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Big interview: Roeser Patrice on Renault Trucks

Out on the test track near Lyon, Patrice Roeser, product manager for Renault Trucks, talks application-specific differentiation between the latest C and K range vehicles

Renault’s automatic transmission is definitively better than a skillfully operated manual, according to Roeser.
Renault’s automatic transmission is definitively better than a skillfully operated manual, according to Roeser.

Straddling two rivers, Lyon has long been a centre of economic activity, and with the rise of the silk trade in Renaissance Europe it became an industrial powerhouse. Today, this legacy lives on in the operations of Renault Trucks, which was founded in 1978 through the merger of Renault Group subsidiary Saviem and Lyon-based truck and bus manufacturer, Berliet.

Threading the strands of history together, Marius Berliet, a self-taught mechanic, founded his company in 1899 after a stint as an apprentice in a silk-weaving firm — before he was ‘smitten with automobile fever’ in the early 1890s, according to an account of ‘Silk and Metal Workers in Lyon’ by Keith Mann.

Upholding this proud heritage of industry and enterprise today is Patrice Roeser, who, as a product manager for Renault Trucks (and now a Volvo Group employee), is tasked with ensuring that Lyon’s manufacturing remains as vital today as it ever was, and that Renault trucks remain indispensable to customers.

The Kerax, first launched in 1997, has long popular in tough off-road applications. Since 2014, however, it has been gradually phased out and replaced by the C and K (2016) ranges, and this division has left Kerax loyalists with two separate value propositions.

Over the course of an expert-led drive around a challenging test truck frequently used to trial firefighting and military vehicles, Patrice Roeser delves into the reasons behind the split and the utility behind the two models.

He explains: “The aim of the C-range is to save the weight and maximise the payload — this truck is built to operate within weight regulations; the K is built for robustness and upwards of 50 tonnes as an 8x4 rigid with a reinforced Optidriver Xtrem transmission, and upwards of 120 tonnes as a tractor unit.

“We had one 8x4 rigid body K tested for two years in a mining application in Turkey before we launched the range this June. It was driven 20 hours a day with an average payload of 72 tonnes, and a maximum of 82 tonnes.”

In the Middle East and Africa, Renault Trucks is primarily pitching the K range as the likely vehicle of choice based on the higher prevalence of strenuous, off-road applications and less stringent regulation and restriction on gross vehicle and gross combination weights.

In these markets, one particular advantage of K models is their high chassis, which grants the trucks an approach angle of 32 degrees. Renault’s literature proclaims the K’s approach angle to the best in class, and queried, Roeser is adamant that this is indeed the case.

He explains: “The big difference between the C and K ranges is the chassis height. The chassis height on the K is quite high, and as a consequence of that you have higher ground clearance on the K range compared with the C range. But you save weight on the C range, so it is better for maximising the payload in countries with strict weight regulations.

“We use exactly the same engines between the two ranges, the 11-litre and the 13-litre, and exactly the same rear frame, which the option of additional reinforcement.”

The C range is in fact only 6cm lower in height, but this critical variance restricts its maximum approach angle to 26 degrees.

It was hard to discern this limitation in the way Renault’s driving experts navigated the precipitous slopes of loose rock on the test track, but in less deft hands it might tell.

The other technology facilitating the effortless navigation of tricky terrain is the Optidriver automated manual transmission.

Renault’s transmission was engineered in tandem with the Volvo I-Shift, with the two brands pooling to develop the gearbox.

Renault’s Optidriver features in both the C and K ranges, and like the I-Shift has 12 gears. It also has a reinforced ‘Xtrem’ version that can be fitted in the K for severe applications, while crawler gears can be added for applications involving high gross combination weights or requiring very slow speeds (0.5kmph).

It is on the test track’s rough terrain and steeply elevated sections, however, that the transmission is fully realised in combination with the differential locks, which prevent wheel spin on loose surfaces, while the manual mode allows the driver to smoothly apply more power at the touch of a button, without even touching the accelerator pedal. This Renault-specific trait, essentially a button-operated cruise control for off-road applications, was designed specifically for developing markets.

Roeser explains: “The manual accelerator is something unique to Renault Trucks. It is relevant for the driver, because when you are on a bumpy hill you can be thrown around.”

