LMS 6202, the "turbomotive"

If this loco is remembered it's usually as 46202 Princess Anne, one of the two scrapped casualties of the Harrow and Wealdstone disaster in 1952.

But I've just found an interesting website about this Stanier Pacific's unique earlier history. Built in 1933, the steam turbine drive seems to have been a technical success, but high maintenance costs (inevitable in an experimental one-off), and lack of interest after Stanier was replaced by Ivatt, led to its being rebuilt as a conventional 4-cylinder engine in 1949.

Makes you wonder what late 1940s turbine materials and manufacturing techniques could have done for the cost-effectiveness calculations, given that jet aero engines were a reality by then. Was 6202 another Great British might-have-been-but-before-its-time, perhaps?

Oh, and it looked fantastic too. To see for yourself, click here:
http://www.dself.dsl.pipex.com/museum/locoloco/turbom/turbom.htm

 

I'm sure it was an expensive bit of kit to replace, and for the last 10 years of that loco's existence as a "turbo" there was always a reason to say "...we've got more important things to spend our money on".

1939-45 - "Don't you know there's a war on? Frankly..."
1945-47 - "Our current express fleet is adequate, and given the Austerity programme, we feel that... "
1948-49 - "We will be moving towards standardised designs, so I'm afraid..."

It was the APT-E of its age, I think. Just let me highlight some of this snippet from Wikipedia on the APT.

Due to ongoing technical problems with these pre-production units, and a lack of cash or political will to take the project forward, the planned APT-S production-series units were never built, but did influence the design of the later InterCity 225 sets designed for the East Coast Main Line electrification. The technology was later sold to Fiat and used as the basis for their Pendolino trains which have been used world wide including the West Coast Main Line

At least with the turbomotive, we never had to buy back our own designs, but only because the rest of Europe was already betting on electric.

 

E S Cox in "Locomotive Panorama" vol 2 devotes but a small paragraph to 6202, because it appears to have been Roland Bond's reponsibility rather than under Cox's wing. Cox says: " a modest and most promising departure from the classic steam locomotive form was not able to provide any real justification for its continuance".
Roland Bond comments that the initial teething difficulties had been largely overcome by the outbreak of war, but that during the war it was difficult to maintain 6202 due to the need for special parts and the like. After the war the loco appears to have spent prolonged periods awaiting or under repair.
6202 as a turbo appears to have worked alongside the other traditional members of the class on the heavy post-war Euston-Liverpool services, regularly taking in excess of 500 tons on what was for a time the fastest train on the LMS at 64 mph average.

46118

 

What a wonderful website this is on though, spent quite sometime browsing it last night, thanks for the link!

 

There are two colour images of 6202 in pre- and post-war liveries on www.elegantsteam.com. Many other goodies as well, though GWR and SR fans be warned, there's a distinct northern bias. (I just love the P2 as streamlined!).

I do find this concept so elegantly simple. Looking at the drawings, you just know it would have worked if properly developed. By 'worked' I mean outperformed any other express steamer of its time, at vastly reduced maintenance cost because there were many fewer parts to go wrong, but of course they would be very expensive when they did need replacing (like a Toyota really, lol). But Stanier was up against the entire human and corporate infrastructure that knew and serviced cylinder locos - huge vested interest.

I note that the French tried to "re-engineer" the basic Stanier design twice, but the war got in the way, in the 'KERBOOM!' sense.

If I were a billionaire I'd have 6203 off the guys at Butterley like a shot - name your price - and get it converted just to see (and hear) what happens.

 

By all accounts, when the Turbo was on song it was an excellent piece of kit, capable of out-performing its conventional Princess sisters. The fact that it was occassionally unwell should not be held against it; it was very much a one-off experiment without the availability of a stock of spare parts interchangeable with other class members when things did sometimes go wrong. But how much potential it had is a different matter.

