The two newest subway car models used on the NYC transit lines have a very distinctive sound to them.
The Bombardier New York City Transit R-142’s acceleration sound takes the form of 3 notes, always in the same order, that sound kinda like a violin: video here
On the other hand, the Kawasaki New York City Transit R-142A and R-143 cars have a very different sound, which is a lot louder: video here
Now, all of the other subway trains just have a single note that seems to correspond to the motor speed, but these cars emit frequencies that don’t seem to have any correlation to how fast anything is spinning, so what exactly are the mechanics behind these sounds?
Not familiar with the NY subway cars, but my wild-arsed guess is that the trains with the steady note have “chopper control”, whereas the ones with the stepped note have “notch control”. To explain this, trains have a series of different speed settings, not so much like gearbox speeds in a car, but more analogous to a car which has a gas pedal which can only be held at say five different points, rather than an infinite number. All trains’ motors tend to be of the notch variety, but “chopper control” gives the driver the illusion of an automobile-type infinite ratio. In a notch control train, the driver will go “ONE clunk TWO clunk THREE” and so on as she accelerates. In “chopper control”, the driver pushes the throttle forward, and the train goes into notch one for a bit, then starts “chopping” in a taste of notch two power, then a bit more, then it’s actually in notch two, then it “chops” in a little bit of three, and so on. This seems smoother.
Of course this is a guess, but it sounds like the likely scenario.
I’ve heard tell that one of the two models actually does have a physical gearbox (if you listen to the R143 video, after the initial pitch rise, you can hear the typical rise-fall sound effect of a multi-ratio vehicle).
Also, from what I’ve read around, all new york subway trains have 3 forward speed settings, labeled (for obscure reasons) “switching”, “series” and “multiple”. This seems odd to me, because the entire NYC subway runs on direct current, in which case can’t they just use a variable resistor?
The pick-up is DC, but the traction motors are AC, so it goes through a rectifier(?) thingummy. I’m also having second thoughts about notch control as you say the cars are new, and notch control is pretty ancient. All I can guess is that the chopper control on some of the cars is not very smooth.
I doubt the gearbox. That is very, very rare in rail. Gearboxes are used in some short Japanese trains that are diesel-hydraulic or diesel-mechanical, but for a 5 car electric subway train, probably not. Heavy trains don’t like mechanical linkages because you introduce clutch mechanisms and gawdnose what all. These trains are better suited to in-bogie traction motors with direct drive, as electric motors provide high torque even from a standing start. They may be geared, but not vartiably so.
I suspect it’s just lag. Being in the cab with drivers in Sydney (hang on, motormen for you NY types), you see them throttle forwards, and the pitch goes up, then there is delay as the speed of the train catches up to the new setting. In other words, the pitch represents power, not speed. Not very technical, I’m afraid, but I hope it explains it. Electric trains at full speed tend to be relatively quiet - well, quieter than you’d expect.
Well, not always at the same rate, but the initial sound never goes above that pitch. It hits the pitch and then fades out and then you hear the secondary noise.
That’s where it gets beyond my ken. I have a vague understanding of the process, but so vague that I’m not confident to try to explain it. I know that DC trains at least, as they approach cruising speed, get into all sorts of weird “weak field” stuff that makes my head hurt. We need David Simmons or one of our other sparky types to come along and put it in plain English.
The AC/DC thing is correct. My Dad is a keen amateur student of the subway and has been since the 40s–I’ll forward this thread to him and see if he has anything to add.
BTW, the TO’s (train operators, can’t call them motormen anymore) find the whine the most annoying feature of the new trains. Otherwise, they like them a lot. The repair guys do find it annoying that they’re so computerized you can’t pop open panels and repair things with your hand tools, usually, but they’ve been pretty reliable. I remember people gasping with delight and walking around them (if it wasn’t too crowded) when they first arrived.
The Sydney version of this is called the Millennium Train. It’s quite a handsome looking beast, but it is so high tech that there are cries of wasted money and over-engineering. It’s been a bug-filled introduction for this train, and it can’t run on some lines because it flips out the signalling infrastructure. It’s not popular with the drivers either because so much of the tech is shrouded in secrecy (corporate carry-on - I got monstered by security for taking a photo of the thing!) that they feel disconnected from the train. Unlike NY, the local drivers prefer the old trains with their “you can pop the hood and know what the bits are” feel to them. The Millennium Train is one of our first forays into AC traction (network is 1500v DC), and it has that constant violin sound (which I quite like).
Yeah, looking out the front window is mostly a thing of the past. Most TO’s have removed the black curtain that’s supposed to block the view but the windows are polarized so the view is sorta psychedelic. I remember standing on Dad’s feet to be able to look out the front of the old R33’s.
A few years ago, I had the misfortune to be on a San Francisco Muni streetcar that decided it was time for a break. While I’ve seen how newer light rail vehicles are being designed so their power conversion and motors make musically harmonious sounds, the Muni streetcars at that time (wretched things from Boeing Vertol) just made random notes, whirs and buzzes. The newer cars from Breda aren’t particularly melodious, either.
Well, this particular car chose to break and instead of the usual buzz and whir it would make starting off, it just went OOOOOOOO! click <pause> OOOOOOO! click. *Very * loudly.
cough cough
