Unusual Rail Joints?

[melmerby]

Hi all

Spotted this in Carlisle yesterday:

 

What's with the 6 hole fishplates?

Why the diagonal bonding wire?

Why paint the Pandrol clips?

[meil]

The clips are painted in the factory to identify left and right hand clips.

 

Also there are many types of "Pandrol" clips depending on the usage requirements.

Edited July 6, 2019 by meil

[TheSignalEngineer]

Yellow bonds are traction return jumpers usually where the track circuit and traction return rails are transposed. 

Edited July 6, 2019 by TheSignalEngineer

[Nimbus]

I note it's not particularly spanner-friendly. Is this design of fishplate 'fit and forget'? 

And presumably it's located where it is for electrical isolation requirements rather than mechanical?

 

The Nim.

[uax6]

A lot of these 6 hole fishplates are bonded to the rails (which presumably helps stop the joint from dipping), and as such arrive on the back of a lorry with 20foot of rail either side to be welded into the track....

 

Andy G

[Trog]

Standard shop made glued six hole insulated joints, the epoxy glue is used as a filler rather than an adhesive. The idea being that by filling any voids between the rail and the plates it makes the joint stronger by allowing the clamping force of the huck bolts to create more friction. You may also see four bolt versions of these joints but apart from where used on tight curves those are usually much older. If you see one of these joints where the glue has started to break out, and it looks like it has been bleeding rusty water, you know that it is starting to fail and that it is time to start thinking of putting in a new one.

 

As for the Pan clips the blue ones are type e2007 right handed with a 12.5kN toe load, while the yellow ones appear to be type e1810 left handed 9kN toe load. Note that e type Pandrol clips should as a rule of thumb not be used in cast iron baseplates except for plain line baseplates marked with the letters SG (Spheroidal Graphite a stronger form of cast iron than the normal grey flake type) and S&C baseplates designed to take a GRN nylon insulator.

 

Should the joint begin to fail you can repair it by cutting off the huck bolts and removing the plates and any glue that remains attached to the rail ends. Then fitting a set of loose encapsulated plates such as those made by the Benkler company, or the older style 666 nylon shelled plate type. This however should really only be done as a short term repair while a replacement with a new welded in shop joint is arranged. Replacing a 6 hole joint with a set of 4 hole plates should be avoided as they are not as rigid. This is particularly important if changing one of a transposition pair like those in the photo above. As by making a pair of a relatively rigid 6 hole shop joint and a more flexible 4 hole dry joint you are basically building a twist fault. 

Edited July 7, 2019 by Trog
Thought of something else.

[phil-b259]

8 hours ago, Nimbus said:

I note it's not particularly spanner-friendly. Is this design of fishplate 'fit and forget'? 

And presumably it's located where it is for electrical isolation requirements rather than mechanical?

 

The Nim.

 

It doesn't need to be 'spanner friendly - the joint is whats known as a 'glued' joint and is pre-prepared in a factory and transport to site as a 30ft - 60ft single length already made up.

 

As you say its purpose is to electrically separate rails and allow for the creation of track circuits.

 

It does NOT require any form of tightening whatsoever during its lifespan and is NOT meant to be repaired in situ.

 

To install / replace one, the rails either side of the old joint are cut at a suitable distance (10 to 20ft typically) , with the new assembly (similarly trimmed if required) deposited in the resultant gap. The new length is then welded to the existing rails either side.

 

That sticker you can see on the rail is effectively the product tag  (much like the label sown into clothes) giving al the particulars of the assembly, and just as with clothes, Insulated joints like the one pictured come in a number of  'standard' types to suit different rail types.

Edited July 7, 2019 by phil-b259

[phil-b259]

9 hours ago, melmerby said:

 

Why the diagonal bonding wire?

 

Because it is necessary to ensure one of the two rails is electrically continuous throughout the layout so as to provide a return path for the traction current!

 

Both OLE and 3rd rail systems rely on the running rails (ideally as many as possible) to return traction currents to the substations - but at the same time the S&T department require the rails to have insulated joints between them or otherwise track circuits would not be possible. On plain line sections we can use things like impedance bonds or fancy electrical solutions to get round the problem of blocking track circuit currents but passing traction ones - but these solution cannot be used through points which requires a different tactic to be employed.

