Category Archives: pantographs and catenary

Rose Quarter, revisited

I thought I’d do a post on the operational side of what’s going on around Rose Quarter after an out of control car careened into some signaling equipment last week, since the only side the public sees is pretty much just the loss of Transit Tracker and maybe noticing trains stopping more near Rose Quarter. A helpful primer on this would be the original post about Rose Quarter signals just to familiarize yourself with how this area works under normal operating conditions.

One of TriMet’s photos of the scene. Only one car was involved; the blue car in the background is a supervisor’s car that was narrowly missed by everything

The Impact’s Impact on Transit Tracker

Preface: I am not a signal tech and have nothing to do with Transit Tracker, so if anyone who has a better handle on this than me wants to step in and fill in the gaps/correct me if I’m wrong, please, by all means do so. For all the folks reading the news about this and subsequently wondering why Transit Tracker was routed through here or “stored” in this box, this wasn’t a mythical box that Transit Tracker lived in any more than your computer is a mythical box that the internet lives in. Transit Tracker for passengers is more of a nice little byproduct of what this box (and other signal relay boxes like it) did, not its primary purpose. To the best of my understanding, while Transit Tracker for bus is GPS-based (and therefore it was not affected), Transit Tracker for rail has been based on what circuit the train is in. The crash affected power to all of the intersections between Rose Quarter and OCC, and I know that’s affected the signals but I’m not sure the extent to which circuit detection was affected, but because Transit Tracker isn’t working I’m assuming that it was impacted. This is a centrally located section of the alignment that I am guessing is not getting standard data on train positioning, so the Transit Tracker method of locating trains to predict their arrival isn’t functional. Since ALL trains pass between these two platforms (remember that Yellow and Green are the same trains) all lines are affected.

I’m not above criticizing TriMet when I think they make bad decisions or plan things poorly, but I think this was unfortunately a situation in which there was no right thing that TriMet could have done that would have made everyone happy:

  • Some people are saying that sensitive equipment shouldn’t have been in a high-risk area. As far as I know, given that Rose Quarter was part of the original alignment (called Coliseum there), that box or something like it has probably been there since the mid 80s. But as a conservative estimate, we know that the equipment was 16 years old, so let’s say it’s been there since the mid 90s at the latest. This is the first time a car has come careening off of I-5 doing about 80mph ass over teakettle onto the platform, so I’m going to say that this isn’t really a high-risk area, it was the site of a freak accident. I have not heard of any other crashes in that area coming anywhere near close to where the box had been. Besides, it was tied to the alignment in that area – where else are you going to put it?
  • The equipment in the box was so old that replacement parts aren’t available. Fine, it’s old, but you know what? It worked. There’s probably a fair amount of infrastructure in use right now that’s equally old and not easily replaced (I think the fact that TriMet spokesperson Roberta Alstadt said that the delay in replacing it is due to finding something that can communicate with the rest of the system pretty much says that the rest of it, if it fails, can’t be easily replaced either). And just imagine the fits that people would throw if TriMet were to announce they were spending millions to retrofit rail equipment that would make Transit Tracker more reliable or fit all the rail cars with GPS as bus routes are being sliced and 20+ year old buses are on the road. Would replacing this before this incident happened have been the best use of TriMet’s limited money? How about putting GPS on the trains when the circuit location system works? Setting up bollards everywhere a car might fly into something? Yeah, it’d be nice to replace all of the old equipment but I think there are higher priorities for TriMet when it comes to replacing old equipment (e.g. BUSES) than this would have been.

Sure, the loss of Transit Tracker is probably annoying to commuters, but trains are still able to safely pass through this area with minimal delay. If anything, I think this shows a strength of rail in that while a fixed right of way is never going to be as flexible as a bus, there are still workarounds to even major issues like this to keep things moving. So now on to what’s going on here operationally:

Special Instruction 79

Those of you following along at home on the radio have probably heard a lot of trains calling in either from OCC westbound or Rose Quarter eastbound to follow special instruction (SI) 79. Remember that a special instruction is a temporary modification to operational rules that can be in effect for up to a year, versus a train order which expires after 24 hours.

The operationally relevant part of SI 79

And now, in English.

Eastbound trains must stop and call Control from Rose Quarter. For most trains, this will be from the eastbound main platform and signal 18G, though the SI is set up to allow for eastbound moves from the special events track, westbound main or trolley barn as well (for a review of those signals, refer to the previous post on Rose Quarter). Since the signals cannot be called normally through train-to-wayside communication to get a proper to proceed, the automatic train stop (ATS) magnet in the platform will be active and the train will be tripped if the operator tried to go.

