|
|
Post by runer100 on Nov 27, 2020 9:06:57 GMT
Hi all,
My house overlooks the central line on the Epping branch and for the last few weeks I've noticed that at about 11am, 3pm and 9pm an old stock (apologies, I don't know which one) goes along the line in one direction and then back again about 15 - 30 mins later. It's incredibly noisy compared to the current trains (which I hardly ever notice any more). It doesn't stop at the station I'm near so it's obviously not in service.
Does anybody know why this happens?
Daniel
|
|
|
|
Post by goldenarrow on Nov 27, 2020 9:22:21 GMT
That is the Central line Rail Adhesion Train (RAT) made up of legacy 1962 stock.
Central, Piccadilly and Metropolitan lines use RAT’s to spray a composite mixture of sand, anti-freeze and metallic shot known as sandite onto the tracks. This helps mitigate against leaf fall which if left unchecked can cause wheel slide through poor adhesion and ultimately damage wheel sets. The racket you refer to is likely coming from the numerous wheel flats the 62 stock RAT has accumulated as it only runs in areas where there is poor adhesion to lay sandite.
|
|
|
|
Post by runer100 on Nov 27, 2020 12:06:47 GMT
Aha...that explains it! Does the RAT run throughout the winter ? I guess most of the leaves will have fallen from the trees soon? Or is the anti-freeze needed until spring?
|
|
|
|
Post by goldenarrow on Nov 27, 2020 12:26:16 GMT
runer100 , RAT's are generally on a 'runs as required' basis for the duration of leafall generally from October till December subject to actual conditions.
|
|
|
|
Post by jimini on Nov 27, 2020 13:10:00 GMT
Sure one of the pros will be along shortly with the full detail, but the normal central lines have de-icing equipment on them too I think, so the RAT isn't necessarily needed for this? Those "D on / D off" signs by the platform starting signals are instructions to drivers to turn it on / off as appropriate, I think.
|
|
|
|
Post by Chris L on Nov 27, 2020 14:06:10 GMT
Sure one of the pros will be along shortly with the full detail, but the normal central lines have de-icing equipment on them too I think, so the RAT isn't necessarily needed for this? Those "D on / D off" signs by the platform starting signals are instructions to drivers to turn it on / off as appropriate, I think. The RAT runs when leaf residue is on the running rails. The sandite improves adhesion for the following trains and stops the wheels spinning and developing flats. |
|
|
|
Post by spsmiler on Nov 28, 2020 9:40:10 GMT
I've seen it a few times this autumn, just north of Newbury Park station there is a road bridge and a footbridge over the line from where its possible to get good views of the train. The footbridge is near to a large Sainsburys and if I get my times right (and it runs to time) I can combine seeing this train with a shopping trip! Below is a still image from video (filmed a few years ago) showing this train approaching the footbridge - I am looking north, the train is heading south, towards Newbury Park station.  CentLine1962StckRAT-NrNewburyPk-Flickr |
|
metman
Global Moderator
5056 05/12/1961-23/04/2012 RIP
Posts: 7,421
|
Post by metman on Nov 28, 2020 10:28:40 GMT
Sure one of the pros will be along shortly with the full detail, but the normal central lines have de-icing equipment on them too I think, so the RAT isn't necessarily needed for this? Those "D on / D off" signs by the platform starting signals are instructions to drivers to turn it on / off as appropriate, I think. The Deicing requirements are different to sandite requirements. As said sandite is placed onto the running rails to help adhesion and on older signalling systems detection, and deicing fluid is sprayed onto the conductor rails to prevent ice build up does not affect the collection of current (which is obviously a bad thing!). Quite often a RAT will also include deicing provision as it makes sense. The A stock and replacement D stock both had this provision the Metropolitan Line - not sure about the Central. |
|
|
|
Post by tom73 on Nov 28, 2020 21:16:23 GMT
Is there some operational reason for the RAT being a full length train?
|
|
|
|
Post by tubetraveller on Nov 28, 2020 21:52:41 GMT
Is there some operational reason for the RAT being a full length train? There are two RATs on the Central Line. A five car unit on the west end of the line and an eight car unit on the East The east requires an eight car train so it doesn't get 'gapped' on some of the more complex pointwork that exists out that way and end up isolated from the electrical supply. |
|
Tom
Administrator
Signalfel?
Posts: 4,196 
|
Post by Tom on Nov 28, 2020 23:29:27 GMT
The five car train ran at the East End of the line last year, so there is no gapping risk.
My understanding was that the 8 car set ran at the East End to provide additional tractive effort.
|
|
metman
Global Moderator
5056 05/12/1961-23/04/2012 RIP
Posts: 7,421
|
Post by metman on Nov 29, 2020 21:24:37 GMT
That was my understanding. This is the same reason the Metropolitan’s D stock RAT is formed from 4 powered cars out of 5. DM-NDM-T(RAC)-NDM-DM
DM - driving motor
NDM - non-driving motor
T - trailer
RAC - rain adhesion car
|
|
|
|
Post by stapler on Nov 29, 2020 21:43:48 GMT
I live half a mile from the line, and if the oaks' leaf dropping is the same there, I'm not surprised the RAT is still at large... I coulddo with some Sandite on my front path.
|
|
|
|
Post by ducatisti on Nov 30, 2020 11:29:56 GMT
How do they decide when to run it?
Does someone go out and rub the rails? Do drivers report slitheriness? Is it more scientific?
|
|
Tom
Administrator
Signalfel?
Posts: 4,196
|
Post by Tom on Nov 30, 2020 12:36:55 GMT
There are a number of methods used. Train Operators reporting poor rail adhesion is, of course, one method. There was for a while a railhead moisture sensor in Hainault depot, and there is now a piece of software known as the Adhesion Controllers Condition Assessment Tool, which considers the source of leaves, falling or fallen, the cause of leaf litter mobility, (whether it is wind or train induced), and rainfall or railhead moisture levels. It's quite a scientific process, and there was a 'leaf fall specialist' within LU who was responsible for developing a lot of the technology. He gave a talk to the London Underground Railway Society about the subject back in 2008. |
|
|
|
Post by wanstead on Dec 12, 2020 19:15:43 GMT
Spotted the RAT stabled at Hainault depot yesterday afternoon which was a nice surprise, presumably it will return to Ruislip in a few weeks.
|
|