 

What we do through pointwork is to only put insulated joints in ONE of the two rails, rather than both thus providing a continuous electrical path for the traction return current to follow. However its not always possible to physically use the same rail throughout the layout - in such cases it is necessary for the rail carrying traction current to swap sides and this is what you are seeing in the photo.

 

The 'other' rail through the layout will be full of Insulated joints so as to create track circuits - and this is why there isn't a second cross bonding present in the photo.

 

I can assure you checking that all the necessary bonding (both S&T and Traction) is in place on complex layouts can be very time confusing plus difficult - even with all the official drawings, but defects in the bonding are very good at causing track circuit failures.

 

Also given the traction currents involved are not trivial - such bonding being missing / lose can easily result in an insulated joint literally blowing itself apart as the current desperately tries to find a way back to the sub!

Edited July 7, 2019 by phil-b259

[melmerby]

Thanks guys, plenty of info there.

The joint is where the middle roads between platforms 3 & 4, which still seem to be well used by the look of the rail head, are connected to the down line at the end of platform 3.

Here (bottom RH) is where that new FB is welded to the bullhead middle roads near this catch point:

 

As a comparison at the other end of the station the line running in to platform 3 from the south has a standard 4 hole joiner which is definitely loose, with noticeable dipping as a train runs over it.

Edited July 7, 2019 by melmerby

[Trog]

1 hour ago, melmerby said:

Here (bottom RH) is where that new FB is welded to the bullhead middle roads near this catch point:

 

 

 

Looks like a forged transition rail to me where the end of the flat bottom rail is reshaped to the bull head rail section then (I think) flash butt welded to a length of ordinary rolled bull head rail. Way over specified for what is required for a light low speed use like this. A FB/BH junction thermit weld would do the job just as well, giving most of the reliability gains of not having a set of BH/FB fishplates and would be a lot cheaper.

[62613]

2 hours ago, melmerby said:

Thanks guys, plenty of info there.

The joint is where the middle roads between platforms 3 & 4, which still seem to be well used by the look of the rail head, are connected to the down line at the end of platform 3.

Here (bottom RH) is where that new FB is welded to the bullhead middle roads near this catch point:

 

As a comparison at the other end of the station the line running in to platform 3 from the south has a standard 4 hole joiner which is definitely loose, with noticeable dipping as a train runs over it.

Looking at the fastenings on both the fishplate and the chair, I'd say that that was shoddy workmanship. Three bolts too short and one too long on the plate, for a start.

[kevinlms]

46 minutes ago, 62613 said:

Looking at the fastenings on both the fishplate and the chair, I'd say that that was shoddy workmanship. Three bolts too short and one too long on the plate, for a start.

Poster said that it was loose & dipping with a train passing over it. Does that suggest that the 3 'too short' bolts, are in fact coming undone?

[Dunsignalling]

1 hour ago, kevinlms said:

Poster said that it was loose & dipping with a train passing over it. Does that suggest that the 3 'too short' bolts, are in fact coming undone?

One of the chair bolts has gone AWOL too.

 

John

[melmerby]

1 hour ago, kevinlms said:

Poster said that it was loose & dipping with a train passing over it. Does that suggest that the 3 'too short' bolts, are in fact coming undone?

It does seem likely. I noticed it because I was standing near the end of platform 3 as a Pendolino passed and the clunking as the wheels sets passed over it was very obvious

[TheSignalEngineer]

Looks like a failure waiting to happen.

[RLWP]

19 hours ago, meil said:

The clips are painted in the factory to identify left and right hand clips.

 

Another tiny detail for the obsessive modeller to recreate...

[jim.snowdon]

5 hours ago, Dunsignalling said:

One of the chair bolts has gone AWOL too.

 

John

I suspect it has never been fitted, due to proximity the fishplate bolt.

 

Jim

[Trog]

9 hours ago, 62613 said:

Looking at the fastenings on both the fishplate and the chair, I'd say that that was shoddy workmanship. Three bolts too short and one too long on the plate, for a start.

 

While we are moaning about it does the plate need a slightly larger worn/new step too.

Edited July 7, 2019 by Trog
Missing word.

[Trog]

7 hours ago, melmerby said:

It does seem likely. I noticed it because I was standing near the end of platform 3 as a Pendolino passed and the clunking as the wheels sets passed over it was very obvious

 

A good reason to do track inspections with the trains running. Your ears always spot more faults than your eyes, and standing out to let a train pass then restarting resets your concentration.

