TII FIRIC OF POW
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ERF has bucked the trend towards small, light, hard-working engines by equipping its E12 eight-legger with Perkins' big, torquey Tx325 Eagle. It offers the promise of trouble-free long service — but at a price.
• It is less than three months since we last tested a Perkins Eagle Tx325 engine in a Sandbach-bred 8x4 tipper chassis. On that occasion it was a Foden from the Longthorne's of Hebden fleet: a day cab model with a 13-speed Eaton-Fuller transmission.
This time our subject is a factory prepared ERF El 2.32 with the same air-to-air charge-cooled 12.17-litre engine but driving through a 12-speed Eaton Twin Splitter gearbox.
It rides on conventional rubber suspension instead of the Foden's optional Paccarsupplied air suspension.
In the three years since Perkins launched the Tx Eagle engines they have been steadily winning the respect of UK truck operators, largely thanks to the sort of no-nonsense reliability that was a feature of the Eagle's Rolls Royce namesake.
That reliability is combined with a string of innovations to make the Tx particularly well-suited to arduous tipper operations.
Those innovations include a replaceable flywheel face; a centrifuge oil filter which is new to the UK and allows 40,000km oil change intervals; an effective sliding-gate exhaust brake; and all-speed mechanical governing which ensures a smooth P1-0 drive for blowers, cranes, tipper rams and the like.
Noise reduction modifications include helical gears driving the fuel pump and compressor.
• DR1VELINE
ERF's standard gearbox is the Twin Splitter which is light and strong; with its overdrive top gear it offers the best chance of good fuel economy with the convenience of side or lower left PT-0 outlets.
ERF sticks with tradition further down the drivetrain by using Rockwell single reduction axles in double-drive format. A combination of cross and inter-axle diff-locks allows the whole bogie to be locked up for those really sticky situations. The low suspension articulation can lift wheels when the truck runs empty off-road, particularly over hard rock surfaces found on quarry access roads in the Peak District and elsewhere. The inter-axle lock ensures that the truck is not left high and dry.
The rubber suspension, supplied by Norde, is maintenance and rattle-free and is less susceptible to rock damage than air bags or even steel springs.
• PERFORMANCE
The engine's Tx325 label reflects its gross power rating of 242kW (325hp): once installed in the ERF its net output is nearer (303hp) with 1,540Nm (1,1351b1t) of torque. In the finest marketing tradition the cab badging retains the suggestion of circa 320hp with the E12.32 tag.
That said, the vehicle still boasts a powerto-weight ratio of around 10hp/tonne, compared with around 8hp/tonne or less for a typical artic.
Acceleration times to 80km/h (50mph) on the test track are comfortably inside the one minute mark and are well up on the results achieved with similar vehicles powered by older designs of engines with less mid-range torque on tap.
Out on the road that healthy output translates into excellent driveability with plenty of lugging power. Not surprisingly the ERF returned near identical productivity to the Tx325-powered Foden; its slower average speed was balanced by marginally better fuel economy.
A glance at our fuel and speed table shows that the ERF recorded the best overall fuel consumption in our comparison group, albeit at the slowest average speed. In the real world, however, the difference in speed would make no difference to its money making potential on the type of journey simulated by our test route.
Its A-road consumption figure is equal to the best in our group, and on the tough motorway section of the route it was comparable with the Scania P113-320.
• BRAKING
Track brake tests were, as with almost every eightwheeler, uneventful. This set-up is inherently so well balanced that it would be hard to get it wrong.
Simply stamping as hard as possible on the pedal as quickly as possible produced effective straight-line braking in shorter-than-average distances.
A welcome addition on this engine is its exhaust brake, which is powerful enough to check the vehicle's speed effectively even at higher road speeds.
This, and the sensible position of the control button close to the base of the steering column, should encourage drivers to make full use of it.
• HANDLING
The rear rubber suspension is stiff enough to keep the truck upright round most curves, irrespective of the speed or load, despite the lack of anti-roll bars.
The nature of the 8x4 chassis ensures that the truck tracks only as cleanly as the drive bogie will al low. Tracking is by no means perfect as neither the rubber suspension nor the ERF bogie are that flexible, but no doubt driver familiarity will compensate for any handling imperfections.
We did not get the chance to drive the ERF empty, but rubber suspended 8x4s are generally stiff and rather bouncy. The ride comfort when fully laden was very good, helped by the optional air-suspended driver's seat.
• CAB COMFORT
ERF offers a choice of day, night (shortsleeper) and sleeper cabs on its 8x4 chassis. The SP4B day cab comes as standard; the night cab comes with curtains all round and a flask and cup tray. The full sleeper cab also has an illuminated headboard.
The trendy dogleg fascia incorporates a neat if unusual set of half-moon instruments, but the tachograph looks as if it was remembered at the last moment. A stubby park brake lever, nestling between the heater and switch controls, is within comfortable reach and leaves the space between the seats fairly clear to ease access to the bunk.
The tip gear control, located to the right of the driving seat, can be used from within the cab or from ground level. Entry to the cab is not difficult with three large steps providing a good purchase, a wide opening door and grab handles either side of the opening.
One minor niggle is that even a slight knock to the composite front bumper could entail re-alignment of the small square headlamps.
Rubber floor mats and some carpet present a good compromise between the need for easy cleaning and creature comforts. The combination of sound-proofing, seat comfort and driving position worked well throughout the two-day test, although we would have preferred a degree of steering wheel adjustment.
• SUMMARY
We had hoped for a higher body/payload potential from an ERF and have to conclude that this is a price that has to be paid for the choice of a 12-litre engine.
On the other hand the Perkins Tx325 does offer good fuel economy, driveability and durability.
After standardising on a Cummins/ Eaton/Rockwell driveline, ERF must have thought long and hard about the move to a Perkins engine option.
Judging by the performance of the Eagle its choice was a wise one.
El by Danny Coughlan