ATS trip and bypass counter inside cab of train

Inside each train cab is an ATS counter like the one pictured, which records the number of times that cab was active (i.e., had an operator keyed in and moving forward) and tripped an ATS magnet as well as the number of times an operator has bypassed an ATS magnet. When you bypass a magnet (also referred to as “key-by”), you have 23 seconds to get past it without it stopping your train. Control keeps a record of the totals in these counters for each train car and cab – it prevents an operator from selectively bypassing an ATS magnet or from tripping and continuing without calling it in. You never bypass a magnet without direct authorization from Control first.

So the operator will tell the controller what car and cab they’re in, and what their new bypass number will be. When they have a fresh parallel walk sign on 1st Ave, they will bypass the magnet so they can proceed forward, ensuring that the switch (topmost one in that picture) is not set against the movement since this area does not currently have signal protection, and also ensure that the intersection is clear of any pedestrian or vehicle traffic. The instructions to stop at 2nd and 3rd and then proceed when safe are slightly different from the standard instructions to SOP an intersection, due to the lack of power at these intersections which means they aren’t displaying parallel green lights. Once into the OCC platform, normal operations can resume as points east were not affected by the crash.

Call board at OCC westbound.
There’s one of these at Rose Quarter eastbound as well.

Westbound the procedure is fairly similar. At the OCC platform, operators will call Control and report their car, cab, and new bypass number. The ATS magnet in this direction is up closer to 2nd Ave by signal 18A.

After getting permission from Control to proceed, trains can proceed when safe through 3rd Ave, which is is street immediately in front of OCC when facing west. They must then stop at 2nd to bypass the ATS at signal 18A, ensuring that those switches in the above picture are properly set for a move into the westbound track (or the special events track if directed there). Once at 1st Ave, the operator will make sure that Rose Quarter is clear and wait for a fresh parallel walk sign before continuing into the Rose Quarter platform and then proceeding as normal to all points west.

This special instruction will be in effect until everything through here is fixed, presumably over the next few weeks. Since all of the steps are packaged into the SI, it cuts down on the amount of radio transmissions for everyone – operators don’t have to call in for permission at each intersection after the initial call to Control, and controllers can grant permission to “follow SI 79” without needing to say all of the steps each time a train goes through here.

Window washer rope around pantograph (Photo by Jason McHuff, more here)

Now consider that the RQ-OCC issues were still going on yesterday and SI 79 was in effect when the window washer’s rope took out Red & Blue Line service downtown (which was pointed out to me was once again the unfortunate car 235) and a semi truck hit a Yellow Line train on Interstate, causing trains to be turned around at 7th or Jeld Wen or Jackson or where available.

Semi vs MAX, picture from Twitter

Yes, there were delayed trains and crushed loads for commuters, but the amount of effort required to keep anything moving at all when that many things go wrong is pretty phenomenal. I do think that there are a number of areas that TriMet needs to improve, such as getting word out to passengers in a more timely manner, not pulling in-service buses out in order to bus bridge (or at least not pulling as many – it leaves bus passengers stranded, puts a lot of strain on the buses left in service). But I still think that it’s good for the public to be able to see “behind the curtain”, so to speak, to get an idea of what’s involved on the back end to get people to their destinations when things go wrong.

Of ice and electricity

Photo of what winter weather may look like, westbound at Hawthorn Farm

Steven Vance recently forwarded me a question about why CTA‘s rails have been sparking. Unlike MAX trains which get power from an overhead wire system, their trains get power through a third rail system. However, arcing in both kinds of power systems during winter weather is typically caused by ice. Ice building up on the wire (or third rail as the case may be) acts as an electrical insulator, preventing the carbon shoe from making contact with the wire where the ice accumulates. This interruption in the flow of the current from the wire to the pantograph is visible as arcing.

Here’s a video of a MAX train pulling into & out of a platform where there was some ice on the catenary, and you can easily see the effect that it has:

To help clear ice from the overhead wire & prevent it from accumulating, a few of the Type 1s (107-112) are equipped with ice cutters which are put into use for major freezing rain/ice events. I don’t have a picture of any of them in use (though I’m willing to accept donations!), but they look like a second pantograph and function by heating/scraping ice from the overhead wire. Unlike the pantographs, ice cutters only draw current to heat the elements and not to provide power to the train, so they won’t arc the same way the pantographs do in ice. Their function is strictly to clear ice from the wire.

Pantograph (left) raised, ice cutter (right) lowered

If you’d ever seen one of these cars and wondered why it has two pantographs, wonder no more! It doesn’t – one pantograph, one ice cutter.

View from above; the ice cutter is the one closer to the coupled end, the pantograph is the one in contact with the wire closer to the vantage point. Bonus cameo appearance by car 235

When good trains go bad: Pantograph edition

Working my way through a backlog of drafts as well as emailed and commented questions.. (and thanks to those who have pointed it out, I’m aware that some links in older posts are no longer working. At some point I’ll go through and see what I can do to fix them, but I think some of those news articles & blogs aren’t around anymore)

Today’s question is about pantographs.

