P2 Locomotive Company and related matters

My interpretation of the Kylchap (and similar) is that the blastpipe pressure is divided between two or more nozzles in series. Would this make it less likely to achieve sonic velocities?

 

Gresley did not need to produce a "go anywhere" mixed traffic locomotive. Actually not strictly true, the K1/K2 class were undoubtedly mixed traffic and did a very good job for their owners. But I suspect that you are looking at significantly later designs.
The K2 may not have been the best riding engine but testing revealed a superiority over the B1 in terms of cylinder performance. I have also read that in terms of brute slogging ability it was the equal of the Black Five.
The V4 was perhaps what you had in mind, but this presents a problem. In testing this machine produced some interesting results. The best engine ever tried on the old Great Eastern was the verdict of some, well the loads handled were well beyond the contrived BR 4MT classification, the little machine was very close to the Britannia. We just do not know enough, there were only the two. We will have to see what gets built after the P2 if we are anxious for our curiosity to be satisfied. Interestingly the V4 was never put through trials against the B1, make of that what you will. On today's railway, given the GE test results, the V4 would be considered the better load hauler. If you were working over a particularly difficult route then it would be back to the old West Highland experience, use a K4.

 

What a Kylchap does, generally, is creating a long chimney for its orifices. By doing so it is not really different from other designs with more orifices. These intermediate tubes take care of equalising the velocity within these tubes. If there would be sonic velocity it would be at the lowest level, in the blast orifices. Given their total area it is extremely unlikely that a double Kylchap ever reaches sonic velocity.
Kind regards
Jos Koopmans

 

Totally agree. They should all have radius entries to improve the entry coeff, someone really should try it out on one of these machines.

Did they mention anything about releasing their FEA report on this topic? I remember it being published that they had outsourced this to a university to study as part of a thesis?

Does this mean all the Axles are going to be 10", or just the crank one? Odd bearings and one off boxes start springing to mind on the latter...

 

I got the impression the report re using a larger axle is not completed but they were optimistic of the outcome, and no mention was made of all the axles being made 10 inches.
Cheers
Dave

 

Pardon my ignorance, but what is the standard size? 9"?

 

Not totally relevant but iirc Britanias ( with similar roller bearing types) have 9 inch axles 1 and 3 and a 10 inch on axle 2 , Clans have all three at 9 inch,
Don't know the dimensions for Tornado, or Duke of Gloucester (Did the Ivatt Duchesses have roller bearings) ? but these are the most useful comparisons
Note to self ; design an oval multi nozzle exhaust system combining the ideas of Geisl, Le Maitre Chapeleon and Porta that can be used to upgrade double chimney locos and call it the 'Koopman'

 

They did indeed!

 

Haven't they got the Timkin bearings already?

I can understand a bigger axle on a 3-cylinder engine crank axle but not on a 2-cylinder Brit..

 

I'm thinking the difference of around 100-150kg or so between the two wont be ill to make up in the springs. I assumed solid axle here.

Depends on how much force the cylinders are kicking out, and it also depends on if the axles are hollow or solid. As above, I made an assumption these are solid, but I know many engines have hollow axles. The hollow ones are considerably stronger/more rigid per unit volume due to enhanced second moment of area. I believe bearings have indeed arrived going by the updates.

 

Believe they have them on order at least ... and do wonder if they are made to order or off the shelf, and if its the latter are they not the nearest metric equivalent...

Beats me too, the thinking being that the thrust of the cylinders is transmitted directly to that axle, indirectly to the other axles ? and yet the Brit 'wheels shifting on axles' tended to be on the smaller axles.
These were hollow axles in the first instance which may be stronger in some aspects but it was believed that they deformed when the wheels were pressed and that the interference fit was compromised as a result...hmmmm. Thik that PoW Tornado have/will have solid axles, and that the new clan will have solid axles. Presume the Duke and the surviving Brits have solid axles or perhaps plugged hollow ones...

