GWR 94xx Pannier Tanks, ex-Edward Thompson Thread.

One of the strangest bits of personal reminiscence I know of are K J Cook's comments about the GWR 9400s in Swindon steam. Cook makes it very clear he didn't approve of the taper boilered 94xx 0-6-0PT, and would have preferred more 57xxs to be built. But the thing that really puzzles me is:
"When putting up the annual locomotive building program to Paddington it was the custom to append a diagram of each class to be built. On this occasion the recommendation was, among others, to build a further batch of 57xx, when Sir James Milne, General Manager, who in years gone by had been a pupil in the loco works at Swindon saw the diagram he said words to the effect that in this year of grace you cannot build a locomotive with a steam dome", and then proceeds to state (indirectly) Hawksworth was CME at the time.

This is interesting if you analyse it.

Hawksworth took office in 1941, at which time construction was largely government controlled.
In Feb 1944 a proposal for 1946 construction went to the board which included 30 0-6-0T without specifying class.
We know from drawings the NRM hold that the 94xx design was in full swing in late 1945, and we also know the first were being constructed in 1946. We can note that after 1944 about 190 0-6-0PT were built with domes (about 90 of which were 57xx), and 220 without. It seems clear that by this date GWR policy was that parallel boilers should be constructed with generous size domes, and pitched low, whilst taper boilers were pitched higher and constructed without domes.
We can surmise that the 94xx were more expensive to construct than the 57s, having more sophisticated boilers.
And, of course, we know that every other company in the country was constructing their locomotives with domes.
Milne had gained an engineering degree before taking a pupillage under Churchward, but after that his career was in management, both for the Goverment and the GWR, so he would have known one end of a locomotive from the other. In his earlier management career he appears to have been a specialist in statistics.

So we have an apparent recommendation to build more expensive locomotives from a senior executive for what sounds little more than a whim, and a whim, in point of fact, that wasn't followed. There are, in my opinion, sound business reasons why the 94s were constructed, but that's perhaps another tale. I include this purely to highlight how odd personal reminiscences can be.

 

The 94xx were classified as Red route locomotives, thus being unusable on a large part of the system and also in many sidings and yards.

 

My impression/guess is that they were intended as a cheaper alternative to more 56xx. The numbers ordered pretty well match the numbers of larger absorbed pre group tank engines that were due to be replaced over the 50s. The bigger boiler and the extra weight = more brake power. Quite a few of the larger 0-6-2Ts like Rhymney Ms & Rs and Taff Vale As were red restricted. Its also worth noting that there was a continuing policy of upgrading weight restrictions where possible. According to RCTS they were used on passenger services in the Newport area, but I suppose the extra braking was of minimal use on passenger trains so it wouldn't make sense to use them on passenger links.

 

K. J. Cook in his book Swindon Steam gives 4 disadvantages of the 94xx compared to the 57xx. Two from the production and maintenance angle and two from the operating point of view.

"Operating:
1. Increased cab width dictated by the No 10 boiler. When leaning out for shunting the driver could not reach the brake valve. Ultimately solved by the additional pivoted handle. C/F 9466.
2. The No 10 boiler turned the shunter from Blue to Red route although all other vital statistics remained the same as the 57xx. Tractive effort was not increased but the increased weight prevented it being allocated by the Running Superintendent for a number of turns for which he desired it.

Construction.
3. The incorporation of the smokebox saddle on top of the cylinders required extra moulding box sections in the foundry and turned the cylinders from the small to large group and put an extra load on the foundry. It may be observed that Swindon only built ten but presumably one or 2 may have been recylindered before scrapping.
4. 2301 class boiler was very simple to construct and above all during repair when a new firebox was required this could be built up as a unit and inserted into the casing whereas the standard 10 firebox had to be in sections, seam-welded in position and a good deal of hand wedge-rivetting carried out."

It should be noted that this should not be viewed with 20/20 hindsight. We know that steam on the Western effectively ended in 1963/4 but when designed and the first built a 30+ year life would have been expected.

I have always wondered why Swindon built 40 8750 class after the first 10 94xx were built under lot 365 and built at Swindon but before the contractors started turning out 94xx. All four 8750 lots (370/4/8/9), presumably authorised under Hawksworth but after Sir James Milne had retired from the railways after nationalisation on 1 Jan 48? The first contractor lot was 382. Have I just answered my own question?

 

It should be remembered that although originally classified by the GWR as Blue route locomotives, post nationalisation the 57xx pannier tanks were re-classified as Yellow route availability which encompassed the vast majority of Western Region track mileage. Some of the 94xx series had a working life as short as four years.

 

I always thought, probably wrongly! that the GWR placed the big order for them to be awkward and lumber BR with something they wouldn't have wanted as they didn't want the amalgamation.

The order was placed with outside builders (RSH) which would make cancellation difficult, if it had been in house at Swindon that would have been easier.

 

I don't think there's any evidence as to why the order was placed, just lots of speculation. Other speculation I've seen include that it was to keep the builders occupied with an anticipated post war slump in demand. My own speculation is that perhaps the GW directors wanted to have the GWs money spent in the west, not diverted elsewhere.
I've also seen it suggested that in the event some of the builders had capacity problems, which was why some of the orders were sub contracted to other builders. You would think that would have given the opportunity to cancel orders had it been desired. Also worth noting that the vast majority were delivered by the end of 1952.

 

The 1600 class were also of very late construction and had short working lives. Surely if there was a short term shortage, wouldn't it have made more sense to give some old locos a life extension to get another, say 5 years, out of them to drag them on until DMU s or 08s were ready to take over?

