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Suburban Steam dwell times


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To minimise time consumed, one should decelerate as rapidly as is safe from an optimised* speed, crucially avoiding sudden changes of rate of deceleration, because they are what fling the passengers about.


Metros have this off to a fine (now software controlled and making as much use of regen as practicable) art, but good suburban operations are pretty smart at it to. I'm not sure we have any 'suburban best practice' in the UK any more, I would look to Denmark, France, and a few other places.

 

I will try to ferret out some UK steam examples, which I think are given for comparison in some of my pre-WW1 electrical textbooks.

 

A brilliant book on this stuff from the pre-electronic age is “Handling London Underground’s Traffic” by J P Thomas, pub1928. Thomas was an electrical engineer who morphed into the chief operating officer. No steam though, electricity is the default.

 

*The key question here is "Optimised for what?". The station-to-station time/distance curve can be optimised for minimum start-to-stop time, minimum energy consumption, or a host of other things, and is usually a "sweet spot" taking several factors into account.

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53 minutes ago, Nearholmer said:

Metros have this off to a fine (now software controlled and making as much use of regen as practicable) art,

 

I lived in Paris for a couple of years. My local Metro station was Laumière on Ligne 5. This was on a long straight stretch under the avenue Jean Jaurès, built, I believe, during the occupation of Paris in WW2. It is very obvious, looking along the line, that the line between stations is lower than in stations, so the gradients give extra deceleration into stations and acceleration from them.

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The conversation about air versus vacuum has piqued my curiosity, and I wonder if anyone reading this has practical experience in driving Westinghouse braked trains, with triple valves rather than distributors (are there any London Underground drivers out there, perhaps).

 

All types of train brakes (so far as I am aware) allow you to make a partial application, and then increase the application, and do this repeatedly until you have reached the maximum brake application the system allows.

 

With vacuum brakes, and with modern air brakes (EP or distributor), you can also make partial releases of the brake, but with Westinghouse automatic air brakes with triple valves you can't. This limitation is one reason why distributors were introduced, from the 1950s (I'm not sure of the date), but London Underground kept Westinghouse automatic brakes for emergency brakes (early EP brakes were not fail safe), and I suppose they must still have them on 1972 mk 2 stock on the Bakerloo line.

 

With vacuum brakes, stopping on a rising vacuum is well-known, but is this a practical proposition with Westinghouse brakes? Once you do a release, you cannot (or should not) immediately reapply the brakes; it takes time for the brakes to release on each vehicle down the train, and each vehicle's air reservoir will be partially depleted. So how exactly do you do a station stop with Westinghouse air brakes?

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7 minutes ago, Compound2632 said:

 

I lived in Paris for a couple of years. My local Metro station was Laumière on Ligne 5. This was on a long straight stretch under the avenue Jean Jaurès, built, I believe, during the occupation of Paris in WW2. It is very obvious, looking along the line, that the line between stations is lower than in stations, so the gradients give extra deceleration into stations and acceleration from them.

I think this was pioneered by the Central London Railway in 1900, but I could be mistaken, Certainly it is a feature of many tube stations.

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I have an inkling that Werner Siemens may have set out the logic behind it at a very early stage, possibly the early 1880s, but maybe even ten years before that (he began to formulate ideas for an ideal urban electric railway as early as 1870), but I too think that the CLR might have been the first extensive real installation to use it, but Budapest metro (only 3 miles long at that stage) opened earlier and I think might have applied it also. 
 

The Siemens team were beginning to get their heads round electrical, let alone mechanical, regeneration by c1881. I’ve got a text book from that date in which it is talked about as “an invisible rope” connecting a car that is slowing down with one that is accelerating.

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24 minutes ago, Compound2632 said:

 

I lived in Paris for a couple of years. My local Metro station was Laumière on Ligne 5. This was on a long straight stretch under the avenue Jean Jaurès, built, I believe, during the occupation of Paris in WW2. It is very obvious, looking along the line, that the line between stations is lower than in stations, so the gradients give extra deceleration into stations and acceleration from them.

 

Yes, a lot of stations do indeed have acceleration/deceleration ramps. The old Post Office Railway had such devices. With regard to Westinghouse on Steam, you can stop  slowly & sedately, by partial application of the brake ( sometimes known as 'giving her 5').  Naturally, it can be a fine art, and as others say,  practice, but it can be done.  Chucking it all in is a sure fire ticket to having all of your passengers up the front end, and lots of cross words..... On the 3rd rail, the compressors come in when a certain low level of air is reached  (about 60 psi) and ISTR there being a compressor every 4th coach, so it's pretty much constant. Brecon Mountain has a twin-line air, driven off a Westinghouse pump. The steam is graduated to deliver up to 100 PSI, although the steam pressure in the boiler can go lower and higher than that. If there is a large brake application, the Westinghouse pump will accelerate, with less back pressure to contend with. Naturally, as the brake pressure rises, the pump slows down. 

