Electrical Interlocking On Mechanical Lever Frame

[Rick_Skateboard]

Hello All.

 

I've been designing a lever frame and I've (mostly) got my head around how mechanical interlocking works, largely thanks to the excellent IRSE books.  Something I am vaguely aware of, but can’t find much information on, is electrical locking added to the original signalling layout.  By this I mean lever boxes that have been added to or modernised at some point in their history.  I’ve been in plenty of boxes that have been changed by track circuiting, point motors replacing rodding, colour lights replacing semaphores, panels added controlling IBH or TCB sections, or a combination of those things.  One thing that I’ve not been able to find any information on is the additional electrical interlocking and specifically how the hardware interacts with the mechanical frame.  I assume it’s something along the lines of a solenoid driving a peg into the tappet bar to prevent it moving?  Or is that way off?  Any info, pictures or diagrams would be great.

 

Cheers

 

Rick

[phil-b259]

On 03/01/2021 at 02:03, Rick_Skateboard said:

Hello All.

 

I've been designing a lever frame and I've (mostly) got my head around how mechanical interlocking works, largely thanks to the excellent IRSE books.  Something I am vaguely aware of, but can’t find much information on, is electrical locking added to the original signalling layout.  By this I mean lever boxes that have been added to or modernised at some point in their history.  I’ve been in plenty of boxes that have been changed by track circuiting, point motors replacing rodding, colour lights replacing semaphores, panels added controlling IBH or TCB sections, or a combination of those things.  One thing that I’ve not been able to find any information on is the additional electrical interlocking and specifically how the hardware interacts with the mechanical frame.  I assume it’s something along the lines of a solenoid driving a peg into the tappet bar to prevent it moving?  Or is that way off?  Any info, pictures or diagrams would be great.

 

Cheers

 

Rick

 

Electric locking is completely separate to the mechanical locking!
 

You do not interfere directly with the mechanical locking when adding what amounts to electrical inputs to the signalling controls.

 

Basically you fit what amount to big electromagnetic locks to the levers themselves - and unless the electric lock is energised (Remember it’s got to be failsafe) then you won’t be able to pull the lever.

 

Those lever locks are in turn wired into what amounts to a relay interlocking which can in theory replace the mechanical one (though in most cases the mechanical locking will be retained as well). That relay interlocking will deal with things like track circuits, point indications, etc without interfering with the mechanical locking - why should it when locking the levers will do the job just as well.

 

Thus in a typical ‘modernised’ box, both will work together - for example track circuits being clear will release the electric locks fitted to point levers allowing the points to be moved. But unless the point lever is in the correct position then the signal lever will be mechanically locked. Finally even if the point lever is in the correct position we won’t release the electric lock on the signal lever unless the points have gained detection. Moving the signal lever then mechanically locks the point lever.
 

Furthermore let’s say track circuits don’t detect a train approaching, then we use the electric lock to stop the signal lever from being replaced fully back into the frame unless a 2 minute timer has finished timing - thus preventing the mechanical locking releasing the points lever and potentially allowing points to be moved right in front of an approaching train if the signal is thrown back and the train cannot stop.

 

As for outputs - well the electric locks also come with circuit controllers built in and that means they can detect where about the lever physically is. As the lever is moved from one position to another various electrical contacts make an break. Depending on what we want the lever to do these contacts may authorise a signal to change to a proceed aspect*, command the relays to start a point machine moving to or alternatively stop the lever mid way to enforce the 2 minute time off if the train has not been proved to have passed the signal. 

 

* yes a mechanical lever frame can thus easily work a 4 aspect signal as it’s the electrical interlocking that uses track circuits and the status of Other signals to determine whether a single yellow, double yellow or green is shown.

 

I am on nights this weekend and may be able to post some pictures of the electric locks fitted at a Reigate box later.

 

In the meantime there are a couple of photos in the links on this page you may find useful.

https://www.railforums.co.uk/threads/lever-operated-signal-boxes-controlling-colour-signals.157149/

Edited January 4, 2021 by phil-b259

[LNERGE]

A short movie of a type of electric lock that i didn't use..

 

 

[LNERGE]

IRSE Green book No3 covers mechanical and electrical interlocking.

[Edwin_m]

This RAIB Safety Digest covers an accident where the electric locking was partly responsible.  The points were worked electrically from levers, and detection was displayed on an indicator and checked in the electric locking for the signal to clear.  Lack of detection didn't physically lock any levers, unlike a mechanical setup where the facing point lock lever wouldn't go fully over unless the point was correctly set. 

 

The signaller, somewhat flustered, failed to check the detector lights behind the levers and concluded from the positions of the levers that everything was correctly set but that there was some fault with the signal.  When they instructed the train to proceed it was derailed on a point that had not gone fully over.  

[LNERGE]

Three of my own boxes have point levers with indication locking. You cannot complete the stroke of the lever until point detection is made. I much prefer this especially in heritage railway boxes. It draws attention to what hasn’t worked. I am however guilty of building two boxes without it on heritage lines and two with. 

[The Stationmaster]

These are examples from a heritage railway but everything is very much in standard WR form as it uses a W Reading locking frame.

