# 1:1 Catenary and Pantograph



## stanman (Jan 4, 2008)

I have subscribed to videos from Asian rail fans for several months. The great majority of the trains are electrically powered, especially high-speed ones. My interest is primarily in European trains, but there's not a great deal of similar information for them. My observations are based on these Asian videos, however from the standpoint of connection of the train to the electrical source I don't believe there would be significant differences between Europe and Asia.

I have become fascinated with the interaction of the catenary system with the train's pantographs. What I've observed is that even with trains moving at speeds well in excess of 100 mph, you can't see any deflection whatsoever in the contact wire as the pantographs travel beneath them. The "droppers" that connect the contact wire to the overhead carrier wire are flexible and won't serve to keep the contact wire steady, thus the weight of the contact wire and the upward force of the pantograph are obviously perfectly balanced.

The design of the pantograph seems to be the key to the flawless operation of this system. Further, the distance between the base of the pantograph and the carrier wire can vary quite at bit, such as when trains enter a tunnel or station. To further complicate things, most trains have multiple pantographs spaced at various distances apart depending on the type of locomotive and the consist, and so more than one pantograph can be under the contact wire within the same span.

I've been reading several articles about the design of these systems. I'm far-too-long out of school to comprehend most of the math, and wish I understood more! In the remote possibility that you may be interested in this subject, here's a link to one article: *Catenary-Pantograph*


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## Madman (Jan 5, 2008)

Thats interesting Stan. I had no idea how much engineering goes into the design of a catenary system.


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## Bill Swindell (Jan 2, 2008)

I believe the messenger wire, which hangs in a catenary curve, is there to hold the contact wire up/level. I do overhead operation in HO scale. In that case, the wire is not heavy enough to hold the pantograph down so we string the wire very tight. This serves the same purpose. I have seen videos of the TGV pantograph at over 200 MPH and it was steady as a rock. It's amazing.


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## Madman (Jan 5, 2008)

I was told by a gentleman that had some ties to the original operation of Penn Central's Metroliner, about an engineering run, where he was aboard the train as it was operating on the North East corridor. It seems that the catenary did not have the correct tension. So the train (Metroliner), moving at a speed faster than normal trains for that track, caused the catenary to slam down onto the roof of the Metroliner, causing a nice long burn mark on that shiny new stainless steel.


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## Tom Leaton (Apr 26, 2008)

When you are in Chicago's Grant Park, you cross the IC and South Shore Line electric tracks on bridges. Looking down from the bridge walkway at passing trains below, you don't observe much wire movement as the pantographs pass by. Those lengths of copper wires, both catenary and messenger, have got to be really heavy.


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## Richard Weatherby (Jan 3, 2008)

I certainly don't understand all that math either, but here is some practical guessimating... 

For some strange reason I believe I have a piece of Penn Central catenary wire laying next to my chair. As you may be aware it is notched down the center of each side. Much like a figure 8 cross section. This notch is where clips are attached and provides a smooth uninerupted bottom surface. This wire seems to be approximately 1/2 inch thick and is worn flat along the bottom. I am estimating the weight to be about a pound a foot. The weight of a couple of wires plus hangers could be a few hundred pounds between upright frames. 

Someday I hope to hang some catenary. I was thinking of using an N gauge or HO gauge rail for the wire. Any thoughts?


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## Madman (Jan 5, 2008)

I'll bet they are Tom. I wish that I could have had just a mile of the catenary that was taken down by Conrail in 1983, on the High Line. The scrap proceeds could have bought me alot of trains.


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## stanman (Jan 4, 2008)

Posted By Richard Weatherby on 20 Jun 2010 09:05 PM 

Someday I hope to hang some catenary. I was thinking of using an N gauge or HO gauge rail for the wire. Any thoughts? 
The LGB contact wire I use is also a figure 8, with grooves on the sides. As close as I can measure, it's about 0.150 inch high and 0.125 inch deep. My guess is that HO rail would be closer to these dimensions than N rail.


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## Chris Scott (Jan 2, 2008)

Stan: Could it be a visual phenomenon? A high speed train is moving so fast you cannot see distinct movements of the wires or panograph, although there is or even must be movement. The anology is the mid 19th century belief that a horse at full gallop at a point in every stride had all four legs off the ground; it why hobby horses at the time and to this day have all four legs in the air. A potographer set up multiple cameras and proved that a horse in fact always has two legs in contact with the ground. The horse was just moving too fast to see it.


