Harrow to Uxbridge Branch Junction Query

[The_Laird]

Does anyone know a reason why, for a considerable period after the introduction of the flyunder connection onto the Uxbridge branch at Harrow North in 1925, a level connection was maintained with the fast down line?  It was eventually removed. I don't really know when, but it was still in place on the 1948 Harsig diagram.

 

http://www.harsig.org/PDF/Uxbridge_Branch.pdf

 

It can also be viewed here.

 

http://www.britainfromabove.org.uk/image/epw018756?search=harrow&ref=55

 

(You need to register to be able to zoom in.)

 

My first thought was that it was to facilitate a connection for any remaining LNER operated goods traffic onto the branch after LPTB had handed over these reponsibilities. However, there would then be a problem on the return trip as there would be access only through the flyunder onto the up local Met line.

 

Also, it was in place when the Met still handled their own goods traffic.

 

 

 

[Engineer_London]

In the 1960s, I rode several times on fast trains over the top connection between Harrow-on-the-Hill and West Harrow.  It was an exhilarating ride.  These trains ran non-stop Finchley Road to Rayners Lane, via Harrow-on-the-Hill platform 1, a few per day at peak times.  My father, a former Metropolitan and LT employee, told me that the non-stop run was Finchley Road - Eastcote in the 1950s.  Going back further in time, the Metropolitan Railway services to Uxbridge did include a variety of non-stopping patterns on the branch, at a time in history when there was heavy peak traffic for Baker Street and the City from key stations such as Ruislip and relatively little from Ruislip Manor and Rayners Lane – both of which were amid fields until the 1930s and almost rural and isolated. 

 

I don’t think that the Working Timetables ever identified trains that would take the connecting line, but this may have been detailed in later LT days on the printed train registers.  Can’t comment on the goods train hypothesis but the connection may have been useful operating flexibility, giving schedulers and signallers an alternative routing option through Harrow’s busy Down platforms.

 

I believe the routing of trains via the connection ended in the late 1960s.  This was possibly because the retaining wall on one side of the connection was in poor condition and on the other side, the cess of the embankment was eroded with cable run posts beginning to lean back and expose their 'roots'. 

 

In my later schooldays I travelled from the Uxbridge branch to Moor Park [six days per week!] and in the early 1970s, the few weekday scheduled fast trains continued to run non-stop both directions Rayners Lane - Finchley Road.  I know of one classmate who boarded a fast train at Hillingdon when he should have waited for the train behind, and therefore missed the change he should make at Harrow.  Somehow he rode not only to Finchley Road but onwards to the City before returning schoolwards, arriving after 11am!

 

The fast trains called at Harrow and West Harrow from about 1974, at the time of staff shortages and many cancellations.  To the best of my recollection the track was disconnected/removed some years later, and it was probably in the late 1980s/early 1990s that the retaining wall beneath the formation was removed. . 

[The_Laird]

Thanks for that info, E_L. 

 

I had absolutely no idea that the connection existed for so long. My trips to Uxbridge always involved a change at HOTH, so I always travelled via the underpass. To be quite honest, I didn't even realise that there were fast services on the branch. I thought all that sort of jazzy stuff was restricted to the main line.

 

It must have involved some neat timetabling, as the terminal facilities at Uxbridge are limited to three roads and those had also to cater for the Met stoppers and the Piccadilly Line service.

[Oldddudders]

Interesting stuff. Like John, I had no idea there was a limited-stop service to Uxbridge. I was well aware of comparable peak hour City trains on the main line, and managed to catch one fast from Finchley Road to Moor Park in about 1963. The A Stock in them thar days seemed to run at warp-speed compared to later, but perhaps that was just teenage wonderment.

[GoingUnderground]

In the 1960s, I rode several times on fast trains over the top connection between Harrow-on-the-Hill and West Harrow.  It was an exhilarating ride.  These trains ran non-stop Finchley Road to Rayners Lane, via Harrow-on-the-Hill platform 1, a few per day at peak times.  My father, a former Metropolitan and LT employee, told me that the non-stop run was Finchley Road - Eastcote in the 1950s.  Going back further in time, the Metropolitan Railway services to Uxbridge did include a variety of non-stopping patterns on the branch, at a time in history when there was heavy peak traffic for Baker Street and the City from key stations such as Ruislip and relatively little from Ruislip Manor and Rayners Lane – both of which were amid fields until the 1930s and almost rural and isolated. 

