New tube for London stock

Curiously, the vehicle in the artist's impression looks to be a similar length to the existing stock, instead of only two thirds the length as those figures imply. Or will the end cars be longer than the intermediate ones?

I am not sure about the NTFL being longer than existing Piccadilly line stock?

If the latest TFL data sheets are correct the 72 stock length over couplers is 119.03 metres whilst the latest NTFL PDF shows the length over couplers as 113.7 metres.

This suggests the new NTFL trains will actually be slightly shorter and this should minimise or avoid entirely the need to cut out doors at shorter platforms.

The big question is the length from coupling to coupling to add/subtract an individual non-driving segment to a train - sadly that is not revealed on the latest Siemens PDF.

If they get that right (which presumably Siemens will have carefully considered) it should then allow them to offer TFL the ability to choose custom train lengths by simply adding/subtracting segments (cars if you must). So the same production line can then deliver train lengths which get reasonably close to the existing rolling stock lengths for use on lines like the Bakerloo which ihopefully will be ordered soon as a follow-on to the Piccadilly fleet.

Further flexibility seems possible due to the length before there are any passenger doors at the cab ends. Assuming the NTFL will eventually get in platform video feeds for boarding monitoring - like the S7/S8 cabs have - it is presumably not essential if the non boarding section at the non driving end and possibly even the front of the train are still in tunnel.  Obviously someone will need to assess whether current signal placement/view is acceptible for conventional driving of NTFL trains during the period before lines move to fully ATO operation at which point presumably they abandon/cover conventional signals like they did on the Jubillee.

Don't the length of the intermediate cars vary?

I shall miss those single leaf doorways at the car ends - when I started travelling to / from school (September 1971!!!) on the Underground this became my favourite part of the train for alighting at Gants Hill as it was closest to the escalators. That said, until the advent of ATO it was always a bit of a 'hit or miss' issue as sometimes the train stopped a little further forwards than usual.

In light rail applications they are often called "floating" sections or articulations. More formally they are sometimes called "suspended" sections.

I'm not sure, however, how well either of these terms will translate to heavy rail. The closest heavy rail example I can think of to compare is a Beyer-Garratt!

When I have seen bogies shared between cars, they are centred on the connection between the cars. The new tube trains have alternate cars with two bogies positioned as we have always known. The wheel-less cars at the even numbered positions show no visible means of support! I wonder how the load is transferred to the adjacent bogies.

Part of the middle section of a Garrett is above the wheeled sections though. Indeed, it is essentially a double-bogie locomotive, with the power bogies extending beyond the end of the superstructure. But then so is a Class 40, as the extreme ends of those locos, the bufferbeams, are also mounted on the bogies.

Do floating cars pivot off the inter-car connection, or off the adjacent bogie? In the latter case, I have trouble imagining movement in the inter-car corridor. But the former suggests that the weight is carried by the bodywork of the adjacent car.

Was there a prototype for the current Victoria line stock or even the S stock.

There were two "pre-production" 2009 tube stock trains. When they were returned to Bombardier for upgrade to production standard, the carbodies were scrapped but bogies and a great deal of the equipment was transferred to new bodies. The first pre-production train didn't have a proper interior and was mainly used to test the ATO/ATP system which could not have been optimised on the 1967 tube stock due to the latter's comparatively poor performance.

The difference between the pre-production and production 2009 tube stock was quite significant although I don't recall details. The difference between the pre-production and production S stock was comparatively small. There were greater differences between S8 and S7 as the opportunity was taken to improve the design in a few places.

I just recalled that the New Train for London project commenced after the collapse of the PPP, with a remaining need for new trains for the Bakerloo line. It was grant funded to provide a prototype train in 2015, which was then twisted to allow half a train! Perhaps that could have been trialed on the Hainault - Woodford shuttle? There was bracket creep on the project, with dreams of driverless trains along the way, and periods of funding shortages, and the milestone morphed to become an invitation to tender for the trains in 2015, which was almost met. In the meantime the Piccadilly became first priority, so here we are still awaiting any new train, the Bakerloo without hope, and now no plans for a prototype!

In the interests of historical accuracy, I should point out that Tube Lines did not 'go bust'. Amey and Bechtel, the two owners of Tube Lines, were bought out by TfL in 2010 (for £310m).

Any images of these two?

2 different comments.

At an IRSE lecture the prototype trains were referred to - including the ATO etc kit mentioned above - and that early on in the project, even before series trains were in build, the prototypes destined to not become series trains, they were both too different and had too many "temporary" mods done to them.
((That's not to say they were never planned for use as series trains, just that they were altered to not be very early on. Returned to Derby for component recovery, as described, but not re-use as vehicles))

A Bombardier technician much later told me there were structural differences in the car bodies, and that those differences were exactly because they had built prototypes. In other words, they prototyped something, and found it was not right, so corrected it for production, that is what prototyping is for. Some of those structural mods he thought were major ones, and others connected with S-stock development, and at least one car was completely dis-assembled.

Don't shoot the messenger, I am only relaying what I heard, I have no working knowledge of these matters, they are outside my area.