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## Semper Vaporo (Jan 2, 2008)

Posted By Chris Scott on 21 Jun 2010 09:40 AM 


Stan: Could it be a visual phenomenon? A high speed train is moving so fast you cannot see distinct movements of the wires or panograph, although there is or even must be movement. The anology is the mid 19th century belief that a horse at full gallop at a point in every stride had all four legs off the ground; it why hobby horses at the time and to this day have all four legs in the air. A potographer set up multiple cameras and proved that a horse in fact always has two legs in contact with the ground. The horse was just moving too fast to see it. 






I think it was the exact opposite... it was believed the horse was too heavy to be able to run without at least one leg on the ground at all times, (somehow they neglected to consider a horse jumping over a fence!) and a photographer proved that there were times when all legs were off the ground. 

Nice animated-photo sequence on Wikipedia at:

http://en.wikipedia.org/wiki/Horse_gait

(Page down to "Pace"). (edit Refer to the paragraphs about "Gallop" (page up once) and the argument about it is briefly discussed. 

The person that hired the photographer [Eadweard Muybridge; see: 

http://en.wikipedia.org/wiki/Eadweard_Muybridge 

was Leland Stanford... a great tie-in to Railroading!

(More editing Further see:

http://en.wikipedia.org/wiki/Sallie_Gardner_at_a_Gallop

Note the typical wikipedia problem of contradiction... one account says that the Royal Society WITHDREW support of Muybridge's study of animal motion and the other says they offered the support. Leaves one wondering just what the truth is.

(Maybe I'll get those links to work someday!)


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## Chris Scott (Jan 2, 2008)

Posted By Semper Vaporo on 21 Jun 2010 09:50 AM 
Posted By Chris Scott on 21 Jun 2010 09:40 AM 


Stan: Could it be a visual phenomenon? A high speed train is moving so fast you cannot see distinct movements of the wires or panograph, although there is or even must be movement. The anology is the mid 19th century belief that a horse at full gallop at a point in every stride had all four legs off the ground; it why hobby horses at the time and to this day have all four legs in the air. A potographer set up multiple cameras and proved that a horse in fact always has two legs in contact with the ground. The horse was just moving too fast to see it. 






I think it was the exact opposite... it was believed the horse was too heavy to be able to run without at least one leg on the ground at all times, (somehow they neglected to consider a horse jumping over a fence!) and a photographer proved that there were times when all legs were off the ground. 

Nice animated-photo sequence on Wikipedia at: http://en.wikipedia.org/wiki/Horse_gait (Page down to "Pace"). (edit Refer to the paragraphs about "Gallop" (page up once) and the argument about it is briefly discussed. 

The person that hired the photographer [Eadweard Muybridge; see: http://en.wikipedia.org/wiki/Eadweard_Muybridge] was Leland Stanford... a great tie-in to Railroading!




Charles:
Looks like it's part, some and both. Obviously due to the number of years since I took History of Photography in college. But as it turns out this all happened just down the road here. Thank you again Wikipedia: http://en.wikipedia.org/wiki/Eadweard_Muybridge

*Eadweard J. Muybridge* (pronounced /??dw?rd 'ma?br?d?/; 9 April 1830 – 8 May 1904) was an English photographer who spent much of his life in the United States. He is known primarily for his important pioneering work on animal locomotion, with use of multiple cameras to capture motion, and his zoopraxiscope, a device for projecting motion pictures that pre-dated the flexible perforated film strip that is used today

Muybridge's The Horse in Motion 









If you select this image from the Wikipedia web page it's a video of the horse in motion:










" In 1872, former Governor of California Leland Stanford, a businessman and race-horse owner, had taken a position on a popularly-debated question of the day: whether all four of a horse's hooves left the ground at the same time during a gallop. Stanford sided with this assertion, called "unsupported transit", and took it upon himself to prove it scientifically. Stanford sought out Muybridge and hired him to settle the question.[2]


In 1877, Muybridge settled Stanford's question with a single photographic negative showing Stanford's racehorse Occident airborne in the midst of a gallop. This negative was lost, but it survives through woodcuts made at the time. By 1878, spurred on by Stanford to expand the experiment, Muybridge had successfully photographed a horse in fast motion.


This series of photos taken in Palo Alto, California, is called Sallie Gardner at a Gallop or The Horse in Motion, and shows that the hooves do all leave the ground — although not with the legs fully extended forward and back, as contemporary illustrators tended to imagine, but rather at the moment when all the hooves are tucked under the horse as it switches from "pulling" with the front legs to "pushing" with the back legs. "



But the basic point relative to Stan's pantograph question, the answer is the same. The motion happens too fast for the eye to see. The motion has to be slowed down in order to see it. Hence a high speed camera is required.


PS: The term _camera_ comes from the camera obscura[/i](Latin for "dark chamber"), an early mechanism for projecting images. The modern camera evolved from the _camera obscura._

If you visit the Cliff House in San Francisco they have a Camera Obscura that you can walk into and see the cliffs and ocean. Cool!


