system. It looks as if it will become a regular
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choice, but as with all such technologies there's a strong requirement for proper and efficient maintenance. We've been talking to a Wabco specialist to find out the pros and cons. Trailer ECAS is common enough in Europe, but now Ince and Wabco are jointly showing that UK operators can also benefit from a full front-to-hack
• units and regular delivery truck chassis. However, Wabco has set the ball :=Frrolling by retro-fitting its first UK system 7 to an existing Overlander semi-trailer 2' used by New for press tests and dealer E demos; other ECAS systems are also
g being added to a batch of new trailers Palready in build. 0
▪ The air-suspended dry freight van has n the Continent, electronically controlled air suspension (ECAS) on trailers is fairly common, but so far as the UK goes it's generally restricted to tractive triple disc-braked axles with a front lifter, but when matched to one of Iveca's newest 440E43 TXP Cursor 10 twin-steer EuroStars with ZF EuroTronic, EBS and ECAS on all bar the steer axle, the combination becomes one really sophisticated package.
But what are the maior benefits of a full ECAS, and are there any implications so far as maintenance of the system goes?
To measure the performance we hitched a drive on the new EuroStar and, judging from just a short trip at 41 tonnes gross, the rig is extremely stable over motorways or twisty A-roads. There's absolutely no rear-end rocking nor tail-end wag during cornering, and even during fierce lane-changing the rear half of the trailer seemed firmly anchored to the road, (A full appraisal and roadtest of this rig will appear in CM 21-27 September.) But smooth and reaction-free as it was, potential users might want to consider the dependability of an extended ECAS system, component reliability and its ease of maintenance.
To find out we visited Casley Diesels, a Colchester-based systems specialist and Wabco service dealership.
Proprietor Jason Casley, who retro
fitted the ECAS to Iveco's test trailer, was busy rectifying an air suspension fault on an 18-tonne rigid. He enthuses about the appeal of a full system and the many options passible.
'it was designed purely with safety in mind, to enhance stability, braking, ride and handling characteristics,' says Casley.
By keeping the combination level front to rear there's an identical footprint at each wheel, and braking is even throughout. Fit the optional traction assist to the trailer's first axle and the tractive unit's second, and it's not only a safer drive but it also reduces lyre wear. Indirectly, he says there's greater protection for the cargo—and it's easier on the driveline and trailer superstructure too.
A combined full ECAS and fast-acting EBS (it can also be retro-fitted) is so ultra-responsive that its reaction times are far quicker than those of the driver, adds Casl%c The next generation, he says, will see an integration of sensors via a CAN bus data link, and a greater sharing of information that will increase stability still further and raise safety levels even above those of today.
System care
Casley concedes that in the early days the reliabikty of electronic components was questionable, but today's generation is lighter, stronger and more powerful than ever, and unit failures are extremely rare.
In fact, it's not so much the electronics that let you down as the bits in between, combined with a sprinkling of human error and neglect.
But to realise the benefits of specifying full ECAS, Casley is adamant not only that service maintenance must be thorough, but that those responsible for it should have a really good appreciation of the basic intelligence, too.
First, the system should contain only clean a4-, so regular purging of the air
tank valves is essential. Proper dryer maintenance is vital, too, otherwise the operation of the valves becomes sluggish and the system is slow to react.
Casley says it's not uncommon to be called out to a three or four-year-old artic to find that the original dryer has never been touched. When it is part of a six-axled outfit that needs a lot of air for both brakes and suspension to function properly, it will be in a parlous state for working at up to 44 tonnes.
You should check the bellows regularly, he adds. Grit can find its way past the rolling edges around the cone, causing the bags to perish and leak. If the leaks increase, the suspension will end up correcting itself all the time. Some suspensions have aluminium cones, and they are corroded by salt spray, again attacking the rubber and causing air to leak.
To track down possible air leaks, raise the suspension fully, then brush soapy water around both ends of the bellows and watch for bubbles. This is a simple test that can be used around the entire system—plumbing, valve connections and all.
ECAS intelligence
Unlike conventional air suspension that uses one valve to measure height and control the air springs, ECAS achieves that control by having an ECU via solenoid valves, using data received from the sensors.
The system then supplies sufficient air into the bellows to maintain a constant level state within pre-determined tolerances. As long as left or right variations are within these limits, it will accept most oscillations caused by uneven loads, extreme cornering on rough roads, and deliver a really smooth ride.
Existing trailers rely on a linkage to operate the air supply valve, and it can readily overshoot these tolerances. The standard valve's 5mm outlet has to supply all six bellows on full air flow, so the system is constantly filling and venting, with its damping valve using up the air as it struggles to compensate.
With trailer ECAS, though, the 22mm feed port supplying each air bag provides rapid air movement, with a fast reaction and response time that gives a positive control of the whole system.
Extra sensors can be introduced to bring in variable ride height or traction assist features.
Generally, ECAS uses very little air, apart from when it strays outside the tolerance zones from time to time. If such deflections are extreme the system inflates rapidly to just within tolerance, then reverts to extremely rapid but finely controlled pulsations as it constantly searches for the ECU's pre-set values against which to monitor its performance.
"The driver won't know it," says Casley, "but ECAS will keep the trailer 'floating' within this tolerance zone, constantly managing the suspension with a level of finite control that a mechanical system cannot possibly achieve."
• by Bryan Jarvis