Double chimneys.

That's precisely what I'm getting at, with change on the distant horizon, there wasn't the desire to spend weeks out on the road testing in all conditions inbetween trips back to the works for adjustment, when you could just be keeping your head down with simple day to day work with little fuss, course it was technically possible to improve loco's, but was it worth it with the likelyhood even then that many would be withdrawn within the next decade ?.

Not sure what your getting at RE: the LNE valve gear, we know why it performed poorly under wartime conditions, but the point was the standards were far easier to live with in that respect with 2 outside cylinders and simple valve gear, starting adding inside cylinders for extra horsepower and exotic valve gear and they start to lose their appeal from a maintenance point of view, at a time when doing so was an increasingly unappealing job, less and less people were then willing to crawl between the frames and under a mucky steam loco to tend to inside motion.

 

Certainly Tuplin's theories were not well regarded by contemporary locomotive engineers. This article http://www.steamindex.com/library/tuplin.htm on Steamindex is possibly useful. Certainly Holcroft and Ell, neither of whom seem to have been especially conservative thinkers were not in agreement!

 

I would hardly call the Gresley/Holcroft derived motion exotic: A 2 to 1 lever with a 1 to 1 on its end, and 3 valve spindles; far fewer parts than an inside Walschaerts! Much easier to maintain.

 

Thanks for the link. Made interesting reading.

 

Interesting though that the earlier Maunsell (Holcroft) three cylinder engines (N1 / K1) were built with conjugated valve gear but rebuilt with three sets of independent valve gear. Indeed they were explicitly designed with that conversion in mind, so they can't have been completely confident of the long-term reliability of the conjugated valve gear, however sound in theory. The later three cylinder engines (e.g. the Schools) were built from the outset with three sets of valve gear.

Tom

 

Never the less, two outside sets of Walschaerts is easier to live with than a Gresley conjugated set, which by default of working off the middle cylinder, means more crawling underneath/inside, I know GWR and other prewar types require similar, but it's the standards and their 50's origins I'm making the comparison with.

 

The only standard with an inside cylinder is DoG, and the only hand lubrication required is for the big and little ends I believe? All the valve gear is either external or sat in an oil bath.

 

The inside cylinder valve was driven and indeed is still driven by the outside gear. The middle cylinder drives a connecting rod. Only the inside big and small ends to deal with. The conjugated gear is under an access panel in front of the Smokebox in most cases, want an exception - see Morayshire. For A3, A4 K4 and V2 you do not have to go between the frames to access it.

As to reports of off beat Gresley locomotives, well yes it can happen. However the middle cylinder does not occupy the same plane as the two outside cylinders. The length and section of the exhaust tracts are not the same as those of the outside cylinders. So, with this in mind, should a Gresley three cylinder locomotive, B17 and D49 classes apart, have a perfectly regular exhaust beat? If the bearings of the conjugated gear are allowed to deteriorate, the war time neglect - which reflects badly on shed management - being the prime cause that memory draws attention to, then the valve setting can go astray.

You don't haul trains without horsepower. If you need it there are only so many variables you can juggle with. You can only take boiler pressure so far on a traditional water leg firebox. Metallurgy limits your degree of superheat. Loading gauge limits cylinder size. The 504 rule dictates driving wheel diameter. Then, if as a designer, you wish to minimise the peak over mean tractive effort difference you go multi cylinder and compound if you know how to make it work. The BR board seriously underestimated the power that would be needed which explains why the East Coast received 3300hp diesel electrics. Strange to say this figure was easy to surpass with steam. Trouble is the people that understood this did not work in the UK.

 

David - I think your argument might rest on stronger foundations were it not for the fact that the Swindon persisted (into the 1950s) in building four cylinder engines with inside Walschaerts valve gear and derived drive to the outside valves!

Thought experiment time: How significant a redesign would it have been for Hawksworth, post war, to have redesigned the Castle with two sets of outside valve gear and driven the inside cylinders with rocking levers, but otherwise kept as much of the design (and therefore presumably success) in common with the pre-war Castles?

Tom

 

Indeed it did Tom, but they were largely pre war designs like the Gresley loco's, and I was making a case for the BR Standards than anything of earlier GWR parentage.

 

Indeed Tom. I've always found it incredible that the GWR persisted with inside gear after say 1920, or post-grouping, when pretty much everyone else had started nailing it on the outside where it can be easily maintained in relative safety. But then again you could say the same about exhaust systems, lubricators, cab ergonomics, low tenders offering little protection etc etc.

