Application Technology

Nothing stands still in the transport sector and that is especially true for railway vehicle design. With over 200km of cables and wiring in an average high-speed train, fastening clips mounted on structural edges are giving engineers more freedom to route parallel cable runs.

With the amount of cable increasing dramatically, the real challenge is how to install cables quickly and easily and hold it securely in place at the lowest cost possible.

HellermannTyton began developing its EdgeClip range in the mid-1990s, primarily for the automotive industry – where considerations of weight and space are of utmost importance. The EdgeClips can guide cables and wires in any routing direction and can be pushed into place easily by hand, which saves time in comparison to riveting metal butts in rail vehicles with tools. The fasteners are also ideal for narrow spaces and applications where drilling holes or using adhesives is not practical. One enormous advantage is that they can be easily pre-assembled on the harness, which saves train manufacturers a lot of time during construction.

“Whereas cables and wires in earlier rail vehicles were mainly to distribute electrical power through the vehicles, today we see data and signal sent back and forth between cars and the locomotive – for passenger comfort but also for more intelligent and efficient operation of the train. At some point you face the question of how to route all this cable once it leaves the ducts and trays in the floor or ceiling – for example, around the doors,” highlights Paul Cocheril, EMEA railway market manager at HellermannTyton. “The traditional method is to use metal butts riveted into place, which is very labour intensive. The butts first have to be installed and often that makes it more difficult to maximise the efficiencies of pre-confection. Metal butts are also relatively heavy, so they add a lot of extra weight to the rail vehicle, without any particular additional structural benefit.”

Paul adds: “Early adopters in the industry are therefore moving away from this approach and are using EdgeClips instead, which are a more efficient solution. These use existing edges to anchor a cable harness firmly and securely – even where strong vibration is a constant factor.”

The EdgeClip was originally developed as a custom product to meet a specific challenge, but has become a standard product for HellermannTyton .

A more recent development of the EdgeClip is a version that routes two harnesses or cables in parallel, one on each side of a surface edge. “The advantages of parallel routing are very clear. Depending on the weight of a harness, let’s say that the harness or cable has to be fastened approximately every 30cm horizontally, or every 50cm vertically. We’re talking about a significant reduction in process costs and time – potentially up to two thirds – compared with the butt and tie method, to secure the same amount of harness or cable in parallel in a carriage,” underlines Paul.

The metal claws at the heart of the EdgeClip withstand vibration and support the weight. Pre-confected with the harness, all it takes is one simple process step – without the need for any tools – to secure parallel cable runs. 

“If you take into account the cost of metal butts and the time spent installing them, the EdgeClip is a highly efficient and economical option. Savings are significant and that can take some of the pressure off overall costs,” comments Paul.

Savings are not just during the initial manufacture of the railway vehicle. The average lifespan of a train is 40 years and as a rule, rail vehicles are modified and refurbished at least once during their lifetime, which includes cable assemblies – these are refurbished about every 20 years.

“What you save on cable assemblies and installation on your average train will be repeated later when the assemblies get their overhaul. This makes using EdgeClips, especially one capable of routing harnesses in parallel, even more attractive. Just imagine the huge increase in long-term cost and time spent on installation when metal butts are used,” adds Paul.

Material characteristics of the EdgeClip and ties make these highly suitable for use in the railway sector. The cable tie is made from heat stabilised polyamide 6.6 (PA66HS), the foot from UV-resistant polyamide 6.6 (PA66W), and the EdgeClip clamp from double tempered and coated steel. They also meet the EU RoHS directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, and meet DIN EN 45545-2 European norm for fire protection on railway vehicles and hazard level HL2 in requirement set R22, R23.

“EdgeClips have long been an unsung hero in many industrial applications and they’re also now on the way to being the product of choice for many applications in railway vehicles. Of course the advantages are multiplied when the same fixing point can be used to route parallel cables. EdgeClips may be hidden behind cladding in railway vehicles, but their cost saving potential is very visible on the bottom line,” concludes Paul.