Monthly Archives: November 2010

Stop (and go) – Part 2

More on light rail braking, which was a surprisingly hot topic – I didn’t realize that dynamic braking on light rail cars would be that interesting in the blogging world, but there we are. Anyway, a belated hello to the people coming over from Reddit.

Disc brakes, also known as Friction brakes

In my last post I mentioned that dynamic braking is the primary method of braking at speeds greater than 3 miles per hour. Slower than 3mph, the dynamic braking blends with the friction brakes. This is because at speeds that slow, the motors-acting-as-generators can’t generate enough power to actually stop the train – remember that dynamic braking works by converting the motion of the train into electricity. Not enough motion = not enough stopping power. So at about 3mph, the friction brakes are applied, and ultimately these stop the train once the dynamic brakes have slowed the train enough.

The friction brakes are located underneath the train on the wheel axles.

Friction brake on a wheel truck in the shop – it’s the part that kind of looks like a sideways Coliseum in the middle

Here is a better un-blurred picture of the friction brakes. Actually all of the photos in that set are worth looking at if behind-the-scenes train stuff is your thing, and considering that you are presently reading a blog entry about the braking systems of light rail vehicles, it probably is your thing.

Inside the cab, the operator can tell if the friction brakes are applied or released with this indicator light, found in Types 1-3. It’s lit while the train is in motion above 3mph because the brakes are released. This indicator goes dark only when the brakes are applied. In the Type 4s, a similar indicator is lit only when the brakes are applied, and is dark when the brakes are released.

If you’re outside the train or in the cab looking at the mirrors, you can tell when the friction brakes are applied by watching the red brake indicator lights above the wheel trucks (Types 1-3) or over the doors (Type 4).

In this animated gif of a train stopping at a platform, you can see the brake light which is above the second passenger window from the door come on as the train almost comes to a stop, then it goes dark again when the brakes are released as the train moves up a bit (probably because the operator stopped on the dead spot) and then back on as the train comes to a final stop to service the platform.

Exterior brake indicator lights, Type 3 & Type 1

Exterior brake indicator lights on a Type 4

On a Type 4, the exterior brake indicator lights are located right above the door open indicator lights – the red light is the brake indicator and the yellow light is the door open indicator. Looking at a stopped Type 4 when the doors are closed, only the brake indicator lights will be lit.

The exception to the rule – brakes applied, but the indicator lights are dark

The exterior brake indicator lights will be dark if no operator is keyed in to the train even though the brakes will still be applied. This can be a useful thing for passengers to know – if you’re running to make a stopped train at the end of the line and you don’t know when it leaves, check the brake lights. If they’re dark, the operator hasn’t keyed in in the cab (and might not even be in the train yet) so you still have some time. If they’re lit, the operator is in the cab so the train will be leaving shortly.

Friction brakes work on a hydraulic system. Occasionally a friction brake will “hang” and will be stuck applied. When this happens, the operator can manually release the brake by pumping off the hydraulic fluid. This is what those boxes labeled “MRU” or “brake release unit” inside the trains are for – this is the manual release unit. The whole procedure for releasing a friction brake is very different in the Type 4s – you can see some of it (how the brakes are pumped off) in this video from earlier this year when a Type 4 had mechanical problems at NE 60th.

Track brake

Track brake on a Type 2

This one I have mentioned before – the track brakes hang between the wheels. The operator applies this to assist in stopping the train, typically on slippery tracks. This is also the brake that will be used in case of emergency during a dead car push. Because it rapidly brings the train to a stop which can be jarring for passengers, it’s not used in normal platform service unless the slippery condition of the rail warrants it.

Trivia: From a speed of 55 miles per hour, a MAX train will take about 600 feet to stop.

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..

Stop (and go) – Part 1

Someone found my site by searching a few permutations of “How do the Portland MAX trains stop?

I liked the question and so here’s your answer:

Multiple Brake Systems

Of course, it’s not going to be a simple answer. There are several brake systems on the MAX trains.

Dynamic braking

Dynamic braking is the primary method of braking used when the train is going faster than 3mph.

I’ve posted this picture before, but it’s helpful in this context so I’m posting it again – Reverser (on left) and Motoring Drum Handle (on right) of one of the low-floor cars. Click for larger version.

On a really, really basic level, you move the train forward by moving the motoring drum handle (MDH) into a propulsion mode, shown in green next to the MDH. This draws power from a substation through the overhead wires, which rotates the train’s motors and moves the train forward.

When you move the MDH into a braking mode (shown in red next to the MDH), that makes the motors stop acting like motors and start acting like generators. The function of a generator is to convert motion into electricity – think of wind or water generators that create electricity from the motion of the wind or water through them. So when the train is in a braking mode and the motors are behaving like generators, they take the forward motion of the train and convert it into electricity. This conversion slows the train down because the creation of electricity happens at the expense of that forward motion. This is a far more effective way to stop a train moving at high speeds than dragging something on the wheels of the train to slow it down would be.