 

Eric Langridge (Under 10 CMEs Vol 2, 2011, The Oakwood Press ISBN 978 85361 716 7) gives a lot of detail of the Britannias' (and Black Fives') wheel shifts in Appendices II and III.

 

This is very interesting and answers a few of the questions I had on the valve gear.

That is disappointing to a degree: I've spoken with Andrew Hardy on a number of occasions and he is normally very balanced on the issue. In fact I would go so far as to say he probably has the best understanding of the P2 and Thompson situation than many of the railway historians and writers around.

RE the V4, a very capable machine, but also much more expensive to manufacture than the B1. What is better - a machine of extraordinary performance, expensive to build and more difficult to maintain, or a simple machine of reasonable to good performance that is cheap to manufacture and easier to build?

The B1 was the engine the LNER needed undoubtedly and that it became the LNER's most numerous and widely travelled 4-6-0 class probably says a lot for the excellence of the design.

 

The answer to that depends on the prevailing circumstances. Pace some of the contributors on here, what was better in France wasn't always the same as what was better in Britain.

Apropos axles, there are surely two quite separate issues. One, which affected various locos over the years, is whether the crank axle is strong enough for the forces exerted by the crank. The other, which affected the Britannias, is whether the wheels are firmly attached, preventing the wheel one side from rotating relative to the wheel the other side.

 

It's not clear cut like that though really is it. Every design is a compromise between competing factors, and doubtless the v4 could have been more complex and more capable, and the B1 cheaper and simpler. Designer needs a crystal ball to understand where the compromise needs to be set for projected loco life...

 

You're quite right that it's not clear cut: however the implication was that the B1 by comparison with the V4 was an inferior machine.

I had hoped my comments would point towards why the B1 was built en-masse and the V4 wasn't. It seems crystal clear to me. There was a war on, and the change in traffic requirements changed what was required. Arguably Thompson's design memorial (some call it his only design memorial) was the B1.

There is no doubting the fact that the V4 was much more complex than the B1. The boiler alone, which was an entirely new design (and the two boilers were not identical - one was built with thermic siphons) ignores other factors such as the valve gear. The B1 on the other hand was made up of standardised parts to the extent that evenV2 type driving wheel centres were used on the original B1 batches.

The B1 was used in the 1948 exchange trials - and what do you know? Was more or less the equal of the Hall and Black Five, each loco being a little better in some areas than the other but no engine coming quite out on top. To me that says more for the quality of the B1, that it stood shoulder to shoulder with two very esteemed locomotive designs, than the comparison with two non-identical prototypes built.

I've always felt the V4 was proof that Gresley was too set in his ways - when the rest of the world was changing direction in terms of their locomotive engineering, he did not change with the times and the V4 was probably the best example of his conjugated valve gear locomotives, in terms of its ability against its size. But was it needed or necessary against the backdrop of war in Europe? I don't believe so.

I feel that whoever took on the LNER CME role, if substantial change occurred, there would always be a backlash against any change from Gresley. It so happened it fell to Thompson: he made the most changes and without his influence I doubt that Peppercorn's A1 would have appeared in the form it did. And what a shame that would have been.

 

It does indeed, unfortunately my copy is out on loan to Clan project associated people, hence im being a bit Vague...

 

Ideally from an engineering perspective you would opt for a very thick walled hollow axle with the largest diameter you could get away with. The larger diameter giving greater torsional and shear capacity, but also has the added benefit of maximizing the surface area of the interface between wheel and axle mitigating against that interface breaking down and causing a slip.
A smaller diameter means the delta between OD of axle and ID of wheels needs to go up proportional to reducing axle diameter, and this delta has a limit (material capacity) as eventually you start cracking the casting or deforming the axle per poisson ratio. Also, it becomes impractical with the temperatures required to achieve it getting too high.

It really is a fine balancing act with little margin for error. Lots of torque going in to the axles, and the difference of a few thou can make or break an interface.

Id be really interested to see some numbers with tolerances. If the axle (or wheel) is even slightly out of tolerance, (as a fact not design that is) then as above, its going to struggle to make good on the demands. Maybe manufacturing quality was patchy...???