73 Stock fault - help identifying sound heard on train

[orestad]

Was on a Rayners Lane train back home from King’s Cross St Pancras when I heard a strange sound coming from my carriage. I assumed it was the air compressors, I’ve never heard a train make that sound as it closes the doors and departs the station. The only time it would stop would be as it’s stationary on the platform.

Cut to two stations later at Holborn, train has issues departing the platform and would keep stalling, opening and closing the doors and not budging more than two inches. Driver eventually kicked us off and had to put the train out of service.

I’ve left the videos I’ve taken with the sound being made. One’s from inside my carriage (might need to put the volume up as it’s heard in the background, but it was very obvious in person) and one as it left Holborn.

I’d appreciate any affirmative answers as to what this sound is for sure and if this could’ve been what made the train go out of service.

Noise in carriage

Noise on platform

 

[Error404]

This is called "repeating line breakers".

The line breakers shut off the 630V to the motors. Like a main switch but also a safety mechanism should anything go wrong with motor circuit - the breakers will open.

The "repeating" is the driver asking for traction, them closing, something wrong with the circuit on that car, they immediately open. And it constantly repeats.

This results in no traction on that motor car. In the case of this stock [1973] the train will be 1/4 down on traction.

 

[Dstock7080]

This is called "repeating line breakers".

The line breakers shut off the 630V to the motors. Like a main switch but also a safety mechanism should anything go wrong with motor circuit - the breakers will open.

The "repeating" is the driver asking for traction, them closing, something wrong with the circuit on that car, they immediately open. And it constantly repeats.

Very nearly, line breakers are as you say 630v equipment and if open and closing would be a loud ‘pop’.
These are repeating contactors, the RPA Rotary Pneumatic Actuator (accelerator) is constantly turning and not engaging.
The result is the same as described above.

reported as door interlocks, below

 

[Mawkie]

Some excellent answers above, but the official report from the driver suggested the Train Operater was receiving a 'motoring on train doors indication' - there is a safety circuit on the train that determines if the doors are fully closed and if it determines they are open (to within a narrow parameter) cuts the power to the motors - this was the pulling away and jolting the OP describes. Sometimes, this is simply people leaning on the door as the train pulls away and is easily resolved with an announcement.

So it appears the train had 2 issues.

 

[orestad]

Thank you very much for the really helpful answers and ideas, I do appreciate them and it’s interesting getting to know the 73 stock like this, I do really like these trains and appreciate the knowledge.

Very nearly, line breakers are as you say 630v equipment and if open and closing would be a loud ‘pop’.

Every time a 73 stock train stalls it does indeed make a pretty loud popping noise, I’m assuming that’s what line breakers sound like?

Sometimes, this is simply people leaning on the door as the train pulls away and is easily resolved with an announcement.

I’ve always thought this was the case when trains stall once or twice, I feel like I’ve had it happen more often recently so I’m not sure if the train doors have just become sticky (if that’s the right word) due to lack of proper maintenance or old age, or if it’s really just someone somewhere on the train being a bit annoying.

 

[Mawkie]

I’ve always thought this was the case when trains stall once or twice, I feel like I’ve had it happen more often recently so I’m not sure if the train doors have just become sticky (if that’s the right word) due to lack of proper maintenance or old age, or if it’s really just someone somewhere on the train being a bit annoying.

The door mechanisms are fairly simple, but still contain a number of moving parts, and are powered by air rather than electricity. The electrical circuit that tells the driver if the doors are closed is still completed by rotating mercury switches! Moving parts do wear out, and it's probably true that LU have been moving towards being a more reactive organisation than a proactive one, but I'm not sure these kinds of things can be attributed to a lack of maintenance in every case.

With that in mind, there could have been a small item jammed in one of the door runners - sometimes rubbish will roll into them from the train floor as the doors open at a station. It often allows the circuit to complete initially (whilst stationary) but as soon as the train op pulls away the safety circuit is broken through the natural forces of acceleration on the door. Having someone lean on a door leaf has the same effect - except their weight maximises the effect upon acceleration.

The Line Controller will often allow for a quick visual inspection, but doesn't hesitate to take the train out of service due to the impact of trains being delayed behind the problem train - particularly those stuck in-between stations.

I think I see from your video the repeating line breakers were in the tail end of the train, so the driver may not have even been aware of them. (Although a good driver would probably have been able to feel the effects on the train from their cab and investigated. )

Lastly, I try not to think of my passengers as being annoying, but >0.01% of them do test my patience.