Suspended due to Poor Weather conditions

[melikepie]

I know this not the most reliable source but
www.mylondon.news/news/london-underground-live-updates-5-25402634

The above mentions that the Piccadilly Line was suspended between Rayners Lane and Uxbridge due to poor weather conditions but makes no mention of the Metropolitan Line. Do each different stock cope differently in those conditions? And I also wonder what the poor weather conditions were.

This concerns both the Piccadilly and Metropolitan which is why I posted here.

[Dstock7080]

The poor weather is leaf-fall related.
Currently ‘73 Stock are restricted by notification to 25mph in open sections, to reduce the risk of wheel-slide and damage to wheels that occur in this season.
S Stock braking is far superior and detects wheel-slide much earlier and deals with it much faster than driver reaction.

[t697]

Quite a tribute to the advance of technology over about 35 years. 73TS was originally fitted with WSP which had to be taken off because it was so inadequate and one of the most unsung successes of S stock is its really good WSP.

[towerman]

73TS was originally built with dump valves on the brake cylinders to stop wheel lock but were so rubbish they caused more flats than they saved,after a few years they were removed.

[t697]

It was mostly the electronic WSP controllers that limited the performance. Two types, about half the 73TS fleet each I think. The dump valves were standard Westinghouse products and themselves a good product although they probably couldn't pulse on and off as fast as ideal for slip control. The WSP controllers were pre-microprocessors. One from Westinghouse and I think primarily working on rate of wheel speed change as its slip detection. The other, Whitedown, primarily working on axle speed comparison as its slip detection. I may have over-simplified this summary. Every axle had a tacho head feeding pulses back to the control unit proportional to rotational speed.

Neither system was good enough. The detection, the correction and re-application regimes were too slow and the systems spent too long with the brakes released or near released. This meant they had to be arranged so that in emergency braking the dump valves were electrically isolated and no slip control could occur.
Typically a train would slip, WSP control would start, the T/Op would sense a reduction in overall brake rate, move the control handle to demand more braking until reaching Emergency at which point WSP would be cut out and likely lock the slipping wheels and cause wheel flats.

As mentioned, the equipment was first isolated entirely then later removed.

[d7666]

Nov 1, 2022 21:15:04 GMT t697 said:

Quite a tribute to the advance of technology over about 35 years. 73TS was originally fitted with WSP which had to be taken off because it was so inadequate and one of the most unsung successes of S stock is its really good WSP.

But must also consider that S stock have AC traction motors and 73 stock DC traction motors.

AC synchronous motors are intrinsically self correcting in slip conditions => motor electrical generic characteristics create conditions that correct slip; series wound DC motors are exactly the opposite => once slip commences their generic electrical characteristics create conditions within motors such that it accentuates slip.

This is one, of several, reasons why Northern and Jubilee lines AC motored 95 and 96 stock cope better on their surface sections in the falling leaf seasons without recourse to RATs, but the Central 92 stock has DC motors, and they have a RAT. No way am I saying 95/96 stock does not have autumn adhesion issues; what I am saying is things would be significantly worse if those were DC motored.

[jimbo]

So d7666 are you possibly hinting that the RAT days could be numbered once the CLIP project is completed on the Central Line? But then again, they provided new ones to work with the S stock!

[d7666]

GMTA. Either you are reading my mind, or you happened to see what I posted originally, then had second thoughts and deleted it.

As I had gone on to speculate about Central RAT post re-traction; after I posted, I then thought, well no, they still have the Met D78 RAT.

What I was really then trying to say was Central 92 stock is DC motors and they have a RAT - so draw your own conclusions - but not Central has a RAT because 92 stock are [so far] DC motors.

So not actually hinting anything no. Can't really say either way. It would be interesting to have a full understanding of all the inputs to why Northern and Jubilee lines don't have RAT or equivalent trains for their surface areas.

Mod edit [Antharro]: Quote removed. Please be selective about the part of a post you wish to quote rather than the whole post verbatim, particularly if you are replying to the previous post in the thread.

[towerman]

Maybe when they start scrapping 73TS they’ll keep some for RATs.

