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Post by downdc on Mar 13, 2023 16:41:59 GMT
Hi all, a bit of a strange sounding question perhaps, but prompted by an observation whilst travelling yesterday, 12/03/23.
I was travelling Watford-Rickmansworth in the morning, during reported ‘severe delays due to a track obstruction at Harrow on the hill’. Right after I arrived at Moor Park, a train arrived on the adjacent platform 3 heading to Watford; the number of people left on the platform after it departed indicated there had been a gap since the last Amersham/Chesham service, as it is very unusual to see any number of people at Moor Park. I also spoke to a few, and it was clear they’d been waiting a while. The scheduled 1123 to Chesham did not show up on the platform 3 DMI, but after a few minutes, the DMI on Platform 1 (not usually in use on the weekend) showed two Chesham trains, a minute apart. As this clearly couldn’t be correct, I waited for a while until a train actually came into view on the northbound main, before crossing over to platform 1.
As the train approached the platform end, it was travelling noticeably faster than usual for that point. One of the passengers I’d previously spoken to commented ‘he’s not actually going to stop’, and I have to say I also thought this may be the case, partly because the train also whistled once it had passed the platform end. (I momentarily wondered if it was travelling out of service to try and get things back on time, and that the DMI was simply wrong, which is not unheard of on the northern Met). As the train slowed over the length of the platform, I actually thought I was going to witness an over-run for the first time. That did not happen, but when the train did actually come to a stop, there was a strong electrical burning type of smell in the air. A sort of mix of hard braking in a car and the smell you get if you accidentally turn on a microwave with something unmicrowaveable inside! We then absolutely MOTORED to Rickmansworth, where I left the train and could still notice the smell upon doing so. It would seem that the train was being driven in something of a spirited manner, presumably in an attempt to recover the service.
I may be absolutely barking up the wrong tree, but could the smell I noticed have been caused by hard braking? And, in the absence of anything obvious from the customer point of view (I.e. somebody standing too close to the platform edge etc), are there any other reasons why an operator would whistle having entered a platform they’re about to stop at? I’m aware from previous experience and also from explanations from the past on this forum that Met trains can non-stop these platforms at line speed; a whistle in this instance would seem quite self-explanatory.
To be clear, I’m not being at all critical of the actions of the train operator, merely curious about what I saw, as always!
Many thanks
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trainwizard
On a quest to find the magic money tree
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Post by trainwizard on Mar 13, 2023 17:01:05 GMT
I may be absolutely barking up the wrong tree, but could the smell I noticed have been caused by hard braking? In my opinion, a missed opportunity for "absolutely braking up the wrong tree"  I am absolutely no expert on what an emergency braking smells like, or anything to do with train brakes, but the smell you described would probably be due to heat/burning caused by the high friction from suddenly stopping a vehicle at a high speed. |
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Post by A60stock on Mar 13, 2023 17:10:23 GMT
Hi all, a bit of a strange sounding question perhaps, but prompted by an observation whilst travelling yesterday, 12/03/23. As the train approached the platform end, it was travelling noticeably faster than usual for that point. One of the passengers I’d previously spoken to commented ‘he’s not actually going to stop’, and I have to say I also thought this may be the case, partly because the train also whistled once it had passed the platform end. (I momentarily wondered if was travelling out of service to try and get things back on time, and that the DMI was simply wrong, which is not unheard of on the Northern Met). As the train slowed over the length of the platform, I actually thought I was going to witness an over-run for the first time. That did not happen, but when the train did actually come to a stop, there was a strong electrical burning type of smell in the air. A sort of mix of hard braking in a car and the smell you get if you accidentally turn on a microwave with something unmicrowaveable inside! We then absolutely MOTORED to Rickmansworth, where I left the train and could still notice the smell upon doing so. It would seem that the train was being driven in something of a spirited manner, presumably in an attempt to recover the service. I have been on a fast train which announced at Harrow on the hill that the first stop would be Rickmansworth and not Moor Park. I made a post about it somewhere and to this day I still don't have an answer as to whether this was intentional or miscommunication between control and the driver. The train did not stop at Moor Park and no, this was not a Chiltern service districtdavesforum.co.uk/thread/30132/moor-park |
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Post by Dstock7080 on Mar 13, 2023 17:13:52 GMT
Indeed, emergency braking - either in 'emergency' position or letting TBC Traction Brake Controller go, would result in emergency application of friction brake only, which would cause brake dust.
As friction brakes are rarely used on S Stock except at designated "friction only" stations to clean the brake block of detritus.
(The "‘severe delays due to a track obstruction at Harrow on the hill" was a shopping trolley lodged under a southbound train entering platform 6, which also damaged pointwork.)
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Post by downdc on Mar 13, 2023 19:21:28 GMT
I may be absolutely barking up the wrong tree, but could the smell I noticed have been caused by hard braking? In my opinion, a missed opportunity for "absolutely braking up the wrong tree" Naturally, it crossed my mind! However, I was aware of the very general principles you describe despite my extremely rudimentary understanding of physics, electricity, electric motors and engineering more broadly; what I was looking for was enlightenment and nuance as I wasn’t at all aware of the specifics of the modern braking technology on S stock trains, regarding regular and/or emergency braking applications… I may also suggest that neither ‘high friction’ or ‘suddenly stopping a vehicle at a high speed’ pertain closely to railway physics but as aforementioned, I am a merely a layman educated mostly by the wisdom found online! |
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Post by downdc on Mar 13, 2023 19:23:36 GMT
Indeed, emergency braking - either in 'emergency' position or letting TBC Traction Brake Controller go, would result in emergency application of friction brake only, which would cause brake dust. As friction brakes are rarely used on S Stock except at designated "friction only" stations to clean the brake block of detritus. (The "‘severe delays due to a track obstruction at Harrow on the hill" was a shopping trolley lodged under a southbound train entering platform 6, which also damaged pointwork.) …which is why I appreciate this reply, I did wonder if the friction element was different as a) that smell is not usual and b) the speed entering the platform seemed higher than usual. Yikes re the trolley, those sound like very complicated ramifications from a very moronic act |
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Post by d7666 on Mar 13, 2023 19:52:33 GMT
There might also have been some accumulated gunge around the brake gear that with a harder than usual application generated enough heat to burn it. Smell of electrical burning is more often than not insulation. You only need some plastic like a carrier bag lodged in the wrong place and melt and burn and hence the smell.
