Great Western Coffee Shop

I was on the Didcot-Gt Malvern stopping service tonight, travelling in coach A (quiet) sadly it was anything but quiet, the engine noise under acceleration was deafening, sounded like the engine/exhaust was trying to break free along with associated vibrations! Definitely not wheel/rail noise as the engine was normal until half  throttle when accelerating from a stop, then incredibly noisy until coasting when the noise stopped suddenly.

I have been going on the class 180s since their original introduction and have never heard it as noisy as this. I think 180106 will be in the maintenance shed very shortly!

It will probably be like that all the time when the IEP trains come along. The bi-mode trains will have under floor Diesel engines. It will be just like the Voyager trains operated by XC which have incredibly high vibration levels due to underfloor Diesel engines. I think underfloor Diesel engines are not very good for long distance journeys. Loco haulage is the way forward.

Loco haulage isn't the way forward. Run round facilities? Finding paths in busy stations for those run round moves?

And it's a bit premature to be commenting on noise and vibration from bi-mode IEPs. They've not been built yet.

Yes, your right. Sorry

No need to apologise. All part of the debate.  :)

IEPs could be noisy, could be quiet.

I will speculate they'll be pretty quiet.   The electric ones all the time, and the bi-modes when running on electricity.

Loco-haulage happens on the ECML (East Coast Main Line), GWML (Great Western Main Line), MML (Midland Main Line) and some London - Norwich, Chiltern Railways and Holyhead - Cardiff services without the locomotives needing to run-round.

In the case of the GWML and MML (and some of those on the ECML), it is avoided by having a locomotive at each end. The rest have a special carriage (known as a DVT (Driving Van Trailer)) at the other end with a cab from which the driver can control the locomotive.

Plenty of more important things to worry about than engine noise with IEP on Great Western though... Just keep IEPs off the long-distance route towards Devon and Cornwall, which will likely mostly be away from the wires for some time yet, and nobody should have to put up with the diesel engines running for too long.

Yep. Perhaps I should've qualified my reply with single loco haulage.

There's some difference between that and fixed formation HSTs, Class 90s, Class 91s, and 67+DVTs.

Yes, there's the Sleeper sets and WAG Express, but they are very much in the minority. I think with good reason. We've moved on. MU and distributed traction seem to be the way forward.

WAG Express is also 67+DVT now, it's pretty much only the sleepers that require run-rounds. Apart from the sleepers, single loco haulage is dead as far as long-term national rail use is concerned.

Personally, I think MUs are pretty definitively the way to go if you don't need the train to run at more than 115mph. Up to that speed, you can use pretty much the full length of the train for passengers and can have corridor connections on the ends. This latter feature I believe should be the case on all such units unless they are long enough (8 coaches plus) that multiple working in service is not intended/practical.

When you get to trains longer than five or six coaches which need to do more than 115mph though, I don't think there's much in it between MUs and loco+coaches+DVT sets. With long formations, the high cost of the loco starts to be balanced out by the cheaper unpowered coaches. Also, with the higher speed the MU alternative is unable to have corridor connections on the ends and parts of the leading vehicle have to be locked out of passenger use for saftey reasons, meaning the non-passenger-carrying length of the loco is not really a problem. Not much in it then, and both options (LHCS and MUs) then have their advantages.

The superior performance, reduced energy use, lower track forces and higher capacity of multiple units make them superior to LHCS regardless of top speed, as every recent train order in this country reflects.

Chris

(Mods! I'm posting this here in response to Chris 125, but I'm not entirely certain it really belongs here).

Hmm, I'm not so sure^

The electrical or chemical energy converted to heat by a train in the course of its journey can be determined by the area under the power-time curve for that journey. It doesn't matter whether the train is locomotive hauled or has distributed traction, for the same train mass the energy 'used' will be the same.

The question of track force is also not as clear cut as the protagonists of distributed traction make out. Modern suspension designs control forces exerted by the train on the track to a level which will not distort the track or causes uncomfortable ride for the passengers. What is more significant in the medium term is the cost of track maintenance which includes both rail wear and formation stability.