 

I don’t think that the Working Timetables ever identified trains that would take the connecting line, but this may have been detailed in later LT days on the printed train registers.  Can’t comment on the goods train hypothesis but the connection may have been useful operating flexibility, giving schedulers and signallers an alternative routing option through Harrow’s busy Down platforms.

 

I believe the routing of trains via the connection ended in the late 1960s.  This was possibly because the retaining wall on one side of the connection was in poor condition and on the other side, the cess of the embankment was eroded with cable run posts beginning to lean back and expose their 'roots'. 

 

In my later schooldays I travelled from the Uxbridge branch to Moor Park [six days per week!] and in the early 1970s, the few weekday scheduled fast trains continued to run non-stop both directions Rayners Lane - Finchley Road.  I know of one classmate who boarded a fast train at Hillingdon when he should have waited for the train behind, and therefore missed the change he should make at Harrow.  Somehow he rode not only to Finchley Road but onwards to the City before returning schoolwards, arriving after 11am!

 

The fast trains called at Harrow and West Harrow from about 1974, at the time of staff shortages and many cancellations.  To the best of my recollection the track was disconnected/removed some years later, and it was probably in the late 1980s/early 1990s that the retaining wall beneath the formation was removed. . 

 

When the Uxbridge Branch opened in 1904, the only two stations on the branch were Ruislip ( a village that can trace its history back to the Domesday book ), and Uxbridge. Everything else between Harrow and Uxbridge, apart from Ickenham, is Metroland, created by the existence of the branch.

 

In the 1960s I too made the same journey 6 days a week from the Uxbridge Branch, to that same educational establishment in Moor Park, familiar to SR enthusiasts as "910", motto "Concordia Parvae Res Crescunt", and also had to avoid the Fast trains.

 

The advantage of the chord was that it gave more flexibility for the "Fast" Uxbridge services as they could run through Harrow, via platform 1. making it possible  to overtake the ex-Baker Street All Stations service that had left Baker Street ahead of it, after the All Stations had left Harrow by holding the Slow in the exit from the flyunder.

 

I can recall seeing an A60 Fast service going through Platform 1 at Harrow in the 1960s, but I cannot remember if it was bound for Amersham or Uxbridge.

 

It would have made sense for the chord to have been used to give coal trains direct access to/from the Uxbridge branch back in the days when coal was burnt at the South Harrow Gas Works, and also for the trains delivering to the coal merchants depots along the Uxbridge branch. There were sidings at Rayners Lane, Eastcote, Ruislip (W. A. Ives was one of the coal merchants with staithes and an office at Ruislip) , Hillingdon and Uxbridge, but all had gone by the late 1960s. The sidings areas became car parks at Rayners Lane, Ruislip, and Hillingdon. The signal box at Ruislip that served the goods yard is still in situ even though it has no purpose today. 

 

I believe that the retaining wall for the chord wasn't removed, just cut down significantly and what was left was given a sloping "top" to minimise rain and frost damage as it was still needed at the exit from the flyunder.

 

Interesting stuff. Like John, I had no idea there was a limited-stop service to Uxbridge. I was well aware of comparable peak hour City trains on the main line, and managed to catch one fast from Finchley Road to Moor Park in about 1963. The A Stock in them thar days seemed to run at warp-speed compared to later, but perhaps that was just teenage wonderment.

 

Met "Fast" services in the 1960s:

Morning Rush hour:

Moor Park - Finchley Road  (Aylesbury then Amersham services)

North Harrow - Finchley Road (Watford Branch)

Rayners Lane - Finchley Road (Uxbridge Branch

 

Evening Rush hour:

Finchley Road - Moor Park (Aylesbury, then Amersham services)

Finchley Road - North Harrow (Watford Branch)

Finchley Road - Rayners Lane (Uxbridge Branch).

