2024 Tube Stock (Siemens Inspiro)

[ThameslinkUser]

Back when people first started mooting air conditioning for the deep level tubes, removing the heat from the platforms and tunnels was cited as a major difficulty. Was that just guff or how has the

Due to the use of regenerative braking in the train, along with fewer bogies and thus less friction, there is a significant amount of heat not being expended through braking that otherwise would. The air cooling is putting out roughly the same amount of heat energy as being saved from the more efficient braking, resulting in roughly the same amount of heat being expended overall as the 1973 stock, requiring no major changes until train frequencies increase a substantial amount.

Of course, LUL is still looking into methods of reducing the platform heat as per the experiment at Holborn disused that, with funding, will be rolled out to Knightsbridge for further live trials.

Knightsbridge hasn’t been chosen as a possible first live deployment just because it’s being upgraded, but specifically because it’s on the Piccadilly line. A lot of new trains will be arriving in a few years time, and while the trains use about 20% less power than the existing trains, and put out a lot less heat, there’s also going to be a lot more trains running on the network. More trains inevitably means more heat, and how to deal with that is a key component of the Piccadilly line upgrade project.


Although currently unfunded, TfL aims to eventually increase train frequencies on the Piccadilly line to 33 and then 36 trains per hour. It is at this point that additional cooling at five Piccadilly line stations would be necessary, according to TfL’s modelling. The five stations would be Knightsbridge, Green Park, Holborn, Leicester Square and Piccadilly Circus. TfL could then identify other locations where the panels could provide a benefit.

 

[Recessio]

I’ve heard the 2024 stock are engineered in such a way the air conditioning wouldn’t make the underground hotter. I think it would only release warm air from the air con when overground or something. I’m not knowledgeable about this.

There was an idea suggested to store heat and "cold" and only release it outside, via phase-change. The key to this is that when a solid melts into a liquid, it has a constant temperature until all the material is fully melted. This is why drinks stay cold until every last ice cube has melted - it cannot increase in temperature until the phase change (melting) is fully complete.

A naive example would be to have the train freeze a big ice cube when outside. Once in the tunnels, use the heat taken from the train via air conditioning to melt the ice cube - rather than venting the heat out into the tunnel air (like traditional air conditioning) this works because all the heat energy instead goes into breaking the molecular bonds that are holding the water molecules together in solid form (ice). When above ground again, use the heat pumps in reverse to freeze the ice cube again ready for next entering the tunnels.

Replace "ice cubes" with "fancy chemical compound with large specific heat capacity ideal for use as a thermal reservoir" and you have the system.

But the idea never went anywhere when traditional air conditioning can be used, because as mentioned further up the thread, the heat "savings" on the 2024 stock from e.g. regenerative braking means that traditional (and cheaper, and smaller) air con units can now just chuck the heats out into the tunnels without worrying about warming them up further.

 

[Silent]

Siemens has started dynamic and climatic testing on the first unit, and has published these two pictures.

First new tube stock, since 1992ts, to not have the car number centred on the train. The cab door also appears to have very thick rubber that it looks partially opened.

 

[trebor79]

Due to the use of regenerative braking in the train, along with fewer bogies and thus less friction, there is a significant amount of heat not being expended through braking that otherwise would. The air cooling is putting out roughly the same amount of heat energy as being saved from the more efficient braking, resulting in roughly the same amount of heat being expended overall as the 1973 stock, requiring no major changes until train frequencies increase a substantial amount.

Of course, LUL is still looking into methods of reducing the platform heat as per the experiment at Holborn disused that, with funding, will be rolled out to Knightsbridge for further live trials.

Ah yes, I remember that being cited as the reason it was possible now. I had always assumed that the existing stock brakes regeneratively too, but maybe not to the same extent or as efficiently as modern electronics would allow.

 

[ThameslinkUser]

I had always assumed that the existing stock brakes regeneratively too, but maybe not to the same extent or as efficiently as modern electronics would allow.

1973 tube stock do not have regenerative braking.

 

[trebor79]

1973 tube stock do not have regenerative braking.

Everyday is a schoolday!
Thinking about it a little more deeply, of course it doesn't as if you use a DC motor as a generator, the voltage varies with speed so the regeneration would reduce as train speed reduced, and unless you did something clever the voltage wouldn't exceed the supply voltage in any case. The power electronics to do that kind of thing weren't really available in 1973.

 

[AM9]

Everyday is a schoolday!
Thinking about it a little more deeply, of course it doesn't as if you use a DC motor as a generator, the voltage varies with speed so the regeneration would reduce as train speed reduced, and unless you did something clever the voltage wouldn't exceed the supply voltage in any case. The power electronics to do that kind of thing weren't really available in 1973.

Although, the class 76 locos were feeding energy back into the 1500VDC catenary between Sheffield and Manchester way back in the 150s. Switching the motors to a full series configuration will increase the total regen voltage giving an output at slower speeds.

 

[trebor79]

I suppose this also explains why the Piccadilly line stations, tunnels and air is noticabely filthier than some of the other deep tubes, due to much more brake dust being produced.

 

[Thirteen]

I wonder if TfL is aiming for July 2025 for the new stock since it'll be 50 years since the 1973 stock will have been introduced.

 

[Mojo]

I suppose this also explains why the Piccadilly line stations, tunnels and air is noticabely filthier than some of the other deep tubes, due to much more brake dust being produced.

I can’t say I’ve noticed any particular issue with the dirt or air on the Piccadilly line compared to other Tube lines.

In any case, 73 Stock has rheostatic braking in addition to friction brakes.

 

[thomalex]

I so find it strange that the lines that presumably do have regenerative breaking, looking at you Central and Victoria line, are noticeably warmer in the summer than the Piccadilly. Presumably something to do with service frequency.

