Transponder or Pantograph?

[Zero Gravitas]

Just heard the guy from the Rail Delivery Group on the Today Programme on Radio 4 (didn't catch his name), talking about the effects of high temperatures on track and OLE.  He referred to the thing I have always called a pantograph as a "transponder".  Was he just wrong or is this a term with which I have been hitherto unaquainted?

 

Thanks very much in advance.

[jim.snowdon]

I think his technical knowledge may be somewhat lacking.

 

Pantographs and transponders are very different things.

 

Jim

[Wickham Green]

Used to be a world where different things WERE different things - now everything seems to have gone transgender.

[EddieK]

I thought a Transponder was a robot in disguise.

 

I'll get my coat....

[Pacific231G]

It was probably just a slip of the tongue. Being live on air is stressful, especially if it's not your profession,  and in the tension of the moment (as opposed to the lack of tension in the catenary) it's all too easy to muddle a word you actually know well. I wonder if he was referring to the train mounted  transducer thar detects section breaks  the remote monitoring equipment that detects overheating rail. I assume that would include a transponder to enable it to be interrogated rather than having tto constantly transmit data. 

He's probably been cursing himself all morning but this may not have been the only interview he had to give. 

What I don't understand is why the tensioning weights didn't as, in principle at least, they should be able to handle any temperature difference. Any overhead lne experts here?  

Edited July 26, 2019 by Pacific231G
More likely reason for a transponder

[Fat Controller]

2 minutes ago, Pacific231G said:

It was probably just a slip of the tongue. Being live on air is stressful, especially if it's not your profession,  and in the tension of the moment (as opposed to the lack of tension in the catenary) it's all too easy to muddle a word you actually know well. I wonder if he was referring to the train mounted  transducer thar detects section breaks He's probably been cursing himself all morning but this may not have been the only interview he had to give. 

What I don't understand is why the tensioning weights didn't as, in principle at least, they should be able to handle any temperature difference. Any overhead lne experts here?  

The SNCF site this morning said that expansion had been so great that the tensioning weights were actually touching the ground, meaning they couldn't tension the wire any further 

[Pacific231G]

9 minutes ago, Fat Controller said:

The SNCF site this morning said that expansion had been so great that the tensioning weights were actually touching the ground, meaning they couldn't tension the wire any further 

Interesting Brian. How many problems have they had in the exceptionally hot weather. Do SNCF paint their rails white? NR were being criticised for this on twitter this  morning as if it was a desperate stop-gap rather than the sensible measure that any halfway competent engineer knows it to be.

[Fat Controller]

8 minutes ago, Pacific231G said:

Interesting Brian. How many problems have they had in the exceptionally hot weather. Do SNCF paint their rails white? NR were being criticised for this on twitter this  morning as if it was a desperate stop-gap rather than the sensible measure that any halfway competent engineer knows it to be.

They seem to have had quite a few problems, especially in those areas that retain the 'Ogee' supports without tensioners (the ex-Midi and PO lines in the SW). The 25kV services to Le Havre/ Cherbourg seem to have been halved: they tend to advise the day before of potential speed restrictions (they also do this during the winter for cold/snow, and high winds).

I can't remember seeing white-painted rail in France, though I've seen lots of it in Italy, especially on the lines that go east- west over the plains of Lombardy.

[Brian The Signal Engineer]

Transponders were used on the ATP project and sat in the four foot (between the rails) and as the APT went over they transmitted certain information to the train, such as Line Speed.... These were powered by the train passing over and had no external connection. They were about 500mm square and about 50mm thick.

With the Azuma's on the East Coast, (cannot said about the GWR) they used the term Balise.
A track mounted spot transmission unit that uses transponder technology. Its function is to transmit/receive messages to/from the train passing overhead.

 

I cannot comment on what the chap from RDG said as I was still in bed!

