So what does happen when you pull the communication cord

[two tone green]

Hi All,

 

Busily building JLTRT BR Mk1 Coaches and have got to sorting out the alarm gear fitted to them. That is the communication cord fitted inside the coach that in some magical way stopped the train.

 

But, its is electrical, is it mechanical. I have looked at various photos on many many web sites trying to find out just what is on the outside of the end walls. I can see the 'junction box' that usually sits on the left side of the corridor connection and what looks like round electrical cable conduit or is trunking carrying a cable inside operating a mechanical system.

 

The JLTRT instructions are near useless at explaining just what all the parts are for. Brian Daniels superb photos have helped but he has used some one else's components and not the JLTRT ones to make up the alarm system on his coaches.

 

Even photos on the web whilst useful don't give the full picture as to what is happening down around the buffer beam. It looks like the conduit arrives down at the buffer beam and then ............................what. I have small brass parts in the kit that I am not sure where they go.

 

Besides Brian's excellent photos, believe it or not, my Heljan O Gauge Mk1's, yes it was me who bought some, have help me with things far more that the JLTRT instruction.

 

So if anyone out there has some very nice buffer beam detail photos of BR Mk1 coaches showing the alarm gear set up it would be much appreciated.

 

Thanks

[Grovenor]

This is how I understand it, maybe others will confirm or deny.

On pulling the cord this is connected mechanically to the valve at cantrail height on the coach end, the flag on the outside of the valve box is simultaneously turned through 90 degrees so it can be seen by looking along the train. The pipe from the valve is connected to the vac brake pipe so when operated the valve lets air into the pipe gradually destroying the vacuum. This is enough to be noticeable the the driver and if nothing is done will cause a gentle brake application. The driver can overide this if he turns on the exhausters and hence is able to stop at a suitable place to investigate the incident. When resolved turning the flag back to its normal position will close the valve and pull the cord tight again. Same thing works with air brakes except it lets the air out rather than in but I assume some extra equipment was needed for dual brake stock.

Regards

Keith

[two tone green]

Excellent Keith, thanks.

 

So down around the buffer beam it is likely that the conduit / pipe bends inwards under the coach floor and connect some place down there.

 

Interesting.

 

Thanks.

 

Any photos though would be appreciated.

[R A Watson]

Basically it just a flap across the open end of a vertical pipe which when lifted allows air into the vacuum system creating a drag on the brakes of the affected vehicle, thereby warning the driver of a problem both by slowing the train (but not stopping it!) and causing the gauge in the cab to show a reduction in pressure.

 

The operation is simply there is a continuous chain passing along the length of the vehicle inside a tube which has sections missing where the alarm points are. When the chain is pulled one end is fixed but the other is attached to a lever on a cross rod visible on the outside of the coach end, this rod rotates and lifts the flap off the end of the previously mentioned vertical pipe allowing the air to destroy the vacuum. The flap and pipe end are inside the "junction box" you see where the horizontal and vertical components meet on the end. Normally the ends of the cross rods have a metal plate known as the flag attached allowing the guard to walk along outside the train and easily see which is the coach with the raised flag, this will be the one in which the the alarm has been pulled.

 

As an additional memoir I have seen - and taken part in - on a preserved line many years ago - the act of climbing a coach end to open the cover and put a matchstick between the flap and pipe end giving a slight leak on the system, late at night after the finish of service. This is very annoying to any guard who has previously upset the C&W department and is preparing his train for a new days running

[PhilH]

As above, causes a reduction of between 5-10 ins on the vac gauge which should be enough to attract the driver's attention.

 

As an additional memoir I have seen - and taken part in - on a preserved line many years ago - the act of climbing a coach end to open the cover and put a matchstick between the flap and pipe end giving a slight leak on the system, late at night after the finish of service. This is very annoying to any guard who has previously upset the C&W department and is preparing his train for a new days running

 

Not only annoying to the guard but also to the driver trying to make the brake, could lead to the engine being booked as a failure if the 'prank' wasn't discovered or owned up to. If it happened to me, as a driver, those responsible would also spend the rest of their lives as eunuchs - you do not pratt around with brakes.

