Track clicking?

[Deleted]

I've noticed this at Ruislip Gardens,South Ruislip and North Acton but it may occur elsewhere.

As trains approach from some distance and after departure you get random clicking noises from the track area.

It sounds like thin metal plates (part of the insulator pots?) being attracted to the conductor rail by the magnetic field caused by the traction current which then drop away after the train has passed.

Is this the cause or is there another explanation?

Andy

[rincew1nd]

I've heard this gentle tinkling sound at quite a few places in the UndergrounD, I've always attributed it to the current flowing through the current rails creating a magnetic field which then attracts the metal carriers on the top of the insulator pots. Happy to be corrected though!

[Deleted]

Ive noticed that! But only on my part of the Central

[Deleted]

I'd always assumed it was the pots wiggling around from vibrations in the track.

[Deleted]

May 2, 2011 8:59:35 GMT @andyjg said:

It sounds like thin metal plates (part of the insulator pots?) being attracted to the conductor rail by the magnetic field caused by the traction current which then drop away after the train has passed.

It's exactly this. Sometimes you can even see the metal plate jinking up and down.

[Tom]

May 2, 2011 23:15:01 GMT bananaman said:

May 2, 2011 8:59:35 GMT @andyjg said:

It sounds like thin metal plates (part of the insulator pots?) being attracted to the conductor rail by the magnetic field caused by the traction current which then drop away after the train has passed.

It's exactly this. Sometimes you can even see the metal plate jinking up and down.

I don't think it has anything to do with magnetism but everything to do with vibration. Remember that shoes slide along the top of the rail, rather than roll like wheels. As each shoe hits the start of a section of current rail, it tries to move the rail. over time, they would move if the rail wasn't tied down with anchors. The clicking noise, I've always thought, was due to the vibrations transmitted by a shoe striking the current rail further along the line.

[mrfs42]

I've only ever noticed on the Central post-ATO, and thought it was some form of inductance vibration - it only happens when there is an unrestricted code feed IYGMD.

I have spent a couple of hours at White City (over several visits!) observing and making notes on this very phenomenon.

[Tom]

White City was one of the other locations I've heard it (though mostly on the EB). Greenford was another.
It would be interesting to see if it still occurs at White City now that the current rail gapping in the area has been modified...

[mrfs42]

I might be thinking of a different click - as to my ears it seems to come from the old Ross Courtneys. However, I have a 'listening' visit programmed in sometime for exactly the reason you surmise.

Just got to finish painting this engine first!

[railtechnician]

May 3, 2011 0:19:14 GMT mrfs42 said:

I might be thinking of a different click - as to my ears it seems to come from the old Ross Courtneys. However, I have a 'listening' visit programmed in sometime for exactly the reason you surmise.

Just got to finish painting this engine first!

Interesting, I've never heard a Ross Courtney click but I've heard track circuits clicking. The West end of Hatton Cross was a favourite for this and in the pitch black one could see the iron filing attracted around the block joint over 8's points glowing red. It was the first point of call for a track failure around the points!

[plasmid]

This happens a lot on the Central EB between Liverpool Street and Mile End when the train is passing at speed through a part of the tunnel which is ventilated.

The rush of air bogs down the front of the train, makes the double doors slam and causes this 'clicking' noise you are all talking of.

[Ben]

There are lots of odd clicking noises, but click never seems to be quite the right word to describe them. Theres the odd electric noise that sounds a bit like 'jolt' when a trains shoes pass onto a near current rail, then occasionally at quiet stations like Ickenham, between trains you can hear a noise rather like that of two knives hitting each other side on, but with a hint of sonority. I guess the latter is something to do with track circuits?

[Deleted]

If it's the track 'twanging' I've noticed it as something that seems to only occur on CWR. It's not just the Underground I've heard it on, but also on some of the Southeastern lines (so that doesn't rule out the 3rd rail) but it sounds as if it's something to do with the train contacting the rails. Points maybe?

[metman]

I hear it all over the met and certainly think it is the track moving and causing the metal parts of the insulator pots moving. It will be interesting to see if it happens where the new aluminium conductor rail and new pots are installed?

[Deleted]

If it is the metallic elements of the pots, the composition of the conductor rail will have no effect on magnetism as it's the flow of current that creates a magnetic field in this case.

That is assuming that the pots still have a magnetic material to part of them.

[rincew1nd]

I am familiar with a variety of railway noises, the noise I'm thinking of is a definite "tinkle".

[metman]

Yes the tinkle!!

[edwin]

Do you mean the sound at the start of these videos?

[Deleted]

No no, this sound happens far before the train comes near the platform, its much more subtle. Its difficult to explain but its like the sound of two pieces of light metal clicking onto eachother

[rincew1nd]

May 4, 2011 0:07:04 GMT edwin said:

Do you mean the sound at the start of these videos?

These aren't the sounds I'm thinking of, these are joint clinks or flange twings; I'm remembering a definite tinkle.

[Deleted]

Thanks for all your replies.

I have seen the light --- well I now know what causes the click/tinkling noise.

I was at North Acton on Friday and happened to be looking at an insulator pot on the positive rail as a train was approaching.

Between the U shaped stirrup that holds the rail and the rail itself is what I've always assumed was a resiliant pad to cushion the rail.

This pad which must be metal and magnetic jumped up a small distance and stuck to the underside of the rail making the clicking noise.

Andy

[Deleted]

It does appear to come from the insulator pots. under each insulator pot is a thin metal 'height adjustment' wedge. Its about ¼" thickness. And its purpose is to adjust for minor deficiencies in track bed and rail height. One or two, or perhaps even three or more of these wedges can be placed under the conductor rail where it sits on each insulator pot.

These wedges are sometimes plastic, but are of the same shape. I was intrigued to what caused this noise until recently where I found one of the wedges beside the track, and dropped it lightly onto a discarded insulator pot. The sound was alike, but not totally exact.

Insulator pots now are of a new design, and look like they can be adjusted by simply screwing the U 'stirrup' onto its base.

[Deleted]

To clear it up...



The noises made at the start of that video. Is that what we're on about?

[Deleted]

I've just tried that link and get a 'This video has been removed by the user.' message so can't comment.

Andy

[Deleted]

I notice a "clink" (new term!) which, I'd say, is almost like two heavy glasses hitting together - coming from down in the track area about a minute before trains appear at quieter District locations like Barons Court and Stamford Brook. I had actually assumed it to be connected to comms - maybe the lightbox displays - since it seems to be just before the destination appears at Barons Court Westbound, anyway.

Will try and record the sound.

[Deleted]

Hello folks,

I have often heard a noise similar to what you describe in the Paris Metro. Would you consider the following attempt of an explaination: Noises are transmitted through metal much quicker and longer than in the air; they are also much more distorted than in open air because a metal bar does not transmit equally all the frequencies, and this differentely than open air does.

So, before the usual train noise can be heard (and in London tube lines, before the wind blows heavily to announce the train!) a different noise, mainly coming from the wheels and the shoes, can be effectively heard, a kind of "cliquetis" of high frequencies...

[Deleted]

In 35 years of travelling on the underground I've heard this noise and for the first time saw the cause today which is as andyjg described. Here's a photo of the bit of metal that jumps up to the live rail.