[DY444]

2 hours ago, Zero Gravitas said:

Just heard the guy from the Rail Delivery Group on the Today Programme on Radio 4 (didn't catch his name), talking about the effects of high temperatures on track and OLE.  He referred to the thing I have always called a pantograph as a "transponder".  Was he just wrong or is this a term with which I have been hitherto unaquainted?

 

Thanks very much in advance.

 

No he was just talking drivel

[Titan]

1 hour ago, Fat Controller said:

The SNCF site this morning said that expansion had been so great that the tensioning weights were actually touching the ground, meaning they couldn't tension the wire any further 

 

Indeed. This can and does happen in the UK. The maximum temperature that OLE equipment is designed to handle is 38C.  The solution in the past has been to send teams out with spades to dig holes under the weights where practical, but if the weights have reached the end of their travel even that might not work. More modern OLE has had the operational temperature range revised to cope with the higher temperatures we have been experiencing, and I am led to believe that the GWML is coping with the heat just fine.

[The Stationmaster]

9 minutes ago, Titan said:

 

Indeed. This can and does happen in the UK. The maximum temperature that OLE equipment is designed to handle is 38C.  The solution in the past has been to send teams out with spades to dig holes under the weights where practical, but if the weights have reached the end of their travel even that might not work. More modern OLE has had the operational temperature range revised to cope with the higher temperatures we have been experiencing, and I am led to believe that the GWML is coping with the heat just fine.

The NR rep at our local Branch User Group (BUG!) on Tuesday evening said that they are very happy with the way the automatic tensioners on GWML catenary are coping with the effect of the high temperatures on contact wire tension and that it was managing far better than BR Mk1 catenary with no need anticipated to have to reduce speeds due to lack of tension in the contact wire.

 

Rail temeprature was a very differeent kettle of fish and on Tuesday they were slightly less than 2 degrees away from linespeed reductions on cwr.

[Trog]

9 hours ago, Pacific231G said:

Interesting Brian. How many problems have they had in the exceptionally hot weather. Do SNCF paint their rails white? NR were being criticised for this on twitter this  morning as if it was a desperate stop-gap rather than the sensible measure that any halfway competent engineer knows it to be.

 

It is a stop gap measure good for 2 or 3 degrees C, and is not a substitute for proper hot weather preparedness.

[Pacific231G]

7 hours ago, Brian The Signal Engineer said:

Transponders were used on the ATP project and sat in the four foot (between the rails) and as the APT went over they transmitted certain information to the train, such as Line Speed.... These were powered by the train passing over and had no external connection. They were about 500mm square and about 50mm thick.

With the Azuma's on the East Coast, (cannot said about the GWR) they used the term Balise.
A track mounted spot transmission unit that uses transponder technology. Its function is to transmit/receive messages to/from the train passing overhead.

 

I cannot comment on what the chap from RDG said as I was still in bed!

I believe the French word Balise (meaning beacon in the navigational sense) is used for ETCS to distinguish them from other types of transponder  used on the railway. Transponder is a contraction of transmitter responder and is a device that transmits a different signal when it receives a transmission (the French word is transpondeur so also distinguished from a beacon) 

Transponders can be active (powered) or (passive) unpowered depending on the relative strength of the received signal and the transmission strength and complexity required. The RFID chips implanted in pet animals are passive transponders and simply transmit a number when they are scanned. Presumably the APT transponders were also passive devices.  Active transponders are most familiar from those fitted to aircraft (developed from the IFF transponders used during WW2)  as they have to transmit a relatively strong signal (strong enough to require a radio licence) back to the secondary surveillance radar scanner. (Primary radar is the one whose signal simply bounces off the aircraft or ship- secondary radar sends a signal that the transponder responds to on a different frequency)  

[Trog]

8 hours ago, Brian The Signal Engineer said:

Transponders were used on the ATP project and sat in the four foot (between the rails) and as the APT went over they transmitted certain information to the train, such as Line Speed.... These were powered by the train passing over and had no external connection. They were about 500mm square and about 50mm thick.

