Anyone Know Anything About Trains?

[David87]

Bit of a sad question about trains here, so I do apologise. I travel to London every week from Essex on the train and when it arrives at the platform, it makes a funny noise when it travels past me (in my anorak). The best way I can describe it would be a bit like an alarm or the noise you would imagine a UFO to make! It's really weird and it makes me wonder every time I get on one.
I don't know the first thing about trains, but I'd like to know the answer to this! I've tried Wikipedia, but with no luck. If it's any help, the trains look like either of the two below. Thanks!

[Marc W]

The only thing I can think of that sounds like that is the door alarm to warn when they are about to open, but I know nothing about trains!

[finlo]

Air compressor for the brakes?

[Chrisgr31]

Are they diesels? As if they are I'll now be listening to see if ours makes a noise but I don't think it does!

[anonymous-user]

Could be the top train. Never seen one of those.

I don't ever recall the "Dusty Bins" (Class 321) ever making that noise.

Edited by anonymous-user on Wednesday 5th November 21:10

[David87]

Good suggestion, but it's not the door alarm. It's only when the train's coming in to the station, when it's doing maybe 5-20mph. Now you say it, I think it's much more noticeable on the top train. It says Siemens on the doors.

Edited by David87 on Wednesday 5th November 21:12

[anonymous-user]

Chrisgr31 said:

Are they diesels? As if they are I'll now be listening to see if ours makes a noise but I don't think it does!

Both EMU's (Electric Multiple Units).

[nownek]

Vibration on the tracks?

You hear a kind of "woo-woo" noise as a train passes a station at speed which could be described as UFO-like although I can't recall hearing it at the lower speeds you mention

[Phil Mycock]

Electromagnetic noise from regenerative braking?

[sa_20v]

Phil Mycock said:

Electromagnetic noise from regenerative braking?

Do they even have that? The 321 must be a twenty year old design now?

[David87]

Phil Mycock said:

Electromagnetic noise from regenerative braking?

Hmm, this sounds credible. Don't know what that is, but it does sound like a very 'electric' sound.
Now you mention it, perhaps the older style of train doesn't really make the same sound.

Edited by David87 on Wednesday 5th November 21:34

[smack]

The motors on the Siemens Desiro class trains make that sound.

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

Your first photo is of one.
http://en.wikipedia.org/wiki/British_Rail_Class_36...


I only know this as I use on SWT's, who have trains (Class 444 & 450's from wikipedia) that make the same sound...

[V8mate]

smack said:

The motors on the Siemens Desiro class trains make that sound.

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

Your first photo is of one.
http://en.wikipedia.org/wiki/British_Rail_Class_36...


I only know this as I use on SWT's, who have trains (Class 444 & 450's from wikipedia) that make the same sound...

Yep - it's just the sound of the motor spinning down, under braking, or spinning up, as the trains go to pull away.

[Olf]

anonymous said:

[redacted]

Really? Where is the second one drawing a current from then?

[miniman]

Olf said:

Really? Where is the second one drawing a current from then?

http://en.wikipedia.org/wiki/British_Rail_Class_321

[Olf]

miniman said:

Olf said:

Really? Where is the second one drawing a current from then?

http://en.wikipedia.org/wiki/British_Rail_Class_321

That's nice but the question still remains. In the second picture, where is the electrical supply to the train?

[Zad]

Centre rail?

[Olf]

Zad said:

Centre rail?

No, that's just rail waiting for installation or removal. See nearest tracks for some more.

[dilbert]

I don't know the exact details of the trains involved, but all of the more modern electric traction systems switch the input power at high frequency to govern the mechanical power at the wheels. Often this can work both ways, with the motors being used as generators to slow the train down.

The whining noise is the sound of the electricity switching on and off very quickly. You mainly hear the vibration that is caused by the change in torque from the motor. It's the sound of a very fast judder, like pushing the train forwards with a million tiny hammer blows.

[cobra kid]

Rail ringing due to rail fastenings and impact attenuation systems??

(Sad due to the fact I work in a laboratory developing them)