Tuesday 27 April 2021

Preparing for the electrical interlocking.

 Preparing for the installation of the electrical interlocking.

27th April 2021.

The project is progressing in several areas at the moment. The two location cases that are to be installed are currently off site at Strathspey S&T’s HQ. Unfortunately I don’t have any pictures for you but I can inform you that the locs have been cleaned down and repainted. The equipment that was in them has been removed. Installation of the track circuit and points detection equipment that is required is currently been installed and the location cases will arrive in a plug and play form. Only the external wiring will need to be connected up once on site. On-site various parts are still being removed, replaced and installed. See the pictures below.

The relay cabinet has seen some attention with it being cleaned down to start with. Some parts that are not required have been removed. The cabinet has had a good clean out, wash and polish. As you can see in this picture, the before and after is quite a improvement. The doors for the cabinet are also down south at S&T HQ. They will be coming north with the location cases. The relays that are required have been looked out of our store and placed in the cabinet. Two polarised relays for the points detection and three others for the track repeat relays and the route release from Boat Of Garten South signal box.

The cable termination board that was in the relay cabinet was life expired so a new one needed to be made up. Again this was done as a homework project off site, thankfully got the measurements correct. On this board there will be the B12 and N12 for the relay control circuits and lever locks. Below that will be the two 19 core cables going to the location cases and 4 wires to the South signal box. This runs to the south box over our telegraph pole route between the two signal boxes, which extends as far as Aviemore.

Once the board was installed into the relay cabinet the two 19 cores cables were terminated this is how it was looking. Still lots to do with the internal wiring yet.

The catch handle has been fitted onto number 3 lever, the yard points FPL. This acts as a switch to energise the release circuit of its own lever lock. If the track circuit is not clear then the points can not be moved.

The catch handles for the signals over the points has been installed too. These ones are behind the frame as a electrical release is only required to pull the levers, not to return them to danger. 

Down stairs. The two transformers for the 110v external and the 24v signal lighting circuit have been boxed, fitted and are ready for use. The current B12 supply has been moved from it’s original position and is now on the new S&T power distribution board. Just require the E&P department to supply us with 3 spurs form the 240v consumer unit to power up.

The p-way has received the step plate IRJ’s that were required to complete the track work for the track circuits. All have now been fitted and are ready for the track circuits to be energised. Once we have received the location cases from S&T HQ!

With us having some much needed better weather, the black paint at the bottom of the signal posts has been applied. Visually, definitely an improvement.

Thursday 1 April 2021

Mechanical Interlocking Completed!


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.