[MikeTrice]

The following photos might help seeing how everything goes together. I am really a Gresley person so my photos of BR stock are limited, but here goes:

 

 

In the above image you can just see the indicator to the extreme right of the photo. The semicircular housing that covers it is where the 90 degree crank is fitted that is connected to the emergency cord.

 

The rod on which the indicator is fitted therefore rotates. There is a crank on the end adjacent to the vestibule that raises the linkage above head height so the rotation can be continued to the other side of the carriage without creating an obstruction in the vestibule.

 

 

This less than ideal photo shows what happens the other side of the carriage. There is a corresponding indicator and rod which connects to the linkage from the other side so both sides of the carriage are linked together. The rectangular box with sloping top is the valve. When the cross rod is rotated the valve opens. The pipe that runs down the from the valve beside the vestibule then goes down to the headstock and on Gresely stock, is simply joined to the vacuum pipe. I have no reason to suspect that BR coaches are any different. So in a nutshell, pulling the cord, rotates the rod opening the valve destroying the vacuum and applying the brakes.

 

Hope that helps.

 

Just found the following photo which show two valves attached to the operating rod. I will leave it to others to explain why two?

 

[MikeTrice]

And without any clothes on, so to speak:

[Dagworth]

 

Just found the following photo which show two valves attached to the operating rod. I will leave it to others to explain why two?

 

One for air and one for vacuum

 

Andi

[brossard]

FWIW here's a picture of the underside of the bufferbeam:

 

 

Unfortunately the side nearest the camera is of the steam pipe (this pipe is shown in other pictures with lagging).

 

Credit to Craig Welsh who posted a series of underframe details here some while ago. I couldn't find the thread when I searched.

 

John

[two tone green]

Superb info and photos. Thanks.

 

So now I know that the vertical pipe is nothing more than a vertical pipe then curves away onto the vacuum pipe its easier to install on my 7mm version.

 

I think I worked out the castings with what looks like one item is in fact three small separate items on a sprue, two being D shaped supports for the linkage. Well there's embarrassing !

 

Thanks again, excellent service.

[two tone green]

John, nice photo and I think you have solved another puzzle I had and that is the steam heat valve and its location. Thanks.

[two tone green]

John, as you have posted a very nice photo of the steam pipe and valve, would this valve be called the steam heat pressure release valve and a now a silly question. Would there be only one on the coach.

 

Reason I ask is that there is only one shown in the parts list, photo list, with X 1 next to it ?

 

Thanks

[brossard]

Glad that the picture is of use to you. Here's another:

 

 

As to whether there is a valve at the other end of the coach, I couldn't say, not being an expert. The other end wasn't photographed. I also don't know what it's called - only noticed it today. It may not be desireable to be able to isolate the steam pipe completely. In cold weather, any water trapped could freeze and potentially rupture the pipe.

 

John

[two tone green]

Thanks John,

 

JLTRT don't have the best of reputations for getting the number of things right in their kits so possibly there should be two of the valves, not sure.

 

But the one in the photo and the one in the kit could well be the same item. Valve handle excepted. More like a tap handle on the kit one rather than a lever in the photo.

 

Thanks for the photos though, a massive help.

[Dagworth]

Glad that the picture is of use to you. Here's another:

 

 

As to whether there is a valve at the other end of the coach, I couldn't say, not being an expert. The other end wasn't photographed. I also don't know what it's called - only noticed it today. It may not be desireable to be able to isolate the steam pipe completely. In cold weather, any water trapped could freeze and potentially rupture the pipe.

 

John

 

There will be one at each end of the coach.

 

Andi

[Grovenor]

There will be one at each end of the coach

Since it needs to be closed at the end of the train to stop the steam escaping and you don't know which end of the coach that will be.

Keith

[Guest Phil]

And seeing as it hasn't been mentioned yet, the nickname for the red-painted flap shaped thingey at cantrail ends of the coach is known as the "butterfly".

[R A Watson]

As above, causes a reduction of between 5-10 ins on the vac gauge which should be enough to attract the driver's attention.

