Fittings of Steel Trough Sleepers
The fittings required for metal sleepers are different form those used for wooden sleepers. Loose jaws, keys, and rubber pads are used to fix rails to steel sleepers.
Loose jaws
Loose jaws (Fig. 10.11) and keys are used for holding the rail and the steel trough sleeper together. The older type of trough sleepers were easily damaged, cracked, or deformed due to the provision of pressed-up lugs. There problems have been solved by introducing spring steel loose jaws, which have been standardized on Indian Railways. These jaws can be easily replaced whenever necessary. They are manufactured using spring steel and the weight of 100 loose jaws is approximately 28.8 kg.
Two-way keys
Two-way keys (Fig. 10.12) are universally used for fixing trough sleepers, pot sleepers, and CST-9 sleepers. A two-way taper is provided at both ends of a twoway key and as such the key can be driven in either direction. These keys are manufactured using a special rolled section. The length of the keys for BG is about 190 mm with a taper of 1 in 32. A gauge variation of ±3 mm can be adjusted by altering the extent to which these keys are driven in.
The various methods of driving keys for different types of sleepers are listed in Table 10.5.
Rubber-coated and epoxy-coated fish plates
Some time back, rubber-coated fish plates were used at insulated joints on Indian Railways on a trial basis. The results indicated that these fish plates get damaged early in service, thereby limiting their life. Therefore, epoxy-coated fish plates are now being tried.
Mota Singh Liner
The holes in trough sleepers get elongated during service due to the wear and tear caused on account of moving loads. The Mota Singh liner (Fig. 10.13) is liner used effectively with loose jaws for overcoming the problem of elongated holes.
Fig. 10.12 Two-way keys
|
Type of sleeper and track |
Direction of driving |
|
Single line |
|
|
CST-9 sleeper (fish-plated, SWR, |
All the keys in one sleeper should be driven in |
|
and LWR tracks) |
the same direction. Keys on alternate sleepers should be driven in the reverse direction. |
|
Steel trough sleeper (all types of |
The outer keys on the sleeper should be driven in |
|
tracks) |
one direction and the inner keys in alternate sleepers should be driven in the opposite direction. |
|
Wooden sleeper |
|
|
> Anticreep bearing plates with |
All keys should be driven in the same direction. |
|
single-key configuration |
Keys should be driven in reverse direction in alternate sleepers. |
|
> Anticreep bearing plates with |
The outer keys on a sleeper should be in one |
|
double-key configuration |
direction and the inner keys in the opposite direction. The pattern of driving keys should be reversed in alternate sleepers. |
|
Double line CST-sleeper |
|
|
> Fish-plated and SWR track |
The direction of 75% of the keys should be in the direction of the traffic and that of 25% should be in the opposite direction. |
|
> LWR track in non-breathing |
75% of the keys should be driven in the direction |
|
length |
of traffic and 25% should be driven in the opposite direction. |
|
> LWR track in breathing length |
All keys should be driven in one direction on one sleeper and in the opposite direction on the next sleeper. The same scheme should be followed up in subsequent sleepers. |
|
ST sleeper |
|
|
> Fish-plated and SWR track |
75% of the sleepers should have all four keys driven in the direction of the traffic and 25% of the sleepers should have the keys driven in the direction opposite to that of the traffic. |
|
> LWR track in non-breathing |
75% of the sleepers should have all four keys |
|
length |
driven in the direction of traffic and 25% of the sleepers should have all the keys driven in the direction opposite to that of the traffic. |
|
> LWR track in breathing length |
Two inner keys should be driven in one direction and the other keys in the other direction. Also, the direction of the keys should be reversed in alternate sleepers so as to prevent relative movement between the rail and the sleeper. |
Fig. 10.13 Mota Singh liner (all dimensions are in millimetres)
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