With the Azuma's on the East Coast, (cannot said about the GWR) they used the term Balise.
A track mounted spot transmission unit that uses transponder technology. Its function is to transmit/receive messages to/from the train passing overhead.

 

I cannot comment on what the chap from RDG said as I was still in bed!

 

 

One of the last APT transponders to be found in the wild.

[Trog]

A modern transponder as used by Pendolinos etc. note how fragile and cheap looking it is compared to the BR equivalent. Not much chance of that still working after you have run a couple of JCBs over it.

[The Johnster]

As I understand it (which I readily admit might not be fully), a transponder is any device that converts one form of energy into a different form of energy.  So, for instance, the cartridge on your old record player was a transponder, converting the mechanical energy from the stylus' vibrating in the groove to electrical energy.  At the other end of the hi fi, the loudspeaker driver unit is also a transponder, converting the electrical signal from the amplifier, which originated as the electrical energy produced by the cartridge,  back into mechanical energy which drove the speaker cone backwards and forwards in a way which produced sound.  So the cone was another transponder, converting mechanical energy into sound energy, and your ears, which picked it up, were yet another transponder converting the sound energy into another form of electrical energy which your brain interpreted as whatever music it was supposed to be.  

 

A pantograph is not a transponder, but in it's original sense as a drawing device it does reproduce and perhaps enlarge (amplify) or reduce the original drawing.  As the device used to pick up power from railway OHLE resembles the action of this device, it is described as a pantograph, but does not actually function as one.  

 

I am being as much of a revolting pedant as I can with this in order to hopefully clear the situation up....

[Titan]

13 minutes ago, The Johnster said:

 

I am being as much of a revolting pedant as I can with this in order to hopefully clear the situation up....

 

Perhaps, although to out pedant you I think you mean signal rather than energy, otherwise things like engines and batteries would also be transponders...

Edited July 26, 2019 by Titan

[Pacific231G]

15 minutes ago, Trog said:

 

It is a stop gap measure good for 2 or 3 degrees C, and is not a substitute for proper hot weather preparedness.

Network Rail claim 5-10 deg.C. from painting rails so surely it's simply part of proper hot weather preparedness not a substitue for it. I trust it's not the only measure taken but with modern paints must be a simple and inexpensive one. A bullhead junction near here has been painted white. I doubt whether BR(WR)/GWR had some magical alternative, they just didn't have modern paints (and steam era trains wouldn't have left the rails white for very long)  and they probably weren't running the network so close to capacity (nor were extreme heat waves so common). 

What does proper hot weather preparedness consist of? Heavier section rail?- very expensive- more expansion joints? also expensive,     substting substituting steel rail with tarmac and steel with rubber tyres?  The Marples solution still very widely used by SNCF whenever their track maintenance gets too far behind.    

 

 

 

[Trog]

18 minutes ago, Pacific231G said:

 

.................  What does proper hot weather preparedness consist of?  ........

 

 

 

 

Try keeping your stressing up to date, ensuring that your breather switches are properly adjusted, maintaining the proper raised ballast shoulder, ensuring that your pads clips and nylons are in good condition so the rail can not move longitudinally, lubricating and adjusting fish plated rail joints, fitting LREPs to tight curves and the switch panels of S&C on timber, that sort of basic house keeping. Going a bit further by removing un-necessary trigger points from the track, such as where failed concrete sleepers have been replaced by odd timbers, or wet spots where the track pumps so reducing the contact area between sleeper and ballast. Painting the rails should be un-necessary* for properly maintained track.

 

* An exception to this is perhaps switches, particularly the blades of switch diamonds which are due to their design are susceptible to heat related expansion problems. But if you see long lengths of plain line in particular painted white, you know that the local maintainers are either under staffed and desperate or sub competent.

[Fat Controller]

Just a thought- might the transponders that were spoken of be responible for dropping the pans at neutral sections or other locations?

