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Electronics can help stabilise a swaying combination.

Electronic aids can make towing safer, but won’t compensate for a badly balanced towing vehicle and trailer.  

Trailer Stability Control (TSC) in towing vehicles is an extension of the towing vehicle’s ESC program and is designed to intervene when vehicle sensors detect a dangerous yawing (‘snaking’) movement of the trailer. If a yawing movement begins and exceeds a certain limit, the towing vehicle is decelerated within milliseconds by throttle closure and brake application, until stability is restored.

By taking advantage of the ESC system’s ability to manipulate engine output and apply wheel-specific braking, TSC seeks to extend the control-enhancing abilities of ESC to the vehicle’s trailer.

Trailer sway can be caused by crosswinds, improper loading of the trailer, incorrect tyre pressure, road conditions or even the ‘wind wave’ from a passing heavy vehicle.

In general, TSC monitors the side-to-side motion of the tow vehicle to determine if the trailer is swaying. If the sensor detects yaw that isn’t caused by the driver’s steering inputs, it begins working to control the unwanted motion. Moderate brake pressure is applied to a single front wheel in an alternating fashion dictated by the severity and direction of the sway. Light brake pressure is applied to the other three wheels, helping reduce vehicle speed in a controlled manner.

AL-KO trailer anti-sway control

al-ko esc AL-KO is best known in Australia for its rubber-bushed, independently-suspended, torsion-bar trailer axles, but the company produces a range of caravan and motorhome chassis in Europe and is well advanced in trailer dynamics R&D.

AL-KO Trailer Control (ATC) consists of an axle-mounted sensor connected to an electro-mechanical actuator.

ATC monitors trailer stability in a similar manner to vehicle ESC and if a snaking motion starts the ATC sensor activates the trailer brakes, to slow the combination and eliminate the yawing action of the trailer.

For the Australian market AL-KO developed a version designed to operate with electric trailer brakes and this was initially offered in 2012 through new caravan outlets. in January 2013 AL-KO  announced the release of  Electronic Stability Control (ESC) technology as a retrofit product for older caravans.

From February 2013, AL-KO began a progressive rollout of its AL-KO ESC Certified Installer Network, with technicians trained  in the installation of the product. AL-KO ESC is available for existing caravans with AL-KO running gear and brakes on approved suspensions. AL-KO claims the cost of retrofitting
ESC to an existing caravan is $1200 – $1500.

The AL-KO system differs from your tow vehicle’s ESC in that it applies equal brake pressure to all trailer wheels.

In July 2017 AL-KO  announced that Electronic Stability Control (ESC) technology is now available for installation to caravans with AL-KO hydraulic disc brakes.

Since its release for caravans with electric brakes in 2012, AL-KO ESC has revolutionised towing safety in Australia. ESC automatically applies the caravan brakes to help maintain control in the event of dangerous towing instability.

While electric brakes are still fitted to the majority of caravans in the market, the growing popularity of caravans with hydraulic disc brakes has led to calls for AL-KO to develop an ESC equivalent to suit this segment.

In response, AL-KO engineers have produced an ESC model that can be combined with an AL-KO IQ7 electro-hydraulic brake actuator, providing smooth braking and a fast response time.

The action is similar to the operation of power assisted disc brakes as fitted to most towing vehicles.

AL-KO ESC is now available for caravan manufacturers to fit to new caravans fitted with AL-KO Hydraulic Disc Brakes and AL-KO IQ7 with an ATM of 1250-2000kg for single axle and an ATM of 2000-4000kg for tandem axles.


Dexter Sway Control

dexter anti swayIn mid-2014 Dexter Axle Co, a leading US manufacturer of trailer axles and trailer brakes for over 50 years, announced the launch of the Dexter Sway Control system (DSC).

This electronic system uses a yaw sensor, similar to the one fitted to your towing vehicle if it’s equipped with ESC. In the event of trailer sway the system applies the brakes on one side of the trailer, independent of driver action, to correct the sway action.

“This next-generation technology detects trailer sway and applies either the left or right brakes dampening the sway much quicker than other systems that apply brakes on both sides at the same time,” explained Bryan Thursby, Dexter’s vice-president of sales and marketing.


Bush travel test

dexter sway contorl -dean rOne of the OTA Team members, Dean Reynolds, has fitted the Dexter Sway Control system to his 20ft Opal 186 caravan.

