Valve gear settings

[JASd17]

Both Seagull and HS make valid points.

I believe it was the Great Western that made more of 'setting-up' the engine correctly prior to Nationalisation, using light sources to help line-up major components during manufacture and overhaul. That was a world away from keeping a loco going when required by the shed, when it was run-down.

With regard to the K4s, how long did they last? American operations tended to scrap and build afresh. What did this policy depend on, boiler condition, or cheaper manufacture and finish of all components in the first instance? Or are any such generalisations out of place?

John

[Seagull]

Great Western express engines were generally physically smaller, but still approached the maximum permissible axle load.
They could thus have a stronger frame structure so were less prone to frame flexing, less prone but not immune.
The Gresley Pacifics especially had little support round the driving axle as it was not possible to fit in frame bracing with the concentrated drive.
This was the downside of the large engine policy, most of the faults on the Pacifics could be traced to weight saving measures.

No-one seemed to have any real problem making their lower powered engines work reliably.
It was the advent of the higher powered and weight limited engines that started to show alignment problems.

Doncaster used wires and rulers to set up the frames when new and the hornblocks were adjusted by the same method at overhauls.
A method that was used in probably every railway workshop except Swindon up to the 1950s and for the first 100 years at Swindon.

Optical setting up would have improved the initial accuracy in the workshop, but there is plenty of evidence to show that with the combination of flexible frames and wear, the accuracy lasted a very short time in service. See Townend's Top Shed book about the replacement hornblocks that were fitted the wrong way round and only found at a works overhaul after the engine had run thousands of miles.

The real answer would have been to fit a stronger frame structure, bar frames, or better still cast steel frames as in the US.
The problem is they are much heavier and would increase the axle load to something like 25 tons on a typical UK locomotive.

Bullied obviously appreciated the problem and had a good try with the Merchant Navys by fitting his chain drive (it was to have been a gear drive) and using the oil bath as a rigid box to add strength around the driving axle. As is well known they still flexed and the leaks from the oil bath were good for lubricating the track and igniting the boiler insulation!

American steam locomotives generally had a shorter life than UK ones, typically 20-25 years as opposed to 40-50 years.
In the UK after 25 years a loco would be rebuilt, largely as it would be put down on the maintenance budget rather than capital expenditure.
In the US they would scrap and build new as their tax laws actually encouraged it.

Alan

[Hatfield Shed]

It's salutary to remember that all of Swindon, Darlington and later Crewe, also had real trouble with designing a pacific frame. Not just to meet strength and stiffness requirements within an acceptable all up weight and axle load, but also for flexibility to get around the tight curvatures at many system locations. Five chain curvature had been a commonplace on the UK steam network in early C20th, and easings to six chain often difficult to accomodate. Not so much of a problem in the USA where cheap land and less crowded locales meant that dated track layouts with small radius curves could be and were significantly eased.

Doncaster were progressing on the pacific frame strength problem by the time of the A4 design, which improved over the A3 by some margin. Where the A3 broke its frame, the A4 typically bent it; real progress considering the heavier boiler and higher applied power to the frame of the A4 compared to the A3. Never seen much information on the Peppercorn A1 and A2 frames which is probably an indication of generally good news.

The interesting comparison to practise in the USA; the renewal approach saw the better organised railways steadily upgrading their fleet of core designs as advances were proven. The Norfolk and Western is a prime example with the Y6 2-8-8-2 series for its coal hauls which were developed continuously, older examples being brought up to current spec at overhaul. Renewing rails in heavier section to accomodate growth in all up weight seems to have been readiy accepted.

[1H was 2E]

With regard to setting up clearances; I read somewhere (do a lot of reading, don't make enough notes) an article by someone who worked at Rugby Testing Station from its opening. He mentioned that an early trial was of a WD 2-8-0, and of course the test rollers produced the first opportunity to watch (at least, safely) the behaviour of the revolving and reciprocating elements of the engine of a locomotive.
He reported that the amount of flexing, whip and vibration suggested that it would be pointless to work to fine tolerances, with some dimensions increasing by about 1/2".