 

Hope this helps,

Ian. 

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Stopping on a rising brake can be done with both vacuum and air systems, but is a fine art.  I once had a cab ride in a 117 from Hereford to Kidderminster (guess what I was getting off there for; clue, it wasn’t to buy a carpet...) with a Hereford driver who was a master of it, and with a ‘strong’ set we ran in to Malvern Link doing 65 at the platform ramp; he cut power, made a full service application on the dry rail, and began blowing the brake off as the cab came level with the shelter, stopping the train beautifully on a rising vacuum with the toilet compartment in the centre of the trailer perfectly lined up with the exit gate.  It was, I thought, a thing of great beauty, admittedly assisted by the rising gradient, but lovely to observe nontheless!
 

Of course the vacuum braked dmus had a dual piped quick release system that allowed this fine level of control.  A normal vaccum brake on loco hauled stock is a different proposition, and a technique that works for one set of coaches may not for a different set.  The number of vehicles, and hence that of cylinders to blow off, each with it’s individual characteristics and with brake blocks at different stages of wear on each set of wheels, has an effect and the powerful ejectors of a steam loco were better at releasing brakes than the exhausters on vacuum equipped diesel and electric locos.  A particular problem was long vacuum fitted freight trains, which sometimes struggled with the inevitable leaks, and could be brought to a stand after a normal application to check speed resulted in a failure to blow the brakes off quickly enough.  The dual pipe air brake was a big improvement, especially in freight work. 
 

Even daily work with the same coaches, the sort of work the OP was discussing, was a highly skilled operation and different driving and braking techniques have been brought up.  Truth is that not all drivers could be bothered with the ‘rising brake’ technique, not all of those that were bothered were masters of of it, and even the masters could be, and sometimes were, caught out!

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3 hours ago, Nearholmer said:

To minimise time consumed, one should decelerate as rapidly as is safe from an optimised* speed, crucially avoiding sudden changes of rate of deceleration, because they are what fling the passengers about.


Metros have this off to a fine (now software controlled and making as much use of regen as practicable) art, but good suburban operations are pretty smart at it to. I'm not sure we have any 'suburban best practice' in the UK any more, I would look to Denmark, France, and a few other places.

 

I will try to ferret out some UK steam examples, which I think are given for comparison in some of my pre-WW1 electrical textbooks.

 

A brilliant book on this stuff from the pre-electronic age is “Handling London Underground’s Traffic” by J P Thomas, pub1928. Thomas was an electrical engineer who morphed into the chief operating officer. No steam though, electricity is the default.

 

*The key question here is "Optimised for what?". The station-to-station time/distance curve can be optimised for minimum start-to-stop time, minimum energy consumption, or a host of other things, and is usually a "sweet spot" taking several factors into account.

It all depends what you want your train timings to deliver.  Even with modern fixed formation stock there are variables to be taken into account principally the impact of the weather  and it effect on acceleration and braking plus potential impact on 'fuel' consumption because even electric train power consumption can be affected by head winds.  with more variable sorts of traction the factors taken into account are considerably increased - the latter years BR point-to-point timings were calculated by computer (latterly an electronic one) in the train performance section of Derby Research.  The Regions then turned these times, were were stated in minutes to one place of decimals, into whole and half minutes (and in some cases also to quarter minutes) and very often the resulting times would be the subject of practical investigation in the event of poor timekeeping especially if rounding was working the wrong way in practice.  Don't forget that with any timings a critical factor is to make sure they are reliably achievable (average) day in and day out

.

But although the normal BR procedure was based on everything being average (condition of loco and train, state of the weather, skill of the Driver) things could still go slightly adrift even with the most carefully calculated times.  There were two early evening Eurostars booked out of Waterloo at a 3 minute headway via Maidstone and the second one of the two invariably lost time beyond Maidstone even if both were initially running precisely on time when they got there - there were no other trains around to interfere with their running.  In the end I traced the reason for the loss of time to a very simple factor - the second train in the flight was driven by an SNCF Driver and he drove according to SNCF training, i.e. see a yellow signal light and apply the brake.   And of course he was bound to see yellow signals because although the timing ensured that both trains would run on greens because f good long sighting on some signals the second train invariably first sighted some signals while they were still showing yellow (and of course Eurostar trains were longer than anything else on the route so they occupied overlap track circuits for a fraction longer than other trains).  Once I'd identified the cause was identified  the problem was relatively simply solved by swapping around various Drivers' turns so that the second train in the flight was driven by either British or Belgian Driver instead of a French one..

