Getting to grips with UXT
Page 10
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It works in the same way: pull up to change up, and push down to change down. This gives a pre-selection of the next gear, and time to operate the clutch pedal before the system decides that the driver doesn't want to change gear after all.
There is no separate switch for the splitter, as this is also incorporated in the electronic gear selection system. It operates as a straight 16-speed gearbox but up to four speeds can be pre-selected.
In practice this can equate to a shift from 111 to 311.
Like Eaton's SAMT, ZF's ES 11 includes a safety feature to stop it banging into neutral if the driver does something foolish.
If the driver releases the clutch pedal too quickly the mechanical linkage keeps the clutch disengaged until the gearchange has been completed. The pedal then starts to press up under the driver's foot as a signal that he can lift his foot off the pedal.
When approaching junctions or traffic lights, where there is need to change down more than four gears, the driver simply presses down on the clutch pedal and holds the gear selector down for a few seconds. Friendly electronics automatically select the
optimum gear.
The high-roof F90 cab gives an impression of space that only the Renault AE can come close to matching. Driving this left-hooker on the right hand side of the road encourages the use of the passenger door. It is not only safer to climb in on the nearside, it is easier as there is no steering wheel to obstruct entry and exit.
Once inside you can stroll across the cab to the driver's seat with no need to crouch.
This is nothing new for MAN's underfloor models — and neither is anything else in the cab, such as the familiar MAN steering wheel in front of the familiar MAN fascia.
Underfloor
Unlike manual versions of MAN's underfloor trucks there is no gear lever to obstruct an easy passage from the driver's seat to the berth.
On the other hand all this space does not include a cubbyhole for oddments such as change for the numerous continental tollbooths.
It's easy to forget that the UXT has permanent four-wheel drive. Like a modern four-wheel drive car, the system doesn't give anything away until you provoke it.
Due to the seasonal Scandinavian axle load restrictions which are imposed during the spring thaws, it was only possible to load the UXT and the tri-axle 13.6m semi-trailer to a gross weight of 32.6 tonnes. This was no match for the 12litre engine, which produces 1,730Nm (1,2751bft) of torque at 1,100-1,500rpm.
When driving hard on twisting roads it is possible to reach a point when the trailer seems to take command.
Even if the UXT 4x4 is slightly heavier than a conventional tractor, it is still not much over seven tonnes; its wheelbase is only 3.5m. However, the speedometer confirms that the UXT can accept much more aggressive driving than a conventional 4x2 tractor and it displays a very high degree of directional stability, even on severely rutted roads. The steering feels very precise with a satisfying self-centering action.
The non-tipping cab is suspended on steel springs, not air, and there is also a Panhard rod to prevent it from moving sideways when the cornering gets brisk.
The grille lifts to give access for most of the daily services except for the dipstick and oil filler which are reached via a hatch on the right-hand side of the truck.
What look like aerodynamic skirts are in fact covers for the engine.
The spare wheel is also concealed by a skirt on the left of the vehicle. As the engine is tilted 90% opening the left hatch reveals the turbo with the cylinder head beyond it.
Retarder
MAN engineering chief Dr Klaus Schubert says that MAN's motive for working on permanent all-wheel drive is to get the power of a retarder down on the road through two axles instead of one.
However, neither of the 4x4 UXTs is equipped yet, simply because no suitable retarders are yet available.
By the time MAN decides to put an all-wheel-driven tractive unit into series production it expects to have a retarder ready, but not before 1995.