Abergynolwyn Blockpost
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- Опубліковано 6 жов 2024
- Tallyllyn Railway - Abergynolwyn Blockpost (Signal box)
Abergynolwyn station was originally a simple wooden affair with a loop and was the furthest point for public passenger train operation, the line beyond here to Nant Gwernol being for goods trains only. A siding was added between 1888 and 1901, re-sited during or after the First World War when a platform for loading vehicles in the siding was also provided.
Over the winter 1975/76 in connection with the extension of the passenger railway to Nant Gwernol a 650 yard platform was created, and the station area signalled using miniature colour light signals controlled, along with the point work, from a substantial signal box which was officially brought into use on May 22nd 1976. A siding was provided and further extended in 1977. The frame is an REC/LMR ex Bold Colliery Sidings with tappet locking.
Nice to see Jon. I volunteered on the TR 25 years ago as a student. Jon and Liz are lovely people. Would love to go back if life and time allowed.
I don't know much about signalling, can someone explain why the frame needs to be locked with an annett key? Where else does the annett key go?
In a safe when not in use so the Controller knows that the station is locked
Another way to look at it is on most railways when signal boxes are not in use the lever frames are locked by the key which is then carried with the train so no one can operate anything without the train being there and the driver aware of it as they have to hand over the key to the operator and with there being only the one key (or the one key released at a time in the case of token working) there can also only be one train in any section preventing collisions with other trains
The principal is called inter-locking. You are only looking at the top half of the signal box. Beneath the lever frame is a very simple mechanical computer that prevents you from signalling a train into an already occupied section of railway by pulling the wrong lever.
Effectively, you would need A and B to happen before you can get C to happen.
Think of it as a modern car that will not allow you to start your engine until it detects that your seatbelt is buckled up and you are covering the brake pedal with your foot.
In this case, putting the key into the frame tells the mechanical computer that the signaller is in possession of the key.
If the key had been handed to a train driver, the signaller would NOT be able to pull certain levers until the key has been placed into another lever frame by the signaller in the next signal box, telling the mechanic computer that the section between the two signal boxes is once again clear of trains.
@@bl7355 Your final paragraph describes the function of the token machines, not the frame key.
I can only think of one reason for having one key unlock the second key which then unlocks the frame, unless that second key is also a token in its own right.
It could be that the first key authorises the blockman to open the box and clear the signals, then with the signals in a particular configuration he can take the second key out to use as a token to give the driver permission to procede to Nant Gwernol. That driver can thus have confidence that no other train can be sent into the final section until he returns it to the blockman. That second key might also unlock the frame at Nant Gwernol for the run-round.
This feature would have value becasue it enables that final section to be worked without the Blockpost at Nant Gwernol being open. Quite how the interlocking works I'm not sure, because that yellow token machine is evidently capable of releasing a token which permits a train to be worked to Nant Gwenol. It must not do so if the second key is not in the frame, which is simple enough. However, if a train has gone to NG with an electric token and handed that token in at the far end, can the frame token be used to work a round trip? I think you could do it, but given that you evidently have a blockman at the other end, why would you?