Intercity Express Programme (IEP) - ongoing discussion

[whole diary]

[stuving]

The generators in 801s are supposed to run hotel services for a unit when loco-hauled, so presumably they reckon 700 kW is enough for that. Each motored car (of five) has an auxiliary power unit rated at 240 kW, but that could be far more than is expected as a demand.

When a train needs to be moved, I expect the aircon (and perhaps some other things) will be shut down for a few minutes. That shouldn't be a big problem unless it has a long hill to climb. But, realistically, shifting 400 t of train up 1 in 100 at 20 mi/hr takes a lot less power that you would think - like 350 kW. And on the flat, it takes hardly any power to keep it moving at 30 mi/hr - 116 kW, by my reckoning.

[Adelante_CCT]

30mph 'off the wires' IIRC^▸ (if I recall/remember/read correctly), I'm guessing the longest distance that would be needed would be Swindon to Bristol Parkway.

[broadgage]

30 MPH of the wires sounds useful and would permit of diversions off electrified routes and also of excursions or specials to non electrified branches.
5 MPH as suggested in a previous post is only a little better than nothing.

[ChrisB]

Please understand this engine would only be used in times of needing to move under own power, not for likes of excursions.

[stuving]

 You may be interested in this article from a Hitachi house magazine*. It's from 2014, but I've not seen it before. It should provide a reliable source, and includes some new points, but I still can't make sense of some of the numbers here and in the requirement.

1. In this paper (as elsewhere) a lot is made of the lightweight construction. But in issue 1 of the requirement (2007, issued with the ITT^▸ (Invitation to Tender)), that was to be less than 362 tonnes for a 260 m (10-car) electric unit, while in issue 5 (2012, part of the contract) it is allowed to be 399.8 tonnes for a 234 m (9-car) electric unit. Presumably Hitachi's design needs that higher limit, since they were preferred supplier for some time before that last issue.

That's a pretty big jump - so much for light-weight aluminium bodies! For comparison, that is from 1.39 t/m to 1/71 t/m, while a TGV^▸ (Train a Grande Vitesse) R^seau with more power and taller bodies is 1.91 t/m. But TGVs have always had a big weight problem (those shared bogies and a 17 t axle-load limit), so just beating that is doing pretty well. It's the original requirement, for less than 1.4 t/m,that looks wildly optimistic.

2. The paper gives the train make-up as DPTS + MS + MS + MC + DPTF (5 cars) and DPTS + MS + MS + TS + MS + TS+ MC + MF^▸ ((in timetables) Monday to Friday) + DPTF (9 cars). It also shows a "traction system" (unit) as containing one (optional) generator driving four motors, which only makes sense if they are all on the one motor carriage.

Now, the requirement allows a slightly slower journey time for even-numbered train lengths, so if that is based on this design it suggests the added carriage will be a trailer. (It also suggest an unhealthy leakage between "requirement space" and "solution space".) So adding a carriage to the current trains will slow them down.

3. Hitachi quote an acceleration 0.7 m/s/s, much better than the "expected performance" curve in the requirement Issue 1. That had 0.58 m/s/s up to a knee at 53 km/hr, and constant-power curve above it. Issue 5 has a similar curve, but says:

N028 The IEP^▸ (Intercity Express Program / Project.) Trains must, at all speeds, accelerate at a rate no greater than that defined in the graph below, unless higher rates of acceleration are demonstrated to be compatible with the infrastructure:

Just how better acceleration might be incompatible with the infrastructure I am not sure.

Anyway, this curve is 0.75 m/s/s up to a knee at 45 km/hr, and a constant power above that that is only marginally lower than in the previous curve. It's possible to work out what power that is, given likely values for mass and drag, and for the 9-car 801 it is about 3600 kW.

4. The traction motor rating is given as 226 kW. I can't find a definitive statement that there is always one engine and four motors per motor carriage, but that seems to be the general view.

Now one motor per axle at 4520 kW looks a bit over the top, but if it is designed to reach 140 mi/hr or more, even uphill, maybe that's what it takes. A typical TGV has 8800 kW for about the same mass, but a bigger frontal area, and a speed of "only" 200 mi/hr or less. Given that at high power air resistance dominates, and goes up with velocity squared, that IEP power does look about right.

It may even be too much - in the sense that it can reach its maximum allowed acceleration at all speeds with less than its full power, and that may be so even with an extra trailer to make a 10-car.

5. The diesels, however, are giving much less, especially on the 9-car bi-modes (for the ECML^▸ (East Coast Main Line)), and even more so if stretched by adding a trailer. This paper says that each diesel generator is rated at 700 kW, which is certainly what MTU^▸ (Motor Traction Unit) say for this model number. Sources (such as WikiPedia, but largely Roger Ford) say the class 800s only have 560 kW from each engine (versus 904 kW for the motors), while the 802s will have the full 700 kW. Bear in mind that the auxiliary power has to come from the diesels, but is additional to the traction power.

I suspect this is reading too much into a (now off-line) Hitachi press statement. Since Roger Ford has also said the 700 kW is still available if an engine shuts down, that means it's just software that fixes this power limit. And if the power is in fact too low to keep to the timetable? Hitachi have committed to the timings in the requirement, not the power power engine, so presumably they would need to tweak the code a bit.

I wonder how much extra short-term power output can be made available by shutting down auxiliaries, both obvious (aircon) and less so (including some internal engine functions). If that's not possible, 2800 kW less auxiliaries (by implication less than 560 kW) does look very low compared to 4520 kW.

