How the Type I Elastic Clip Fastening System Works
The Type I elastic clip fastening system uses a shoulder design on the sleeper and is intended for 50 kg/m and 60 kg/m steel rails. It relies on omega-shaped elastic clips, often called omega fasteners, to press the rail foot onto the sleeper pad through a constant elastic force. Gauge covers are built into the assembly for track adjustment, and the system also provides height adjustment, so the same fastening arrangement can hold the rail in the correct position through the range of adjustment needed on site.
Component Structure and Rail Matching
Two clip types are used inside the system. The longer Type A rail clip serves both 50 kg/m and 60 kg/m rails, while the Type B rail clip is used in defined positions where the gauge baffle arrangement requires it. The baffle layout differs between the two rail sections, as the table shows.
| Rail section | Gauge baffle arrangement | Clip used |
|---|---|---|
| 50 kg/m rail | Baffles in middle type and joint type, at 14 pairs and 20 pairs respectively | The 14th gauge baffle is mounted on a Type B clip; all remaining baffles are installed on Type A elastic bars |
| 60 kg/m rail | One baffle type, divided into 6 and 10 pieces | Used only with Type B elastic clips |
The gauge baffle has two duties: it adjusts the gauge of the track, and it transfers horizontal thrust out of the rail. Because the baffle bears against the rail foot, the parts around it must be strong enough to carry that thrust without movement, which is why the clip type and the baffle position are fixed together in the design.
Clip Material and Spring Behaviour
The omega-shaped elastic clip is made from 60Si2Mn or 55Si2Mn hot-rolled spring steel of 13 mm diameter, grades covered by the GB/T 1222 spring steel standard. Hot-rolled spring steel in this range gives the combination the fastening needs: high elastic limit so that the clip can be deflected on installation and still return a stable clamping force, and enough fatigue resistance to survive millions of load cycles without losing that force. Diameter is the main control on clamping force, which is why the 13 mm section is specified rather than a thinner bar. During installation the clip is driven into position over the rail foot and the shoulder; the stored elastic energy of the omega shape provides the toe load that holds the rail down, and the same shape allows the clip to be removed and re-installed with hand tools.
Gauge Adjustment and Insulation
A rail nylon insulator supports the baffle and rests on the shoulder of the sleeper. The insulator has two duties that must both be met. It has to be strong enough to bear and transmit the horizontal forces coming through the baffle, and it has to provide enough insulation performance to prevent leakage in track circuits. Because the two inclined planes of the rail insulator are made in interchangeable thicknesses, gauge distance can be adjusted by fitting the appropriate insulator rather than by moving the sleeper or re-drilling any part. Height adjustment works in the same way, so a track that has settled can be brought back to level with the same fastening components.
Frequently Asked Questions
Q: Which rails does the Type I elastic clip system suit?
The system is designed for 50 kg/m and 60 kg/m steel rails and uses a sleeper shoulder design with omega-shaped elastic clips.
Q: What is the difference between the Type A and Type B rail clips?
The Type A clip is longer and serves both 50 kg/m and 60 kg/m rails, while the Type B clip is used at the positions where the gauge baffle is mounted, including the 14th baffle on 50 kg/m rail and the baffles on 60 kg/m rail.
Q: How many gauge baffles are used?
On 50 kg/m rail the baffles are divided into middle type and joint type at 14 pairs and 20 pairs; on 60 kg/m rail a single baffle type is used, divided into 6 and 10 pieces.
Q: What material is the omega clip made from?
60Si2Mn or 55Si2Mn hot-rolled spring steel of 13 mm diameter, grades specified by GB/T 1222, chosen for elastic limit and fatigue resistance.
Q: What does the gauge baffle do?
It adjusts the gauge of the track and transfers horizontal thrust from the rail foot, working with the clip that holds it in position.
Q: Why is a nylon insulator fitted under the baffle?
The insulator supports the baffle on the sleeper shoulder, carries the horizontal forces passing through it, and insulates the rails so that track circuits do not leak.
Q: How is gauge adjusted without moving the sleeper?
The two inclined planes of the rail insulator are made in interchangeable thicknesses, so gauge distance is set by choosing the insulator thickness, with height adjustment available in the same assembly.