Clunk and Loud Noise - EMU's

[bluenoxid]

Could anyone break the reasons for the noises in this part of the train down into something basic. My head says that it they are linked to the brakes and the sections without power (my head has gone blank).

http://www.fixmytransport.com/problems/798

On 0710 stansted express from Liverpool St. In third carriage (disabled toilet and space). Very loud humming noise can be heard and felt as a vibration. Once or twice something goes clunk and it disappears for a few seconds. Can't be heard in other carriages.

I travel on stansted express regularly and there is quite often a loud clunk that seems to occur when the train slows down. Very loud and makes everyone jump every time.

I live in DC territory now (overhead that is)

 

[87015]

Could anyone break the reasons for the noises in this part of the train down into something basic. My head says that it they are linked to the brakes and the sections without power (my head has gone blank).

http://www.fixmytransport.com/problems/798

I live in DC territory now (overhead that is)

The humming is presumably the aircon (or a PA system on the blink) if near constant.

Occasional bang is the VCB opening/closing at neutral sections and the 379s do make quite a racket when doing so (as do most new units, to be fair)

 

[The_Stig]

Could anyone break the reasons for the noises in this part of the train down into something basic. My head says that it they are linked to the brakes and the sections without power (my head has gone blank).

http://www.fixmytransport.com/problems/798






I live in DC territory now (overhead that is)

The first one sounds like the battery charger and transformer pump cutting out and then restarting when the VCB trips during a neutral section. If it is OLE.

 

[Phil6219]

It wasn't someone flushing the toilet was it?

Just an idea as modern stock has those retention ones which work in a very similar way to modern aircraft lavatories, which scare the hell out of unsuspecting people when they go "whoooosh"

Just a thought given you said it can't be heard in other carriages otherwise my money would have been on passing through neutral sections.

Phil

 

[barrykas]

I always thought the humming was the electricity, as I suspect the location in question is underneath the pan...

 

[bluenoxid]

Cheers Guys

 

[John Webb]

I believe the hum is the transformer converting the 25kV from the Overhead line to a lower voltage for the motors and their control equipment to use. Hence it stops as the neutral section is being passed.

 

[westcoaster]

I believe the hum is the transformer converting the 25kV from the Overhead line to a lower voltage for the motors and their control equipment to use. Hence it stops as the neutral section is being passed.

That's what I thought it was but it could be the ACM'S or MCM's . Also that hum grates on me so much, when I go pass or not at work ill move carriage so I don't have to hear it.

 

[swtandgw]

That's because the third coach (the one with the accessible toilet) is the PTSO (Pantograph Trailer Standard Open), where the transformer equipment and pantograph are located.

Whenever the train passes what's called a neutral section, or in cases where the train is dual voltage, and is switching to AC (overhead) power from DC (third rail), the 'clunk' comes from the VCB (Vacuum Circuit Breaker), which is more prominent if you sit right underneath the lower roof where the recess for the pantograph is situated. It gave me a right jump when I was travelling from Bletchley on a Southern 377/2 last year, after it passed a neutral section before (IIRC) Tring!