[jimbo]

They already convert two 3-car units each season to run at each end of the Picc, so presume these could transfer to the Central but would need the auto-drive system installed. Could run with a non-converted 3-car to make a longer train, but this was not found necessary on the Picc.

Could the longer Picc cars fit through the Central Line tunnels? Well, the final train was originally fitted as a test train, and was taken through by battery locos overnight, so it has happened. But these days they would probably do the trip by road to avoid making a safety case.

[metman]

I would imagine a couple of 1973 stock trains for RAT duties would be maintained after their withdrawal.

There’s a lot of trees on the East End of the Central so like the Met, there is a heavier leaf load.

[d7666]

The way these projects go, no doubt 92 stock will be available for RAT when 50 stock takes over the Central . Except by then Central will be on GoA99 ATO and no one will know the road so can't run anyway. That's after some 73 stock sits in store for 10 years then scrapped .

Mod edit [Antharro]: Quote removed. Please be selective about the part of a post you wish to quote rather than the whole post verbatim, particularly if you are replying to the previous post in the thread.

[jimbo]

Are we assuming that the new Picc trains will no longer require the operation of RAT trains? The new trains will be to the latest standards and include auto-sand hoppers, as S stock, for poor adhesion conditions. However, there are still RATs operating on the Met. line!

[Colin]

The sanding system only works in CBTC area's as far as I understand it.

[100andthirty]

This is a very complicated subject. The issue of DC motors vs AC motors is a red herring though. It is general LU practice on trains with WSP that, when wheelslide protection is activated, the dynamic brake is dumped and braking is carried out pneumatically.

WSP systems generally compare the speeds of all four axles on a car. If there's a significant discrepancy it determines there's slip. There's also another factor. If the system detects an unfeasibly high deceleration rate, the WSP determines that slip is occurring*.

The ATO/ATP systems add to the complexity.

On the axles with the ATP tachos, (two per train end) the system compares the speed between the two axles and looks for an unfeasibly high deceleration rate. If there's a discrepancy, in simple terms, the system decides it's lost and applies the emergency brake.

One of the reasons for a great deal of care of adhesion levels on the Central line is that it was LU's first ATO line operating in the open (ignoring the original trials on the District and Woodford Hainault). When originally delivered there was no WSP as it was believed that the dynamic brake would self correct in poor adhesion. In practice all trains tended to get wheel flats, and an excellent WSP was retrofitted. The original plan of open ATO was for the deceleration rate to be 0.75m/s2 which is very high for open running in leaf fall. Later an option for 0.6m/s2 was added - still high.

In comparison, Jubilee and Northern have much more control over braking rates and 0.4m/s is not uncommon. But, and there's a big but, these trains have a blended braking system. At low brake rates, the system tries to brake using the dynamic brake, and the trailer cars do little or no braking. But if wheel slip is detected, the dynamic brake is discarded and friction brake is applied to all cars. This means that brakes are suddenly applied on the trailer cars which can cause the issues described above with the ATP tachos.

Re S stock, a great deal of work has been done simulating the effect of sanders on S stock braking but as I understand it, sanding has yet to be commissioned. I hope I'm wrong!

And Elizabeth line trains always have a proper speed reference signal as the axles at the cab ends are unbraked.

* the very latest WSP systems have been further developed and they compare speeds of all axles on the train and operate dump valves appropriately. The very latest systems have another feature whereby the brake demand is adapted depending on the assessed adhesion which will vary along the train. The driver - or ATO - might be demanding a medium brake rate and the brake system will decide to apply a low rate at the front of the train, medium in the middle and high towards the rear. I don't know of any practical applications of this system but someone else might be along with more knowledge

[spsmiler]

Nov 6, 2022 12:20:09 GMT Colin said:

The sanding system only works in CBTC area's as far as I understand it.

so when the entire Met has been converted to CBTC the D78 RATs will be withdrawn?

Nov 3, 2022 4:42:02 GMT jimbo said:

Could the longer Picc cars fit through the Central Line tunnels? Well, the final train was originally fitted as a test train, and was taken through by battery locos overnight, so it has happened. But these days they would probably do the trip by road to avoid making a safety case.

