'Britain's Most Powerful Steam Locomotive' - The P2?

[70014IronDuke]

Would suggest that the formula quoted is fanciful.
The figures produced suggest steam locos having a similar power output to a Class 91. Common sense indicates that this is wide of the mark.

Agree. I think these figures give the theoretical indicated HP (ie at the cylinder. and not at the drawbar). However, this assumes the boiler can produce steam to keep the train moving at 60 mph. If it can't, well. ..... the HP figures are simply fiction.
I don't think anyone would deny that a P2 'must be up there' with the best in terms of power output for a British express passenger steam locomotive (especially with a 250 psi boiler), but I would posit these figures are double reality in terms of drawbar HP.

Of course, to keep this on topic, I believe the SR PR department did use tractive effort figures to boast that the Lord Nelsons were the most powerful British locomotive when they were first delivered - much to the chagrin of the Swindon folks. So the P2 Foundation people are only following that example.

 

[Pigeon]

Then add in the ability of the loco to get rid of exhaust steam; the less effort required to do so, the more power available to do work. The higher the temp and pressure of the exhaust steam, the easier this becomes.

The higher the temperature and pressure of the exhaust steam, the more energy is being chucked up the chimney. You want to get both as low as possible, and then exhaust into an exhaust tract that produces as little back-pressure as you can arrange; large valve openings, short and direct large-diameter exhaust steam pipes, an efficient and free-flowing blastpipe design, and then make sure the drivers know to drive with as short a cut-off as they can manage.

 

[Pigeon]

I would posit these figures are double reality in terms of drawbar HP.

Yeah, they are. The real-world power output of a Duchess is roughly the same as a Deltic, as long as the fireman can keep up.

 

[Cowley]

Yeah, they are. The real-world power output of a Duchess is roughly the same as a Deltic, as long as the fireman can keep up.

I reckon an averagely performing Deltic would run rings around a perfectly performing Duchess (and I am a huge steam fan*) any day of the week.
The difference also being that the Deltic wouldn’t need a lie down afterwards. Just a quick refuel, a brush to get the flies off the windscreen and then on with the job.
I’m being slightly tongue in cheek here but that’s the difference.
Whenever I used to speak to footplatemen that’d worked steam and then moved onto diesel, they used to say that getting into a diesel meant you knew what you would get when you turned up the power - no variables (well not many) etc.
Hard to imagine the difference unless you’ve experienced a footplate on a steam locomotive being working hard.

(* I say huge, I’m quite tall)

Edit - Just to note that 55009 on its recent railtour topped Shap with 12 aircon mk2s at around 50mph (Grayrigg at 60).
I’m not sure what the fastest Duchess run with a similar loading is. Does anyone know ?

 

[Pigeon]

Source is a bunch of logs of ascents to Ais Gill collected by the Duchess of Hamilton crew for various different engines on Cumbrian Mountain Express duties. Best performances were Deltic and Duchess with not a lot to choose between them.

 

[theageofthetra]

In the US it was unions who made mechanical stokers compulsory (though taking into account the rubbish coal they had to use and the increasingly massive fire boxes )- why did we not have the same here? - a Duchess or a rebuilt Merchant Navy with a mechanical stoked tender of Welsh steam coal could have been how much more efficient?

Many of our export locos such as SA Garrets had mechanical stokers despite being narrow gauge.

 

[chorleyjeff]

While comparing standing starts from Hellifield to Ribblehead with equal loads would indeed be "interesting" - I don't think it would be a true test to compare maximum power outputs - even if the locos were worked to the maximum attainable (while, of course, observing any line speed restrictions).

The reason is that the maximum speed attainable with a 10 coach load + passengers (say, 375 tonnes gross trailing load) would be - guess - something like 55 mph, and the average speed significantly less - at around 45 mph? (IF anyone knows better, please correct my assumptions.)

Such a run would favour the P2, which, with its smaller driving wheels, would probably be able to reach its maximum power output at around 50-55 mph. I suspect the Stanier pacific, with 6'-8" drivers, will probably be at its maximum theoretical power output around 60-65 mph.

I'd posit that a fairer practical comparison would be on a run from (Newcastle)-Darlington-York, with Darlington passed at a controlled speed for both locomotives of (say) 60 mph with trailing loads of 400 tonnes, and both trains permitted to exceed 75 mph south of Darlington.



Is there anyone alive today who worked a P2? The last locomotive running as a 2-8-2 would have been 1942? Assuming the fireman at the time would have been, say, 20, that would make him 96 or so? I suppose it is possible, but not much chance. Fantastic challenge for the P2 boys to find someone!

Ten coaches for an 8P is no test at all. Get sixteen on which was what they were made for to make a real test. To see how they would do on the level how about Preston to Lancaster ? Enough for a decent blow but ok for a human to fire.

 

[Flying Phil]

In the US it was unions who made mechanical stokers compulsory (though taking into account the rubbish coal they had to use and the increasingly massive fire boxes )- why did we not have the same here? - a Duchess or a rebuilt Merchant Navy with a mechanical stoked tender of Welsh steam coal could have been how much more efficient?

Many of our export locos such as SA Garrets had mechanical stokers despite being narrow gauge.

I thought that there were a few mechanical stokers tried on BR locomotives, but the need for specially graded coal to go through the worm feed - and the fact that they actually burnt more coal/BHP made them uneconomic and so not used.

 

[TheEdge]

In the US it was unions who made mechanical stokers compulsory (though taking into account the rubbish coal they had to use and the increasingly massive fire boxes )- why did we not have the same here? - a Duchess or a rebuilt Merchant Navy with a mechanical stoked tender of Welsh steam coal could have been how much more efficient?

Well, even the largest British locos could still be fired with a stout man and a shovel. As you say some of the later US locos had truly enourmous fireboxes where I would guess it would be impossible for a man to fire it in any meaningful way.

 

[Pigeon]

I thought that there were a few mechanical stokers tried on BR locomotives, but the need for specially graded coal to go through the worm feed - and the fact that they actually burnt more coal/BHP made them uneconomic and so not used.

Yes. Unlike a fireman, they couldn't direct the incoming coal accurately to shape the fire for best combustion, so a lot of it was wasted. They were "quantity rather than quality" sort of devices. So, in a way, was the boiler on a Bulleid Pacific, and I would expect the combination of the two to have returned horrendous coal consumption.

 

[Warwick]

That's one of the reasons that U.S. locomen marvelled at the GWR "King" when it was shipped over there. They were used to seeing black smoke from improperly burnt crushed coal coming out of locomotives chimneys, not the clean exhaust that the "King" was producing.