It’s fair to call a truck’s braking system an engineering masterpiece, but only few of us ever pause to appreciate the immense amount of development work going into it behind the scenes. The braking system is not only essential from a performance point of view, but also from a maintenance and payload perspective.
The trailer braking system is especially underrated, even though it’s equally important for road safety and load capacity as every kilogram saved on the brake is payload won. Finding the right balance between functionality and cost efficiency – i.e. reducing unwanted bulk – has therefore become the supreme discipline of modern engineering.
Munich-based family business Knorr-Bremse is one company that is renowned for going the R&D extra mile. At the 2012 IAA, the company caught the industry’s attention with the launch of a new generation TEBS module offering added value through the integration of Electronic Levelling Control (ELC) and a second, trailer-based CAN bus. In 2014, it will use the industry gathering to unveil a new trailer disc brake called ST 7-430. By the time we will be able to experience the new unit live in Germany, it will have gone through a straining three-year development and testing process. An early prototype of the 430 model was already on display back in 2012, but it took until now for it to get clearance for serial production.
“It’s long and complex process to develop a new brake,” says Rudolf Ober – head of the Trailer Product Line at Knorr-Bremse’s ‘Centre of Competence’, specialising on Air Disc Brake technology – revealing the initial target was to develop the lightest two-piston disc brake for 22.5-inch wheels on the market. “Usually there are 10 to 15 people involved during the design process, but the closer we get to serial production, the more staff we need. Think purchasing, logistics and final assembly – it’s a real team effort.”
The result of that effort is a versatile disc brake for Europe’s standard nine-tonne axle that can save the trailer OEM up to eight kilograms per axle compared to its predecessor – mostly due to a new, optimised calliper casting.
To slim down the calliper, Knorr’s engineering team used the latest in modern computer modelling. “The real challenge is finding the best balance between braking torque and weight saving – how much weight can you shed before you lose too much torque?” says Ober, pointing out the team at Knorr-Bremse followed a precise development plan covering the entire process from market analysis through to final field test.
“The trick is not to lose focus on what you really want to achieve,” Ober adds. “We always had to remind ourselves that we were looking at a classic nine-tonne application, just so we wouldn’t over or under-engineer the brake. It’s a question of experience – a computer can only think in the direction you guide it to.”
Once the right design was decided upon, it had to undergo a stringent testing regime. “Safe to say we’ve built a few hundred prototypes by now,” says Ober. “The brake was first tested in our main R&D centre in Munich before it went on our test rig in Aldersbach, right next to our main production plant. Then we presented our test data to the relevant authorities to get the green light for a real-life fleet trial.”
Out in the field, the brake had to undergo a second, equally strenuous test cycle, covering some 600,000km since the start of 2014. “At the end of the day, nothing can really compare to a fleet trial because nothing is more real than reality,” says Ober. “We can calculate everything, analyse and re-assess it as much as we want – but it is indispensable to ensure that rig test and calculation are in correlation with real life. Nothing will give us the same insight as actual driver and fleet owner feedback.”
According to Franz-Josef Birkeneder, head of Knorr’s Aldersbach facility, it’s that wealth of industry feedback that eventually got the ST7-430 to market.
“We want to learn as much as possible from the drivers we interview. How does the vehicle handle in the cold or in the event of an emergency brake? Does the driver trust it? How fast should the brake lining wear to work in with the maintenance regime?”
While the ST7-430 had to prove itself in the field, Knorr-Bremse’s logistics team began streamlining the sourcing and production process to ensure the company would be prepared for volume production come autumn.
The manufacturing plant in Aldersbach, for example, underwent a substantial upgrade that saw forklifts banned from the assembly area. Instead, Knorr-Bremse introduced a system of automatic carriages that will provide parts on a just-in-time basis right where they’re needed – much like in the automotive industry.
By the time we will be able to see the brake in Hanover, the plant actually produces up to 8,000 air disc brake units a day, with added capacity available. Many a large-scale European fleet will have trialled the product already, and leading OEMs will have had a chance to give it a go. What’s more, the ST7-430 will already be examined by Knorr-Bremse’s local staff in the US, South America and Asia. While the lion share of R&D work will remain in Germany, Knorr-Bremse is well aware that localisation is crucial for long-term success. “It’s a question of producing a well engineered volume product that still gives our regional teams enough room for differentiation,” says Birkeneder. “We always try to share our knowledge globally and I like to think every new development will inspire our international team as well as our clientele to go above and beyond.”
For now, however, all eyes are on the upcoming IAA in Germany, when the ST7-430 will officially be presented to a global audience. Behind the scenes, it will already be in serial production by that time: A leading Knorr-Bremse customer already started producing trailers fitted with the brand new ST 7-430 in August.