[Hatfield Shed]

That might well be ES Cox. Doncaster had some early insight into this when the K3's conjugating lever ends were found to be impacting locations which they easily cleared when cycled through their movement at low speed. One attempted correction was to experiment with aluminium for these levers, to reduce the moving mass and thus the kinetic energy in the lever that produced the bending when the motion was reversed. We are spoiled nowadays with high speed photographic technique revealing just what the parts of fast moving mechanisms actually do.

[LNER4479]

So there I was recently, explaining to a young lady how the valve gear of a steam loco effected the necessary steam distribution to the cylinder, to ensure that the engine started in the desired direction ... [etc]

Blimey! You certainly know how to show a girl a good time

Best quote I heard about East Coast pacific handling: 'That (pointing to the regulator) is the on/off switch; and that (pointing to the reverser) is the volume control!'(!)

Which rather points towards the 'get the gear wound back and regulator fully open as quickly as possible' technique.

[notascoobie]

So there I was recently, explaining to a young lady how the valve gear of a steam loco effected the necessary steam distribution to the cylinder, to ensure that the engine started in the desired direction ... [etc]

Blimey! You certainly know how to show a girl a good time

Best quote I heard about East Coast pacific handling: 'That (pointing to the regulator) is the on/off switch; and that (pointing to the reverser) is the volume control!'(!)

Which rather points towards the 'get the gear wound back and regulator fully open as quickly as possible' technique.

I had a major success during the "Great Gathering" when the Boss finally understood the difference between 1928 Corridor tenders, streamlined non-corridor tenders and streamlined corridor tenders. By the time of our golden wedding she might understand the finer points of conjugated valve gear events .................. or she'll have dumped me if she's got any sense!

Vernon

[Hatfield Shed]

So there I was recently, explaining to a young lady how the valve gear of a steam loco effected the necessary steam distribution to the cylinder, to ensure that the engine started in the desired direction ... [etc]

Blimey! You certainly know how to show a girl a good time ...

Good time or not, it was with serious intent; she's employed as a history teacher. The curriculum for one of the courses she is teaching covers the industrial revolution; and it's somewhat challenging when the teacher has a pre-Newtonian grasp of Physics and no clue how the same electricity can make the oven hot, the freezer cold, and her i-device do all sorts of things. From a small group of us she got a four hour crash course from Abraham Darby to the Wright brothers.

[Horsetan]

.....The real answer would have been to fit a stronger frame structure, bar frames, or better still cast steel frames as in the US.
The problem is they are much heavier and would increase the axle load to something like 25 tons on a typical UK locomotive.....

Mmm, I did wonder what might have happened if the German standard Einheitsdampfloks, on their bar frames, with a maximum axleload of 20 metric tonnes, had been scaled down to fit the British loading gauge.

[Hatfield Shed]

The 'scaling down' is a matter of lowering the boiler centre line, and mounting the outside cylinders closer inboard, to clear the more restricted UK loading gauge: for a machine that then looks very similar in concept to an A3, or A4 without streamlined casings; the difference being the greater axle loads the German designers were prepared to place on the carrying wheels, in order to reduce axleload on the driven wheels. You might lop a ton or two off the all up weight thanks to the structure reduction implicit in arranging major components more compactly.

Informal trials of the UK plate frame vs German bar frame were conducted in Turkey, and the plate frame did rather better in respect of the 'rough shunt' scenario. It might well outperform the plate frame in other respects in normal operation, but the well recognised German proclivity for maintaining equipment correctly would have to be taken into account.

Unlike a built up frame, whether of bar or plate type which are readily repaired by component replacement, the cast frame was designed not to break under normal service loads because it was essentially unrepairable. At the state of engineering technique when cast frames were introduced, there was not the analytical capability to fully analyse and design for the strength, stability and fatigue resistance required. The natural consequence was to go for 'plenty strong enough' and thus the weight. It would make a very interesting contemporary exercise to design, build and operate an optimised cast frame on a high power UK design, in comparison with what we know of plate frame. I suspect there need no longer be a weight penalty for the cast frame.