Midland Railway back blinder

[paratom]

I have posted this topic on RMWEB but thought I would post here as well to see if the replies are similar to the ones I had on RMWEB

I am creating some 3D printed parts for a MR lower quadrant signal as some of these parts are no longer available from Wizard Models. I believe the back blinder had the job of not allowing any light from the signal not to be projected backwards and to cause confusion for drivers who were not familiar with the route. I can't see how light could have been seen from the back of the signal lamp as the lens was in the front but maybe I am missing something here. Did this also apply to ground signals as well ? I assume the circled in red on the photo is an arm repeater contact box. As an experiment I'm going to try and light the signal lamp that will be 3D printed out in clear resin with a recess for a .5mm LED feeding the wires up through the inside of the signal post and through the side into the signal lamp. I've often thought it would be nice to be able operate a layout in a night time setting as it can be quite atmospheric if you use the right light. I would be most grateful for any replies.

 

[mickoo]

The blinder it's self is the oval disc to the rear base of the lamp housing. There is a small hole in the lamp housing rear (visible above the blinder disc) that let white light through to the rear, when the signal arm dropped the blinder lifted and obscured the hole.

My understanding is that back blinders were a secondary indication if the engine had to pass the signal for whatever reason, or as a double check once passed at speed. Rather than getting out of the cab and standing on the ground waiting to see if it cleared, they could look from the cab at the small white light to the rear, when it went out they could proceed, mind that doesn't seem very fail safe if the lantern failed. The small whiter light was different from the front side red/amber or green so the driver knew he was looking a the backside and oncoming trains in the reverse direction would not be confused when they saw the white light.

I'm not really up to speed with signaling aspects, but that's how I understand back blinders to operate, also interesting to see the feedback switch as well, never seen that before.

 

[LarryG]

I remember part of sitting the eyesight medical at Manchester Hunts Bank for a footplate job was knowing the difference between a white light and an amber light....... It was a pin prick of light down a long corridor.

The blinder covered the rear facing white light when the signal was in the 'off' position, or maybe 'on'...I have forgotten! It could be a simple arc-shaped casting on an arm.

 

[KitPW]

I'm not so familiar with MR signals but a typical GWR signal lamp had a large glass on the front to light the signal glass (red/green depending on whether on or off) and, where the back of the signal was visible from the signal box, the lamp had a small back light (clear glass to show white). The backlight is obscured by the "blinder" which co-acts with the signal arm - when the signal is on, the backlight can be seen from the box; when the signal is off, the backlight is obscured so the signalman gets a positive indication that the signal has answered the lever. If the signal fails and returns to "on", the co-acting blinder also moved to show the backlight, indicating to the box that the signal had failed safe. Where the back of the signal could not be seen from the signal box, there was no backlight in the signal lamp and no co-acting blinder on the signal arm: most often, this situation occurs where the signal box can see the front of the signal and can therefore see whether red or green is showing - the backlight would be redundant.

 

[simond]

And of course, if the Bobby couldn’t see the back of the lamp, either the stick was pulled, or the light wasn’t lit…