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Post by d7666 on Mar 13, 2023 19:55:08 GMT
I may be absolutely barking up the wrong tree, but could the smell I noticed have been caused by hard braking? In my opinion, a missed opportunity for "absolutely braking up the wrong tree" It was Moor Park not Barking...........  |
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Post by zbang on Mar 13, 2023 20:48:56 GMT
Smell of electrical burning is more often than not insulation. You only need some plastic like a carrier bag lodged in the wrong place and melt and burn and hence the smell. IME, the first thing you'll smell is burning dust and other collected detritus; it starts to smell long before the motor insulation does. |
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Post by downdc on Mar 13, 2023 20:51:36 GMT
In my opinion, a missed opportunity for "absolutely braking up the wrong tree" It was Moor Park not Barking........... Please, no Moor! |
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trainwizard
On a quest to find the magic money tree
Posts: 139
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Post by trainwizard on Mar 13, 2023 21:36:18 GMT
It was Moor Park not Barking........... Please, no Moor! I'm glad to have started it but perhaps we should put the brakes on this pun train and get back on topic. |
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metman
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Post by metman on Mar 13, 2023 21:48:37 GMT
It’s quite a common smell on the network or it used to be. The previous A stock always had that smell when the Westinghouse brake was used and was quite a common smell at Moor Park as trains can brake quite late off a fast run.
Lorry brakes have a similar smell if used on a hard brake.
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Post by melikepie on Mar 13, 2023 22:00:41 GMT
In my opinion, a missed opportunity for "absolutely braking up the wrong tree" It was Moor Park not Barking........... In that case shouldn't it be "Parking up the wrong tree"? |
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Post by Dmitri on Mar 14, 2023 0:25:57 GMT
What are S stock brake blocks made of? In our metro, brake blocks are made of plastic composite of sorts, so burnt plastic smell after heavy pneumatic braking is normal.
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Post by d7666 on Mar 14, 2023 1:31:39 GMT
I was not suggesting that motor insulation was burning.
I stated that recognisable smell of electrical burning arises from insulation, which is polymer based, as is a plastic carrier bag, and suggesting that a melting carrier bag trapped by friction braking would generate a similar smell, as well as all the other gunge that accumulates there, dust included.
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Post by downdc on Mar 14, 2023 6:26:51 GMT
It’s quite a common smell on the network or it used to be. The previous A stock always had that smell when the Westinghouse brake was used and was quite a common smell at Moor Park as trains can brake quite late off a fast run. Not at all common in my current experience, and I was wondering if that what was to do with how the braking works now as opposed to previously, as has been confirmed. Certainly, this train seemed to brake quite late off a fast run! As for the dearly departed A stock, the sensory elements that remain most clear in my memory are not the smells, but unquestionably the cacophony of characterful sounds, including of course exhausting the brake air at terminus stations. Ah, wist! |
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Post by t697 on Mar 14, 2023 6:29:41 GMT
Sorry,something went wrong and I can't edit my mess above. Anyway, S stock uses the same brake block compound as other LUL fleets. There is a specific thermosetting resin binding the friction material fillers. This produces a distinctive smell when used hard,as would be the case for a high speed emergency brake as seems to have been the case in the Moor Park example quoted in the OP.
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Post by bigvern on Mar 14, 2023 8:14:39 GMT
The electrical smell you get from braking is the regenerative resistance banks which have to dissipate heat,if a harder service brake has been called for it creates more heat especially at a higher speed, The resistances heat up and can cause a metallic electrical type smell,
This was common on the Jubilee, Victoria and Northern line trains when the traction performance was increased and often dust has also built up on the resistance bank, occasionally enough to cause a 'smoldering' incident.
However in normal service the trains have been conditioned so won't cause this smell normally.
As regards brake blocks these are normally used when regenerative braking is to weak to slow the train at around 5mph or so.
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Post by grumpycat on Mar 14, 2023 19:43:33 GMT
Yep. It's more of a burning smell it happened for some reason on a DLR train I was on
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Post by downdc on Mar 14, 2023 22:37:16 GMT
The electrical smell you get from braking is the regenerative resistance banks which have to dissipate heat,if a harder service brake has been called for it creates more heat especially at a higher speed, The resistances heat up and can cause a metallic electrical type smell Touching once again on my electrical ignorance, I did wonder about this, however, also returning to barking (braking/parking) up the wrong tree, I may have been off with ‘electrical’ burning smell. I’m not sure, it was definitely a noxious/unpleasant sort of a smell, I would have thought given what Dstock7080 explained, it was likely the ‘thermosetting resin’ described by t697. Thermosetting is a new term to me, and one I like! |
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Post by brigham on Mar 15, 2023 8:56:07 GMT
Phenolic resins are thermosetting. Instead of softening with heat, like thermoplastic ones, they char, with a horrible unnatural smell.
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