Engineering a simpler approach to screwed fastening systems
Developed as the latest evolution of Pandrol’s proven SD Fastening System, SD/QuickFit introduces switch-on/switch-off functionality to support simpler, more efficient track installation and maintenance.
Railway installation and maintenance teams are under increasing pressure to work safely and efficiently within limited access to the track. Labour constraints and the physical demands of track work are also creating a need for simpler, more mechanised ways of working.
Traditional screwed fastening operations can involve significant manual handling. Clips may need to be individually positioned, released and secured, often requiring more than one engineer and repeated work at track level.
SD/QuickFit has been developed in response to these practical challenges. By adding switch-on/switch-off functionality to Pandrol’s proven SD Fastening System, QuickFit reduces manual fastening operations and supports one-person and mechanised working where applicable.
See the engineering behind SD/QuickFit
Developed around the practical demands of track installation and maintenance, SD/QuickFit introduces switch-on/switch-off functionality to the proven SD Fastening System.
Created in partnership with UNESCO, this film explores the engineering journey behind the innovation and how its components work together to support simpler installation and maintenance.
Bringing mechanisation to screwed fastenings
Pandrol has long supported mechanised installation through its threadless fastening systems. The challenge for its engineering teams was to bring similar operational benefits to a screwed fastening without moving away from the established principles of the SD system.
With QuickFit, tightening the coach screw moves the clip from its maintenance position into its in-service position on the rail. Loosening the screw reverses the movement, returning the clip to its parked position.
The result is a guided, retained clip that can be switched on or off through the normal screw action. This reduces the need for engineers to reposition the fastening manually.
Making more of the insulator
A key part of the innovation lies in the plastic insulator.
Its primary purpose remains electrical insulation, helping to prevent electrical leakage into the sleeper. For SD/QuickFit, its geometry also plays an active role in controlling the clip’s movement.
As the coach screw is tightened, the clip travels along a built-in ramp in the insulator, guiding it towards the rail and into its in-service position. When the screw is loosened, the clip moves back to the maintenance position.
This controlled movement reduces manual repositioning while allowing the fastening to remain pre-assembled. Sleepers can therefore be delivered to site with the clip held securely away from the rail seat and with no loose fastening components.
Once the rail is in place, the fastening can be switched into service through the coach screw action.
From engineering concept to working system
Although the final movement appears simple, achieving it required extensive research, testing and collaboration between Pandrol’s technical teams.
The development process moved from digital simulation to physical prototypes, with multiple design iterations used to refine the relationship between the clip, coach screw and insulator. Each stage gave the team a clearer understanding of how the components needed to interact to produce controlled and repeatable movement.
This process was not simply about moving a clip. The engineering challenge was to add new functionality while retaining the fundamental performance and reliability of the SD Fastening System.
QuickFit is therefore not a standalone product or a completely new fastening system. It is the latest evolution of SD, developed around the real installation and maintenance challenges experienced by track teams.
Simpler installation and maintenance
Because the clip moves through the coach screw action, QuickFit reduces the manual operations associated with preparing, positioning and releasing screwed fastenings.
During installation, the retained parked position supports the supply of pre-assembled sleepers. Once the rail has been threaded into position, tightening the coach screw moves the clip into service.
During maintenance, loosening the coach screw returns the clip to its maintenance position. This can be particularly valuable for activities that require fastenings to be released across a section of track, including rail replacement and rail stress management.
For track teams, SD/QuickFit offers several practical benefits:
- Simpler installation and maintenance operations
- Less manual clipping, declipping and repositioning
- Reduced time spent handling fastenings at track level
- Support for one-person working where applicable
- Greater compatibility with mechanised working methods
- More efficient use of available labour and track access
Built on the established strengths of SD
SD/QuickFit builds on the proven SD Fastening System, which has been designed to deliver robust performance while improving the efficiency of track installation and maintenance.
The compact SD clip uses less steel than comparable legacy screwed fastening designs. Its lighter weight can make components easier to handle while also supporting more efficient material use and transportation.
Clip geometry also plays an important role in long-term performance. The SD clip has a higher natural frequency than comparable legacy tension clamps, reducing its sensitivity to vibrations generated by passing trains.
Certain excitation frequencies can create increased vibration and damaging amplitudes within a fastening clip, contributing to fatigue over time. By moving the clip’s natural frequency away from these critical ranges, the SD design improves robustness and helps reduce the risk of vibration-related fatigue.
The natural frequency of the SD clip is above 1,000 Hz, compared with approximately 550 Hz for the comparable legacy SKL clip. This significant increase supports greater durability under dynamic track loading.
The wider SD design also provides:
- High electrical resistance to support signal integrity
- Increased contact between the clip and rail
- Geometry designed to help prevent ballast entrapment
- A sealed screw and insulator interface that helps keep dust and debris out of the sleeper or slab track
- Tighten-to-contact assembly for controlled fastening installation
- A compact design suitable for a wide range of rail applications
These are established strengths of the SD Fastening System. QuickFit adds a new operational capability, making it easier to move the clip between its parked and in-service positions.
Supporting conversion from SKL to SD
QuickFit is currently available as an option for SD-RE, which is designed for compatible SKL-shaped rail seats.
For infrastructure owners considering a move from SKL to SD, this retrofit capability can allow compatible existing sleepers to be retained. This provides a more practical route to adopting the SD Fastening System without automatically requiring the wider sleeper installation to be replaced.
Customers can therefore benefit from the lighter SD clip, its higher natural frequency and the wider performance advantages of the SD design, alongside the installation and maintenance functionality introduced by QuickFit.
Practical innovation built around track teams
SD/QuickFit demonstrates how established fastening technology can continue to evolve around changing operational requirements.
The innovation begins with a practical challenge: reducing the amount of manual work involved in screwed fastening installation and maintenance. The solution is an engineered interaction between the coach screw, clip and insulator that turns a familiar fastening action into a more efficient process.
By combining switch-on/switch-off functionality with the established strengths of the SD Fastening System, QuickFit supports simpler operations, more efficient use of labour and greater mechanisation where applicable.
It is practical engineering innovation, developed around the way track teams work.
Wherever your track goes, we go with it.
Discover SD/QuickFit
Explore the SD Fastening System and discover how QuickFit could support simpler, more efficient installation and maintenance operations.
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