Current and Proposed New-Builds

The GWR carried on with inside valve gear right up to Nationalisation, after everyone else had switched over to outside Walschearts gear. Although, all industrial locos continued with it too apart from the three Bagnalls

 

There were several other outside valve gear industrials predating the SCoW Bagnalls including a couple of preserved examples HE1690/31 Cunarder and HC1208/16 Illingworth. Others that escaped included a couple of large Hunslet sidetanks for Bridgewater collieries and even some 0-8-0 tanks built by Nasmyth Wilson for Manchester collieries.

 

Ta, not that well up on industrials. I like that 0-8-0 tank

 

Mean machines.

 

The Southern Railways Z class was an 0-8-0 tank locomotive and in my opinion a much better looking locomotive than the one above.

 

I suspect just workshop and drawing office practice - I believe the cylinders and valve chests and much of the motion is identical to the Atlantics, so saving time and pattern making.

Also worth noting, as @Jimc has pointed out on occasion, that inside motion doesn't actually afford a financial saving in preparation if the crews are allotted a fixed allowance of time for prep based on engines having inside motion; and changing that allowance would require negotiation about shed terms and conditions. So there is little to be gained on a small class by providing outside motion unless you have a long-term plan to renegotiate rates.

Tom

 

Thanks Tom. I'll accept the point about prep time agreements (still a factor in Bulleid's time), but in view of the adoption of Walschaerts gear on "J2" No.326, the argument of commonality with the "J's" rather goes out of the window in my view. It's hard to see reversion to Stephenson gear for the "K" as anything other than retrograde. D.O conservatism seems more likely to my (admittedly cynical) mind.

IIRC, wasn't No.326 regarded as a better runner than No.325? Unless the Walschaets kit was supplied under outside contract (I'm thinking workshop tooling here), it's something of a mystery to me. I still suspect that had the "K" class enjoyed outside valve gear, the accounting sums which pointed to the Maunsell moguls as group standard might have produced a different result. The working history of both types clearly shows which were better built!

 

I suppose that a lot of this comes down to opinion and subjectiveness. Your comments infer that Walschaerts is a better valve gear than Stephenson's link. Is it? There's a strong argument for saying that it isn't when it comes down to steam distribution. The advantage of Walschaerts is that it can be fitted outside, so making access for maintenance and preparation much easier whereas provision of an outside link valve gear is not an easy option For a long time it was also thought that a constant lead was a good thing to have and better than a variable lead gear, such as Stephenson's link. Stephensons link also comes in two versions, one with maximum lead at full gear and another with maximum lead at mid gear. Many early locos had the former arrangement, which is a big disadvantage on a passenger loco but the latter arrangement is a positive advantage.
The Stephenson's link black 5 44767 was a one off but why build it unless it was perceived to offer advantages over the standard version with Walschaerts? I know vert little about Billington's locomotives but I would not condemn him for using Stephenson's link unless I had done a very careful analysis of the design.

 

But which valve gear was better, and in what circumstances? I've seen claims that the Churchward/Pearce implementation of Stephenson's gear produced better valve events, and also that well designed Stephenson's gear was more consistent between forward and reverse. Which gear has the most bearing surfaces to maintain? Which has the greatest capital cost in manufacture? Which is cheapest to maintain? I find it very difficult to believe that if Walschaerts gear was superior in every respect it wouldn't have been quickly adopted: I think it much more likely that each had its advantages and disadvantages and it was a question of picking the best compromise for each design and its planned usage. Its hard to believe that Ivatt would have bothered to trial Stephenson's gear on 4747 if Walschaerts were obviously superior in every respect.

 

Having fitted 4747 with Stephensons what attempts were made to compare it with the Walschaerts/Poppet valve fitted locos?

 

I don't know what formal testing there was but, in my personal experience, (4)4767 is a good bit stronger than a standard Black 5 when on the move, more like a class 6. It's survival as a unique loco to the end of steam says a lot for it.

 

The Raven vs Gresley Pacifics debate is interesting, because fundamentally the comparisons of the time showed the NER machine to be a better locomotive than the A1s as built, particularly in terms of economy (water plus coal).

The clear difference between the two classes was, fundamentally, development. The Raven Pacifics were simply not as open for new development as Gresley's A1s were. Borne out by the fact that the A2s were rebuilt with Gresley A1 boilers and tenders, and scrapped pre-war, and the A1s, later A10s, became A3s and were transformed.

There is a fascinating piece I discovered recently on Edward Thompson regarding the Raven Pacifics, as it happens. This is taken from Steam World no.62 of 1992:

It is interesting because this proposal would have been the first two cylinder Pacific in Britain, ahead of the Standard 7MTs.

Raven's Pacifics were the best of their time; but clearly the past and Gresley's A1s showed clear room for development, and were the future.

 

I certainly don't regard Stephenson's as inferior to Walschaerts..... just a damned sight less accessible when fitted between frames. The same argument applies, of course, to inside Walschaerts gear (sorry, all you Swindonites). My comment regarding LBSCR 325 (Stepehnsons) vs 326 (Walschaerts) simply refers to a recorded observation, which I can't remember where I read anyway! Whatever, both were withdrawn pretty much simultaneously in 1951.