But then what happens to that new electricity that was converted from the motion of the train?

In the Type 1s, that extra electricity is just given off as heat from the motors. It works, in that the train slows down which was your primary goal of braking, but it’s kind of a waste of that electricity.

The  Type 2s, 3s, and 4s, however use regenerative braking. I’ve mentioned circuits before in the sense of currents through the rails shunted by the axle of the train wheels. Now think bigger – a circuit going from a substation, along the catenary and down the pantograph to the train, out through the wheels and along the rails back to the substation.

More or less like that

When one of those low-floor cars slows down using dynamic braking, that created electricity isn’t just wasted as heat into the air. Those cars channel most of that energy back into that circuit, where another train can use it.

Think of it this way the next time you’re in a train braking to stop at a platform – if it’s not a Type 1, the extra electricity from your train slowing down is being sent back into the overhead wire. The next train can pick up that electricty created by your train and use it to propel forward instead of drawing all of its power from the substation. This is much more efficient, because the energy converted from your train isn’t completely wasted, and less power needs to be drawn from the substations when you take power from another train’s braking.

This blog discusses how regenerative braking works in detail with helpful diagrams if you are interested in a longer explanation.

More to come.

MAX in the movies

There’s a new Portland blog called TriMet Diaries that is just getting started but looks very promising. Recently they posted a video called F*ck You TriMet: A Love Story. It’s very nicely shot and the music is good, but I think I’ve spent too much time on the trains to be able to appreciate it in any romantic sense.

We see the girl leaving Papa Haydn East, located on 5829 SE Milwaukie, far from any light rail platform. She then hoofs it up to Overlook Park, about 6 miles north of there (when there was a perfectly good stop for the 19 right across the street from the restaurant)…

…only to just miss a southbound train.

Meanwhile, on the west side, the guy runs across the pedestrian bridge at Sunset TC and down to the platform, where he just misses a Red Line.

What remains unexplained is why he passed up the Blue Line behind it (which generally speaking would be scheduled about 7 minutes later..)

Blue Line to Gresham, as indicated by the sign in the window

So then the girl decides to walk to…wherever she was going to go, except she goes past the Palms Motel, which is farther north of Overlook Park. That southbound train she missed wouldn’t have helped.

That’s pretty much the end of it – I guess it was a love connection missed because they both missed their trains, or as Josh said they didn’t know about Transit Tracker. Still, light ribbing over the geography aside, it’s beautifully shot and always nice to see the trains in other people’s art.

One of the commenters on the Oregonian mentioned The Hunted regarding the geography in the film clipI thought of that movie after seeing this too. Not so much for the liberties taken with geography, but because it’s one of the few movies that features a MAX train*

*that’s actually an articulated bus, on the Hawthorne Bridge (the MAX trains go over the Steel Bridge in real life) and it’s been a while since I’ve seen the movie but I vaguely remember the train sounding like a freight train instead of light rail in that part of the movie.

I didn’t take either of these next two pictures of the artics that were made to look like Type 1s for The Hunted.

Car 301 looks nothing like that, but altogether not bad for a fake train

And stored under the bridge

Anyway, back to the Love Story TriMet video. I liked the way it was shot and seeing the trains featured in it, so I went to the director’s vimeo account to see if he’s done anything else MAX-related and found this one:

It’s got some really nice shots of an eastbound Type 4 on the Blue Line and a northbound Type 3 on the Yellow Line.

I know that there was a MAX train in Extraordinary Measures, but I haven’t seen the movie and can’t find any clips of it on Youtube. Offhand I can’t think of any other movies that have our trains (or buses made to look like trains) in them.

 

Edited: Forgot about What the Bleep Do We Know? when I posted this morning, but that’s got some footage of Goose Hollow & the Robertson Tunnel.

Bob R also mentioned Zero Effect and Leverage as other media that have featured TriMet.

BREAKING NEWS

!!!  PRIORITY ONE  !!!

BUS DRIVER WHO IS PAID BY THE HOUR WORKS A LOT OF HOURS, GETS PAID FOR IT.

SOMEONE LET THE MEDIA KNOW, THIS IS IMPORTANT!!!!


Oh wait, they already know.

This really isn’t as much of a shocking new paradigm as the Oregonian would like it to be. Any moderately bright middle schooler could do the math for you. Remember grade school math word problems? “If a bus driver at the top of the pay scale makes $25.13 per hour for the first 8 hours, and then 1.5x that an hour for every hour after the first 8, and they work 9 hours a day, or 10, or more, how much money do they make?” The pay scales have been posted on TriMet’s website for a long time now – this isn’t news, nor is the concept of overtime.

The operators who are making well above the average are the ones willing to take every minute of overtime offered, working every holiday, working more than 8hrs/day, and working as many days off as allowed (operators can’t work more than 13 days in a row). And operators aren’t the ones who write the runs – if there are runs that pay 10, 11 hours a day, ultimately someone is going to sign them (usually the highest seniority people, but not always). Why should the operators who sign runs written with a lot of overtime have to apologize for it?

