Slick Strato cuts costs
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• When Seddon Atkinson introduced its Enasa-cabbed Strato range of tractive units in 1988 it was obvious that a lower specification cab would be needed for multi-wheelers.
At last year's Birmingham Motor Show the company introduced the TC range which, although making use of the same cab shell as the Strato, is a lighter and lower-cost option. In rigid chassis form, the first new multi-wheelers from Seddon Atkinson since the 400 Series could be the answer to re-establishing its position with the construction industry and tippermen.
The cab is mounted on a less sophisticated suspension, using rubber bushes at the front and a pair of coil springs with shock absorbers at the rear. Carpet is replaced with rubber flooring and the driver's seat has a mechanical suspension instead of air.
Out go the premium cab's remote headlight adjustment and washers, an electric window for the driver, side blinds, map reading lights, alarm clock and voltmeter, but the adjustable steering column and heating and ventilation remain unchanged.
The cranked chassis on both six and eight-wheelers allows the use of 295/80 tyres at the rear. A Rockwell SRHD bogie with inter-axle diff-lock replaces the old Seddon Atkinson design and is used in conjunction with Hendrickson Norde rubber suspension rated at 20 tonnes. Front axles are plated at 7.5 tonnes giving a further 600/ 1,200kg of load tolerance.
The variety of power units and transmissions will add to the six and eight-wheelers' appeal. Cummins' 8.3-litre 6CTAA rated at 197kW (265hp) is offered alongside the 10-litre Cummins LTA 275 for the 6x4: the 8x4 has the choice of the Cummins LTAA 275 and 325 or the lower revving and more torquey Perkins Eagle 325Tx.
Now ZF is able to supply Seddon Atkinson with the lightweight 9S-109 nine-speed synchromesh gearbox it becomes the standard fitment on most models, with the Fuller RTX 11609 and Eaton Twin Splitter relegated to the options list.
This week CM was able to try out the new driveline. matched
to the lesser Cummins L10 power option and 5.75:1 fmal drive ratio in both the six and eight-wheeler models.
The large cab looks a bit out of place on the low body line of a 6x4 but is a perfect match for the taller eight-wheeler. Three external steps are fitted, which is an indication of the climb needed to reach the driving seat.
Once inside there is no difference in layout between the six and the eight-wheeler. The ribbed floor covering ends flush with the door opening making it easy to sweep out: the fully adjustable seat and steering wheel allow for a range of driving positions. With the more stable ride of a rigid chassis the mechanical suspension seat is quite adequate for road use but proved rather too stiff over the worst sections of our off-road test route. Directional control is good and both models have useful turning circles.
Handling 24.39 tonnes the Cummins LTA 275 gave a lively performance with good acceleration over the flat with strong pulling power up hills. It leaves the eight-wheeler relatively under-powered, but it still cruised consistently about the legal limits and was about half a gear down on the hills. Larger (200mm-wide) Lucas brakes front to rear give ample smooth stopping power.
The ZF nine-speed box will be the first choice of those who are predominantly weight conscious, and even though our test vehicles were almost new gear changing was surprisingly slick.
Whether nine speeds are sufficient will depend on the severity of the operational terrain— we found no obvious gaps during our test run.
The ratios certainly manage to offer good restart gradeability with an adequate high-speed cruising capability.