Mechanical interlocking completed
1st April 2021
It has been a very interesting part of the overall project this one. I now have a big appreciation for what the locking fitters of old and current do. First of all the planning of the work, then doing the work. There is very little room for error when creating the locking bars as well as the cutting of the notches in the tappets. Then trying to fit the locking bars in the channels, some of the locking bars designed to fit under the tappets and the others on top of the tappets. It has been a very challenging job indeed.
This is how we were looking at the end of the weeks work, the stop board removed from the end of the up platform and the new DN starter on the up platform brought into use as it is solely controlled by the mechanical interlocking. 4 7 16 still require the electrical interlocking to be completed before being brought in to full use.
This is a look at one of the newly made locking bars. This one is for insuring that 2 points are set for the main line and that 3 FPL is reverse. Only then can 16 signal be pulled or 12 the King lever for locking out the signal box. This is for single line working from Aviemore to Broomhill.
This is one of the existing locking bars that had to be modified. Before it was 8 signal locked 19 points. Now that it has been changed it is 8 signal locks 17 signal and 19 points. There is a second bar that locks 8 signal to 18 FPL.
This is the before and after of cutting the notch on 2’s tappet. The lock piece is used to give the size of the notch that needs to be cut. This notch is for the locking bar between 2 and 7 signal insuring that 2 points are normal before 7 signal can be pulled.
Once all the new and modified locking bars and the tappets with there notches cut in the correct positions. This is how both the top and bottom locking boxes were looking. In my opinion it is one of the most important parts when it comes to signalling. With out it, it would be almost impossible to run the trains safely.
This next little video is NOT the full locking test but it gives you a feel to how much goes into this. A full independent interlocking test was done after this video was shot, by a college who was not involved in the work. The mechanical interlocking was found to be working correctly and fit for purpose.
This is a very big step forwards. Next we will be moving onto the electrical interlocking. This is required to supplement the mechanical interlocking to insure that safety is maintained.