I've often wondered whether reopening Brighton works to loco construction had a bearing on so many LBSC locos being recorded as taken out of traffic in tired condition when so many Ashford and Eastleigh products soldiered on for several more years.

So far as the application of inside gear to the "K" class, I only intended to infer that I regarded outside motion as a lot easier (ergo cheaper) to access, in this instance, specifically when compared to the Maunsell moguls which were adopted as SR standard, allegedly on grounds of maintenance costs.

Looks wise, I find the "K's" a very attracive design as built, but looking at the rather similar Egyptian moguls, I don't think outside Walschaerts gear would have detracted one jot from their appearance.

For the record, I'm rather more interested in poppet valve gears in any event!

 

Anyhow, on the topic of new builds, I like the LBSC K class too and think it would be an excellent choice.

 

4767 was tested against 4757 (Caprotti), 4764 (Walschaerts) and 4766 (Walschaerts with double chimney) in July and August 1949. These tests were conducted on the St Pancras - Manchester route with 310 ton trains. The reported noted, "... there are no marked differences in the coal and water consumptions of the four engines tested"
"The Caprotti engine was stronger in the gear, at earlier cut-offs, than the other engines ... otherwise there was no great difference in the general performance." (From 'Stanier 4-6-0s at Work', A.J. Powell (1983) Ian Allan ISBN 0 7110 1342 X).

I've also read, but cannot find, that 4767 was tested at Rugby and the power output was not as high as that of a 'standerd' Black Five. This was in marked contrast to every report of the engine from enginemen that I've ever read, in BR service and preservation alike. Steve's comments in #731 above confirm.

 

That's an interesting point about the Raven A2 boiler and the proposed effective shortening of the boiler by moving the front tubeplate back. The boiler was simply too long, and the last part didn't add to steam generation because the flue gases had cooled too much by the time they got towards the front. Sometimes less is more, as it were. Certainly modifying the valve gear on the A1s after the 1925 trials against the Castles made a tremendous difference to their performance. That early valve gear will account for their poor economy, of course. I think that the Raven locomotives were possibly not as good as the Gresley ones when it came to loads on the track either? They had a very long wheelbase, and I'm pretty sure there were more route restrictions on them than there were on the A1s.

 

I'm not aware of any head-to-head tests, but both classes were subject to dynamometer car tests and also had a twirl on the rollers at Rugby. You'd need to find the individual results and try to match them up. Unless they were seeking the same answers and using the same criteria, any comparison from this could be misleading.

 

I suspect you are being too harsh on Billinton and his Drawing Office.

At the time, the Brighton mainline freight services were handled by a mixture of fairly small 0-6-0s. The best of them - RJ Billinton's C2s - were getting on for twenty years old. The more modern Marsh C3s turned out to be far worse than the locos they had nominally been designed to replace. The C2s were in the process of being reboilered to C2x, but that could only be a stopgap as loads rose. So even though it was less of a freight line than some, the LBSCR clearly needed a modern freight loco. More generally, the Locomotive Department as a whole was still recovering from the low ebb it had reached under Marsh, a situation which no doubt consumed much of Billinton's energies to tackle.

The loco that emerged - the Billinton K - introduced several new features to Brighton, notably the first loco on the LBSCR with a Belpaire firebox, and the first with a leading pony truck. In the circumstances, given a small drawing office and those new features to concentrate design effort on, the decision to reuse the cylinders etc. from the Atlantics to save time can hardly be a major criticism. The significant failing was not the inside motion, but the short travel valves. Even so, they proved good slogging goods engines well up to the standards of the Maunsell N, though less suited than the N class when the need arose to run fast passenger services. Given the valve gear, that's probably not much of a surprise.

As for inside Stephenson valve gear: they were broadly contemporary with the Churchward 43xx, and few people criticise the capabilities of those locos! The obvious difference is the better valve events of the Churchward design, but it came from a Drawing Office further along the progression to designing modern locos - indeed, as recounted by Holcroft, the 43xx practically designed itself because there was a solid groundwork of standard components already designed. Lawson Billinton's near contemporary Urie, on the LSWR, was building various types of outside-cylinder "get-atable" 4-6-0s at the same time, but they still had somewhat hamstrung valve events until "Ashfordised" by Maunsell in the early days of the SR. No doubt an equivalent process of "Ashfordisation" of the Billinton K could have produced an inside-valve gear Stephenson, long valve travel Belpaire 2-6-0 very similar in capabilities and general conception to the GWR 43xx - but in the circumstance, with the N class being a known quantity; already fitting SR the composite loading gauge without further modification and kits of parts awaiting assembly at knock-down prices from Woolwich, the decision to standardise on the N as the prime heavy goods engine rather than an updated Brighton K can hardly be seen as anything other than inevitable.

Tom

 

Check out the Thomson rebuild 'Q1' tank .. its sort of 'Cuddly' looking