Bulleid rebuilds - Was it for the better?

There was referewnce to rebuilding the Bulleid pacifics in the P2 thread. Slightly in devils advocate mode I am creating a new thread basically queerying if Bond did the right thing. Taking what was changed was it justified?

1. Air smoothed casing - at average SR speeds any airflow issues are negligible and the problems of maintenance were real. I would not fancy ballancing on a ladder with a hod of hot sand trying to fill a sandbox through a sliding door. Conclusion an improvement
2. Chain driven valve gear - in an internal combustion engine the chain only travels one way and is held tight across the working area by a tensioner on the return side and all points have fixed relationships. With the axle moving vertically and the chains having to cope with bi-direction use they were a weak point. If modern neoprine seals had been available in 40s the oil bath may have leaked less. The actual valve gears were both Walsharts so effectivly no change.
3. Steam reverser - the Eastleigh steam reverser didnt work that well on LSWR designs so conventional screw reverse would at least stay in place.
4. How much was actually changed in the rebuilds - remarkably little. Some railways so called rebuilds were virtually new locos. The Bulleid rebuilds contained 90 of the original loco, Most of the boiler (smokebox modified) wheels , frames, cab, outside cylinders were retained. The wide chimner and multiple jet blast pipe was retained.

Were they an improvement - probably as the essence of a good design was retained whilst removing their weak points. Were the critisisms real or simply engine men dont like change.

 

In a word - NO.

 

In a word, Yes. (No capitals needed.) It was far too long ago to bother or to waste much time about.

PH

 

You can say that about anything in history so, by your argument, nothing historical is worth talking about.

 

Wasn't the real Achilles' heal the reverser rather than the valve gear per se? One wonders what the reputation of the originals would be now had they been built with the Ashford reverser (which was always highly regarded) rather than the Eastleigh one (which wasn't).

OK, that wouldn't immediately solve the problems of stretching chains or oil leaks, but in some ways those issues strike me as similar in nature to any other loco which gradually gets rough as things wear. (Nobody berates Gresley pacifics just because the conjugated valve gear isn't as efficient after 70,000 miles as it is when freshly outshopped). Whereas the drifting of the reverser would be the kind of fault that would, at the very least, reduce a driver's confidence in his steed! Maybe if they had had a decent reverser in the first place, the other problems would not have been considered serious enough to warrant a rebuild.

Tom

 

Of course not, because in 1950 40% of MNs and 29% of the Light Pacifics were out of traffic for one reason or another which represents an amazing unavailability, unmatched by any contemporaries.

 

Hardly my point of view at all. It is just that this particular issue has been done to death and everyone approaching it does so from pre-conception. Just read S.E. Townroe (whom I did meet) about the labour requirements of keeping these machines in service. Too many railway enthusiasts do not have the slightest idea about costs; just witness other threads about keeping outgoings under control!

PH

 

I can only assume the rebuilds improved the locos. My assumption is based on the fact that all of the MNs and most of the BBs & WCs were rebuilt. The rebuilding was not suspended after the first few entered service and performance & reliability data was then available and could be compared to the unrebuilt variety still in service.

 

I can't add a lot to the discussion, but I know the Salisbury driver who achieved the xxty miles an hour with 34092 back in the 80s, and his view was that the rebuilt locos were better, and another former Salisbury driver I know agrees with him.

 

In order to improve availability the answer is yes. To make the level of attainable performance more uniform, the answer is yes. To ease preparation time you can argue about. Was the rebuild as good as it should have been and the answer is no. Strange that given the thousands of power reverse mechanisms at work in the world that we had such a lack of success with them in the UK, the more so given the fact that the Hadfield was used so frequently by Beyer Peacock.

 

Without a detailed audit of the true operating costs and the rebuild costs up to withdrawal it is impossible to decide. Remember at the time the rebuilds were planned to be in service much longer.

 

Presumably the BR Management had those figures.....

 

BR did monitor the running costs. That is one reson why the rebuilds were authorised, before later decisions which resulted in a more rapid run-down of steam operations than was envisaged at that time. The rebuild benefits were not all positive - the increased weight meant a reduction in route availability and I wonder what effect the increased hammer-blow had on track maintenance costs.

 

I have been watching the discussion so far but not commenting in order to see if a consensus developed. Two issues seem to have been highlighted availability and that steam reverser. i can't fathom out why the Ashford reverser was not used either.

Availability was an ssue. I believe at one time in the 60s there was a suggestion of re deploying LMS Princess Coronation class locos displaced by WCML electrification.

Costs is an interesting issue. Were proper records kept. I have been re reading Dick Hardys book and he admits that when in east anglia availability was king and he sometimes had no idea of the costs of say fitters time.

61624 mentioned hammer blow. Whilst it is true that weight of the rebuilds was higher hammer blow comes from the ballance weights correcting horizontal reciprocating mass having a vertical component for each wheel revolution. As the reciprocating masses stayed the same I would suspect there was no change in hammer blow. if there is an expert on hammer blow who disagrees I will be interested in the issues

 

No I didn't! It was Miff what done it!

 

I think the weight consideration is an important one. The light pacifics were built as a high power, go-anywhere design. That was important particularly west of Exeter, where gradients were tough (such as the 1:36 straight off the platform from Ilfracombe) but strctures were lightweight (such as Meldon viaduct). In the circumstances, the rebuilds could have had all the reliability in the world, but it would have been no use if they couldn't venture west of Exeter! I suspect that was at least part of the reasoning behind not rebuilding all of them, with the rebuilds going to the eastern section and the unrebuilts cascading west. Certainly by the late 1940s / early 1950s, the operating department desperately needed something to replace the aged Adams and Drummond 4-4-0s and Maunsell moguls, even the most modern of which were essentially a generation old in design but pulling heavier, more modern rolling stock.

With regard the availability quoted earlier, how much (if any) was down to the boiler rather than the valve gear? Certainly later in life both classes were derated to 250psi from 280psi, since the extra pressure turned out not to be needed in most circumstances. Lowering the pressure in that way should have improved boiler reliability, I'd have thought. Out of interest, what was the reliability of the Hawksworth "Counties" like when new?

Tom

 

Apologies 61624 - I do find a lack of clarity between posts an issue.

 

"Certainly later in life both classes were derated to 250psi from 280psi, since the extra pressure turned out not to be needed in most circumstances. "
I believe only the MNs had 280psi boilers and the first of those was reduced to 250psi before nationalisation, hardly later in life.

 

D.W. Winkworth's volume, Bulleid Pacifics, includes lots of statistics and good, balanced overviews of the class I feel.

My personal view (purely from an academic point of view based on that I've read and observed, and not from any real hands on experience with the locomotives) is that they were neither the worst Pacifics nor the best that British Railways inherited, and in their rebuilding the major talking points (inaccessibility of components, the amount of oil used, and other disadvantages of the original design) were improved, but not necessarily enough to combat the still quite high coal and water consumption (in comparison to other Pacific classes). Neither better nor worse than the originals, just moving the problems from one part of the engine to another (arguably Thompson did the same with his Pacific classes). I don't think even Bulleid Pacific fanatics could argue that they were the best, most efficient Pacific locomotives in British Railways' arsenal (despite being undeniably impressive, and in my view handsome).

If you were going to build a new Bulleid express locomotive today there's no doubt in my mind that you wouldn't built it according to Bulleid's Pacific design as built, but rather what he wanted to do all along, which was a Mikado or a "Mountain" (4-8-2) with Caprotti valve gear and roughly the same all welded steel boiler. Would have been an interesting prototype with a fair bit of Gresley's COTN's DNA in it.