First presented at the IAA Commercial Vehicles in 2016, awarded the Trailer Innovation prize in 2017, and in series production since 2018: The SAF INTRA CD TRAK hydraulically driven axle from the SAF-HOLLAND Group brings the drive to the trailer – a profitable assistant, particularly for walking floors and tippers on construction sites or landfills. Meanwhile, the “additional drive at the touch of a button” is technically sophisticated and has been tried and tested in numerous applications – time for some expert tips and tricks for practical application.
When is it worthwhile for a contractor to equip his trailers with the SAF INTRA CD TRAK hydraulically driven axle for work on construction sites and landfills instead of, for example, relying on an all-wheel drive tractor unit?
“First off, to make one thing quite clear: We will not be able to replace a classic 4×4 tractor unit with the SAF INTRA CD TRAK,” begins Elmar Weber, product management SAF-HOLLAND. “However, we still see good opportunities for our driven trailer axle, because all-wheel-drive tractor units have become fewer and fewer in recent years. In contrast to the pulling additional drives in the front axle, the SAF INTRA CD TRAK also implements traction more efficiently as a pushing axle. Articulated lorries benefit from these physical advantages, particularly when starting off.”
At first glance, some fleets may argue that SAF HOLLAND is offering a technology that is hard distinguish from their existing axle. While accepting that the operating principle of the hydraulic motor in the hub unit is the same (“and the manufacturer is also the same in many cases”), there are some key, fundamental differences.
“Before I address the control system, I would like to point out two differences in the motor: The engine displacement volume on the SAF INTRA CD TRAK is greater – this increases the torque, but the possible speed is lower overall at a maximum of 13 km/h,” says Weber. “In practice, this means that when tipping or pushing off, the load is shifted to the rear and the permitted axle loads can be exceeded. The torque that the engine then brings to our driven axle is higher than would be the case on a front axle of a truck. Our intention when developing this was to establish ‘power vs. speed’ or better: ‘to push powerfully from standstill rather than drive fast’”
Another difference is the fact that the wheel bearings in the SAF INTRA CD TRAK axle are grease-lubricated, as is standard on European trailer axles, he adds.
“Our goal was to be able to use the same components for wear parts such as brake pads or brake discs as for the other axles from the SAF-HOLLAND Group. This makes it easier for workshops to store and work on the trailer. Semi-trailers with the SAF INTRA CD TRAK axle will remain in the fleet for a long time, so that after more than six years the wheel bearings will certainly need replacing.
“Even though wheel bearings are not classic wear parts, we can still rely on standard parts from SAF-HOLLAND. With regard to the control system of the SAF INTRA CD TRAK axle: It functions completely differently from a tractor unit with a hydraulically driven front axle. It is essential that the control system in the trailer is matched to the hydraulic equipment of the tractor unit.”
Weber explains that in order for the interaction with the additional drive in the trailer to function smoothly, the tractor unit needs a hydraulic system with forward and reverse, a switch plus status and fault light and must be able to transmit CAN bus signals to the trailer.
“Furthermore, it should have a two-stage tipping valve, which is additionally controlled by a solenoid valve. For the details, there are specific technical documents and calculation tools,” he expands. “However, it is even more important to contact our fleet consultants if you are interested, and to discuss the combination of SAF INTRA CD TRAK and tractor unit on an individual basis. We would be happy to help you select the right equipment for your tractor unit. Scania Germany, for example, is currently preparing a complete equipment package for our driven axle.”
According to the product expert, most users are opting for the rear axle, but a third of customers are also choosing the middle axle.
He adds: “The advantage of the middle axle may be that the third axle might no longer have ground pressure if it is frequently necessary to tip at soft breaklines. Ultimately, it’s the haulier himself who decides on the positioning of the driven axle when configuring the vehicle.”
Drivers can activate the SAF INTRA CD TRAK additional drive at the touch of a button but Weber advises the point its pressed can vary from truck to truck, driver to driver.
“This depends on the power take-off of the motor vehicle, when and how it can be switched on,” he says. “The advantage of a power take-off on the engine side is that it can be engaged while the vehicle is in motion. Personally, that’s the solution I prefer.”
The SAF INTRA CD TRAK system can be switched on up to a speed of 8 km/h. Once the maximum possible 13 km/h is reached, it switches off, but remains active. Weber explains that, if the speed of the vehicle falls below 11 km/h, it switches on again. If the articulated lorry is travelling at more than 50 km/h, the system is completely deactivated: “Prerequisites for this are an automatic transmission and a power take-off on the engine side.”
Weber says that the SAF INTRA CD TRAK really demonstrate its strengths on loose soil: “The trailer has a speed surplus to the tractor in order to be able to push at all. On dry, non-slip ground, wear is generated, therefore the drive should only be used on loose soil. The tread pattern should be adapted to the application; a coarse tread, for example, does not clog so quickly.”
Driver training is always appreciated when any new technology. While SAF HOLLAND can be easily contacted to pass on its expertise on the new driven axle, Weber doesn’t believe it is always necessary.
“We are happy to engage in dialogue with drivers, we do not offer special training. However, we observe that drivers who use the SAF INTRA CD TRAK adapt their driving style and driving strategy in the terrain over time,” he says, adding that the manufacturer can offer drivers and companies a range of support from technical literature through to a calculation app.
“But personal dialogue with our fleet managers is always the best place to start. Literature and contacts can be found on our website www.safholland.com,” he notes.
Finally, Weber is asked what are the effort and costs involved in retrofitting vehicles already in use with the additional drive?
“Retrofitting is technically feasible, but should also make economic sense. Investment in the driven axle pays off best if the system is already installed ex works and can be used longer than a comparable tractor unit,” he concludes.
