Safety critical rail applications for which AFS, and in particular its C50L® and BobTail® lockbolts and lockstuds, have provided major advantages over conventional threaded fasteners are to be found in both the switch and crossing zones of the permanent way. The key benefits are immediately recognisable to any engineer familiar with AFS’ Huck® fasteners.
The speed and ease of installation of Huck® products increases productivity and reduces labour costs. Consistent, high clamp force and mechanical strength ensures maximum joint integrity, extending its life and that of associated components. Inspection is a simple visual process to confirm correct installation. In contrast to conventional threaded nuts and bolts, Huck fasteners will not loosen, even under the constant and often extreme vibration experienced in permanent way applications.
The benefits to the rail network are faster patrolling and reduced spanner work for maintenance teams. Permanently tight fasteners also mean reductions in vertical impact loading, subjecting point operating mechanisms to less vibration. This extends operational life and reduces the risk of failure of other components.
More recently, the permanence of AFS’ Huck fasteners has contributed substantially to the UK rail systems fight against a menace that costs an estimated GB£16 million annually and impacts the convenience and safety of rail users and staff. The theft of copper cable is a really serious problem. Searching for a more robust replacement for easily removable standard nuts and bolts used at spider junction boxes, Network Rail engineers carried out a series of rigorous trials in Newcastle upon Tyne, UK, leading to the issue of a Certificate of Acceptance authorising the use of Huck fasteners and associated tooling in this application.
Conventional threaded fasteners were replaced with Huck C50LR-BR20-12G and C6LB-R12-12G fasteners, attaching cable to both track and junction box. John Rickers, AFS Telford systems development manager, is confident the solution provides a superior upgrade and a significant deterrent to thieves. “Stolen cable is not only expensive to replace, but incurs significant labour costs as well as inconveniences rail customers.
When a cable is stolen, the area has to be located, isolated, re-jointed and tested, often requiring specialist teams to carry out the repair. Conventional nuts and bolts, unlike Huck fasteners, can be removed relatively quickly. The longer a thief spends attempting to remove fasteners, the higher the probability he will be caught in the act.”
Ironically, ‘permanence’ has in some applications been a limiting factor for Huck products. Many safety critical rail applications require regular disassembly for maintenance and adjustment, and Huck fasteners’ ‘fit and forget’ strength clearly does not help here. Recent developments at Alcoa Fastening Systems’ headquarters in Waco, Texas, USA, though, present the rail industry with a new Huck product, which successfully combines the security and vibration resistance of a Huckbolt® lockbolt with both rapid and easy assembly and disassembly with standard hand tools.
At first sight, Huck 360® lockbolt (pictured above) looks very much like a conventional threaded bolt and nut combination. In fact, there are very significant technical and even more significant performance differences. For the Alcoa Fastening Systems’ development team, the goal was simple – to design a high strength bolting system that resists vibration loosening no matter how extreme the environment, delivers superior fatigue strength, and holds tight under high cyclic fatigue loads. And just to add to the challenge, it must also be capable of rapid installation and removal using conventional tooling.
Jonathan Craven, AFS Telford operations director, explains how Alcoa Fastening Systems’ ingrained instinct for effective innovation has delivered a new product with unique capabilities.
“Huck 360 lockbolt has a shallow proprietary thread form that concentrates 27% less axial stress in the root than conventional bolt threads. This stress concentration is the primary contributing factor leading to stress corrosion cracking and fatigue failures. Huck 360 lockbolt’s thread flanks are effectively locked preventing the nut from moving relative to the bolt – in contrast to a conventional threaded bolt where thread flanks are able to slide when subjected to transverse vibration, resulting in the nut moving relative to the bolt.”
“Additionally, when the Huck 360 lockbolt nut is tightened, it plastically deforms around the thread. The resultant intimate contact is circumferential, helping to generate vibration resistance previously only achievable by using a lockbolt.”
Huck 360 lockbolt nuts can be simply hand spun onto the bolt unlike conventional lock nuts where prevailing torque requires almost immediate use of a tool. This significantly speeds up assembly times, with final setting carried out with a conventional torque wrench. An assembly speed comparison video at www.huck360.com provides an excellent visual demonstration.
“We recognise that the rail track sector is understandably extremely cautious in assessing new product developments for safety critical applications,” says Jonathan Craven. “We are confident that, as engineers are able to assess first hand the capabilities of the Huck 360 lockbolt, it will gain approval and come to make a very substantial contribution to rail safety, efficiency, and economics.”
Having spent a decade in the fastener industry experiencing every facet – from steel mills, fastener manufacturers, wholesalers, distributors, as well as machinery builders and plating + coating companies, Claire has developed an in-depth knowledge of all things fasteners.
Alongside visiting numerous companies, exhibitions and conferences around the world, Claire has also interviewed high profile figures – focusing on key topics impacting the sector and making sure readers stay up to date with the latest developments within the industry.