 

The blue boxes on the bottom of the tappets contains electric locks or circuit controllers (the latter also have a locking function because as well as being able to provide locks at each end of the lever/tappet stroke they also apply a 'check lock' in the manner described above by 'LNERGE'  in that the lever is held part way through its stroke until an electrically worked item has completed it move to the required position).    On this articular frame levr No. 24 has a circuit controller although you can't make it out on the photo unfortunately.  Levers 8 and 14 - which you can make out - work a facing Point Lock (FPL) so are electrically locked by track circuits hence their electric locks.   So in this instance the electric locks are carrying out functions which are not convered by the mechanical locking.  But this sort of locks and circuit controllers could be sued to completely replace the mechanical ina. signal boc because they physically prevent the levers from being moved

 

 

 

And this is the actual 'electric interlocking' which controls - in association with various inputs (e.g from a track circuit) and switches - those lever locks.  Using nice solid old-fashioned shelf type relays of various sorts.  This type of relay will work reliably for many years provided they are propery looked after and regularly checked.

 

 

 

[Rick_Skateboard]

Thanks for all the replies. 

 

So it seems (as is usually the case) that different companies used different arrangements for the electrical locking.  It would be great if you could post some photos of the electric locks and how they interact with the lever, Phil, thanks.

 

14 hours ago, phil-b259 said:

 l am on nights this weekend and may be able to post some pictures of the electric locks fitted at a Reigate box later.

 

Another thing I've never quite got my head around is the way the lever movement in an arc is transferred to the tappet bars moving in a straight line up and down/forwards and backwards.  I guess this too is different on different frames.  Most of the nicely made scale lever frames you see have the tappets laid out flat behind the frame, which is probably the easiest way to do it on a model.  I think I have seen that arrangement in use on some real lever frames, but having it all down under the frame seems to be more common. 

 

What I'm hoping to build is something based on a Highland Mainline station like Dalwhinnie, where the line goes from single to double.  AB to Tokenless.

 

Cheers

 

Rick

 

[phil-b259]

Hope this may be of use.

 

 

 

Edited January 4, 2021 by phil-b259

[phil-b259]

Not the best video unfortunately

 

https://drive.google.com/file/d/1fU4aBjtPf0pFB-JeH_Oon0uQWb3xkb20/view?usp=drivesdk

Edited January 4, 2021 by phil-b259

[The Stationmaster]

14 hours ago, Rick_Skateboard said:

Thanks for all the replies. 

 

So it seems (as is usually the case) that different companies used different arrangements for the electrical locking.  It would be great if you could post some photos of the electric locks and how they interact with the lever, Phil, thanks.

 

 

Another thing I've never quite got my head around is the way the lever movement in an arc is transferred to the tappet bars moving in a straight line up and down/forwards and backwards.  I guess this too is different on different frames.  Most of the nicely made scale lever frames you see have the tappets laid out flat behind the frame, which is probably the easiest way to do it on a model.  I think I have seen that arrangement in use on some real lever frames, but having it all down under the frame seems to be more common. 

 

What I'm hoping to build is something based on a Highland Mainline station like Dalwhinnie, where the line goes from single to double.  AB to Tokenless.

 

Cheers

 

Rick

 

The link shows fairly clearly how the lever motion is transferred to the tappet in the   locking on a WR 3 bar VT lever frame (similar on a 5 bar frame)

 

https://www.s-r-s.org.uk/SignallingPapers/02/3barV5.html

 

And these photos might help starting with a box with the locking at a very early stage of assembly before moving to a working one.

 

 

 

 

 

 

[TheSignalEngineer]

2 hours ago, The Stationmaster said:

The link shows fairly clearly how the lever motion is transferred to the tappet in the   locking on a WR 3 bar VT lever frame (similar on a 5 bar frame)

 

https://www.s-r-s.org.uk/SignallingPapers/02/3barV5.html

 

This link has a good drawing showing the typical method of the locking directly activated by lever movement,

Another common method is locking activated by the catch handle driving a rocker or cam which checks that the lever is able to move by driving the tappet to the mid position. This will lock conflicting moves before the lever can be moved then on completion of the movement release of the catch handle drives the tappet to the full normal or reverse position to line up the release notches.

[Rick_Skateboard]

Thanks again for the replies, the wealth of knowledge on the forum is great.   The photos and video of the locks and rotating contacts are brilliant Phil, and Mike's pictures of the locking frame under construction are a great help for what I'm hoping to replicate in the future.  

 

I did a bit of research myself, armed with the knowledge from reading the replies on this thread, and came across this: https://www.festipedia.org.uk/wiki/S%26T_reference_folder_1969 which I found very helpful.  I feel like I've closed a gap in my understanding, so thanks again. 

 

I'd like to make a miniature lever frame that is as close to scale model and operates as closely to the real thing as is realistically possible.  I was planning to use the MSE frame as a base, but I wonder if just the cast levers might be better, built into a scratchbuilt frame, or possibly the whole thing scratchbuilt?  Inevitably some things will be impossible to scale down; I think an overscale amount of movement will be necessary to make mechanical interlocking work properly for example.  That also makes me wonder if locking driven by the catch handle will be possible on a small scale due to it being such a small movement?  Has anyone tried or managed to make a small scale electric lock?  Or is there a suitable off the shelf item that could be used or adapted?  

 

I'll have to do more research on the arrangement in the Highland Mainline boxes, I think a lot of them were modified by the LMS or BR, so probably don't have much of their original Highland Railway equimpent left.  

 

Cheers

 

Rick

[Dagworth]

Does anyone make a model lever frame with electrical locking of the lever positions and with switches activated by the levers?

 

Andi

[Miserable]

1 hour ago, Dagworth said:

Does anyone make a model lever frame with electrical locking of the lever positions and with switches activated by the levers?

 

Andi

There's this. I think they have a UK agent or something, https://modratec.com/