New Build P2

I remember reading once that the mentality on the GW originally was by keeping the gubbins between the frames it was at least afforded some protection from the road and the elements...not sure I buy it, but it's what I read!

 

Interestingly, in Locomotives of the LNER 2A, sources in the Doncaster drawing office at the time were of the opinion that the A2/2 class were designed round their connecting rods.

 

I'm not sure that the exact stats for the trials is hearsay. I have tended to ignore the commentary by both the time keepers (who definitely had their own bias) and Bert Spencer in favour of Peter Grafton's more objective, historical/bibliographical account of Thompson. Bert Spencer I had dismissed purely because it is one thing to say Thompson was bitter and determined to rid the LNER of Gresley: actually explaining the reasoning behind certain technical decisions of Thompson's in the context of the war/supplies and so on and putting the full picture of his rebuilding program is a different matter. However...

I will concede that happily. Particularly after rereading Peter Grafton's section on page 40 of his book - Freddie Harrison and E.S. Cox confirm to some extent Bert Spencer's feelings and on that basis it was remiss of me to dismiss him so quickly.

So my inevitable question - what are their general held views of the Thompson Pacifics?

 

In his book "Swindon Steam", K J Cook says of his time at Doncaster (M&EE of Eastern and North Eastern regions 1951-9) "Perhaps I was able to heal a little of the discord brought in by Edward Thompson's tragic desire to obliterate Gresley."

Incidentally I understood that one of the reasons for inside valve gear on the 2Cyl GWR locomotives was that it was considered that connecting and coupling rods needed more maintenance than valve gear, and putting the valve gear inside meant it didn't have to be taken down every time the big bearings needed attention. The valve gear on the 4cyl prototype, #40 wouldn't have worked with outside cylinders either.

 

I'm not sure that the exact stats for the trials is hearsay.

Coial consumption figures are not the issue here, so the stats you have quoted are largely irrelevant. The boilers on these locos were more or less pure Gresley and although the valve gear was different and may have had some slight impact it isn't what most dispassionate views consider when comparing Thompson v Gresley design It is the mechanical aspects of the design that matter and this translates into quantifiable values such as repair costs ad less quantifiable ones such as ride qualities. It is evidence on those grounds that you should be looking for if you want to make a credible case. That is probably where Townsend or Harvey woud make a contribution (and possibly Meacher too) but I can't claim to have studied all the available literature. Personally, I don't much care either way, (I'm shallow, I think that the Gresley locos looked almost perfect and the Thompson ones looked awful) but I don't think you are ever going to make a convincing argument using spurious data.

 

Points taken, happily. I will start researching.

 

Which is pretty much the ultimate 'cart before horse' story, is it not? Crazy.

Regarding Gresley's 2:1 gear; in fairness, it wasn't designed with wartime expediency in mind, but for a different age, and as others have said, when it worked, it did so very well. The idea of 'beefing it up' was a good one, and as we saw latterly with the BR Standards, improved lubrication facilities made routine servicing much quicker & easier. This would have helped too.

I cannot, for the life of me, regard Thompson's Pacifics as good-looking, and the other old adage, of 'handsome is as handsome does' is probably appropriate as well. Theory & practice are sometimes unhappy bedfellows.

 

I'm afraid that anyone who thinks any of Thompson's bastardised pacifics has any aesthetic appeal needs to go to Specsavers in a hurry :nerd:

 

Totally agree, although I would think their eyesight was so poor they would not be able to find the store.


P.s. Old engineering maxim "If it looks right it probably is right" Apply the inverse of this to tell you all you need to know about the Peppercorn 'Pacifics'!

 

All this Thmpson/Gresley/Peppercorn debate has moved a long way from the P2 - I just wonder if anyone's asked Dorothy Mather about Thompson... after all, she was working in the drawing office at Doncaster. There can't be many people around still who were there at the time! In Glancey's book she is quoted as saying, "Pepp was working under Thompson. Do you know what Thompson said? If Pepp married me, he would never get the CME's job. Well...."

Foxy

 

A few nuts and/or cotter pins and the relevant bits of a walschaerts gear are off. Maybe more difficult for outside Stephenson gear, which the GWR were wedded to for so long.

Probably, if Thompson was insistant on equal length con rods. There may be some esoteric reason for Equal length rods, but the number of successfull locos with unequal length rods suggests that Thompson was something of a fanatic in this area. Surely it couldn't be JUST because the GWR used them? Still, plenty of CMEs have had bizarre hobby horses to ride, often for no better reason than aesthetics or sheer bloodymindedness.

Back to the P2 debate - it would be a magnificent sight, but honestly I reckon it's too big and too specialised. If I had the money I'd build another A3 - closely followed by a K3, V3, and O2

 

It has just occurred to me that if the A1SLT use the Diagram 118A boiler on the P2 that will push the boiler pressure up from 220lbs to 250lbs, I am useless with figures, does anyone know how much that would raise the original 43,460lb nominal tractive effort?

Foxy

 

I would have though you'd reduce the cylinder diameter to keep it the same?

 

A quick calculation gives 49,386.

 

It occurred to me today (whilst staring at my desktop background of 241A65, the French 4-8-2), if they can run a large eight coupled loco over there with no problem, why should there be a problem here? Are our curves any tighter, really?

 

Ooof! That's a lot of grunt! Yes, Sheff, reducing the cylinder diameter might make sense (if only to reduce steam consumption) - I wonder if the 71000 boys would lend the patterns for their Caprotti cylinders? Now, THAT would save a lot of money! Was the stroke the same?

Foxy

 

I'd be more worried about the additional forces for which you'd need to beef up the chassis etc, rather than the steam consumption, which ought to be no higher for normal running unless you utilise all that extra TE for an extended period.

 

What? You mean like 4472? ......runs for cover.....

Foxy

 

P2 originally 21 x 26, dUKE 18 X 28... Ive definitely heard tell that the cylinders will be resized to give a TE at 250psi approx same/slightly more than the original P2
so thats >19.5 inch x 26. This has the added advantage of reducing the size of the Loco across the cylinders.

Im sure that redesigning the cylinders will be an exciting exercise for somefolk...

 

That's a good point, anything to help with the loading gauge!

Foxy