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Signal Box Types

Midland signal boxes were very standardised

The Midland Railway was always fiercely independent and signalling was no exception. They were one of only four pre-grouping railway companies to set up their own signal works. This was at Derby and by about 1870 the company was producing their own signal boxes instead of relying on either specialist signalling contractors or local builders.

Midland signal boxes were very standardised as they were prefabricated in sections (or “flakes”) at Derby then transported to site on a special train. New signal boxes could be very quickly erected and in a special exercise in 1920 they carried out the task in a mere 85 minutes! Because of their prefabricated nature, MR boxes lend themselves to being neatly labelled – with only a few exceptions. The basic design of the boxes changed very little during the time of the Midland Railway and were perpetuated by the LMS. Not only did the Midland Division of the latter company erect Midland pattern boxes into the 1920s, the influence of the Midland Railway can be easily seen in the later LMS designs.

Type 1 Signal Box

The earliest of the standard Midland boxes, not surprisingly, are categorised as “Type 1”. These are easily distinguished by the front windows of the operating floor being only two panes deep (Original Design style). Mainly due to a conscious effort by the Midland Railway to replace their older, smaller signal boxes in the 1880s, very few Type 1s survived into the later years of the 20th Century and none exist today.

Type 2 Signal Box

The first major design change took place in 1884. Type 2 boxes differed from their predecessors in that the front windows were deeper with three panes (Design A style). The end windows remained only two panes deep. In 1892 there were subtle changes which resulted in the Type 2b; a narrow post which separated two window frames on the door end was dispensed with and the width of vertical boarding changed from 6″ to 3 1/2″ – although as repairs to earlier boxes employed the new style this change is somewhat blurred. There was a short period of overlap with Type 2a boxes being built until 1893. The Type 2b remained standard until the Type 3 was developed but examples continued to be erected until 1901.

Type 3 Signal Box

The next significant change in design came with the arrival of the Type 3 making its debut in 1898. The two pane end windows were also deepened to three panes to improve visibility and match the front (Design A style). Another variation which appeared with the Type 3 was a new pattern of window with only one horizontal glazing bar at two thirds height. These “Design B” windows were a distinguishing feature of Type 3b boxes. The Type 3b actually pre-dates the 3a by two years.

In 1906 the Type 3 gave way to the final variant. This time it was the horizontal boarding below operating floor level which underwent the change.

Type 4 Signal Box

The Type 4 has ‘lapped boarding’ instead of ‘weather boarding’. Whereas in weatherboarding the horizontal timbers are simply overlaid over one another, lapped boarding has a tongue and groove appearance with a distinctive wide area between the timbers.

A further fundamental development at this time was the use of concrete bases. Midland Railway signal boxes seem to have always been prone to rotting of their lower timbers which is hardly surprising given they were set into the ground. Concrete bases were intended to overcome this. As a consequence of the need for the site to be prepared prior to the erection of a Type 4 box, the Signal Department were now dependant on the Engineer to lay the concrete base prior to work commencing.

Initial examples were Type 4a and 4b with Design A and Design B windows respectively. In 1908 a third window variant appeared – Design C without a vertical glazing bar.

During World War One, labour and materials were scarce and expensive which lead to the Type 4d in 1917. This design dispensed with decorative features like the finials on the ends of the roof and, for some reason, reverted to Design A windows.

From 1920 onwards

Even after the demise of the Midland Railway in 1923, its successor the LMS continued to refine the Midland Railway signal box design. In 1926 Midland Railway pattern boxes with Design C windows appeared and have received the Type 4e designation.

From 1930 up to and including the Second World War, the LMS built its own design of signal box. Latterly designated Type 11, theses boxes were an amalgam of Midland and LNWR – substituting the latter’s pitched roof with gables for the former’s hipped roof but retaining the distinctive Midland Railway windows.

However, like Midland Railway signal boxes, there are variations in window designs. A fourth variant arrived on the scene in 1933 when the distinctive triangular pieces in the upper corners of the windows were dispensed with.

Whereas Midland boxes were almost exclusively constructed of timber, LMS Type 11 boxes were built with brick as far as the operating floor or all timber.

How old are the various types?

  • Type 1 signal boxes – 1870-1884
  • Type 2a signal boxes – 1884-1893
  • Type 2b signal boxes – 1892-1901
  • Type 3a signal boxes – 1900-1906
  • Type 3b signal boxes – 1898-1906
  • Type 4a signal boxes – 1906-1917
  • Type 4b signal boxes –
  • Type 4c signal boxes – 1908-1915
  • Type 4d signal boxes – 1917-1928
  • Type 4e signal boxes – 1926-1930

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