The Anonymous Widower

Stadler Flirt And Bombardier Aventra Tri-Modes Compared

In this post, I will assume that a tri-mode train is capable of the following.

• Running using 25 KVAC overhead and/or 750 VDC third-rail  electrification.
• Running using an on-board power source, such as diesel, hydrogen or Aunt Esme’s extra-strong knicker elastic.
• Running using stored energy for a reasonable distance.

I would suggest that a reasonable distance for battery power would include routes such as.

• Northallerton – Middlesbrough
• Ashford – Hastings
• Lancaster – Barrow
• Preston – Burnley

Preferably, the trains should be able to go out and back.

The Stadler Flirt Tri-Mode

What we know about the Stadler Flirt Tri-Mode has been pieced together from various sources.

The tri-mode trains for South Wales and the Class 755 trains for East Anglia use the same picture as I pointed out in Every Pair Of Pictures Tell A Story.

This leads me to surmise that the two trains are based on the same basic train.

1. Three or four passenger cars.
2. A power-pack in the middle with up to four Deutz 16 litre V8 diesel engines.
3. 25 KVAC overhead electrification capability.
4. 100 mph operating speed.

This is a visualisation of the formation of the trains clipped from Wikipedia.

One of the routes, on which Greater Anglia will be using the trains will be between Lowestoft and Liverpool Street, which shows the versatility of these trains.

They will be equally at home on the rural East Suffolk Line with its numerous stops and 55 mph operating speed, as on the Great Eastern Main Line with its 100 mph operating speed.

South of Ipswich, the diesel engines will be passengers, except for when the catenary gets damaged.

In Tri-Mode Stadler Flirts, I said this.

I would expect that these trains are very similar to the bi-mode Stadler Flirt DEMUs, but that the power-pack would also contain a battery.

As an Electrical and Control Engineer, I wouldn’t be surprised that the power-pack, which accepts up to four Deutz diesel engines, can replace one or two of these with battery modules. This could make conversion between the two types of Flirt, just a matter of swapping a diesel module for a battery one or vice-versa.

Note that the three-car Class 755 trains for Greater Anglia have two diesel engines and the four-car trains have four engines.

In the July 2018 Edition of Modern Railways, there is an article entitled KeolisAmey Wins Welsh Franchise.

This is said about the Stadler Tri-Mode Flirts on the South Wales Metro.

The units will be able to run for 40 miles between charging, thanks to their three large batteries.

So could it be that the tri-mode Stadler Flirts have three batteries and just one diesel engine in the four slots in the power-pack in the middle of the train?

The Bombardier High Speed Bi-Mode Aventra

In the July 2018 Edition of Modern Railways, there is an article entitled Bi-Mode Aventra Details Revealed.

As is typical with Bombardier interviews, they give their objectives, rather than how they aim to achieve them.

In Bombardier Bi-Mode Aventra To Feature Battery Power, I said this.

The title of this post is the same as this article in Rail Magazine.

A few points from the article.

• Development has already started.
• Battery power could be used for Last-Mile applications.
• The bi-mode would have a maximum speed of 125 mph under both electric and diesel power.
• The trains will be built at Derby.
• Bombardier’s spokesman said that the ambience will be better, than other bi-modes.
• Export of trains is a possibility.

Bombardier’s spokesman also said, that they have offered the train to three new franchises. East Midlands, West Coast Partnership and CrossCountry.

Very little more can be gleaned from the later Modern Railways article.

Good Customer Feedback

Would they say anything else?

But Bombardier have claimed in several articles, that the Aventra has been designed in response to what operators and passengers want.

Performance

The Modern Railways article gives this quote from Des McKeon of Bombardier.

From the start we wanted to create a bi-mode which would tick all the boxes for the Department of Transport and bidders.

That means a true 125 mph top speed and acceleration which is equally good in both electric and diesel modes. We have come up with a cracking design which meets these criteria.

I also think it is reasonable to assume that the performance of the proposed trains is very similar or better to that of Bombardier’s Class 222 train, which currently run on the Midland Main Line.