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2 minutes ago, The Stationmaster said:

depends what you want your train timings to deliver.


As I said “Optimised for what?”.

 

It is complex enough on a line with trains of identical performance (let the computers drive) and identical stopping patterns.
 

My very limited ‘train spotting’ these days consists of pausing occasionally to watch the WCML when out on a bike ride, or when my son plays footy on a pitch overlooking it,  and I’m always pondering the complexities of mixing-up different forms of traction, massively different loads, varied stopping patterns, different performance profiles etc etc. Hats off to the people behind it!

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2 minutes ago, Nearholmer said:


As I said “Optimised for what?”.

 

It is complex enough on a line with trains of identical performance (let the computers drive) and identical stopping patterns.
 

My very limited ‘train spotting’ these days consists of pausing occasionally to watch the WCML when out on a bike ride, or when my son plays footy on a pitch overlooking it,  and I’m always pondering the complexities of mixing-up different forms of traction, massively different loads, varied stopping patterns, different performance profiles etc etc. Hats off to the people behind it!

 

Docklands Light Railway is a classic example. Mind you, I haven't been on it since "Ooh, I can't remember when..."

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15 minutes ago, Nearholmer said:


As I said “Optimised for what?”.

 

It is complex enough on a line with trains of identical performance (let the computers drive) and identical stopping patterns.
 

My very limited ‘train spotting’ these days consists of pausing occasionally to watch the WCML when out on a bike ride, or when my son plays footy on a pitch overlooking it,  and I’m always pondering the complexities of mixing-up different forms of traction, massively different loads, varied stopping patterns, different performance profiles etc etc. Hats off to the people behind it!

Freights are whole different kettle of fish.  All the BR Regions did it their own way when it came to freight timing although I think the Western system was probably the best because we used three different sets of timings based on the booked load of the train for all the various speed bands/train classifications while the other Regions weren't quite that sophisticated.  As I've mentioned in the past,  in the early 1990s there were even freights running on what had been the LMR using former steam era timings for diesel hauled trains.

 

Best of all were the Derby computer timings for Class 60s (which the Regions were not supposed to alter and in any case they came rounded to half minutes) and they were individual timings based on the load, and even the type of wagons, for each train booked for Class 60 haulage.

 

Some of the most interesting passenger train timings I've come across were on the Sydney (NSW) suburban system where detailed timings went down into seconds for different types of train which in fact didn't turn out to mean all that much in the reality of a timetable using no finer measure in its timings than half minutes.  But really unusual by UK standards was there use of 18 second station dwells on the Sydney city loop which are mathematically related to the minimum achievable headway on 5 aspect signalling (and regularly achieved except at the busiest station in the peak where they were extended to 36 seconds

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On 27/09/2020 at 08:20, Jeremy C said:

I didn't know this. Did they use a two-pipe system?

 

I cannot imagine this working with vacuum brakes; the reaction time is too slow.

No, single pipe Westinghouse. Release brake on stopping, hold train on loco brake. same principle as the Southern 4SUB units.

 

Having worked on LT, BR on loco-hauled suburban at Kings Cross and SR EMU stock and various other stuff, have a bit of experience of each.

 

We had an LNER 0-6-2T on hire at the KESR one year, the driving technique on that was at a station to open the regulator, reverser in id-gear; right away, reverser in full forward and GO! I must admit I've never seen a steam loco pull away so quick from Rolvenden, most impressive. That's how they were built to run so I as told.

 

Single pipe Westinghouse, easy to use with some skill, jut remember you only have 3 brake applications before you run out of auxiliary air. The knack was to make a small application, then a bigger one when you judged the right place, and hold it there. Release at the last few seconds for a smooth stop on the mark. On the Waterloo & City Westinghouse only, it was possible to stop remarkably accurately on the air brake.

 

Diesel loco-hauled suburban out of KX/Moorgate, hit platform end at about 45/50 (on the open sections) drop vac to 10", then release. On a DMU it was possible to hit the platform at Finsbury Park on the up main at 70, drop the brake on and stop on the 2 car mark AND get a smooth stop. 

 

It was only with the advent of electronic brakes/WSP/interlocks that station dwell times have increased considerably. The last thing you wanted with slam-door stock was to creep down a platform and risk doors being opened too soon, plus we had a timetable to try to keep to.

 

As with all train driving, it depend on the skill of the driver, his route knowledge, rail conditions, load and the state of the train brake. Anyone can drive a train and make it go, it takes an expert to stop it in the right place.

 

Thinking back to dwell times, the Metropolitan District Railway was running 30 train per hour through Charing Cross in the early 1900s using steam traction, vacuum brakes and mechanical signalling. Crossrail is having to struggle trying to develop a modern system to give 24 train per hour. Says it all really.