токоприемник, a search which has brought a lot of people here,
presumably from Russia.

Why don’t pantographs wear out or break?

Oh they do.

Not my picture – this is the broken pantograph outside the tunnel by Goose Hollow that tied up the alignment for about 7 hours, January 31, 2009 

Pretty much everything on the train is breakable (this is not an invitation), though instances of something serious like a pantograph breaking are rare. Mechanics, operators, supervisors, and even the public tend to notice excessive arcing that often indicates something is wrong before a pantograph reaches a breaking point. Arcing when the lines are icy or where wires cross – such as around Pioneer Courthouse – is not unusual, but repeated arcing when it looks like the overhead is perfectly clear is not normal and could be indicative of something wrong with the pantograph.

As mentioned in the earlier pantograph post, the part of the pantograph that makes contact with the overhead wire is called the carbon shoe. The carbon on this is a lot like pencil lead – if you ran your finger over a carbon shoe, it’d leave a dusty black streak on your hand. This is the source of the gritty black dust on the trains which is most noticeable around the coupled cabs.

Carbon shoe dust

Also previously mentioned, the overhead wires are staggered so that they make a zigzag motion over the pantograph. This ensures that the carbon shoe wears down evenly across the length of its surface. Under normal wear and tear, a carbon shoe can last from 9 months to a year before it needs to be replaced.

It can happen sometimes that rather than sweeping back and forth over the carbon shoe, the catenary will instead wear a narrow groove into the carbon, causing the wire to become stuck in the groove and wear just that part of the carbon shoe down. Potentially the wire can saw down into the pantograph if the groove is not noticed and fixed – remember that the spring-loaded pantograph puts a considerable amount of upward pressure on the overhead wire. A groove in the carbon shoe will require the train be pulled out of service so that the carbon shoe can be replaced before the pantograph breaks. This is one potential cause of a pantograph breaking.

Another cause can be extreme heat, and we’re getting near that time again.. well, maybe, if we get any proper heat waves now that it’s summer. As I posted last year, hot weather causes the overhead wire to sag when the weights on the catenary poles hit bottom and can’t provide enough tension in the overhead wire.  When this happens, train speed is reduced to prevent the pantograph from getting caught in or pulling down the overhead wire, which would do significant damage to both.

It’s also possible that damage to the overhead wire can break a pan, such as intentional vandalism. This is part of the reason for sweep trains every morning as well as regular walking inspections of the overhead wires to check for any damage or anything else that looks questionable.

How can you tell something broke?

Aux Fail (the red light on the console), trailing Type 1 cab WB at Jeld Wen Field

In Type 1-3 cars, often the first visible indication that an operator sees that something went wrong with one of the pantographs is the “AUX FAIL” annunciator in the console lighting up (the reason why it’s lit in the above picture was actually for an HVAC fault in the Type 1, not anything with the pantographs, but I don’t personally have any pantograph problem photos. There are several different kinds of mechanical problems with the trains that will cause an aux fail). Type 4 consoles are different; the AUX FAIL annunciator reads AUX FAULT instead, there is also a MAJOR FAULT annunciator (though you can’t really see the annunciators in that linked picture), and there is also the TOD, or Train Operator Display screen next to the speedometer which displays mechanical problems with the train. And it goes without saying, but the train will also not operate properly if the pantograph is breaking or broken (moving sluggishly or not at all, lights going out, etc). Operators notify Control if there is any indication of a mechanical problem – an aux fail could be something benign like the HVAC blowers not working, but it could also be the first clue you have that your pantograph is currently being shredded.

So yes, pantographs can break, but it’s rare to have your trip disrupted because of a broken pantograph. The parts of them that are designed to wear out (such as the carbon shoe) are monitored and replaced when needed.

Of course, no post about broken pantographs would be complete without this (non-TriMet) video. Not really sure what the backstory of it is – some of the comments say it was done as a test but I don’t know if that’s true.

Washington Street

Washington Street in Hillsboro

Washington Street is the pre-empted area at the western end of the Blue Line. In this picture, you can see the pre-empts (all yellow horizontals since there are no trains moving through) on both sides of each intersection, though they’re a little easier to see on the left. Also in this picture, the way the overhead wire zigzags is clearly visible – remember this is done to evenly wear down the carbon shoe on the pantograph.

Another one for the electricity fans

I think I should just change the name of this blog to “Arcings of a TriMet Pantograph” since far and away that’s the sort of thing people are searching for when they end up here.

The other night I was on foot downtown; got this video.

And a still from the video:

pantograph arc at night

Which looks neat and all in a special-effects kind of way, but it’s not really a best practice..