Midland Railway back blinder.

[animotion]

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 would be most grateful if someone could clear this up for me.

 

 

[The Stationmaster]

The purpose of the back blinder was to allow the Signalman to observe at night the proper working of those of his signals which could only be seen from the rear.  The same applied to ground signals.

[ikcdab]

And just to expand on that.  You will see a tiny lens in the back of the lamp case.  If the signalman could see this light at night then he knew the signal was at danger.  When he lowers the arm, the blinder covers the rear lens and obscures the light for the signalman.  He therefore knows that the arm is then off.

At blue anchor on the WSR, the down starter is immediately outside of the box.  In that case, the signal had a blinder on the side of the lamp case, not the rear so that the signalman could see it.

Ian

[Dave John]

Look carefully at the signal lamp in that picture,  you can see a small lens on the rear of the lamp. That is to allow enough light  to be projected backwards for the blinder to act  as the Stationmaster describes. 

 

 

[Stephen Freeman]

Just to confuse matters still further, if the rear of the signal was not visible to the signalman then the back blinder wasn't always fitted! Probably depended on the Company policy. Indeed might not even have a had a rear light at all.

Edited December 3, 2022 by Stephen Freeman

[animotion]

Thanks for the feedback. I hadn’t noticed the small lens on the back of the signal lamp. On the information I have received  I assume that the back blinders were only fitted to signals where the rear of the signal was visible from the signal box.

[Michael Hodgson]

6 minutes ago, Stephen Freeman said:

Just to confuse matters still further, if the rear of the signal was not visible to the signalman then the back blinder wasn't always fitted! Probably depended on the Company policy. Indeed might not even have a had a rear light at all.

On some designs of signal the blinder was important as it prevented risk of the the arm falling off the post, being fitted on the opposite end of the spindle to the arm.  It could also contribute to the counterweight effect required to ensure the arm returns to danger if the wire should snap.   It was necessary for fail safe reasons that the blinder obscure the light when the signal was off rather than when it was on, as inability to see the lamp could also be used as a way of detecting a lamp having blown out in strong wind. 

 

Where the signal was not visible from the box, electrical contacts could be mechanically connected to the arm to indicate whether it was on/off/wrong, and a pyrometer in the lamp housing could be used to operate an electrical indicator in the box to warn the signalman that the lamp was unlit.  This explains the presence of electrical wiring attached to signals which are mechanically worked and oil-lit.

[Grovenor]

1 hour ago, Michael Hodgson said:

Where the signal was not visible from the box, electrical contacts could be mechanically connected to the arm to indicate whether it was on/off/wrong, and a pyrometer in the lamp housing could be used to operate an electrical indicator in the box to warn the signalman that the lamp was unlit.  This explains the presence of electrical wiring attached to signals which are mechanically worked and oil-lit.

Like the one in the picture, the arm repeater contact box can be seen on the other side of the post to the lamp.

[Stephen Freeman]

6 hours ago, Grovenor said:

Like the one in the picture, the arm repeater contact box can be seen on the other side of the post to the lamp.

I thought that was what it was.

[animotion]

On 03/12/2022 at 11:03, Grovenor said:

Like the one in the picture, the arm repeater contact box can be seen on the other side of the post to the lamp.

I assume it is the item circled in red on the photo. 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. 

[Stephen Freeman]

If you are using resin for the lamp don't forget to paint it silver first otherwise you will get light coming through where you don't want it.np

[Grovenor]

7 hours ago, animotion said:

I assume it is the item circled in red on the photo.

Yes, that is the arm repeater contact box. A pin on the back of the arm slides in the slotted lever to accomodate the different pivot centres of signal arm and contact box.

[Michael Hodgson]

What I like about that photo is the way the wiring is led below the platform so it doesn't interfere with the lampman's access, before being routed sharply back upwards to the telegraph pole.

[animotion]

Thanks for the replies. I wonder how much electricity those live wires carried? Does anyone know when the Midland Railway started using arm repeater contacts, not that I am thinking of adding them to the model in 4mm.

[5BarVT]

1 hour ago, animotion said:

I wonder how much electricity those live wires carried?

My guess is 1.5V dry cell one each for lamp repeat and arm repeat with Earth return.  Though later on, LMS used to put power down pole routes (red insulators on extended arms at the top).

Paul.

[Michael Hodgson]

1 hour ago, animotion said:

Thanks for the replies. I wonder how much electricity those live wires carried? Does anyone know when the Midland Railway started using arm repeater contacts, not that I am thinking of adding them to the model in 4mm.

Negligible on those.  Pretty well everything in a remote semaphore box used very little electricity - they often weren't on mains power, so there was a need for a fair bit of routine maintenance.  S&T didn't just fix faults, they would come and replace dry cells/recharge accumulators etc fairly regularly, and in many places a lampman also came once a week to clean, refill and trim oil lamps in signals and even the lamp above the booking desk.  Heating and cooking used the stove or even an open fire.  A lot more labour needed on the old railway, not forgetting the lengthman patrolling the section and hammering keys back into the chairs on bull head rail.  It's only in later days that signalmen gradually started getting such luxuries as electric lighting, electric heaters, Baby Bellings to cook their lunch and the like.

[animotion]

12 hours ago, Michael Hodgson said:

Negligible on those.  Pretty well everything in a remote semaphore box used very little electricity - they often weren't on mains power, so there was a need for a fair bit of routine maintenance.  S&T didn't just fix faults, they would come and replace dry cells/recharge accumulators etc fairly regularly, and in many places a lampman also came once a week to clean, refill and trim oil lamps in signals and even the lamp above the booking desk.  Heating and cooking used the stove or even an open fire.  A lot more labour needed on the old railway, not forgetting the lengthman patrolling the section and hammering keys back into the chairs on bull head rail.  It's only in later days that signalmen gradually started getting such luxuries as electric lighting, electric heaters, Baby Bellings to cook their lunch and the like.

On 03/12/2022 at 11:03, Grovenor said:

Like the one in the picture, the arm repeater contact box can be seen on the other side of the post to the lamp.

I assume it is the item circled in red on the photo. 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. 

[animotion]

So this begs the question the Midland Signal in the photo has an arm repeater electrical box which I presume was fed to the nearby signal box and if that was the case would it not have made the back blinder redundant as the repeater would tell the signalman what position the arm was at.

Edited December 7, 2022 by animotion

[5BarVT]

5 hours ago, animotion said:

So this begs the question the Midland Signal in the photo has an arm repeater electrical box which I presume was fed to the nearby signal box and if that was the case what it not have made the back blinder redundant as the repeater would tell the signalman what position the arm was at.

Sort of, you need the lamp repeater as well before you could do without the blinder (which I think the signal may well have).

But . . .

Could the repeater have been added later.  Wouldn’t take away the blinder when it was already there.
Paul.

[Compound2632]

The person to ask is Dave Harris, the Midland Railway Study Centre Coordinator, as signalling is his thing. Bottom of page here.