 

Peculiar railway the GW. It developed a rather appealing character and by the time of Churchward's retirement this was well established. The old joke about railways for which the design of a new locomotive type was merely the old one with the salient dimensions increased by 10% could well have had the company in mind. But it knew the value of a strong, recognisable, familiar and unchanging identity.
But to be constructing the designs it did in the 1940s and 50s particularly in the light of what was happening in the rest of the world and forgetting the lessons of GJC's example - strange, very strange. Churchward was open to what was happening elsewhere. Hence obtaining the French Compounds. Though it was a pity he made fundamental mistakes when he rebuilt them. Post Churchward the company could be accused of being self satisfied, a bit of an island. The locomotive world moved on. But for the GW it was a case of more of the same, give or take 10%.

 

Decidedly non trivial I believe. The detailed geometry of the valve gear is very complicated. I don't pretend to understand it, but there's info on Don Ashton's pages on valve gear, unfortunately they currently seem to be down.

 

And they did the number one thing on the tin: help deliver a profitable railway.

Its a big mistake to consider that things were unchanged. There were detail design and construction improvements going on all the time. You only have to read Cook's book to understand that they were constantly working on important detail engineering to increase time between overhauls, reduce costs, all real engineering, but which doesn't impress in the pages of a magazine. Take high superheat for example: reduced coal consumption, but increased oil consumption and wear from lubrication problems, which are hidden but nevertheless real costs. Who can really say at what point, bearing in mind all the expense of rebuilding boilers and changing the lubrication systems, there was a cost justification in business terms for increasing the level of superheat instead of what they were doing? We can be confident that in the early days before WW1, when the GWR had more superheated locos than all the other lines put together, that there was no business case for the higher level of superheat that Churchward had tried and rejected. There's an assumption it was justified after WW2 when it was introduced. In between, well after the grouping all resources were required for dealing with the absorbed stock, and obviously none were available in WW2. The Castles and Kings were both required in short order so there was no time for major development then, and in the 30s they were working on the rather more significant if less headline gathering engineering stuff. Its hard to see *when* a big change should have been made.

Sure goodness only knows what would have happened if the GWR had sold the LMS a bunch of Castles and they were run with the engineering traditions and crew training present on the LMS, and doubtless it would not have been pretty - the GW board probably did the LMS a big favour there, but the GWR could and did rely on the men they had, and bearing in mind that they made a profit its hard to say they were categorically wrong.

 

Profit - a dirty word, but probably the raison d'etre that railways even exist.

 

re Churchward and the GWR i think you have to try and understand something of the man and how he influenced everyone in the drawing office. he inspired incredible devotion and loyalty. Collett was principally interested in the efficiency of the machine shop and works. he had no need to change the Churchward design precepts. Hawksworth was a Churchward 'pupil' and devoted to his old boss, though did in the case of the 15XX class produce an outside walschaerts valvegear loco.

the Stars, Castles, and Kings were designed around a few basic Churchward precepts. firstly nothing 'outside' to muck up his idea of aesthetics, and the inside conn rods had to be the same length as the outside con rods. what Churchward and Willie Pearce understood about loco valvegears and valve events was years ahead of most other railways at the time.

the Holcroft conjugated gear was quite different to the Gresley arrangement and employed more pivots and wasnt so susceptible to the problems with the Gresley gear. Holcroft went on to design a 4 cylinder conjugated gear that was applied to steam locos albeit in the form of miniature locos for the famous miniature loco designer and builder 'LBSC'.

the thing about chimneys isnt the height of same above the smokebox but the length of same including the petticoat pipe. ideally this should be 7 times the diameter of the petticoat pipe 'choke', but often was much shorter on large boilered locos in the UK.
cheers,
julian

 

Was Churchward concerned about aesthetics? His engines were very austere compared with both those before and those on other railways (by the standards of the time). It seems he would have preferred a black livery for locos and he did of course abolish the cream upper panels on coaches. His one concession to appearance was to get Holcroft to make the running plate less angular.

The need to get between the frames for lubrication probably just wasn't an issue in his day while access to the solid big ends he introduced was easier with inside eccentrics.

Unlike the other big four companies there was by the 1930s a far greater extent of standardisation, with no other major constituent company, so the benefits of maintaining that could have been weighed against any benefits of improvements.

 

Quite right. The locos did what the traffic department asked of them. I'm sure that adding all manner of fancy improvements may have enhanced the bottom line figure but with plentiful supplies of cheap, good quality steam coal, making a case for expensive mods that would make the locos more expensive to maintain would not have been an easy matter. A natural reaction would have been "we're making a profit so why fix what isn't broken?"