 

 

 

Not only annoying to the guard but also to the driver trying to make the brake, could lead to the engine being booked as a failure if the 'prank' wasn't discovered or owned up to. If it happened to me, as a driver, those responsible would also spend the rest of their lives as eunuchs - you do not pratt around with brakes.

 

Normally I would agree with you but in this instance the driver was in on the secret with our staff looking on from round the corner.

 

The guard in question was becoming a bit of a pain with his expressed knowledge and this was a way of reminding him he did not know everything about everything.

 

The whole episode was carried out well before services started and during initial formation of the train that morning when there were no public on site.

[woodenhead]

Normally I would agree with you but in this instance the driver was in on the secret with our staff looking on from round the corner.

 

The guard in question was becoming a bit of a pain with his expressed knowledge and this was a way of reminding him he did not know everything about everything.

 

The whole episode was carried out well before services started and during initial formation of the train that morning when there were no public on site.

 

So sometimes it is ok to mess with the braking system on a train - hmm I wonder how HM inspectorate would view such a prank.

[R A Watson]

You are missing the point, times and ideas were different in the late sixties, but we had no intention to send a train out in a dangerous condition, just to teach the person a lesson that his knowledge was not as extensive as he thought.

 

If you had experienced an aprenticeship at that time you would know this form of instruction was widespread throughout industry although I have never met anyone who recollects this sort of prank being carried out when, to use the modern phrase, safety was compromised.

[The Stationmaster]

Normally I would agree with you but in this instance the driver was in on the secret with our staff looking on from round the corner.

The guard in question was becoming a bit of a pain with his expressed knowledge and this was a way of reminding him he did not know everything about everything.

The whole episode was carried out well before services started and during initial formation of the train that morning when there were no public on site.

 

I'm sorry but I agree absolutely with Phil on this. When I was carrying out training and exams on a heritage railway in the I did purposely create minor vacuum faults but I only used the common ones which could (and did) readily happen in everyday railway work; it didn't need any fiddling with mechanisms which were usually very reliable in normal operation. And all of that was, I reiterate, for examination purposes when we were not involved in public operation. The time to find out how good or 'clever' people are is when they are being examined or re-assessed and I can't recall anyone doing something like that, as a prank or otherwise, in more than a few years operational involvement on the big railway.

 

Back OT and could TTG possibly post a pic of the 'steam valve' to aid identification please?

[woodenhead]

I presume it is a similar arrangement on MkII, MkIII and MkIV stock, a colleague of mine on a recent journey down the ECML witnessed a person having a seizure of some sort and someone pulled the cord which stopped the train somewhere near Stevenage, the train then re-started and moved to Stevenage for the emergency services to take the person off.

 

However, on a recent journey by Pendolino I noticed that the emergency cord appears to have been replaced by emergency communication with the driver. I think this is probably a preferable solution - no sudden braking, no stopping in the middle of nowhere out of reach of any emergency services if it is a personal incident rather than a mechanical incident. Clearly the old mechanical solution was an effective one but given today's ease of communication with the driver something less immediate is probably the way forward, do other trains use this or is it just the Pendolino?

[Guest stuartp]

_{On second generation DMUs/EMUs the brakes are electrically operated - the driver's brake handle is simply a 4 position switch which tells the brake control valve what to do. The passcomm is also an electrical switch - operating it opens the electrical circuit which holds the brakes off causing a full emergency brake application which the driver cannot override until the train has stopped.}

 

_{Clearly this isn't great if some well-meaning passenger has just brought the burning train to a stand in a tunnel or on top of a viaduct. For this reason later units (including Pendolinos) have a system called Passcomm Override which allows the driver to judge whether this is a safe place to stop and override the passcomm if necessary.}

 

_.

[two tone green]

Hi,

 

As requested, a small picture of the offending item as per the destructions from JLTRT. Top of the page, first item.

 

Not the best of images but not having a camera with me capable of taking macro shots this will have to do sorry.

 

Thanks for all the help and advice and I'll remember not to pull some pranks on the railway at home.

img-725044847-0001.pdf

[two tone green]

Hi again,

 

Suddenly remembered, IPhone has a camera and this is the steam valve.

 

Actually it is a very fine casting with some lovely detail on it.

 

Not the sharpest of images but may be better than the instruction sheet image.