 

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Very informative.

 

On the last point: a major factor in all that is the safe distance between trains then and now. The Met and District at that time ran with vanishingly small or no overlap beyond signals, trains separated by “the thickness of a stick” when the line was congested, and they had multiple low-speed tail-end collisions as a result, mostly causing only damage and embarrassment, but some causing death/injury. Even ‘moving block’, which I’m pretty sure is what cross rail uses, is likely to be slightly more restrictive than that with heavy main-line-type trains. On the  automated lines on the Underground, sustained operation at 36tph is possible, but becomes a bit fragile because the slightest delay in door closing (passengers holding the doors etc) messes-up the heartbeat, so I think maximum timetabled is 32tph, with the ‘spare’ being used for (automated) recovery, but I’m now four years out of that world, so things may have moved-on.

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11 hours ago, roythebus said:

No, single pipe Westinghouse. Release brake on stopping, hold train on loco brake. same principle as the Southern 4SUB units.

How did the buffers remain compressed then, as mentioned in this post?

Or is this from an earlier time when the guard's handbrake held the train buffers compressed (difficult I would have thought). Or could it be a myth? I can imagine it as a theoretical possibility, but am struggling with it as a practical proposition.

 

11 hours ago, roythebus said:

Single pipe Westinghouse, easy to use with some skill, jut remember you only have 3 brake applications before you run out of auxiliary air. The knack was to make a small application, then a bigger one when you judged the right place, and hold it there. Release at the last few seconds for a smooth stop on the mark.

That is exactly the information I was looking for. Thank you.

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1 hour ago, Jeremy C said:

How did the buffers remain compressed then, as mentioned in this post?

 

Good question. I have to confess that I can't locate my reference for this. I had thought it was in Nock's The Golden Age of Steam (a slightly dicey reference even though he was a Westinghouse employee - but signalling, not brakes, I believe), but it isn't. Where else have I read a popular history of the Buckjumpers?

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You can 'spring' a train into motion using compressed buffers, but only from a terminus or bay with a solid set of buffer stops to squeeze the train up against; you obviously need something to push against.  Set the train back on to the stop and keep steam on until the buffers are all compressed, then apply the train brake.  When departure time comes, apply the straight steam brake on the loco and release the handbrake, if you haven't already ,and release the train brake.  Nothing moves.  When you get the right away, release the loco straight steam brake; the buffers will decompress and the train will spring the loco forward.  You are under way and can put the loco into forward gear and open the regulator.

 

This cannot be done at a through station where there is nothing behind the train, nor can it be done if the stock is articulated or close coupled, as much suburban stock was, including the 'Jazz' stock.  I am at a loss to explain what 'Buckjumping' is precisely, and as I believe it is a commuter's term rather than one that originated on the railway proper I suspect it describes something not quite the same as what it purports to describe.  A J69 has small driving wheels and can pull it's train away from a standing start pretty smartly, and the small pistons reduce piston surge to an acceptable level, a very good tool for intense services between close stations using close coupled slam door stock which can empty a train in a few seconds, and refill it in a few more!  Add the N7s for 'outer' suburban jobs and you have what you need for what was the most intense steam operated service, as Clarkson would say, in the World, and a pretty reliable one at that.

 

 

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I've not used the spring compression of buffers, it's not really possible in service. the only time was on arrival at a terminus on loco hauled stock, apply train brake, just as the train is about to stop, apply loco air brake fully, that compresses the buffers on the loco and first coach which saves having to set back to ease the coupling to unhook.

SUB stock only had centre buffers in the inner end. It was possible to break couplings on an 8 or 12 car formation by partially releasing the Westinghouse brake. It was possible for the rear 4 (or 8) to be applying while the front 4 were releasing due to the different air flows in the brake pipe.

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Ther's plenty of video of the Isle of Wight trains (all air braked compartment stock) coming into the platforms pretty quickly and stopping fairly abruptly. 

 

Not UK practice, but the Mumbai Chhatrapati Terminus has a dwell time in the order of a few seconds for suburban trains - platforms on both sides of the train, doors permanently open, and a new crew in position ready to jump in to take the stock back out again.

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The Waterloo & City line uses the turnover crew in the peak hour. As one train arrives at Bank, another crew is ready in position to take it out again, same at Waterloo in the "fiddle yard".

 

The Indian Railways are something else when it comes to crush loadings, having seen it at first hand. when I was there in 1987 the service from Mumbai and Madras was nowhere near as intensive as it is these days. The EMU stock had the same controllers and brake as the SR BIG/CIG/CEP etc stock. they weren't too concerned about draughty cabs as it was a bit warmer over there.

 

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