After all, you won’t want times between London and the East Midlands to be longer.

Distributed Power

Distributed power is confirmed in the Modern Railways article, by this statwment from Des McKeon of Bombardier.

The concept involves underfloor diesel engines using distributed power.

But distributed power is inherent in the Aventra design with the Class 345 trains.

I found this snippet on the Internet which gives the formation of the nine-car trains.

When operating as nine-car trains, the Class 345 trains will have two Driving Motor Standard Opens (DMSO), two Pantograph Motor Standard Opens (PMSO), four Motor Standard Opens (MSO) and one Trailer Standard Open (TSO). They will be formed as DMSO+PMSO+MSO+MSO+TSO+MSO+MSO+PMSO+DMSO.

Eight cars are motored and only one is a trailer.

The snippet has a date of August 13th, 2016, so it could be out of date.

It would also appear that the Class 720 trains for Greater Anglia, which are built to cruise at 100 mph, do not have any trailer cars.

It will be interesting to observe the formation of the Class 710 trains, when they start running in the autumn.

Surely to have all these traction motors in each car must be expensive, but it must give advantages.

Perhaps, each motored car has a battery to handle the regenerative braking. This would minimise the power passed between cars, which must be energy efficient for a start.

Consider the following.

• An MS1 car for a Class 345 train weighs 36.47 tonnes.
• A typical car can accommodate a total of about 175 seated and standing passengers.
• With bags, buggies and other things passengers bring on, let’s assume an average passenger weight of 90 kg, this gives an extra 15.75 tonnes.
• Suppose the battery were to weigh a tonne
• So I will assume that an in service MS1 car weighs 53.2 tonnes.

Calculating the kinetic energy of the car for various speeds gives.

• 75 mph – 8.3 kWh
• 90 mph – 12 kWh
• 100 mph – 14.8 kWh
• 125 mph – 23 kWh

Considering that the  Bombardier Primove 50 kWh battery, which is built to power trams and trains, has the following characteristics.

• A weight of under a tonne.
• Dimensions of under two x one x half metres.
• The height is the smallest dimension, which must help installation under the train floor or on the roof.

I don’t think Bombardier would have trouble finding a battery to handle the regenerative braking for each car and fit it somewhere convenient in the car.

Underneath would be my position, as it is closest to the traction motors.

So just as traction is distributed, could the batteries and diesel power be distributed along the train.

Underfloor Diesel Engines

The full statement about what Des McKeon said, that I used earlier is as follows.

The concept involves underfloor diesel engines using distributed power, but that designing from scratch enabled Bombardier to fit these without having to substantially raise the saloon floor height on any of the vehicles.

When asked about which diesel engines would be used, Mr. McKeon also confirmed that there were at least two potential suppliers, and that the diesel engines fitted would comply with the latest and highest emissions standards.

Conversion to pure electric operation is also a key design feature, with the ability to remove the diesel engines and fuel tanks at a later date, if they were no longer required.

One of my customers fror data analysis software, was Cummins, who have supplied Bombardier with diesel engines in the past. One thing that impressed me, was that they have an ability to reposition all the ancillaries on a diesel engine, so that, if required for a particular application, it could be fitted into a confined space.

I believe from what I saw, that Cummins or one of the other diesel engine manufacturers could supply a low-height diesel engine with an adequate power level to fit under the car floor without raising it by an unacceptable amount.

If you travel on one of London’s New Routemaster buses and sit in the back seat downstairs, at times you can just about hear the diesel engine, which is placed under and halfway-up the stairs, as it starts and stops. But generally, the engine isn’t audible.

A typical Volvo double-decker bus like a B5TL, is powered by a 5.1 litre D5K-240 engine, which is rated at 240 bhp/177 kW.

By contrast, the New Routemaster is powered by a Cummins ISBe engine with a capacity of 4.5 litres and a rating of 185 bhp/138 kW. One of the major uses of a larger 5.9 litre version of this engine is in a Dodge Ram pickup.

The two buses do a similar job, but the New Routemaster uses twenty percent less power.

