Largest Mechanical Signalbox

[GWRPannier1501]

Whats the largest mechanical signalbox you can think of, both in the UK and abroad.
What about the largest in use on a “heritage” railway (not counting Exeter West etc).
I’ll start with Reading Mainline West with 210 levers

 

[John Webb]

Are we talking about boxes still in use in the UK, or any signal box that has existed on the UK network?

If the former, then Shrewsbury Seven Bridge is not only the largest mechanical box in the UK but in Europe as well.

If the latter, then York Locomotive Yard box at 295 levers was, I think, the UK's largest-ever mechanical box.

 

[MadMac]

Whats the largest mechanical signalbox you can think of, both in the UK and abroad.
What about the largest in use on a “heritage” railway (not counting Exeter West etc).
I’ll start with Reading Mainline West with 210 levers

Spencer Street No. 1 was slightly larger than Severn Bridge Junction until its closure in 2008. In terms of still-operational mechanical boxes, I think you’d be hard pushed to beat Severn Bridge Junction nowadays.

 

[Harpo]

Whats the largest mechanical signalbox…………… in use on a “heritage” railway

I did wonder about Kidderminster and found the SVR wiki showing its 62 levers.

Kidderminster Station signal box (1987 onwards) - SVR Wiki

www.svrwiki.com

 

[John Webb]

.....What about the largest in use on a “heritage” railway (not counting Exeter West etc)....

Princes Risborough North - largest GWR box left in the UK? North end of the box retains the frame that was last used to control the station area and the branch junctions. That is being restored as a demonstration box for the public to see.
The frame in the south end of the box, disused for many years, is being restored to control the Chinor and Princes Risborough Railway's signalling on the platform they restored a few years ago. See https://www.risboroughbox.org.uk/ (Although I couldn't see a lever count on their site.)

 

[ac6000cw]

I did wonder about Kidderminster and found the SVR wiki showing its 62 levers.

Not quite as large, but on the GCR, Swithland Sidings box is a 55 lever ex-GWR frame (the top half of the building was originally ex-GWR Aylesbury South box, but I don't know if the frame is from there).

Loughborough Central box is an original GCR box (called Loughborough North originally), with a 50-lever McKenzie and Holland frame.

Bit of a tangent, but anyone know what was the largest miniature power lever frame used in the UK i.e. using miniaturised mechanical interlocking? There were some quite large ones installed at major stations, replacing several large traditional mechanical boxes.

 

[bleeder4]

Are we talking about boxes still in use in the UK, or any signal box that has existed on the UK network?

If the former, then Shrewsbury Seven Bridge is not only the largest mechanical box in the UK but in Europe as well.

If the latter, then York Locomotive Yard box at 295 levers was, I think, the UK's largest-ever mechanical box.

A recent booklet from a railtour I went on says that, now that the one in Australia has closed, the box at Shrewsbury is now the largest operational mechanical signal box in the world (not just Europe - it specifically says the world).

 

[John Webb]

......Bit of a tangent, but anyone know what was the largest miniature power lever frame used in the UK i.e. using miniaturised mechanical interlocking? There were some quite large ones installed at major stations, replacing several large traditional mechanical boxes.

This is complex, as only very early power schemes had full mechanical interlocking controlling lever movements. Even in the early 1900s some of the mechanical locking was being replaced by electric locks.
The Westinghouse L frames did away with mechanical interlocking, using electric locking on the lever slide bars. One of the first installations was at North Kent East Junction in 1929 as part of the massive 1920s resignalling of the lines to London Bridge etc.

The GWR installed three new miniature lever power boxes around Paddington around 1932/3 - two had mechanical locking and only one had electric interlocking. My source does not cite the number of levers the mechanical boxes had.

 

[ac6000cw]

This is complex, as only very early power schemes had full mechanical interlocking controlling lever movements. Even in the early 1900s some of the mechanical locking was being replaced by electric locks.
The Westinghouse L frames did away with mechanical interlocking, using electric locking on the lever slide bars. One of the first installations was at North Kent East Junction in 1929 as part of the massive 1920s resignalling of the lines to London Bridge etc.

