Diesel Headcode Discs - Black Edge Surrounds

[Holmesfeldian]

 

Not the best photographic example but the clearest one I could find on google (1971, Crewe Works - OPC postcard) and it demonstrates one of the subtle locomotive detail nuances that has long fascinated me.

Can any of the experts please offer suggestions as to why certain locos for a limited period had the thin black surrounds around Headcode discs.

I was once told that it was introduced to help identification of oncoming trains in the half yellow warning panel period but as can be seen it continued into the BR blue era to a limited degree

When was this spec in force and which works / depots applied it please?

 

[Spannerman]

Great photo.

This is only speculation but if the yellow paint end faded due to the quite harsh chemicals put into the automatic washing plants of the time, a black surround would give a clearer outline to the disc.

Obviously on what looks like an ex works paint job fading isn't yet an issue.

 

Nik

[Holmesfeldian]

Here's a green HYP Class 24 with similar accoutrements.

Picture by Dave Marks on Flickr : Return race spl 1967 

The loco for the return Chester race Special has been replaced by a Type 2 (class 24) diesel here seen approaching Bromborough. The cheery Chester driver acknowledges my camera.
https://www.flickr.com/photos/90752501@N07/8385004306/

 

Edited September 23, 2018 by Holmesfeldian