In such a scenario the driver might depress or release the accelerator involuntarily, thus increasing or cutting the revolutions — a common cause of stalling on steep inclines.

With the manual accelerator, he continues, “because you do not touch the pedal, it keeps the same rpm all the time — providing the necessary torque at a constant revolution.”

This Renault feature was developed for an African market in 1986 owing to the extreme unevenness of many of its roads, and was introduced as standard on the first-generation Kerax back in 1997. In many developing markets, it is features like this that have built the reputation of the Kerax over the years.

Another feature born out of Africa, but equally applicable in many Middle Eastern scenarios, is Renault’s careful fine-tuning of the off-road mode on its transmission to help drivers get out of literally sticky situations.

Roeser explains: “In the off-road mode, we have increased the speed at which you can switch from forward to reverse by a factor of 10, allowing you to reproduce the manoeuvre that you perform with a manual gearbox: when you are stuck in muddy situations and escape by rocking backward and forward.”

Renault has removed the requirement for the driver to engage the brake before switching into reverse. Instead, the driver simply takes their foot off the gas, engages reverse, reapplies the accelerator and the truck automatically brakes and, in short order, begins to reverse.

I was invited to take the wheel and try out the manoeuvre, and the action was remarkably rapid and smooth. Roeser confidently affirms: “It is even better than a manual gearbox.”

While the on-road mode was released with the second generation of Kerax in 2006, Renault held back and only released the off-road version after a further two years of rigorous testing.

Equally rigorous trials preceded the introduction of the new T, D and C ranges in 2014. Roeser notes: “During the first phase of development of the full range of trucks — T, D, C, K — we conducted tests over two million kilometres. The K range then underwent a further 1.5 million kilometres of testing before its launch outside Europe in June 2016.”

These tests included a 6x4 K range truck, used as a rigid body-cum-tractor for a logging application in Cameroon — pulling 85t for a year and a half —and equally tough mining work in the Democratic Republic of Congo.

In all these scenarios, even skilled manual drivers were bested by the automated manual transmission, and from a driver training perspective, Renault’s team estimates that even a relatively unskilled driver could be taught to master the basics of the automated transmission within two days.

Astonishingly, over the course of the total 3.5 million kilometres of testing, not a single concern was raised about the trucks. “Nothing, not even a small thing,” confirms Roeser.

The pitch is compelling, not least because so many features of the C and K ranges, the spiritual successors to the Kerax, draw upon Renault’s extensive experience in challenging environments. Renault Trucks has not adapted its vehicles to the challenges of the Middle East and Africa; the vehicles are born of them.

Renault’s air filtration system was developed by its teams on the ground in Algeria in the 1960s to deal with the highly dusty conditions.

Roeser explains: “We had some trouble with the air cartridge — with it clogging all the time — so to solve this concern, the Renault Trucks guys in Algeria had the idea to prevent the dust from entering the air cartridge. They came up with a very simple system: a cyclonic air filter in between the air duct and the air cartridge.

“In fact, they showed this solution to the development centre in Lyon and the guys said this was a marvellous system because there were no wearing parts — it’s a just a shape that exerts pressure. It’s a very simple solution, it doubles the cartridge life for the customer, and it’s also their gain in terms of lower maintenance costs. Now, each time we develop a new truck we include this cyclonic air filter.”

Just to be sure, the C and K range also come with a double cartridge as standard, and can also be fitted with a larger double cartridge where it is anticipated that the trucks will be operating in particularly dusty environments.

Engaging the brakes

The flipside of powering up your vehicles is slowing them down again, so Renault Trucks’ C and K ranges have several options in terms of their braking combinations and functionality.

After wheel brakes, the C and K ranges use three types of retarder: the engine brake, or Optibrake, with a power output of 303kW on the 11-litre engine or 414kW on the 13-litre engine; an exhaust brake with an output of 203kW or 227kW; and a Voith hydraulic retarder on the transmission with a power output of 450kW for both engines.

Roeser notes: “First is the wheel brake, the normal one, with either an electronic VBS or a mechanical lever — the latter being preferred in markets that like to avoid electronics.

“After that we have the hydraulic retarder provided by Voith. This solution is very efficient at high speed on good roads. When you are at or above 40kmph it is very efficient, because it uses the speed of the propshaft.