 

I well remember the "Roar" as a Bo-Bo ran through platform 6 with a fast service from Aylesbury to Liverpool St ,just as I ws getting off a slow from the Uxbridge Branch in Platform 5.

 

Line speed was 70mph between Neasden and Finchley Road, but the volume of traffic into town in the mornings meant that often the Fasts ended up being held at signals anywhere between Preston Road and Finchley Road due to congestion. However, you weren't imagining it as in the evenings on teh way home, bouncing off the cushions was the order of the day until the 60mph limit was imposed (in the 1980s?) because of the state of the track. So I cherish the memory of doing the alleged 74mph between Kilburn and Neasden on the final leg of the A60 Farewell Tour - just like the old days!. (End of BOF reminiscences).

[Unicorn1]

As a lad myself and a few other keen bus spotters would often wait at Uxbridge for a fast MET train into London. I recall there was a stripped 'flag' shown in the front of an A60 driving car on these services. The main highlights were thrashing past Neasden Depot - and the liberal use of the whistle by the driver.

Happy days.

Les

[GoingUnderground]

As a lad myself and a few other keen bus spotters would often wait at Uxbridge for a fast MET train into London. I recall there was a stripped 'flag' shown in the front of an A60 driving car on these services. The main highlights were thrashing past Neasden Depot - and the liberal use of the whistle by the driver.

Happy days.

Les

You mean the yellow and black striped Weak Field flag. I remember seeing it on many A60 trains, but as i usually went for the Fast services myself, I can't remember if it was used on all Met services or just the Fast ones. I have a funny feeling it was all of them, or else the trains that weren't running with the Weak Field would have delayed the Fast services between Finchley Road and Wembley Park. during the Rush Hour services.

 

When the Weak field is set, it allows for a higher top speed, but lower acceleration. - Ideal for services north of Finchley Road, but not what was needed between Baker Street and Aldgate when the A60s ran with Circle and Hammersmith services, initially COP Stock but later C69/72 Stock.

 

Does anyone know if the Weak field setting was turned off or on at Finchley Road or Baker Street before entering or after leaving the Circle line? I think it wasn't as I'm sure the Fast Uxbridge that I used to catch home in the evenings at Farringdon was displaying the flag when it came into Farringdon. There is a picture from 1976 on page 44 of John Glover's "London Underground Rolling Stock in Colour" of an A60 train approaching Farringdon from Kings Cross with the Weak field flag clearly visible. Judging by the illumination, the picture would have been taken in the late afternoon. Was it on its way to Aldgate to become my 'Fast Uxbridge' home?

[Nearholmer]

What I do know is that Met drivers used the term "putting the chimney up" to mean raising the weak field flag, with some distant folk memory of switching steam locos from condensing to not when they got to Finchley Road.

 

On most trains with field-weakening, it is configured as a step (or several) beyond normal series/parallel, so it being enabled doesn't affect acceleration, just permits a higher top speed. I doubt that the A stock was different from this, but it may have been - I will consult a man who has the wiring diagram for A stock stored between his ears, if he doesn't see this before I get to him.

 

Kevin

[The_Laird]

 

<<<The advantage of the chord was that it gave more flexibility for the "Fast" Uxbridge services as they could run through Harrow, via platform 1. making it possible  to overtake the ex-Baker Street All Stations service that had left Baker Street ahead of it, after the All Stations had left Harrow by holding the Slow in the exit from the flyunder.>>>

 

Yes, that all makes sense, except that the arrangement seems a little asymmetrical, in that there was no similar provision for up fasts. I could see that potentially having a bit of a stacking effect.

 

 

[GoingUnderground]

 

<<<The advantage of the chord was that it gave more flexibility for the "Fast" Uxbridge services as they could run through Harrow, via platform 1. making it possible  to overtake the ex-Baker Street All Stations service that had left Baker Street ahead of it, after the All Stations had left Harrow by holding the Slow in the exit from the flyunder.>>>

 

Yes, that all makes sense, except that the arrangement seems a little asymmetrical, in that there was no similar provision for up fasts. I could see that potentially having a bit of a stacking effect.