I can see the newspaper headlines ... "Train Banned From Tracks Because It Does Not Have Safety Case"

I can think of reasons why 1973ts trains would be banned from the Central line, these relate to them possibly being too long for the sharp curves in the tunnels or issues related to non-standard position leccy rails. But especially if that type of train has previously been hauled on that section of track by battery locomotives then 'needing a safety case' to do this again would sound OTT

[100andthirty]

Adding to my previous post:

The 1973 tube stock's lowest brake rate is pretty high - just under 0.6m/s2. With this brake rate and no WSP it's not surprising there are wheel flats

Reponding to spsmiler: Rail adhesion trains are part of the process of managing adhesion levels on the Metropolitan line together with foliage management, and leaf clearance. WSP and sanders will do a good job unless the leaf film is very tough/the coefficient of friction is very low. Under those circumstances, neither sanders nor the action of WSP will help.

Lastly, one 1973 tube stock car has operated through the Central line routinely. It's the track recording car.

[Colin]

Nov 6, 2022 13:07:39 GMT spsmiler said:

so when the entire Met has been converted to CBTC the D78 RATs will be withdrawn?

I'm only a driver - I'm no expert on the technicalities of the subject nor in a pay grade that has knowledge of future plans.

Having said that though, my understanding is that the sandite applied by the RAT is a mixture of a gel, sand to aid grip and metal particles which assist completion of track circuits. Given that the tracks have no circuits in CBTC world and S stock can (in theory at least) apply its own sand as required, I suppose it could be argued that the RAT's on the Met will be rendered pointless.

But then again, what about the Chiltern trains? I don't know how CBTC will "see" them. Will they still operate the track circuits? Do they carry their own sanding facility? It might well be the case that the RAT's will need to be retained for the Chiltern trains.

[spsmiler]

Nov 6, 2022 15:06:19 GMT Colin said:

But then again, what about the Chiltern trains? I don't know how CBTC will "see" them. Will they still operate the track circuits? Do they carry their own sanding facility? It might well be the case that the RAT's will need to be retained for the Chiltern trains.

Unless they use axle counters or something I do not know about I suppose that they will still use track circuits. All I do know is that the adopted solution will not require any special equipment on the train - beyond the train stops which nowadays all non automated trains using this route need. 

In the past I've seen LU Rat trains, Chiltern water jetter trains and Network Rail (or Railtrack) RHTT all passing through Rickmansworth - this short video shows the RHTT and Chiltern water jetter plus LU Track Recording Train.

re: the reply to me by 100andthirty about the Track Recording Train, so obviously the length of the 1973ts trains is not an issue for the Central line but the trailer possibly will not have any power collection shoes, whilst the two 1960ts DM's will have special 'high lift' power collection shoes, as these are needed for trains to pass through the original Central London Railway tunnelled section of the Central line. Even if unpowered.

[t697]

The thought that S stock on its own would be able to cope in Met line autumn leaf fall is very complimentary to the wheelspin/slip/slide control systems but I'm afraid rather too much so. It has always been the intention to retain rail head treatment and LUL does that using RAT trains, spending quite a lot converting two D78 trains for the purpose replacing the previous A stock conversion. Further, the D78 RATs are being equipped with ATC so they can continue to operate out of Neasden depot to/from all parts of the north ends of the Met line.
And yes the re-signalling will allow for operation of Chiltern trains.

[Tom]

Nov 6, 2022 15:06:19 GMT Colin said:

But then again, what about the Chiltern trains? I don't know how CBTC will "see" them. Will they still operate the track circuits? Do they carry their own sanding facility?

The CBTC will see them via the axle counters in the same way that they see LU-operated trains in the CBTC area today. There is, naturally, a lot more to it than that, but it's the simple answer. There will not be track circuits, but it might be that the axle counters give more reliable detection than track circuits do in leaf-fall conditions where there is a strong possibility of rail head contamination.