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## Richard Weatherby (Jan 3, 2008)

Are we suggesting there are times when the pantograph may not be in contact with the wire?


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## Chris Scott (Jan 2, 2008)

Posted By Richard Weatherby on 21 Jun 2010 10:52 AM 
Are we suggesting there are times when the pantograph may not be in contact with the wire? 
Clever!









No, the wire and pantograph move up and down together as the train moves forward at high speed.


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## Semper Vaporo (Jan 2, 2008)

I am certain there are slight (very short) moments when the pantograph separates from the overhead wire, (train lights used to blink periodically, but I don't know about modern trains). But it is a wonder that a spring/shockabsorber truck mounted car, (I'd hate to ride on train without them!) can maintain such contact without an extremely obvious ripple in the overhead wire as the pantograph passes under it.

How thick is the contact wire? How heavy? How tightly is it stretched? I assume it must be extremely rigid. The pantograph must be really well oiled to respond to the car bouncing and maintain contact with the wire without pushing up hard enough to deform the wire as it passes.


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## Totalwrecker (Feb 26, 2009)

Carbon is used on the shoes to prevent wire wear. It's easier to replace the shoes. 

John


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## jgallaway81 (Jan 5, 2009)

The weight of the contact wire, combined with the tension it is under would create some incredible static inertial forces... ie an object at rest... Lets say that the wire is exerting a downward force of one hundred pounds... the tensioning adds an additions 25 pounds of force. This means that the pantograph could have an upwards force (created by its spring rigging) of even one hundred pounds, and the wire should not move, because its downward force exceeds that of the pantograph pushing up.

just my thoughts.


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## stanman (Jan 4, 2008)

I have - many times - stopped and started these videos in an attempt to see if there is movement of the wire. Haven't caught any yet.

Here's a video showing pantograph arcing on an icy wire. Lots of horizontal movement due to zig-zag, but I don't see any vertical movement. *Pantograph Arcing*


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## Chris Scott (Jan 2, 2008)

Ultimately I think this is an academic question. If not for high speed electronics technology the trains simply could not run at high speeds. So all things like pantograph's, wire, loads, suspension ad infinitum are constantly monitored in nanosecond time slices and adjusted at the same rate. I do know railroads and equipment makers maintain specal railcars for data collection and analysis as part of their overall scheme of things.


A spin through the info brought up by searching Google via, "how does a high speed train pantograph work", will solidly convince if you are at all even to an infinitesimal degree skeptical, that these high speed and rail folks are pretty sophisticated.
Stan:
With respect to detecting any movement via video... 

At 100 mph the velocity is 147 f/s; at 200mph 293 f/s. A video frame rate is nominally 25 frames per second. I think there's a mismatch between these two for being able to see any wire/pantograph movement even slowing the video way down.










But this is all a moot point, we're quickly moving to MagLev...


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## Semper Vaporo (Jan 2, 2008)

It won't be just an academic question for many years to come. MagLev may eventyally come, but even when it does prove ecconomical to do, it won't take over all the electrified lines for many, many years there after.

As for electronic monitoring, I am sure the faster lines have computerized controls, but I doubt if the pantograph is motorized such as to vary its position against the overhead wire as the vehicle bounces and the distance from track to wire varies along the line. It has got to be just some spring tension holding the pantograph up and the overhead wire keeping it down.

The spring tension would have to be strong enough to move the pantograph up as fast as the distance from the carbody to the wire increases and yet weak enough that when the distance decreases the wire is not lifted too far out of place.

One of the web references I read (probably one of the wikipedia articles about catenary, I think) mentioned having to set the tension on the wire such as to get the shockwave/vibration caused by the pantograph touching the catenary wire to move faster than the train is moving. This to keep from setting up a standing wave in the wire, causing premature wear at support points.

That comment indicates (to me) that there must be some displacement in the wire caused by the pantograph, but how it can travel faster than the train is confusing. The train would just keep re-creating the displacement at the speed of the train. But if it were to travel at the same speed I can see where the displacement might be cumulative and eventuallythe wire might deflect so high as to either break the wire or at least be out of reach of the pantograph extension limits.


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## stanman (Jan 4, 2008)

I think I remember reading (but can't find it right now) that the catenary-pantograph interface is one of the factors limiting the top speed of the TGV.


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## stanman (Jan 4, 2008)

Something not too good is happening in this video. At about 1:43 (the second train) you see that the last pantograph is unstable and is oscillating. At about 2:00 you can see the result of this on the catenary as it sways considerably after the train has passed.

Pantograph problem[/b] 

What I've learned from all this is - these systems are more complex than I had imagined.


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