 

It didn't need a similar provision for Fasts southbound. In fact you couldn't have had one unless there was an additional flyunder or flyover built to take the Uxbridge branch over to the east side of the Main line. but there wasn't space physically and it was unnecessary as you will see if you look at the post 1948 track plan for Harrow itself. It has a scissors crossover between the southbound Aylesbury/Amersham/Watford line and the southbound Uxbridge line north of Harrow, and another scissors between the Fast and Slow southbound lines south of Harrow. With 6 minutes at Rayners Lane between the All Stations Baker St and the following Fast Aldgate there was plenty of time for the Baker St service to be in Platform 5 at Harrow, or further along the slow line, before the Fast from the Uxbridge branch crossed over the scissors to run through Harrow on Platform 6. In the Rush hour all the All Stations services, be they from Aylesbury/Amersham, Watford or Uxbridge, to Baker St, Liverpool St. and Aldgate used Platform 5, and the Fast services ran through on Platform 6. 

 

As trains had to arrive at Baker St in the right order, the All Stations services were held at Wembley Park until the relevant Fasts had overtaken them. That is why some Fast services were, in turn, held outside Wembley Park whilst the All Stations resumed their place after being overtaken by a Fast in Wembley Park. Hence my comments earlier about it being a slower.ride to work than it was coming home.

 

The 1960s Rush Hour Met was a very intense, and complicated service to operate, but it worked very well indeed, most of the time, I very rarely had cause to complain whilst I was using it from 1960 through to 1980..

[roythebus]

From my short days on the Met, the A60s "should" (had to) raise and lower the weak field flag at Finchley Road. This was in the Sectional Appendix with a reminder in the WTT.  Very often the motorman would conveniently forget! This did give slower acceleration but a higher top speed.

 

Line speed was indeed a creditable 70 mph and it was great to be rushing along in an A60 at time warp speed! 75 was often achieved down the bank from Chorleywood to Ricky, through Neasden on the s/b, and down Willesden Green bank. 

 

The WTT showed the platform routing at HotH. Remember the Met used to carry newspaper traffic in those days, the guard would help road the papers at Baker Street and drop them off at stations beyond Harrow, always the Evening News and Evening Standard!

[Metropolitan H]

Yes, the A60/A62 Stock did achieve 70+ m.p.h. - but there was a down side. The motors were only designed and tested for 60 m.p.h. with no overspeed allowance - the relevant BS standard didn't require an overspeed test at the time - and it caused a lot of bogie damage through fatigue etc. That - and the fear that trip cocks would be wrecked in contact with trainstops at more than 60 m.p.h. was why we lowered the line speed to 50 m.p.h. about 10 - 15 years ago. We knew the TOs would still overspeed to 60 m.p.h. - but is saved a lot of motor repairs and bogie repairs.

 

Regards

Chris H

[Nearholmer]

Aha ..... Now, what is the answer to the WF question in post 8?

 

K

[GoingUnderground]

From my short days on the Met, the A60s "should" (had to) raise and lower the weak field flag at Finchley Road. This was in the Sectional Appendix with a reminder in the WTT.  Very often the motorman would conveniently forget! This did give slower acceleration but a higher top speed.

 

Line speed was indeed a creditable 70 mph and it was great to be rushing along in an A60 at time warp speed! 75 was often achieved down the bank from Chorleywood to Ricky, through Neasden on the s/b, and down Willesden Green bank. 

 

The WTT showed the platform routing at HotH. Remember the Met used to carry newspaper traffic in those days, the guard would help road the papers at Baker Street and drop them off at stations beyond Harrow, always the Evening News and Evening Standard!

 

If the WTT said raise/lower at Finchley Road, then apart from relying on memory, there is pictorial evidence, as I quoted earlier, that motormen did "forget", and probably on a regular basis, or it would have been quite a coup if the photo that I mentioned earlier happened to have been the only time that the motorman "forgot".

 

Harrow also received newspaper deliveries by Met, as I can remember seeing them being unloaded from the guards area on to the platform from Uxbridge bound trains in the evenings on my way home from school.