[TheSignalEngineer]

11 minutes ago, Trog said:

 

A good reason to do track inspections with the trains running. Your ears always spot more faults than your eyes, and standing out to let a train pass then restarting resets your concentration.

When doing any inspection or testing of points equipment I always liked to see a train go over them as it gave you far more information about the state of the equipment. You can often hear something starting to work loose before you can see it.

[phil-b259]

Here is an example of a ETE (traction) bonding plan.

 

Note that although it is of a DC Conductor rail electrified area, 25KV installations will be pretty similar in principle.

 

The rails which carry traction current AND track circuit current are shown as solid lines, those which carry only track circuit currents are shown as lightly dashed lines, with heavily dashed lines representing the conductor rail.

 

Insulated rail joints (like the one which kicked off this thread) are shown by black squares in the rails.

 

Bonding cables are generally identified with letters (don't know what they mean - I'm not an ETE man)

 

As you can see all the rails carrying traction current are in fact linked together - this is deliberate as it provides the maximum number of return paths.

 

The Black square between the two rails is an impedance bond (or 'spider' as some call it). Its job is to connect both rails together so they both can be used for traction return on plain line sections, but at the same time fool the track circuit currents that there is in fact no connection between the rails (or the track circuit wouldn't work).* If you look at the lowest two lines you will see where on one side of the insulated joints both rails are shown as solid lines indicating traction current is split between them while on the other side only one rail is used for traction current.

 

Note also that just as railway modellers are recommended to not rely on switch blade contact to pass currents - the same is true on the real railway. You will note that specific stock to switch rail ETE bonding is shown on the plan - however It should also be understood that similar stock to switch S&T bonding is also required - but as the plan is for the ETE department, S&T bonding is not shown.

 

Finally, just as modellers are told not to rely on fishplates to pass power between sections of track - again the same is true on the real railway. Every single non insulated joint in an area with electric traction fitted that is going to have traction return currents passing through it must also have beefy cabling installed to bridge the joint. Similarly every non insulated joint within a track circuit must also be bonded - though if the rail concerned is not going to carry traction current the bonds can of course be much smaller

 

 

* You need to have an understanding of the academic topic AC Theory to appreciate how it works in practice.

 

 

 

 

Edited July 8, 2019 by phil-b259

[phil-b259]

Oh and this is the track circuit arrangement for the above area

 

 

[jim.snowdon]

2 hours ago, phil-b259 said:

Oh and this is the track circuit arrangement for the above area

 

 

A p/way engineer's delight - all those insulated joints on, and in between, the fronts of points. I can't believe that they were all essential. It reminds me of an exercise on the signalling design course where, as a track engineer, I challenged such an arrangement and the instructor had to admit that not only was the offending joint unnecessary (in the example) but that he had never thought of it from the track perspective. Your example is a classic case of one where getting the design right requires coordinated input from signalling, track and, going by the ELR, electrification engineers, for both the conductor rail layout and the negative bonding, during the design process rather than after it. It's one of those applications where axle counters would be helpful by eliminating the joints.

 

Jim

[PatB]

I do hope that traction current and TC  current are supplied from separate transformer windings or you'll get all sorts of mysterious shorting problems via the common return when you plug your layout in ;-). 

[phil-b259]

31 minutes ago, jim.snowdon said:

A p/way engineer's delight - all those insulated joints on, and in between, the fronts of points. I can't believe that they were all essential. It reminds me of an exercise on the signalling design course where, as a track engineer, I challenged such an arrangement and the instructor had to admit that not only was the offending joint unnecessary (in the example) but that he had never thought of it from the track perspective. Your example is a classic case of one where getting the design right requires coordinated input from signalling, track and, going by the ELR, electrification engineers, for both the conductor rail layout and the negative bonding, during the design process rather than after it. It's one of those applications where axle counters would be helpful by eliminating the joints.

 

Jim

 

You should see the bonding plans for the south end of Redhill*......(IIRC one track circuit has close to 30 IRJs in it in total thanks to the layout).

 

HG and GB being the most likely culprits - and also ones garuntee to totally lock up Redhill if they misbehave....

 

(* Surrey that is)

 

Edited July 8, 2019 by phil-b259