This van has a tandem heavy duty axles and suspension and tares at 2200kg. His towing vehicle is a 2014 Jeep Grand Cherokee Laredo diesel with eight-speed auto gearbox and air suspension.

Although Dean has a set of weight-distribution bars he didn’t fit them for this extended test.

The route was a three-month journey to the Northern Territory and WA Kimberly area: a 14,000-km round trip from Melbourne.

Dean chose the Dexter system because it worked like his towing vehicle’s electronic stability control, providing automatically-applied, selective braking to both sides – or one side only – of the trailer axles, to control sway.

“I saw the Dexter system first on the Outback Travel Australia website and then checked it out at the 2015 Melbourne Caravan Show,” said Dean Reynolds.

“I liked the fact that it worked like the Jeep’s ESC and that it was the latest in technology: designed, built and backed by one of the biggest axle companies in the world.

“Retro-fitting it to the Opal van was easy enough for the MT&CS crew and it’s been a great investment.”

Like all visitors to the remote northwest area, Dean and wife Anita encountered strong cross-winds at times, along with the wind-rush of oncoming triple- and quad-trailer road trains. The inevitable swaying movement of the van was quickly brought into line, Dean said.

“We didn’t ever need the full capability of the Dexter Sway Control system, but it was very reassuring to know that it was there for us in the event of an emergency,” Dean Reynolds concluded.

In conjunction with this on-road appraisal Allan Whiting caught up with MT&CS during their testing program in Melbourne. It was a very, very interesting morning.

The test rig that MC&CS has been using wasn’t suitable for filming, being a skeletal rig, with a 1.5-tonne block and wires and data sensors all over the place. (Also, I suspect, Dexter doesn’t want people to see what’s possible and ‘try this at home’!)

I couldn’t believe the stable behaviour of the non-ESC tow vehicle and DSC-equipped trailer, through what were tight S-bends among trees, on a mixture of surfaces at relatively high speed.

I could have managed this test course at that speed in the solo vehicle, but could not believe it possible with the two-tonne trailer behind. However, it was a doddle.

At one point, during a tight gravel section, I felt the rear end of the tow vehicle break away in a power slide and anticipated a power jack-knife to follow instantly, but the trailer braked left side and right side and pulled the tow vehicle straight.

A typical lane-change manoeuvre at 80km/h was as stable as it would have been without the trailer behind, thanks to the Dexter DSC system. I’m convinced.


Bosch TSC

Bosch Australia has launched an innovative trailer safety system featuring trailer-ABS and sway-mitigation technology. It’s the first TSC system to combine these two features.

This Trailer Safety Control (TSC) system is for fitment to caravans and trailers equipped with electric brakes and towed by passenger and light commercial vehicles.

“Despite the end of volume passenger car production in Australia in 2017, Bosch Australia’s 200-strong automotive engineering team is busier than ever,” said Gavin Smith, President of Bosch Australia.

“Trailer Safety is a great example of how to apply existing capability to an adjacent niche and with global potential.”

Bosch said that in 2016, loss of control accounted for 30 percent of caravan accident claims, with oversteering and fishtailing among the main causes.

The need for a solution to this problem was identified by the Australian Vehicle Safety Systems engineering team, resulting in an R&D project in 2014. The parent company acknowledged Bosch Australia’s local engineering capability and that led to the establishment of a Bosch Global Centre of Competence for Trailer Safety in Australia in 2015.

The 2018 Bosch TSC system is the first to incorporate trailer ABS and sway mitigation for new caravans and trailers with electric brakes.

Mounted on the trailer, the system comprises an Electronic Control Unit (ECU) with integrated motion sensor and wheel speed sensors. These sensors determine the movement of the trailer and the speed of each individual wheel, respectively.

The ECU is being manufactured at Bosch’s production facility in Clayton, Vic.

Bosch has been a leader in automotive Antilock Braking (ABS) and Stability Control (ESP) for 40 years and Mark Jackman, the head of Bosch Australia’s Vehicle Safety Division said: “Our extensive vehicle safety systems experience is carried over into the Trailer Safety Control system”.

With the support of DexKo Global, Inc, a global leader in trailer running gear, chassis assemblies and related components, and the parent company of both Dexter and AL-KO VT, Bosch is in the final stages of development of the new TSC system.

The system is being offered initially in Australia and the USA, where electric trailer brakes are popular fitments. In these two markets there are approximately one million new trailer registrations annually and 12 million registered trailers.


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