 

Yes, the A60/A62 Stock did achieve 70+ m.p.h. - but there was a down side. The motors were only designed and tested for 60 m.p.h. with no overspeed allowance - the relevant BS standard didn't require an overspeed test at the time - and it caused a lot of bogie damage through fatigue etc. That - and the fear that trip cocks would be wrecked in contact with trainstops at more than 60 m.p.h. was why we lowered the line speed to 50 m.p.h. about 10 - 15 years ago. We knew the TOs would still overspeed to 60 m.p.h. - but is saved a lot of motor repairs and bogie repairs.

 

Regards

Chris H

 

You can't keep a good motorman down! I am surprised at the worry over tripcocks, as, IIRC, the Bo-Bos were supposed to have a top speed of 60mph.

 

Aha ..... Now, what is the answer to the WF question in post 8?

 

K

It did increase the top speed, but lower the acceleration. It may have worked differently on BR, but that's how it worked on A Stock.

 

To quote J Graeme Bruce on page 151 of "Steam to Silver", 1975 hardback edition, on the A60/62 train performance: "The required train performance necessitated the provision of two accelerating rates and two balancing speeds, A flag switch indicator was installed to control not only the motor field strength but the accelerating rate,. With the flag switch down, for operating in the inner section, the master controller would give both accelerating rates but only full-field strength on the motors would be provided, and consequently a low balancing speed. With the flag switch raised only the low accelerating rate could be used, but the balancing speed would be increased by the selection of 60% field strength for the motors. This field strength provided a maximum speed of 60m.p.h. for the outer suburban sections."

 

Weak field giving lower acceleration but higher maximum speed has also been stated on the District Dave forum, http://districtdavesforum.co.uk/thread/24813/weak-field

[Nearholmer]

Thanks, Keith.

 

Very unusual, I think, but probably designed that way to be gentle to the traction power supply system.

 

K

[Metropolitan H]

A couple of points to remember.

 

- The electrification north of Rickmansworth was done in post-war austerity times, so the sub-station spacings are large. Lower acceleration and hence lower peak currents means less traction supply volt-drop - helping to ensure the Volt-Amp relays don't drop out.

 

- As the inter-station distances were longer "Out-town" the reduced acceleration rate didn't markedly affect running times, with the higher top speed making the difference.

 

- The A Stock were specified / designed post Suez when fuel shortages were a real problem - another reason for de-tuning them.

 

- I know the M-V Bo-Bos were good for 60+ m.p.h. but the trucks and motors were more rugged than those on A Stock - and the line speed was still 60 m.p.h.

 

- Above 60 m.p.h. there is a real concern regarding damage to tripcocks - especially middle position ones, if not properly latched up - from repeated striking of train-stops.

 

- Although not in the rule-book, a clever TO will accelerate an A Stock to circa 50-60 m.p.h. with the Flag down, then centre the key lift the flag and open up again - getting better acceleration and higher top speed.  

 

Regards

Chris H

[GoingUnderground]

Thanks, Keith.

 

Very unusual, I think, but probably designed that way to be gentle to the traction power supply system.

 

K

 

Being kind to the traction power supply is not unknown on the Underground. One example was the O/P stock where the original design was for all cars to be motored, but due to the inadequacies of the traction power supply, trailer cars were introduced to a design that would have allowed them to be converted to motored as originally intended once the power supply had been uprated. Similarly, the '38 stock, where Graff-Baker diluted his original idea of a high speed tube train with all cars motored with the introduction of the trailer car intro the formation to avoid traction current supply problems (Page 21 - Piers Connor's "The 1938 Tube Stock"). 

 

 

A couple of points to remember.

 

- The electrification north of Rickmansworth was done in post-war austerity times, so the sub-station spacings are large. Lower acceleration and hence lower peak currents means less traction supply volt-drop - helping to ensure the Volt-Amp relays don't drop out.

 

- As the inter-station distances were longer "Out-town" the reduced acceleration rate didn't markedly affect running times, with the higher top speed making the difference.

