses the eco-roll function when it realises there is an opportunity to disengage the clutch and coast, dropping the revs down to 600. The driver has control of the sensitivity and can adjust the speeds at which the eco-roll is activated. If the driver thinks it’s coasting too often they can reduce it.
The Detroit DT12 used with the 16 litre is now the OBX option which includes an off-road mode. In this mode, on the bottom six gears there is extra torque launch available, plus a ‘rock free’ mode which enables the driver to put power on and off to rock the truck out a hole, with a power on and then clutch off action.
There is also adaptive cruise control available and it’s relatively simple to adjust the following distances as you drive along. Of course there’s now the obligatory, and soon to be mandatory, automatic emergency braking, and this along with the adaptive cruise control are standard. All of the other add-ons remain optional, including lane keeping assist and sideguard assist.
From the point of view of this driver, I would be happy if all of them were available all of the time. Yes, you do get some false positives sometimes, but you never get false negatives.
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