The saving is probably explained because the New Routemaster is effectively a battery bus with regenerative braking and a diesel engine to charge the battery.

I am led to the conclusion, that Bombardier plan to fit an appropriately sized diesel engine under the floor of each car in the train.

Bombardier built the 125 mph Class 222 train, which have a 19-litre Cummins QSK19 engine rated at 750 bhp/560 kW, in each car of the train. I can’t find the weight of a car of a Class 222 train, but that for a similar 220 train is around 46.4 tonne, of which 1.9 tonnes is the diesel engine.

Applying the same logic, I can calculate the energy for a single-car of a Class 222 train.

• A typical car weighs 46.4 tonnes.
• A typical car can accommodate a total of about 75 seated and standing passengers.
• With bags, buggies and other things passengers bring on, let’s assume an average passenger weight of 90 kg, this gives an extra 6.75 tonnes.
• So I will assume that an in service car weighs 53.2 tonnes.

Remarkably, the weight of the two cars is the same. But then the Aventra has more passengers and a heavy battery and the Class 22 train has a heavy diesel engine.

As both trains have the same FLexx-Eco bogies, perhaps the car weight is determined by the optimum weight the bogies can carry.

Calculating the kinetic energy of the car for various speeds gives, these figures for a single car of a Class 222 train.

• 75 mph – 8.3 kWh
• 90 mph – 12 kWh
• 100 mph – 14.8 kWh
• 125 mph – 23 kWh

I will also adjust the figures for the proposed high speed bi-mode Aventra, by adding an extra tonne to the weight for the diesel engine and fuel tank.

This gives the following figures for a tri-mode 125 mph Aeventra.

• 75 mph – 8.5 kWh
• 90 mph – 12.1 kWh
• 100 mph – 15 kWh
• 125 mph – 23.5 kWh

Note that increase in speed is much more significant, than any increase in weight of the car, in determining the car energy.

I will now look at how the high speed bi-mode Aventra and a Class 222 train, running at 125 mph call at a station and then accelerate back to this speed after completing the stop.

The high speed bi-mode Aventra will convert the 23.5 kWh to electrical energy and store it in the battery.

After the stop, probably eighty percent of this braking energy could be used to accelerate the train. I m assuming the eighty percent figure, as regenerative braking never recovers all the braking energy.

This would mean that to get back to 125 mph, another 5.1 kWh would need to be supplied by the diesel engine.

In contrast the diesel engine in the car of the Class 222 train would need to supply the whole 23 kWh.

As the time to accelerate both trains to 125 mph will be the same, if Bombardier are to meet their probable objective of similar performance between the following.

• Bi-mode Aventra in electric mode
• Bi-mode Aventra in diesel mode.
• Class 222 train.

This means that the size of diesel engine required in the bi-mode Aventra’s diesel in each car is given by.

560 * 5.1/23 = 124 kW or 166 bhp.

The quiet Cummins ISBe engine with a capacity of 4.5 litres and a rating of 185 bhp/138 kW from a New Routemaster bus, would probably fit the bill

Could we really be seeing a 125 mph bi-mode train powered by a posse of Amrican pick-up truck engines?

The mathematics say it is possible.

If you think, I’m wrong feel free to check my calculations!

Last Mile Operation

The Modern Railways article, also says this about last mile operation.

The option for last-mile operation or for using this technology through short sections, such as stations will also be available, although Mr. McKeon said this is not in the core design.

I think there is more to this than than in the words.

The South Wales Metro is making extensive use of discontinuous electrification to avoid the need to raise bridges and other structures. I said more in More On Discontinuous Electrification In South Wales.

The ability to run on a few hundred metres of overhead rail or wire, without any power would be very useful and allow electrification to be simplified.

Imagine too a section of line through a Listed station or historic landscape, where electrification would be difficult for heritage reasons.

The train might glide silently through on battery power, after lowering the pantograph automatically. It would raise automatically, when the electrification was reached on the other side.

And then there’s all the depot and stabling advantages, of using batterry power to cut the amount of electrification and improve safety.