 

- The A Stock were specified / designed post Suez when fuel shortages were a real problem - another reason for de-tuning them. .....

 

Would "Post War austerity" really have had an effect? You may be right, but I can't recall seeing/reading anything to that effect. Food rationing, the final part of post war rationing ended completely in 1954. I suspect that the real reason was the Conservative governments of the time were not interested in spending on rail infrastructure. The motor industry was developing and many politicians saw the future for transport as being the private car, not public transport. Why would they spend more than the minimum.

 

The trains are much more lightly loaded at the ends of the system, you could usually find a seat if you boarded before Harrow. The actual rate of acceleration of the train depends in its total mass (weight), including passengers, at the time. So the lower acceleration available would have a lesser effect anyway.

 

Your comment about fuel shortages post Suez is interesting, and I can remember seeing in 1973 or thereabouts the petrol rationing coupons that my parents still had from the petrol rationing after Suez. But that was for petrol, not coal, and the Suez rationing only lasted about 7 months, late '56 to 14 May '57 according to Wikipedia. So would it really have had an impact on A Stock design when the Underground was powered by the coal fired power stations at Neasden and Lots Road? Again, I can't recall reading anything saying that Suez had an effect, but maybe I've just missed/forgotten it. Building A Stock as cheaply as possible because it was publicly funded rail vehicles may have had a more significant impact on the design IMHO.

[Lord of Narnia]

The A stock overall was a very good design and as we know lasted well. This may have been down to sound design or it's relatively generous size of fleet which was never really tested until later in life.

 

The bogies I feel where based on the successful district K2 design but adapted for rubber suspension and considering the previous dreadnought stock fox bogies fell apart one could speculate that the ride into the Chilterns was not the best!

[Nearholmer]

The section of the Met that is on embankments, through Kilburn etc, is quite notorious for having a poor formation, so that the bridges stand pretty solid, and the embankments between them slump down. This means that it tends to turn into a series of dips and humps, causing lots of vertical accelerations.

 

K

[roythebus]

The A60s had a good ride quality at all speeds when I worked on them in 1973/74. My fiancé liked riding in them at the time, especially when the compressors started running. whether other young ladies experienced similar sensations I never asked...

 

The BR system of weak field on souther EMUs automatically gave weak field and quick acceleration. The main line stock was fitted with a series/parallel switch for use on the folkestone Harbour branch which limited the sequence to series running only, but with quick acceleration up from the Harbour. I'd sometimes use the switch on the South Western to get very quick acceleration, then flick the switch to parallel to get the top speed and weak field!

 

ISTR the Met was 4-tracked late in the 1950's. As a 10 year old I travelled on the A60s when they were new and remember seeing the signs by the track north of Harrow saying that the rails would be energised form a certain date. I was also impressed by the 60 speed limit boards at places like Wembley Park and Harrow! Petrol rationing was introduced in late 1973 during the Israeli conflict; that was what made me have to leave LT employment, I simply couldn't get enough petrol to get to work at Ricky as I lived in Northampton at the time. Another guard there lived in Bristol!

[bécasse]

An important issue with Underground trains is the heating effect they create in the tunnel sections even on the sub-surface lines (and, of course, it is an even greater issue on the tubes). Thus, while the traffic department may desire higher speeds with more motored axles on the trains to achieve them, if the ventilation engineers can't develop affordable planes to evacuate the extra heat from the tunnels, any plans for higher speeds are dead in the water. Ventilation engineering in tunnels isn't an exact science, even today, and the problems are made worse by the fact that temperature rises tend to be cumulative so even well ventilated tunnels gradually warm up over the years and it is almost impossible to cool them again.

[GoingUnderground]

The A60s had a good ride quality at all speeds when I worked on them in 1973/74. My fiancé liked riding in them at the time, especially when the compressors started running. whether other young ladies experienced similar sensations I never asked...

 

 

.....ISTR the Met was 4-tracked late in the 1950's. As a 10 year old I travelled on the A60s when they were new and remember seeing the signs by the track north of Harrow saying that the rails would be energised form a certain date. I was also impressed by the 60 speed limit boards at places like Wembley Park and Harrow! Petrol rationing was introduced in late 1973 during the Israeli conflict; that was what made me have to leave LT employment, I simply couldn't get enough petrol to get to work at Ricky as I lived in Northampton at the time. Another guard there lived in Bristol!