Why is there so much overtime available anyway?

Well, it’s kind of funny.  See, we’ve had this hiring freeze due to budget problems…

PORTLAND — TriMet officials said declining payroll tax revenues and pressure to crunch the budget will likely cause yet another round of route reductions and another increase in fares as well.

TriMet officials said they need to cut the budget for the next fiscal year by $27 million. Proposed changes include a 5-percent administrative cut, a salary and hiring freeze, reductions to bus and MAX service and a five-cent fare increase.

I forget exactly when the hiring freeze started – I would have guessed in 2009, but I did some searching and found this KGW news article on the hiring freeze dated February 10th of this year. Okay, let’s start with that date. Now here’s why this is funny – these are the job openings that have been posted at TriMet since February 10, 2010 (and the associated salary range for each, not including benefits):

  • Manager, Benefits; $72,776.00 – $109,165.00
  • Senior Accountant – Treasury & Cash Management; $51,652.00 – $77,479.00
  • General Manager (heh); $215,000
  • Field Outreach & Community Relations Representative; $12.56-$17.58/hr
  • Deputy General Counsel – Real Estate; $93,360.00 – $140,038.00
  • Real Property Specialist; $56,340.00 – $84,509.00
  • Executive Director Capital Projects (after Neil transferred to General Manager); actually I don’t know what this compensation range is, but according to that list of salaries, Neil made $184,690.92 so we’ll go with that.
  • Contracts Administrator III; $56,340.00 – $84,509.00
  • Director Transportation Operations; $85,986.00 – $128,977.00
  • Systems Engineer II-Network; $72,776.00 – $109,165.00
  • Service Worker; $15.78 – $21.04/hr
  • Director Safety & Security; $85,986.00 – $128,977.00
  • Administrator, MTP Contracts; $22.75 – $34.12/hr
  • Manager, Facilities Systems; $72,776.00 – $109,165.00
  • Receptionist; $12.56 – $17.58/hr
  • Legal Assistant; $19.05 – $28.57/hr
  • Coordinator, Operations Services; $20.83 – $31.24/hr
  • Facilities Specialist; $19.05 – $28.57/hr
  • Maintenance Supervisor; $27.09 – $40.63/hr
  • Accounting Manager; $72,776.00 – $109,165.00

Heckuva hiring freeze there…

Not counting the hourly jobs (because I don’t feel like doing the math) or the Executive Director of Capital projects (because I don’t have the range), that’s a total range from $935,768 on the low end to $1,331,514 on the high end of salaries of jobs posted at TriMet during this supposed “hiring freeze”.

You know what’s missing from that list? Bus operators. I don’t remember offhand the last time minirunners (part time bus operators) were hired, but I’d guess it was around the end of 2008. We have the money for all those other jobs, but no money to hire bus operators – in fact, bus operators were asked to take voluntary unpaid leaves of absence!

But buses still have to go out even when we’re short on operators – spend about 5 minutes on Twitter when a bus doesn’t show up to see how much people love it when their bus is a no-show. If we’re not hiring more operators to fill out the ranks, the only alternative is to have operators work overtime to keep things moving. Many operators are willing to take on overtime because hey, if you can do the work, it needs to get done, and you can make time and a half on it? Why wouldn’t you take it? So a lot of operators do. I don’t see why people have a problem with this – if operators didn’t pick up RDO work or if none were willing to work overtime, there would be a lot more buses & trains canceled due to no operator available to take them out. It’s mutually beneficial to the operators who want the overtime and the transit-dependent who want their buses to show up.

Here’s a thought for you – if there were enough operators to cover all the work, there wouldn’t be so much overtime available.

It’d be a lot cheaper if TriMet would hire minirunners again. They start at the bottom of the pay scale – a whopping $13.83/hr. Sure, operators who have been picking up the overtime would lose a lot of that and there’d probably be some grumbling about it, but overtime (though nice) is not guaranteed. Paying a newcomer $13.83/hr for their shift versus paying $37.70/hr (time and a half for the top rate of bus operator pay) would be a lot cheaper for TriMet to do, and you’d see fewer operators making these apparently oh-so-extravagant salaries. Actually I’d kind of enjoy it if TriMet posted openings for minirunners again – to all of the people whining about the work bus operators do and what they get paid for it: that would be your chance to either turn in your application to be a bus driver yourself or forever hold your peace.

Edited to add: Been talking about this with someone else, who said that there could be a budgetary reason why TriMet feels it makes more sense to pay lots of overtime than it would be to hire new minirunners.  Maybe that’s true – neither of us are TriMet financial planners with particular inside knowledge into that.

But I think it would be kind of nice if there was an official TriMet response to this media frenzy over operators who work a lot of overtime and make the money that they do because of it. TriMet doesn’t seem to mind paying it, so they should stand up for the operators that take on that work.