Of course there may be mis-statements even in this source. For example: "Because the coupling or uncoupling of cars in a trainset occurs during commercial service at an intermediate station, the automatic coupling device is able to perform this operation in less than 2 minutes." Oh no it's not! The requirement says:

TS1980 The design of the IEP Units must ensure the time to add or remove Intermediate IEP Vehicle is minimised and is in any event no greater than 8 hours.
TS1589 With regards to IEP Unit reconfiguration it must be possible to reconfigure software and control systems within 15 minutes when Intermediate IEP Vehicles have been added, removed or replaced.

*"Development of Class 800/801 High-speed Rolling Stock for UK^▸ (United Kingdom) Intercity Express Programme"; Hitachi Review Vol. 63 (2014), No. 10 p 647
http://www.hitachi.com/rev/pdf/2014/r2014_10_105.pdf

[IndustryInsider]

30mph 'off the wires' IIRC^▸ (if I recall/remember/read correctly), I'm guessing the longest distance that would be needed would be Swindon to Bristol Parkway.

30mph is what I thought as well, and is backed up with what's contained in the original train specification:

"TS1949
Limited Movement:
Limited Movement is defined as the ability whilst with a Crush Laden Load to:

^ on level track, reach a speed of at least 30mph from stationary within 5 minutes,
^ start on and climb any gradient encountered on the IEP^▸ (Intercity Express Program / Project.) Network,
^ start on and climb a gradient of 1 in 37.

It is accepted that 30mph may not be achieved whilst climbing gradients."

So, accepting that certain aspects of that specification have since changed, I would be very surprised if that has changed to as little as the 5mph ChrisB is suggesting!

I do agree with him that it will be only used on the main line when dealing with infrastructure failure or train failure.  Excursions or specials will no doubt just use a bi-mode set!

[paul7575]

Of course there may be mis-statements even in this source. For example: "Because the coupling or uncoupling of cars in a trainset occurs during commercial service at an intermediate station...

Surely that part of the source document is attempting to describe multiple operation, and splitting/joining of more than one trainset in servcice, e.g. 5+5?

Paul

[stuving]

Of course there may be mis-statements even in this source. For example: "Because the coupling or uncoupling of cars in a trainset occurs during commercial service at an intermediate station...

Surely that part of the source document is attempting to describe multiple operation, and splitting/joining of more than one trainset in servcice, e.g. 5+5?

Paul

Of course it is, but it says "trainset", a word it uses elsewhere to mean "unit". It also says that a twelve-car train has to be made up of more than one unit:

The 12-car maximum configuration for commercial operation is formed by linking two trainsets together and adding or removing standardized intermediate cars.

which is not what the requirement says.

This kind of article for a house magazine ought to be written to the standards of technical journal, though its audience is wider. However, often they are written by managers senior enough to be out of touch with the smaller details. Most of the authors being Japanese probably doesn't help either.

[stuving]

So, accepting that certain aspects of that specification have since changed...

That requirement was marked "Issue 05 19/07/12 Formal Issue for Contract", and the contract was signed in July 2012. So I've been assuming that any further change to that requirement could only be made by a formal contract renegotiation; not something you'd do unless it really mattered.

[IndustryInsider]

I hadn't realised it was so recent.  So, there we have it - 30mph unless on a steep uphill gradient.

[TonyK]

I hadn't realised it was so recent.  So, there we have it - 30mph unless on a steep uphill gradient.

As said before, the longest stretch this will be needed for is just out of Swindon to Bristol Parkway, then to the depot a mile away.

The train controller may need to consult other bits of software before raising the speed, whether its power comes off 25 kV or from the on-board generator. For example a temperature reading may tell it that something can't run at higher power. The generator controllers will report whether they can provide more power, which will depend on the auxiliary load among other things, and that is the issue here. If more power is available, why would the train controller apply a lower speed of 100 mi/hr if it can go faster?

Aye, ye cannae beat the laws o' physics!

[IndustryInsider]

5. The diesels, however, are giving much less, especially on the 9-car bi-modes (for the ECML^▸ (East Coast Main Line)), and even more so if stretched by adding a trailer. This paper says that each diesel generator is rated at 700 kW, which is certainly what MTU^▸ (Motor Traction Unit) say for this model number. Sources (such as WikiPedia, but largely Roger Ford) say the class 800s only have 560 kW from each engine (versus 904 kW for the motors), while the 802s will have the full 700 kW. Bear in mind that the auxiliary power has to come from the diesels, but is additional to the traction power.

Interesting video of the Virgin Trains East Coast launch train from a few weeks back accelerating away from a stop on diesel power.  Acceleration, at low speed at least, looks pretty decent.

https://www.youtube.com/watch?v=w9w9amWKhV4

[stuving]

Interesting video of the Virgin Trains East Coast launch train from a few weeks back accelerating away from a stop on diesel power.  Acceleration, at low speed at least, looks pretty decent.

And so it should - it won't be power-limited until around 18 mi/hr. Below that it's limited by adhesion, the force (not strictly TE) from the motor/drive systems, or the controller setting an acceleration limit (which may be based the first two things). As the engine's weight sits on the motored axles, even that gives it (in theory) more adhesion and potential force at low speed.

[paul7575]

Apparently an IEP^▸ (Intercity Express Program / Project.) ran to Reading West Jn and back yesterday evening, en route from North Pole to Old Dalby

There's a video on youtube of it passing through Twyford platform 1:

https://www.youtube.com/watch?v=L7lR5wfj54Q

Paul

[ChrisB]

In Virgin colours too....