Really!!!! And to think that I used to avoid the trailer cars because of the noise and vibration!

 

Quadrupling between Harrow and the junction for the Watford branch was originally planned as part of the 1935-40 New works programme, and some civil engineering work had been completed before work was suspended in 1940.

 

Approval to restart was given in 1956, and the new lines opened in phases in the early 1960s. All electric services began running through to Chesham on 12 September 1960. Aylesbury trains continued to be hauled by Bo-Bos to Rickmansworth and a loco change for the rest of the journey to Aylesbury until 9 September 1961, when the service was cut back to Amersham, permanently. The quadrupling was fully complete by 1962.

[GoingUnderground]

An important issue with Underground trains is the heating effect they create in the tunnel sections even on the sub-surface lines (and, of course, it is an even greater issue on the tubes). Thus, while the traffic department may desire higher speeds with more motored axles on the trains to achieve them, if the ventilation engineers can't develop affordable planes to evacuate the extra heat from the tunnels, any plans for higher speeds are dead in the water. Ventilation engineering in tunnels isn't an exact science, even today, and the problems are made worse by the fact that temperature rises tend to be cumulative so even well ventilated tunnels gradually warm up over the years and it is almost impossible to cool them again.

The problem with reversing the heating effect is that the ground surrounding the tunnel will also have been warmed and represents a very substantial heat reservoir, the same principle as night storage heaters, heat up a large mass with cheap electricity, and then let it radiate the heat back when electricity is expensive. So cooling the tunnels will also end up having to remove that large heat reservoir in the surrounding earth to restore ambient temperatures to the pre-warming levels. Air has a very low thermal capacity when compared to soil/clay, so it takes an awful lot of cooler air flowing through the tunnel for a considerable period of time before it has any significant effect. That is why it is so hard to cool them again. 

 

Cooling would be more effective if a liquid coolant were used, such as installing water pipes inside the tunnels or putting them in the surrounding earth and running chilled water through them, but that is very expensive to install and operate, not to mention the disruption to services that installing the pipes might cause.

 

The heating isn't just caused by the trains, there is also the lighting and the escalators contributing to the heating effect. Humans also radiate heat. It is our own body heat that keeps us warm in bed on a cold winter's night, the duvet or blanket and eiderdown simply help us retain the heat that we lose from our skin.

[stewartingram]

 

 

The heating isn't just caused by the trains, there is also the lighting and the escalators contributing to the heating effect. Humans also radiate heat. It is our own body heat that keeps us warm in bed on a cold winter's night, the duvet or blanket and eiderdown simply help us retain the heat that we lose from our skin.

 

 

There is considerable other electrical equipment down there as well. I work on maintaining the comms equipment, which itself produces a lot of heat (PA amplifiers and RF equipment for instance are often too hot to touch, even though the rooms that these are in also have  air-con, that extracted heat has to go somewhere as it is rarely taken up to the surface). With the current trend of more and more announcements, the equipment just cannot get cool. I am frequently tasked to rooms that are too hot for the equipment to work in, reaching temperatures in the 30 and 40 degree C range.

 

Stewart

[TravisM]

As a lad myself and a few other keen bus spotters would often wait at Uxbridge for a fast MET train into London. I recall there was a stripped 'flag' shown in the front of an A60 driving car on these services. The main highlights were thrashing past Neasden Depot - and the liberal use of the whistle by the driver.

Happy days.

Les

 

The "striped flag" that was shown in the cab was the weak field indicator which gave a additional stage of weak field.  This gave higher top speed at the cost of slower acceleration.

 

In the 80's, I remember beating the crap out of a BR Class 115 from Moor Park by leaving at the same with the weak field flag down to out accelerate it then when ahead, pulling it up to give it the higher speed but having to brake hard to stop at Northwood.  Beat it by a good few seconds, happy days.

 

Julian Sprott