Future Fuels

The Modern Railways article, also says this about future fuels.

Mr McKeon said his view was that the diesel engines will be required for many years, as other power sources do not yet have the required power or efficiency to support inter-city operation at high speeds.

Running at high speeds in itself is not the problem, as a train with good aerodynamics and running gear will run easily without too many losses due to friction.

The biggest use of traction energy will be accelerating the train up to operating speed after each stop.

It is too early yet to judge whether fuels like hydrogen will be successful, but other areas will improve and make trains more efficient.

• Improved aerodynamics.
• Better traction motors.
• Better batteries with a higher energy storage per kilogram of battery weight.
• More efficient, quieter and less polluting diesel engines.
• More intelligent control systems for the train and to inform and assist the driver.

I also think there is scope for electrifying sections of track, where energy use is high.

Interior And Passenger Comfort

The Modern Railways article finishes with this paragraph.

In terms of the interior, Mr. Mckeon said the aim was to offer passenger comfort to match that on an EMU. The key elements of this are to have less vibration, less noise and an even floor throughout the passenger interior.

I believe my calculations have shown that using batteries to handle regenerative braking, substantially reduces the size of the diesel engines required, to about that of those in a serial hybrid bus, like a New Routemaster.

These smaller engines are much quieter, with much less noise and vibration.Their smaller size will also make  designing a train with a uniform even floor a lot easier.

Comparing The Two Trains

Operating Speed

The maximum operating speed of the two trains is as follows.

• Tri-Mode Stadler Flirt – 100 mph
• High Speed Bi-Mode Aventra – 125 mph

This would appear to be a point to Bombardier. But could the speed of the tri-mode Stadler Flirt be increased?

125 mph Flirt EMUs do exist, but these don’t have the power pack in the middle, which may have the capability to introduce unwelcome dynamics into the train.

On the other hand, the high speed bi-mode Aventra, is dynamically at least, very much a conventional non-tilting high speed train., even if the way the train is powered is unconventional.

UK high speed trains have generally been capable of greater than 125 mph.

• The InterCity 125 set the world record for a diesel train at 148 mph, on the first of November 1987.
• The InterCity 225 was designed to run at 140 mph (225 kph) with in-cab signalling.  In 1989, one train achieved 161 mph.
• Class 395 trains regularly run at 140 mph on HS1 and have run at 157 mph.
• Class 800, Class 801 and Class 802 trains are all designed to run at 140 mph with in-cab signalling.

I can’t help thinking that Bombardier’s engineers know a way of obtaining 140 mph out of their creation.

Calculation shows that the kinetic energy of one car of a high speed bi-mode Aventra travelling at 140 mph is 30 kWh, which is still easy to handle, in a train with a battery and a diesel engine in each car.

Could this train be the ideal classic-compatible train for High Speed 2?

Battery Range

I said earlier that the range of the Tri-Mode Stadler Flirt will be forty miles on batteries.

So how far will Bombardier’s high speed bi-mode Aventra go on full batteries?10 and 17

I speculated that these trains are formed of cars with a 50 kWh battery and a small diesel engine of about 124 kW in each car.

In an article in the October 2017 Edition of Modern Railways, which is entitled Celling England By The Pound, Ian Walmsley says this in relation to trains running on the Uckfield Branch, which is not very challenging.

A modern EMU needs between 3 and 5 kWh per vehicle mile for this sort of service.

So the range could be somewhere between 10 and 17 miles.

But the more efficient the train, the greater the distance.

Reducing energy consumption to 2 kWh per vehicle mile would give a range of 25 miles.

Adding More Cars

Adding more cars to an Aventra appears to be fairly easy, as these trains can certainly be ten-car units.

But doing this to a Tri-Mode Stadler Flirt may be more difficult due to the train’s design. Five or possibly six cars might be the limit.

June 30, 2018 Posted by AnonW | Transport/Travel | Aventra, Class 222 Train, Class 755 Train, FLEXX Eco Bogie, High Speed Bi-Mode Aventra, Tri-Mode Stadler Flirt | 3 Comments