Testing of Fastenings

Both elastic and rigid fastenings are tested in the laboratory for their suitability in the field. The vibrogir and pulsator are used to test these fastenings.

The vibrogir is used in laboratories for checking the effectiveness of various fastenings. With the help of this equipment it is possible to produce high-frequency vibrations in the laboratory, very similar to those produced on a real track. By applying a frequency of 50 Hz, the rail and sleeper are made to vibrate at a rate of 700-800 Hz with an acceleration of 70 g and an amplitude of the order of 0.1

0.3 mm. One hour of working of a vibrogir corresponds to almost 4.05 GMT of traffic and 300 hours of its working creates the same effect on a fastening as 20 years of service under normal track conditions.

The pulsator not only simulates vibrations just like the vibrogir, but also applies vertical and lateral pressure on the rail fastening at a frequency of 250-500 cycles/ minute.

Tests carried out with the help of vibrogirs and pulsators clearly establish the superiority of elastic fastenings over rigid fastenings.

Summary

Fittings hold rails in position and thus help provide a smooth ride. Fish plates and bolts are used to join the rails in series while different types of fastenings are used to fix the rails to the sleepers. The traditional rigid types of fastenings are not able to meet the challenges posed by heavy dynamic forces and become loose under high-frequency vibrations. Elastic fastenings are found to be very suitable for highspeed tracks. New design of elastic fastenings are being developed to overcome as many drawbacks as possible.

Review Questions

1. With the help of a suitable sketch explain the assembly of the Pandrol clip in elastic fastenings for concrete sleepers.

2. Illustrate with sketches the various fastenings used to fasten rails to sleepers. Discuss their merits and demerits.

3. Explain briefly the functions of the following in a railway track.

(a) Hook bolt

(b) Fish plate

(c) Tie bar

(d) Cotters

(e) Screw spike

4. What do you understand by anchors and what are their functions in railways? What are the advantages and disadvantages of bearing plates?

5. Name the different types of track fittings. Name the different types of spikes generally used and draw a sketch of any one of them.

6. Draw the details of a rail held to a wooden sleeper by the following.

(a) Dog spikes on an MS bearing plate

(b) Anticreep keys on a CI bearing plate

(c) Pandrol clip on a CI bearing plate

What are the advantages and disadvantages of these fastenings?

7. What is the difference between an ordinary fish plate and a combination fish plate?

8. What are the requirements of an elastic fastening? Briefly describe the various elastic fastenings being used on Indian Railways.

9. Describe the various type of fittings used for wooden sleepers and steel trough sleepers.

10. What are the requirements of an elastic fastening? Draw a sketch of an elastic rail clip and explain how it is fixed to a concrete sleeper.

11. Describe the functions of a rubber pad. Draw a dimensioned sketch of the same.

12. Differentiate between the following.

(a) Fat bearing plate and canted bearing plate

(b) Dog spike and screw spike

(c) Ordinary fish plate and combination fish plate

(d) Cotters and liners

(e) Elastic rail clip and spring steel clip

(f) Glass-filled nylon liners and Mota Singh liners

13. Write short notes on the following.

(a) Loose jaw

(b) HM fastening

(c) Pilfer-proof elastic fastening

(d) Vibrogir and pulsator

11

Other Fittings and Fastenings | RAILWAY ENGINEERING - Contents | Creep of Rails