 

[Thirteen]

Geoff Marshall just posted a video on YouTube about the 2024 stock from his visit to Siemen's test facility in Germany:

The Piccadilly Line is getting New Tube Trains! Built by Siemens, they'll be in passenger service in 2025. We got an invite out to their test track acility in Germany to go and have a ride on the first one off of the production line.

A totel of 94 trains are on order, with the first being built by Siemens in their Austria factory, producation will then switch to a new factory at Goole in Yorkshire, where the majority of the trains will be constructed.

NOTE:
We were all restricted to seeing just the front carriage of the train, which meant we couldn't go and see one of the shorter carriages, nor check out the accessible area of the train which we would have liked to have seen.

 

[Fazaar1889]

Geoff Marshall just posted a video about the 2024 stock:

Great video. I was hoping that we'd be able to see what the full train looks like when looking from one end to the other, through all the bendy bits

 

[thomalex]

Great video. I was hoping that we'd be able to see what the full train looks like when looking from one end to the other, through all the bendy bits

I notice that Geoff says they do feel quieter, although yes this is a test track. I would think though with these being the first deep level tubes with no open windows and ventilation it should make a difference to noise levels especially in the tunnels. Will certainly be exciting to try them out when they arrive.

 

[Silent]

Although s stock are still quite loud. The new Aventra's seem noticeably quieter though. I wonder if the bogies make a difference to noise levels. It would be interesting in how the bogie less cars would feel when running.

 

[Sorcerer]

Just watched Geoff Marshall's video as well. I like the stock and am impressed with all the engineering behind it such as working nine coaches onto just ten bogies, but the smaller square windows rather than rectangular ones do make the trains look and possibly feel more cramped despite the walk-through carriages. I expect that the smaller coaches will be quieter than the larger ones.

 

[Thirteen]

I would guess the compromise of smaller windows to enable AC is a big deal. With traverse seating, it's fairly difficult to look out of the windows anyway.

 

[Basil Jet]

I suppose this also explains why the Piccadilly line stations, tunnels and air is noticabely filthier than some of the other deep tubes, due to much more brake dust being produced.

IIRC the 1959 stock on the Northern Line was the last tube train to rely on friction braking. More recent trains have used the rheostatic (dustless) brake to slow the train and only used the friction brake to stop and hold the train, which would produce very little dust.

 

[Lockwood]

Really? You're facing the window. Or the person opposite with a bit of window over their shoulders

 

[trebor79]

I think giving up some window space to allow for air conditioning ducts is a fair trade off.

 

[61653 HTAFC]

We can barely get decent window alignment on intercity stock, let alone on the Tube!

 

[Mikey C]

These really feel like a major leap forward, a next generation with the reduction in bogies and increased number of cars, which will also help reduce the gaps on curved platforms too I imagine.

 

[AM9]

We can barely get decent window alignment on intercity stock, let alone on the Tube!

I reawlly don't see window alignment as that important in trains that the majority of journeys will be in tunnels. Who wants to sit admiring the signal cabling and the state of the tunnel lining rings, that is assuming crush loading doesn't even allowing a view of the other side of the car?

 

[A60stock]

A significant proportion of the Piccadilly line is above ground

 

[AM9]

A significant proportion of the Piccadilly line is above ground

That's not what I was referring to, - I said: "the majority of journeys will be in tunnels". The Piccadilly line trains, (like most of the Tube lines), are almost continually hevily loaded for most of the day in Zone 1, whereas they get progressively more empty as they travel out through to their country terminii. During the peak hours, there may be some loadings where they are about 1/3 full at the beginning/end of their runs, but outside those hours, there are generally plenty of seats in zones 4-6.

 

[A60stock]

Absolutely no chance whatsoever.

Back on topic, I used the Picc line yesterday for the first time in a while, and the current stock is frankly knackered.

What did you notice, specifically that makes them knackered? I used them recently too but can't seem to work out what it is, given that the interior still looks modern.

 

[birchesgreen]

What did you notice, specifically that makes them knackered? I used them recently too but can't seem to work out what it is, given that the interior still looks modern.

It might be psychological as we know the replacement is imminent.

Windows ARE important underground, to see which station you are arriving at. The PA doesn't always work or is drowned out plus many people have hearing difficulties, eyeball 1.0 out of the window (if you can of course) is a handy back-up.

 

[61653 HTAFC]

I reawlly don't see window alignment as that important in trains that the majority of journeys will be in tunnels. Who wants to sit admiring the signal cabling and the state of the tunnel lining rings, that is assuming crush loading doesn't even allowing a view of the other side of the car?

Which was precisely my point- posts here and elsewhere grumbling about "tiny submarine portholes" when (a) the busiest bit of the line is underground, and (b) the seating is longitudinal anyway, so "alignment" isn't really a thing.

Also a big "booo!" to those who want the Bakerloo bumped up the queue for new stock, or even want the outgoing Picc stock to move over. The Bakerloo is my favourite line precisely because it still has a few normal seating bays.

 

[Recessio]

It might be psychological as we know the replacement is imminent.

Windows ARE important underground, to see which station you are arriving at. The PA doesn't always work or is drowned out plus many people have hearing difficulties, eyeball 1.0 out of the window (if you can of course) is a handy back-up.

One of the new features is replacing the paper advertising boards with electronic displays - these can display which station it is, interchanges and service updates in nice big font, for those passengers that have hearing difficulties or if the noise drowns out the PA.

 

[birchesgreen]

One of the new features is replacing the paper advertising boards with electronic displays - these can display which station it is, interchanges and service updates in nice big font, for those passengers that have hearing difficulties or if the noise drowns out the PA.

That will be interesting, the existing scrolling displays are not very good a lot of the time.