 

AIUI there was a WR management change in the early 60s which led to a much accelerated withdrawal of steam. As late as 1957 they were building a new set of boilers for the 47xx class, which surely meant that they were anticipating the class running to at least 1970. But in any case who knows what the cost/benefit was? Steam was relatively cheap to build, and clapped out Victorian survivors (the 16s were replacing locomotives built before 1906) would cost a lot more to maintain and be a lot less reliable than modern locos. Something had to run the services reliably so to a good extent it was inevitable that at the end of steam some locomotives would have a very short lifespan. There was a precedent: the last of the broad gauge Rover class ran less than four years before the end of the 7 foot.

 

I always thought, probably wrongly! that the GWR placed the big order for them to be awkward and lumber BR with something they wouldn't have wanted as they didn't want the amalgamation.

The order was placed with outside builders (RSH) which would make cancellation difficult, if it had been in house at Swindon that would have been easier.

Er, no. Please see RCTS "The Locomotives of the Great Western Railway" Part One Preliminary Survey, Page 33. "Lots 381-389, although issued by the Western Region....."

Lot 382 was the first 94xx contractor lot for 9410-59 built 1950-1. Same series Part 5 Six-Coupled Tanks page E81.

 

Hello Jim,

Just a few points. And rather randomly.

There is a book analysing the GWR board minutes; I don't have a copy, but it is in Newport South Wales Central library, and Adrian Vaughan was involved. It would appear that the GWR after WW2 wanted to spend quite a lot of money on locomotives that I can't recall why this evening.

The 94xx comprised a 57xx chassis with a standard 10 boiler plonked upon it. The 57xx chassis had quite an elderly pedigree being identical to an 1880's chassis of a class of loco that I haven't bothered to look up this evening.

The 15xx class also around the same time as the 94xx seemed also to be an anomaly.

Cheers,
Julian

 

The order for 200 94s went through the GW locomotive cttee in Dec 1947. It was certainly last minute. There would have been chaos if all decision making had stopped in 1947 because the merger was coming up, and continued to be stopped in 1948 while new policy was decided, but it still raises an eyebrow. It appears to have been up for discussion for some months beforehand with smaller orders under discussion.

The 94 chassis was certainly basically the same configuration as classes going back to the 1813 class or earlier, but it definitely wasn't the same. Over the period there had been all sorts of changes, suspension arrangements being an obvious one. The 94 didn't have coil springs in the cab like the 57s for example. An obvious exercise would be to go through a drawing list for the 94s and see how many were new.

OTOH valve gear design looks old fashioned with end supported links. A new design of inside valve gear with centre hung links had been worked out for the 56s, but later six wheeled tanks reverted to end supported like their predecessors.

It might be interesting to look at valve travel. The pre group 0-6-0T were in what's now considered short valve travel era. Long travel valves were a Churchward innovation. Did it change? What about valve events on the 15s? Was valve travel as important on these small engines as on the big metal? Oh to be able once more to email Don Ashton.

 

IF the GWR was so short on tank locos, why didn't they follow the LNER and take on some 'Austerity' saddle tanks after WW2, much the same as after WW1 when they utilised the ROD 2-8-0s?

 

Good question. The Western were a bit prone to "not invented here therefore we don't like it" so it was a bit surprising that they seemed to make good use of the ROD s. The LMS also took some and they didn't have them long.

 

Hello Jim,

And thank you for your very interesting reply.

Yes, the 1813 class.

If my memory is correct, the GWR had claimed compensation prior to Nationalisation for ultimately it's shareholders that partly involved expenditure on new locos required, and if not spent would not be paid.

Of our old late friend Don Ashton, who disliked top suspended links, on Stephensons valve gear, I would often remind him that 'City of Truro' went 100 mph with top suspended links and with slide valves and no superheat in 1904.

Cheers,
Julian

 

100 mph (ish). I'll say it to save our Southern correspondent the trouble...

 

They didn't need any.

The GWR had plenty of it's own own 0-6-0 PTs at the time but some were quite old. Remember that Churchward never built any 0-6-0 tanks as he had plenty, apart from Holcroft doing 5 for the Cornish Minerals Railway replacements as the 1361 class in 1910.

 

The point about valve events, and “long” or “short” travel is that they become progressively more important the faster you go. The reason for that is because the effect of constriction in the steam circuit depends on the absolute time the valves are open. So set the same Loco with the same valve gear positions and drive at say 25mph and 50mph will give different results: at the higher speed the valves are open for half the time, but the mass-flow rate through the steam circuit is the same, and you might thereby run into throttling at the higher speed that isn’t apparent at the lower speed.

(Thought experiment: if you replaced the main steam pipe on a loco with a half inch pipe, it would have no problems starting from rest. It might be a bit hamstrung by time speed got up to a couple of mph though).

I guess the point in this discussion is that sometimes people get hung up on “long valve travel” as if it were inherently a good thing in itself. Whereas really it is related to the target operating speed. Clearly better understanding of valve events was important in the Churchward era for locos designed to cruise at 70 or 80 mph; rather less important for a loco designed for shunting or low speed work.

It’s why, incidentally, that the LMS 2P 4-4-0s were well-regarded as pilot engines on the S&D when slogging up long climbs at 25 or 30mph, but we’re basically a hindrance when put on the front of a Duchess heading to Crewe. Same loco, same valve events, very different outcome at different speeds.

Tom

 

As the speed goes up, the cut-off setting gets shorter. Whatever the valve travel is in full gear, reducing the cut-off means reducing the actual valve travel, so does that eventually reduce how far the ports open as well as for how long?