[Pacific231G]

2 hours ago, The Johnster said:

As I understand it (which I readily admit might not be fully), a transponder is any device that converts one form of energy into a different form of energy.  So, for instance, the cartridge on your old record player was a transponder, converting the mechanical energy from the stylus' vibrating in the groove to electrical energy.  At the other end of the hi fi, the loudspeaker driver unit is also a transponder, converting the electrical signal from the amplifier, which originated as the electrical energy produced by the cartridge,  back into mechanical energy which drove the speaker cone backwards and forwards in a way which produced sound.  So the cone was another transponder, converting mechanical energy into sound energy, and your ears, which picked it up, were yet another transponder converting the sound energy into another form of electrical energy which your brain interpreted as whatever music it was supposed to be.  

 

A pantograph is not a transponder, but in it's original sense as a drawing device it does reproduce and perhaps enlarge (amplify) or reduce the original drawing.  As the device used to pick up power from railway OHLE resembles the action of this device, it is described as a pantograph, but does not actually function as one.  

 

I am being as much of a revolting pedant as I can with this in order to hopefully clear the situation up....

Not quite. What you're talking about is a transducer, defined by my OED as a device that specifically turns a non-electrical signal into an electrical signal but often generalised  to one that turns a signal in one form of energy into an eqivalent signal in another. It's not about converting energy but information so your record player will use the signal it receives from the transducer in the pick up cartridge and turn it into a fairly loud sound including all the clicks and pops of a well played record.

(Curiously the term transducer doesn't appear to be used for the devices that convert electrical signals into light and back again for fibre optic  cables- those seem to be called transmitters and detectors- but, according to the IET,  a fibre optic transducer is a device where pressure, temperature ,strain or whatever directly modulates the light travelling along the cable) 

 

A transponder is a contraction of transmitter responder and defined as a device that responds to receiving one signal by transmitting  a different signal. So, a radar reflector is not a transponder but any device that receives a radio signal and responds with a different radio signal is. You could certainly have a tranponder that detects Beethoven and responds by transmitting the Arctic Monkeys or more prosaically receives a signal asking it what train it's installed in and responds appropriately.

 

Pantograph comes from the Greek  pant meaning all or universal and graph meaning to write so "universal writing" that as you say reproduces an original drawing (and can be easily arranged to reduce and enlarge it) It is though a purely mechanical device that simply causes two pens to make the same movements;  It isn't converting between different forms of energy.

In its original form the railway pantograph does sort of vaguely resembles the drawing device (if you don't  look too closely) in that it is a parallelogram but you need the externally extended arm that railway pans. dont have to actually reproduce a shape. However, the word's been used  well beyond its original meaning. Such is the English language.

 

Edited July 26, 2019 by Pacific231G

[Edwin_m]

Perhaps the person quoted in the OP was thinking of (or pondering on) the transformer the pantograph is connected to? 

[Trog]

9 hours ago, Fat Controller said:

Just a thought- might the transponders that were spoken of be responible for dropping the pans at neutral sections or other locations?

 

The pans don't drop at neutral sections but a set of breakers automatically actuated by permanent magnets (much like those used to give the danger warning at AWS ramps) disconnects the loco electrically from the wires. So that its power draw does not strike an arc across the insulated section. If traveling in the coach on an EMU with the pan on the roof you can often hear the breakers working as they make quite a loud noise. Unlike AWS magnets the magnets for a neutral section are in pairs one on each end of a sleeper*. There are two pairs of magnets one at the start of the neutral section to turn the loco off, and a second pair at its end to turn the loco back on.  * On newer installations you might see pairs of rail mounted magnets instead.

[The Johnster]

Heat buckling might be solved in some cases by changing the local environment.  Back in my railway career in the 70s, a well known local blackspot was between Cadoxton and Barry Dock, where a bare rock face reflected heat on to the railway.  Not sure what eventually solved the problem, but it doesn't seem to occur now, but I thought at the time that planting a few bushes and keeping them trimmed to shade the spot might have worked!