It was possibly the most successful steam locomotive to run in Britain which did not adhere closely to Stephenson's format in Rocket, and ranked highly in the rest of the world (where steam turbines were also tried). But turbines have severe problems when applied to railway operation. In fixed land use (power staions, etc.) or aboard ships, they were developed to a high state of efficiency, but these applications were able to exploit the turbine's advantages. An efficient turbine produces power over a very limited rpm range, and the smaller that range, the greater the efficiency. They also perform best at fairly high rpm. In the power stations, they would run continuously at their peak rpm / efficiency, and once underway, would also do so aboard a ship, for days and possibly weeks at a a time. This isn't possible with a locomotive, which must start and restart a train possibly many times in a single journey, and work its train at various speeds throughout that journey, varying it with speed restrictions, signal aspects and timetable requirements. It cannot maintain a constant, efficient rpm, but must forever be running either side of it, and accelerate its train from rest. This means that it must be designed to run over a large range of speeds, so can never attain peak efficience anyway. Gas turbines suffer similarly: although once airborne, an aircraft can again maintain a fairly constant throttle position.

6202 was very much a compromise based on the standard Lizzies, and it might have been better to have started from scratch. With a reciprocating engine, rpm needed to be kept down for a variety of reasons, reciprocating balance being only one of them, so large coupled wheels were needed for express work. There were no such problems with a turbine, which has an entirely rotary motion, so rpm (of the coupled wheels) could be increased, allowing smaller wheels, but more of them, within the same wheelbase. This would have reduced axle loads and improved adhesion. The gearing was also a weak part of the design, more so than the turbine, and the need for it would have been reduced with smaller drivers.

For an experimental engine, it was good and came very close to success, but didn't quite achieve it. But it stands at the top of the great experiments, which include Fowler's high-pressure 'Fury' and Gresley's water tube boilered 'Hush-Hush', No. 10000. To be fair to them, they all tried to achieve greater efficiency by moving away from the Stephenson formula, which even the 5AT project stays with.

 

If you bother to look at the weblink, you'll see that 6202 had a separate reverser turbine linked though a clutch.

Thanks 2968 for your helpful explanation.

 

You're welcome, but the reverse turbine was a BIG problem as it was engaged by a dog clutch (to save absorbing power by permanently driving it when going in the forward direction, causing 'windmilling'); it wqas responsible for a significant number of the engine's failures. It was also much smaller than the forward turbine, so reducing its power in reverse.

6202 was a good starting point for development, but it would have taken a lot of work to make the system reliable and efficient on a daily basis, and I don't feel that geared drive was the solution. Of course, turbo-electric drive had already been tried (Reid Ramsey, et al), and while it overcame some of the problems, including reverse power and the strict correlation between turbine rpm and engine speed, it brought forth a whole raft of others, weight and speed not the least of them.

 

The LMS Society's LMS Journal, Volumes 10 and 11, have a very interesting article about 6202 in them. Well worth a read.

 

New build project? :lol:

On a more serious note it would be interesting for the NRM to have a section on these experiments perhaps with a mock up turbine (or do people prefer it just focusing on 'standard' practice and operations) perhaps alongside Ellerman Lines.
I realise they have a lot of work on at the moment but I gathered the long term plan was to do more 'themed' areas rather than just having engines around a turntable.

Ben

 

Found their website but full back issues aren't online. So how much do they charge for a copy or photocopy? Issue 10 has a photo of 6202 at speed on the front cover, and coincidentally (??) the latest issue, no 26, has the profile photo of the loco that appears in the website that I originally linked.

 

I get mine from Transport Diversions Emporium (are we allowed to plug companies?). They are £9. 95p each + p&p.

 

I have read one or two favourable accounts of this engine, one of whose attributes was the constant, gentle exhaust on the fire, ideal in a high speed, long-distance engine. The reverse turbine was only really to get the engine to and from shed. It was not anticipated it would be shunting, or working for any length of time in reverse. For the same reason, none of the big passenger engines had rear sanders, or vacuum bags fitted on the front buffer beam.

 

That's the one, mate. Sorry, I was trying to multi-task!