The GWR installed three new miniature lever power boxes around Paddington around 1932/3 - two had mechanical locking and only one had electric interlocking. My source does not cite the number of levers the mechanical boxes had.

Thanks for the info John - I'd forgotten that this was really the era of hybrid mechanical and electric interlocking.

Having done a bit more web searching, according to this webpage, in 1928 a new London Bridge signalbox was equipped with 311-lever Westinghouse type-K mechanically interlocked power frame (weighing 23 tons!), I guess possibly the largest of that type installed in the UK before the electrically-locked type-L frames became available in 1929 (London Waterloo had a 300+ lever type-L frame from 1936, albeit divided into three sections).

(I find the evolution of early power-signaling equipment quite interesting - doubtless partly because I'm an electronics engineer, and also watching a video many years ago about operating a 1932-vintage US General Railway Signal Co. 'pistol grip' 144-lever power frame in the - long gone - Union Avenue interlocking tower in Chicago. A photo of it taken in 1963 by Marty Bernard).

 

[david l]

I did wonder about Kidderminster and found the SVR wiki showing its 62 levers.

Kidderminster Station signal box (1987 onwards) - SVR Wiki

www.svrwiki.com

Bury South on the East Lancashire Railway is a 68 lever frame.

 

[matchmaker]

Not quite as large, but on the GCR, Swithland Sidings box is a 55 lever ex-GWR frame (the top half of the building was originally ex-GWR Aylesbury South box, but I don't know if the frame is from there).

Loughborough Central box is an original GCR box (called Loughborough North originally), with a 50-lever McKenzie and Holland frame.

Bit of a tangent, but anyone know what was the largest miniature power lever frame used in the UK i.e. using miniaturised mechanical interlocking? There were some quite large ones installed at major stations, replacing several large traditional mechanical boxes.

The 1908 installation at Glasgow Central -374 levers - was the largest ever British electro-pneumatic frame. The largest mechanical frame in Scotland is Stirling Middle at 96 levers, although all the points are now power operated and the signals colour light.


Photo from Network Rail.

 

[ac6000cw]

The 1908 installation at Glasgow Central -374 levers - was the largest ever British electro-pneumatic frame.

Thanks for the info .

Equipment supplied by 'McKenzie, Holland and Westinghouse Power Signal Company', which after a few more mergers and takeovers became 'Westinghouse Brake and Signal Company' in 1935 - and is part of Siemens today.

 

[bluegoblin7]

Bit of a tangent, but anyone know what was the largest miniature power lever frame used in the UK i.e. using miniaturised mechanical interlocking? There were some quite large ones installed at major stations, replacing several large traditional mechanical boxes.

This is complex, as only very early power schemes had full mechanical interlocking controlling lever movements. Even in the early 1900s some of the mechanical locking was being replaced by electric locks.
The Westinghouse L frames did away with mechanical interlocking, using electric locking on the lever slide bars. One of the first installations was at North Kent East Junction in 1929 as part of the massive 1920s resignalling of the lines to London Bridge etc.

The GWR installed three new miniature lever power boxes around Paddington around 1932/3 - two had mechanical locking and only one had electric interlocking. My source does not cite the number of levers the mechanical boxes had.

Of course, London Underground, later Transport, continued to specify mechanically-locked miniature lever frames - both the manual 'N' style and the remote-worked 'V' style - until the early 1990s.

Acton Town was the largest frame ever installed on LU, with 191 levers to the N-style. It lasted approximately 30 years from 24 January 1932 to 11 July 1965.

Harrow-on-the-Hill is the largest operational frame on LU with 95 levers - a modified 'push-pull' N-style allowing each lever to, in theory, have two routes available.

For the sake of interest, the largest V-style frame on LU was Wembley Park with 60 levers - opened 29 October 1984 and closed at end of traffic on Friday just gone - early hours of 30 May 2025.