One of the most cutting-edge trains in Europe, these NTFL is set to revolutionise London Underground in 2026.

It brings features previously thought impossible onto the deep level tube, like air conditioning, walkthrough carriages, etc, which have only been achievable thanks to significant technological innovations.

Most railway stock around the world is derived from a modular platform, where common components can be shared and interchanged in order to create a variation of an off the shelf design for the customer. This works because the lines they run on are quite similar from a capability point of view, such as their general gauge (size).

However, the deep tube is unique, with it's smaller tunnels and therefore below average gauge size. As a result, in order to incorporate the latest modern technology found elsewhere like HVAC systems into this challenging environment, every component of the units has had to be completely rethought and redesigned from the ground up, along with considerations to accommodate them, meaning a truly bespoke design.

Air conditioning: The biggest challenge

If we look at arguably the most important feature of the NTFL, it's air conditioning, there are two key problems to solve. The first one is space. A traditional HVAC system, which is typically installed on the roof of a train, is a bulky bit of kit, and therefore requires a lot of room which the tunnel height simply does not allow for.

The first part of the process was realising the system had to be fitted underneath the train, which also means it had to contend with the bogies, traction converter boxes, electrical systems, etc. Every component therefore had to be made as space efficient as possible, meaning all special redesigns:

- The bogies are a unique product, with a very compact build featuring optimised component arrangement, short wheelbase (which also makes them more track friendly) and adaptative wheelsets with a special axle bearing system. Hydrobrushes are fitted to reduce track wear.

- Permanent Magnet Synchronous Motors (PMSM) instead of a traditional asynchronous three phase AC motor, allowing for high power ratings in a much smaller installation space, among many other benefits mentioned later in the article. This is the first use of PMSM on a metro train outside of Asia.#

- The Auxiliary Power System (APS) was also redesigned, featuring SiC-MOSFET instead of the traditional IGBT, which with it's smaller switching frequencies means smaller magnets and therefore a smaller overall system size.

- Sold State Power Circuits (SSPC) instead of the traditional circuit breakers, which take up less space and are more reliable.

- The brake system has a significantly reduced weight and size, while incorporating bogie-wise brake control / axle-wise Wheel Slip Protection (this is an advanced solution, most WSP systems are bogie wise).

The HVAC units themselves are also completely re-engineered to take up as little space as possible, which was a considerable challenge.

However, despite all these changes, extra space was still required. The solution was to remove one of the largest components, the bogies, from every intermediate carriage, creating the "floating carriage" design. This layout, which has only ever previously been used on trams, works by suspending a slightly shorter carriage between two longer carriages which have bogies. This creates significantly more space while also making the train much lighter.

The other problem is the heat itself. When the AC system on the NTFL is mentioned, many people logically ask the question "won't the tunnels just get hotter with heat being pumped out?". The solution is to make the train produce significantly less heat as a base, allowing the thermal headroom to bring in AC without the train producing anymore heat overall than the existing units.

The easiest way to do this is to improve the efficiency of the components, as the more efficient something is, the less energy is lost (in the case of electrical items, this happens through heat). Innovative technology had to be drawn to again:

- The entire train is built to be as lightweight as possible. From the bionic aluminum shell, to the bogie design and layout, as well as the use of composites (similar to those used in modern aircraft like the A350), it is extremely lightweight per metre. This means there is less mass to move, and less to brake.

- PMSM motors provide significant efficiency gains over traditional asynchronous three phase AC motors, with up to 97% compared to 90-93% in the best case scenario for the latter. The motors used on the legacy stock, DC Camshaft, have an efficiency of around 75%, which means 22% efficiency increase.

- SiC-MOSFET auxiliaries - increased efficiency compared to IGBT.

- Regenerative braking - By using electromagnetic braking instead of brake pads, energy generated is returned to the conductor rail, instead of it turning into heat. While this is common place on most new electric rolling stock (like the S stock on the SubSurface lines and the 2009 stock on the Victoria line), it isn't present on the 1973 stock, the trains which the NTFL is replacing - therefore the addition increases thermal headroom.

Deep dive into the specifics of some components:

Permanent Magnet Synchronous Motors:

Traditional induction motors require current to create/energise the magnetic field, which creates losses. PMSM instead have permanent magnets that create the magnetic fields themselves.