Track wear is certainly dependent on axle load, but that is not the only consideration, suspension characteristics play a significant role as do wheel diameter, tyre profile and the unsprung mass of the wheel set. So although a locomotive has a higher axle load than a driving wheel of a train with distributed traction, the wear it causes may not rise pro rata as the larger diameter wheel will have a larger contact area between it and the rail so the absolute value of the stresses in the wheel and rail may not be so different. In any case any greater wear caused by the locomotive may be cancelled out by the train of lighter trailer coaches causing less effect on the track than the bogies of the train with distributed traction. It is not possible to make a blanket statement that A is better than B - each case has to be worked out on its merits.

An indication of the wear caused by different items of rolling stock can be seen in Network Rail's table of track access charges which can be found here < http://www.networkrail.co.uk/using-our-network/cp5-access-charges/ > and scroll down to Track Access Price Lists. The individual classes of rolling stock are listed, but there are also default charges (in pence per vehicle mile) which read:

Locomotive            66.15 Multiple unit (motor)   29.45 Multiple unit (trailer)   13.84 Coach                      12.18

So, two motor vehicles in a train cost the TOC the same as one locomotive.

As I understand the matter, trains with distributed traction have two advantages over LHCS. The first is that, at least since the length of the leading vehicles which can be occupied by passengers in trains operating at over 100 mph has been increased, more of the train's length can be used by passengers. This is only true for trains with a driving cab at each end - if the train consists of several multiple units the space taken up by the unused cabs is lost for revenue generating purposes. The second is that with multiple power units redundancy is increased. However, this will not be reflected linearly into improved reliability as there are many other reasons for train failure - problems with doors or brakes or windscreen wipers will be the same whatever the traction scheme.

And don't forget that DRS is taking delivery of 15 Class 68 diesels and will soon receive the first of Class 88 electro-diesels; LHCS haulage is very much part of their specification.

Life is never as clear cut as one would hope!

I do not know about the rails and sleepers, but the need for tamping ballast could related to axle load in a similar relationship to that between road axle weight and pavement (road construction) wear, which is related to the 4th power of the axle load (ref HD/24/06 (http://www.dft.gov.uk/ha/standards/dmrb/vol7/section2/hd2406.pdf)).

An interesting and detailed discussion of the issue, 4064ReadingAbbey. It is not a clear cut argument.

However, the length of the loco argument only applies at one end of the train, the other end can be a driving trailer carriage with exactly the same amount of furnishable space as an equivelent MU. So:

• When the top speed is 115mph or less, the multiple unit wins hands down as it loses very little furnishable space for cabs, whereas LHCS has the length of the loco
• When the top speed is greater than 115mph LHCS loses some length (say Y metres) at the driving trailer end for saftey reasons, however the MU loses 2xY metres (Y metres at each end)

Of course, this argument can be made largely irrelevant if the signal positions are designed for LHCS, since the loco would in theroy then only need to be platformed at one of the termini.

There was an article in Modern Railways some time ago about retaining mark3 coaches (with TraXX locos if I remember correctly) on the London-Norwich service and if I remember correctly the author was of the opinion that solution would be kinder to the track than a new EMU.

It is, 100 tonne (plus) locomotive is very unkind to the track one of the reasons why HST's have 2 locomotives (power cars).  The 100 tonne mass at speed on a curve with a cant pull place considerable lateral force on the track which means more frequent tamping, where as multiple units with distributed mass cause less force.

The other problem with a single locomotive is one power plant failure results in a total train failure on a multiple unit one or even two power plant failure the train can continue.

If LHS was the most economic and practical means of operating trains the TOC would be choosing LHS over MU's

What are the respective axle loads for a loco, powered car and trailer?

This discussion seems to have deviated from the topic name - Noicy Class 180.

Another sick class 180 tonight, the stopping service started from P3 at Oxford rather than Didcot, and was already minus an engine in carriage B (info from TM) but every restart from a station the engine in carriage A (ironically the quiet coach) made an awful grinding noise that set up vibrations and resonances in the coach structure until the train reached coasting speed.