Headcode discs folded upwards

[BusDriverMan]

Can anyone explain the significance of folding a BR diesel headcode disc upwards, exposing the marker light?

 

As seen on the first image here:

 

https://www.2d53.co.uk/Headcode/headcodeC.htm

 

Quote

When open, the disc showed a white face, with a light shining through a hole in the lower half of the disc. Closed, by folding the top half down, the white face and light were obscured. The disc could also be folded up, obscuring the face but leaving the light visible. The lights were independently switched.

 

Why would you have the marker light switched on but not also show the disc?

[Dagworth]

The discs folded upwards to allow the lamp housing to be opened to change a dead lamp.

 

Andi

[BusDriverMan]

oh gosh, as simple as that?! Cheers 😄

[Steven B]

Nothing stopping you having folded up and folded down on the same end at the same time:

(David Christie on Flickr)

 

Manchester Piccadilly by Paul Townsend, on Flickr

 

 

Steven B

[Jeremy Cumberland]

The class 24 picture comes as something of a surprise, since the year is 1972 when disc headcodes were still in use. I wonder whether the discs folded up were meant to be open, which would indicate a class 4 train, which I think was how parcels trains were then designated (express parcels were class 3). ECS (as per the caption) would be bottom left on its own.

[11613]

Was the intention also to allow the entire light (usually_ but not always-bigger than the glass in the disc) to be larger and brighter at night?

D1 has an ex works photo as-new with them all closed up not down?

[russ p]

4 hours ago, Jeremy Cumberland said:

The class 24 picture comes as something of a surprise, since the year is 1972 when disc headcodes were still in use. I wonder whether the discs folded up were meant to be open, which would indicate a class 4 train, which I think was how parcels trains were then designated (express parcels were class 3). ECS (as per the caption) would be bottom left on its own.

 

It maybe that the loco has just gone onto the train and the discs have yet to be set. Not sure if drivers side tail lamp is illuminated 

[Wickham Green too]

Also begs the question of how on earth you['re supposed to reach the top one to fold it one way or t'other !!?!

[russ p]

11 minutes ago, Wickham Green too said:

Also begs the question of how on earth you['re supposed to reach the top one to fold it one way or t'other !!?!

 

That's what the ladder section is for next to coupling. The handrails also assisted when doing it from platform height

[Izzy]

This aspect of the discs being folded upwards was something I noticed quite some years back when making my class 15. After a lot of searching and asking questions back then I found no one really knew why, but that this practice was especially widespread on the exGE lines. One thought was that the white dots showing was used for routes but this has never been confirmed one way or the other. The dots showing is particularly noticable on early diesels in the plain green livery and less so once yellow panels and ends arrived.

 

Bob

[russ p]

3 minutes ago, Izzy said:

This aspect of the discs being folded upwards was something I noticed quite some years back when making my class 15. After a lot of searching and asking questions back then I found no one really knew why, but that this practice was especially widespread on the exGE lines. One thought was that the white dots showing was used for routes but this has never been confirmed one way or the other. The dots showing is particularly noticable on early diesels in the plain green livery and less so once yellow panels and ends arrived.

 

Bob

 

In the days before headlights folding them upwards meant you could have a bit more light on the job when away from signal boxes 

I can personally vouch for this as did it with 20s on Boulby trains in the 80s to get a better look at features in grinkle tunnel!

[dave75]

2 hours ago, russ p said:

 

It maybe that the loco has just gone onto the train and the discs have yet to be set. Not sure if drivers side tail lamp is illuminated 

One suspects there maybe a EE type 3 on the other end of that train awaiting release.

[bécasse]

On 23/07/2024 at 20:58, Izzy said:

This aspect of the discs being folded upwards was something I noticed quite some years back when making my class 15. After a lot of searching and asking questions back then I found no one really knew why, but that this practice was especially widespread on the exGE lines. One thought was that the white dots showing was used for routes but this has never been confirmed one way or the other. The dots showing is particularly noticable on early diesels in the plain green livery and less so once yellow panels and ends arrived.

Didn't the GE still use purple as well as white discs at that period for certain routes - could the folded up disc be meant to replicate a purple disc?

[Izzy]

58 minutes ago, bécasse said:

Didn't the GE still use purple as well as white discs at that period for certain routes - could the folded up disc be meant to replicate a purple disc?

 

Oh, that's something I've not heard about before. Thanks. Would explain things, especially as the photos of the time do show the same combination of disc positions on various locos, up/down/open.

 

Bob

[Jeremy Cumberland]

On 23/07/2024 at 18:13, russ p said:

It maybe that the loco has just gone onto the train and the discs have yet to be set. Not sure if drivers side tail lamp is illuminated 

Entirely possible. I am pretty sure neither tail lamp is illuminated, but this doesn't tell us much.

 

The class 24 picture is clearly in daylight, and being taken in August 1972, is from 1950 Rule Book era. This did not require headlamps to be lit during daylight, except during fog or falling snow, and "where otherwise specified" (Rule 119). Rule 124 then says

Quote

When it is not necessary for the electric lamps to be illuminated, the appropriate head lamp code indication must be given by the display of discs placed on the brackets provided.

This suggests that discs were mandatory during daylight, and lit lamps on their own (which, as I recall, were difficult to see) were not sufficient during the day (but they were at night). However, it also seems clear that there was a lot of local variation. For example, I don't think discs were used on the Woodhead electrics beyond the 1950s, and instead electric lamps were used at all times of day.

 

At least one photo I've seen, of class 20 D8077 at Parkhead depot in 1962 with all discs closed upwards, suggest that this might have been the usual way at one time and in some places of covering the discs, the revealed unlit lamp not signifiying anything. At night, lit lamps on their own would suffice, and the disc position (open or closed upwards) would not matter, at least so far as rules 119 and 124 were concerned.

 

The new Rule Book came out in October 1972. This required headcodes and light engine tail lamps to be illuminated all the time (but separate tail lamps, where used, need only be lit after dark, during fog or falling snow and when passing through tunnels, as per the 1950 Rule Book). The 1972 Rule Book doesn't really say anything about showing discs. There is probably a presumption that discs would be displayed on locomotives that had them.

[Izzy]

I have wondered if it was just a way of saving time/effort when a different headcode was needed at night to during the day and the lights could be lit without the hassle of altering the discs in the dark.

 

Bob

[bécasse]

12 hours ago, Izzy said:

 

Oh, that's something I've not heard about before. Thanks.

This Cecil J. Allen photograph shows the purple discs well. The photo dates from early LNER days but I can assure you that they remained in use a long way into the BR era.