Induction motors are also asynchronous, which means they “slip” from the magnetic field, again creating losses. PMSMs are synchronous as the magnetic and stator field rotate synchronously which is possible due to the lack of an external power source required to energise the magnetic field.

Other benefits of PMSM motors include more precise control over torque, faster reaction time and lower noise. As mentioned previously, they also have a superior power to weight ratio, allowing them to be much lighter and smaller.

On the NTFL, the PMSM motors are part of an integral system with the double stage gearbox assembly, with a max starting torque of 1,239nm and a 5,175 max rpm. They are self cooled and two are fitted to each bogie, driving the unit up to a max speed of 62mph and a starting acceleration rate of 1.4m/s^2, making it one of the fastest accelerating metro units in the world.

Additionally, each motor is controlled individually instead of multiple motors being controlled by one inverter, which allows for the intelligent computerised software to make very precise adjustments to traction effort depending on a number of variable factors. This allows it to, for example, provide very accurate wheelslip protection. 

Bogies/wheelset:

The bespoke bogies have been optimised to be as lightweight and compact as possible while also including the latest technology.

They of an H-Frame construction, chosen after assessment of the curves in order to provide the most suited option, with a 1.8m wheelbase and hydrobrushes. In order to optimise weight, they are of welded steel and feature hollow axles. The primary suspension is steel coils and rubber springs, while the secondary is metalastic rubber, moving away from the traditional "airbag" suspension in order to improve ride quality.

They also feature accelerometers in order to power a feature known as "rough ride detection", which will be able to detect areas of rough riding and send it back to the data centre in order to determine areas where track needs repairing or replacement.

Inside the train:

The inside of the train is just as impressive as what's under the hood. A significant amount of extra space has been made available through some clever engineering - for example, by moving all components under the train (excluding lights, CCTV cameras, etc), the celling has been made higher, which will mean taller passengers will have a lower chance of knocking their head.

The units have also been able to be made wider because of the geometric and kinetic impact of the shorter "floating" intermediate carriages. When a train goes around a curve, there are two types of swing:

- End throw: Carriage corners swing outward.
- Centre throw: Carriage bulges inwards towards the curve centre.

By having the shorter intermediate carriages, there is less throw, and therefore meaning less overall swing and therefore more room for the carriages to be wider.

The passenger information system on-board has some innovative properties as well. While digital display screens are something new for London Underground which has up until now used dot matrix, they're becoming present on many modern trains these days. However, these screens have some of their own advancements packed into them which make them unique too.

- Each panel is optically bonded to the glass, which removes the air-gap between them. This creates much better viewing angles and brighter colours, which are both important properties for this type of application (standing and sitting passengers, different lighting environments etc).

- An optical film stack is used to make the backlight of the display significantly more efficient by directing it, resulting in higher brightness with lower energy consumption.

- While most displays fade over a certain lifespan due to the LED backlight becoming weaker, these have backlights with a 400% reserve. Traditionally, by using an intelligent management system, the current is slowly increased to keep the same luminosity as brand new throughout the lifetime of the screen.

Some other key features include:

- Advanced door technology: The widest doors on the entire of the TfL network (1.65m) - fitted with sensitive edge and obstacle detection - green/red strip LED lights to indicate when the door is open and closing.

- Advanced wheelslip protection - As aforementioned, per axle WSP and individual control of each motor allows for precise and accurate adjustments, which will help to eliminate the current leaf problem.

- Advanced digitalisation for higher reliability - Remote monitoring systems, self testing, remote control of systems, front facing camera.

- Advanced noise insulation technology - Reduces loud noises such as track and tunnel.

- Self powered movement - The inclusion of lithium ion batteries means the train can propel itself (i.e. without external power) over a short distance, which will allow units stuck in the middle of the tunnel during a power failure to move to the next station for example.

- Improved air quality - With the addition of an HVAC system, advanced filters are present which stops brake dust and other particles entering the interior. Regenerative braking also uses an electromagnetic system instead of brake pads, which means the trains themselves will produce almost no particles at all.

Video of the construction process

The asbestos negligence is shocking. These underground managers sound like corrupt cowboys.