“The engine brake is really efficient when the revolution of the engine is high, but the speed of the truck low — so it’s a very complimentary braking system with the hydraulic retarder.”

Though the engine brake is weighty, its use is a point of solidarity between C and K ranges. Applying his brake to the lengthy conversation, Roeser concludes: “The engine brake is very, very efficient for the cost. It’s close to 50%.” Under the hood.

The 11-litre and 13-litre engines fitted in the Renault Trucks C and K ranges provide six power options from 380hp to 520hp, with torque values that span the 1,800Nm to 2,550Nm range. However, which engine is suitable for which customer remains highly dependent on the proposed application.

Roeser expands: “The first point is the weight; the 11-litre is 200kg less, which for some customers is very important. Equally, most of the time, especially in Europe, 380hp to 460hp — or around 400hp — is sufficient for construction activities, as well as longer range applications with 4x2 and 6x4 tractors.

“If you are in a predominantly flat situation with a rigid trucks carrying up to 38t, then a 11-litre, with 440hp to 460hp, is the most efficient, because you won’t request the full torque from the engine. Equally, if you have a 4x2 tractor towing 40t, 80% of the time an 11-litre will be the best choice for fuel economy.

“But if you plan to use a 6x4 tractor to pull 100t on a slippery road, then for sure you are going to request the maximum torque, and the fuel consumption of a 13-litre engine will be less compared to a 11-litre engine. With the 13-litre you have more torque, and for high gross combination weights it is interesting.

“The 13-litre 460hp engine definitely covers range of needs of the customer. The 400hp engine is for very specific demands — some of which are highly situation dependent.

“It is a question of how you use the engine — what exactly is your power request?”

The most important Renault Trucks factory is an assembly plant located in Bourg-en-Bresse, 70km north-northeast of Lyon. Spread across a 120ha site, the facility has a workforce of 1,500 people, 250 of them employed on a temporary as per the varying production demands.

On any given day, the plant can produce up to 125 trucks over the course of a single shift across two parallel assembly lines. Each line is 600m long and it takes a truck approximately four hours to go from a bare chassis at one end to a completed vehicle at the other.

Each vehicle then undergoes a further 1.5 hours of testing, which alongside administrative tasks, results in a total production timeframe of six hours to take each truck from parts to a final product ready for delivery to the customer.

The assembly lines uses a system of automatic guided vehicles and overhead cranes to move truck frames along the assembly lines as parts are brought in from adjacent loading bays and delivered from the integrated 9,000m2 parts warehouse located in the same space and under the same roof.

The factory can produce 1,000 different variants of Renault’s current range of trucks, and was until recently producing a legacy line of Kerax trucks on a tertiary assembly. This line will soon be dedicated to an order of 1,600 8X8 vehicles for the Canadian military.

On the main lines, Renault interchanges the assembly of two- and three-axled tractor heads and three- or four-axled rigid body models to maintain an averaged five-minute interval, or tag time, between each assembly stage along the production process.

As is standard, the vehicles produced at the factory are equipped with Euro VI engines and aluminium fuel tanks, air tanks and wheels; for the Middle East, it is typically Euro III and these parts are requested in steel.

While the factory predates Renault Trucks’ incorporation into the Volvo Group, the facility now operates according to the principles of the Volvo Production System, which was established group-wide in 2008.

The facility has since emerged as one of the Volvo Group’s best performing, and routinely produces 85% of its output without any errors being flagged. Most errors that do crop up involve not Renault but third-party components, such as the fifth wheels couplings, and are resolved without trouble.

Vehicle production at the Bourg-en-Bresse site dates back to 1964, when the a factory was set up to produce a range of off-road trucks, articulated haulers and rigid dump trucks.

Today, the factory modifies its production to accommodate changes in the type or volume of Renault Trucks’ orders every six months. A lead time of two months is required to increase the size of its workforce, and three-months is required to familiarise the workforce in case of changes, such as the introduction a model.

In 2015, the factory produced 25,000 vehicles, which is a considerable step down from the 45,000 trucks it produced in 2008 across two shifts, but also a confident step back up from the 14,000-unit low in 2009.

From the time a client places an order, Renault ensures its trucks are delivered in nine weeks (and is targeting eight weeks), while rigid body trucks are delivered in 10 weeks.

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