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

An interesting post, but it's a bit odd to find it in the 'Steam Traction' section! Thread drift strikes again, I guess...

Noel

 

Mind you, to play devil's advocate, isn't this one of those situations where we enthusiasts have to beware of headline dimensions? There were probably dozens - at least - of drawings to fully specify the 94 chassis, and I suspect relatively few of them would be affected by a wheelbase change. If the diesel chassis had different frame plates and stretchers, but the same axle boxes, brake and suspension components as the steam engine, would it be reasonable to describe it as developed from the 94 chassis? It would be unlike Swindon to design new components if existing ones were going to be satisfactory. But I know stuff all about diesel locomotive design, maybe everything had to be designed new. I have absolutely no idea!

 

The situation with locos like the 94xx tanks is that they were to replace a similar number of pre grouping locos which were due for replacement. The modernisation plan then happened not long afterwards, so this resulted in them having a short working life.

this was not anticipated at the time of their construction, otherwise, undoubtedly they wouldn't have been built and the pre group types would have been given another overhaul to get them to jog on just a bit longer until the class 14s or whatever were ready.

 

Agreed but that fact regarding the D95xx from 94xx came from a class 14 owner who had spent many years overhauling them to return them to active service; I presume his was the "voice of experience".

 

As a bit of an aside, I came across a letter from Don Ashton today which inexplicably I had inserted into Jim Russell's volume 2 of GWR locos on the 15xx. Don had run the original gear on the computer simulator and it came out quite ok. Don had a copy of the original Swindon drawings for same.

Don Ashton did a redesign for 5" gauge using a drop link that was omitted from full size, and without the end of the combination lever colliding with the rear of the cylinder block. Which presupposes why the drop link was missing from the original design in full size, if Don could work it in. I know why they did it and how, but not why they didn't come up with what Don Ashton did as an alternative many many years later!

 

With the full support of BR nationally, and as part of a considered programme to assess whether diesel hydraulic or diesel electric was a better long term solution.


Sent from my iPad using Tapatalk

 

I think we're getting into the minutiae of valve gear design where I for one should tread very carefully... Am I right in thinking that the drop link doesn't move (well, other than as an extension of the crosshead), and its effective function is to change the vertical location of the lower end of the combination lever? The implications of that start to make my head ache, but am I right in thinking the purpose of the drop link is to provide the correct geometry for the other components, rather than being of benefit in its own right? Don's variation was, if I read him correctly, intended to provide an appropriate implementation for model engineers rather than an improvement on the full scale gear. However I am *way* beyond my comfort zone here and welcome correction.

 

David Clough has written well on the hydraulic programme; it was a thought through attempt to assess whether the hydraulics were a better standard to follow than the diesel electrics. Western Region was chosen as a test area because it was relatively self contained and could cope with re engining at the border. At a time when electric heating (let alone air conditioning) was not widely established in use, it’s harsh to judge them too strongly for that misjudgment amongst so many others in that era.

That question needs to be considered separately from the two other major failings of the modernisation plan era. One of those was the failure to understand the traffic requirements for a diesel railway, leading to the proliferation of types (e.g. cl14, cl 22) that served disappearing markets. The other was the lack of foresight about the size of the railway.

All of this was in the context of BR already having staffed huge amounts of money up the wall on BR Standards that, whatever their engineering and operational merits, represented an evolutionary dead end and huge commitment of resource to build at a time when other railway administrations were moving away from steam.


Sent from my iPad using Tapatalk

 

I do wonder about two other factors in that - regional individualism in the early post nationalisation period, and making effective use of people and (rationed) materials. Put those together with lack of information on future plans, and I can see why projects that “shouldn’t” have happened in a rational world did happen.


Sent from my iPad using Tapatalk

 

One should also take note of managements - once big fish in a little pond - unable to accept being little fish in a much bigger pond hence working to maintain their "empire" for as long as possible; a situation not helped by a British Transport Commission whose Government-led officials favoured road funding at the expense of railways. The Government's consideration of railways as the milch cow to fund many road projects didn't help either IMHO.

 

But going back to the 94s, the actual result of the large order for 94s was that the WR had a much more homogenous fleet until the end of steam than it would have had otherwise. I think you can make a sound argument that in the event, with the end of WR steam when it was, introducing a small number of thoroughly non-standard BR 'standard' classes did more harm than good when it comes to spares stock and standardisation, and was arguably much more about internal politics than running a better railway.

 

As steam heating was being phased out, how difficult would it have been to fit a diesel-hydraulic loco with a small electric generator for train heating and auxiliaries? And what is done about train heating now with preserved diesel-hydraulics?

 

I don’t believe it’s technically difficult, but space means it’s impractical on at least the Westerns.

As for preserved locomotives, I think they generally run without heating or, on the main line, with a generator car.


Sent from my iPhone using Tapatalk

 

I'm sure I've read somewhere there is a rough design for a small donkey engine and ETH generator to be fitted to Westerns, in the space that could be vacated by the steam heat boiler. It would've meant the ETH supply would've been constant, and not variable such as on Deltics

 

I agree with this. The only real result of the standard classes was to add another 12 types to the mix for spares etc and they did not really replace much of old types. In fact withdrawals of the standards started slightly before the last pre grouping types had gone.

The Britannias though were a useful addition to the LMR which was short of Pacifics, as all 55 eventually ended up there

 

Not a problem for Germany's equivalent of the Hymek:

https://en.wikipedia.org/wiki/DB_Class_218

The WR hydraulics had to be compressed to fit within the restricted British loading gauge, so internal space may have been an issue. On the other hand, if the steam heating boilers and tanks were removed, that might have created space for some ETH equipment.

 

Point of order: with the 'Sprinter" and 'Turbostar" DMU families featuring hydraulic transmission, I'm unconvinced the WR tech can be deemed a failure, thus IMO, the official reasons for the demise of the 1st gen diesel hydraulics (i.e. standardisation and obsolete train heating systems) actually stand up pretty well. We should also keep in mind this was the era before the IC125s and before OHLE on the East and West* coast mainlines kicked off the renaissance of rail travel, when business was still in what, at times, looked like a death spiral.

* yes, I know phase 1 of the WCML was completed earlier .... but we're still speaking of the time when Hoovers took over for the northern stretch.

 

The class 127s on St Pancras - Bedford had hydraulic transmission too.

 

Whats the position with Hydraulic transmittion in Germany at the moment?

 

On the 15xx valve gear: if space was short, they could always have folded it in half, Fletcher-Jennings style That essentially doubles the length available! (I'd like to see that sort of monstrosity drawn - though preferably subsequently hung and quartered ...)

As for the supposed shortcomings of the 15xx valve gear: is there any evidence that caused actual operational problems for their normal service duties, as opposed to an apparent infelicity in a theoretical treatise on a computer spreadsheet? There's a world of difference between how much effort it is worth expending to optimise the valve gear on a machine designed to cruise for long periods at 70 - 80mph, and one that is a crash-bang-wallop shunter that makes trips between carriage sidings and terminus at 25mph max.

Tom