[100andthirty]

Sandite is, indeed sand and some condictive particles bound together with something that has the consistency of wallpaper paste. It's the binder that helps the sandite persist after the first train has passed. The Network Rail railhead treatment trains aalso waterjet the rail head...think a Kercher pressure wash on max strength steriods. The pressure is some 1500 bar (22500 psi or 750 times the pressure in a small car tyre). The water jet cleans leaf debris and any other contaminents including rust and then sometimes sandite is applied afterwards. Chiltern trains have sanders operated by WSP. Sanders on main line trains are generally fitted in front of the 3rd axle.

[d7666]

Nov 6, 2022 13:03:02 GMT 100andthirty said:

This is a very complicated subject. The issue of DC motors vs AC motors is a red herring though. It is general LU practice on trains with WSP that, when wheelslide protection is activated, the dynamic brake is dumped and braking is carried out pneumatically.

Not a red herring. You have mis-read if you are refering upthread to my comments.

What I posted about DC v. AC was about wheel slip not slide; slip [wheel rotating faster] is under traction; slide [wheel rotating slower] is under braking; my posts say nothing about braking by any means, or slide, or WSP.

[t697]

S stock having all axles motored including the ATC tacho axles still has to be careful about wheelspin or slip in motoring whichever you choose to call it. Some ATC systems have better diverse speed detection such as Doppler radar, but not the system finally chosen for SSR.

Whilst agreeing the point about a degree of natural spin control with the AC motors, it's not that difficult to have good spin control with DC motors. Even the electro mechanical spin correction control on 73TS is quite effective in motoring.

[d7666]

Nov 6, 2022 18:10:48 GMT 100andthirty said:

Sandite is, indeed sand and some condictive particles bound together with something that has the consistency of wallpaper paste. It's the binder that helps the sandite persist after the first train has passed. The Network Rail railhead treatment trains aalso waterjet the rail head...think a Kercher pressure wash on max strength steriods. The pressure is some 1500 bar (22500 psi or 750 times the pressure in a small car tyre). The water jet cleans leaf debris and any other contaminents including rust and then sometimes sandite is applied afterwards. Chiltern trains have sanders operated by WSP. Sanders on main line trains are generally fitted in front of the 3rd axle.

NR is also re-looking at plasma torch treatment. This autumn season there is a MPV carrying plasma torch kit under trial; it has been on a preserved line somewhere, they have got to the stage where it needed real live testing on a real line with real falling leafs.

Some with long memories may remember BR tinkered with plasma torch 50 years ago
www.old-dalby.com/Plasma%20torch.htm
and
www.traintesting.com/images/975018%20AND%20975019%20PLASMA%20TORCH%20CLASS%20101.jpg
you can just about see the torch flame immediately to the rear of the rear bogie of the leading car.

Just as a pedantic point, while LU RAT dispenses Sandite, NR RHTT dispense TrackGel, which is not quite the same thing. TrackGel comes in several variants, usually indicated by a two digit number; not sure if the same variant is used everywhere. IIMU RHTT do not dispense TrckGel over LU infrastructure.

[d7666]

Nov 7, 2022 0:01:02 GMT d7666 said:

Just as a pedantic point, while LU RAT dispenses Sandite, NR RHTT dispense TrackGel, which is not quite the same thing. TrackGel comes in several variants, usually indicated by a two digit number; not sure if the same variant is used everywhere. IIMU RHTT do not dispense TrckGel over LU infrastructure.

I plead guilty to unexplained acronyms :

RHTT = railhead treatment train
MPV = multi purpose vehicle

[spsmiler]

re unexplained acronyms: IIMU = it is my understanding?

[d7666]

Nov 7, 2022 16:56:15 GMT spsmiler said:

re unexplained acronyms: IIMU = it is my understanding?

AFAIK yes.

[brigham]

Are any of those actually acronyms?

[class411]

Nov 8, 2022 9:32:06 GMT brigham said:

Are any of those actually acronyms?

Well, 'RAT' is. But, on the whole, that battle is on the verge of being lost.

Partly because there are far more initialisms than acronyms, and partly because 'initialism' is a bit of a mouthful.

And if the rule was to be enforced, you'd need TLI's* and ETLI's*








*TLI : Three letter initialism, ETLI : Extended Three Letter Initialism.