46235 City of Birmingham

I prefer to see it as a pause to let lesser railways catch up - helped by Stanier and Gresley going off to do missionary work among the heathen.

 

known as *correct* for short.

 

Gresley Was Right.

 

The one thing I'd like to see done with 46235, is to have the sloping top fitted to the smokebox. As the loco had been like 6229 a streamliner, so considering Hamilton has been put back into the "bathtub" and 6233 Sutherland never had it you'd have the three versions of the class back in existance.

 

Would be a nice variation I agree.

 

I would think that the lower back-pressure of the double Kylchap also makes a difference.

 

He knew it was God's Worst Railway.

 

As Tom has said here, a three cyl loco is at a disadvantage over a two or four cyl loco at the moment of starting (but only at that point.). Holcroft realised this many years ago when investigating why a Schools struggled to start trains that 2 cyl but smaller 4-4-0's could easily manage. There are other things that can come into play, as well, such as the design of piston valve heads. Again, a read of Holcroft's Locomotive Adventure will explain this.
Gresley originally designed his pacifics with a maximum cut-off of 65% because he wrongly believed that you didn't need the traditional 75% with a three cylinder loco and thought it would save both the use of steam and reduce slipping at starting! I believe that they were altered to 75% during the war after Gresley's death. What I'm not certain of is whether that alteration only applied to forward gear. Certainly the reverser indicator on 60007 only goes to 65% in back gear and it does tend to stick a lot more when trying to start in reverse.

 

It clearly didn't.
But the big difference was that while Gresley, landed with an unsatisfactory fleet, concentrated on building new designs, (that weren't always entirely satisfactory either), Collett, knowing by 1930 that he had a suite of designs that were basically satisfactory, concentrated on building them better. You only have to look at the drawing registers to see that there was a lot of design work going on, but it wasn't the sort of work that excites the more naive enthusiasts. Collett was undoubtedly a man for ten 1% improvements, not one 10% improvement, and arguably in doing so he served his company well throughout the 30s.

 

Bittern has the same unequal scale on the reverser, so I would guess it was only done one way. I can't say I noticed any issue starting in reverse, but it was a rather less strenuous load and gradient than you're used to. It might have been that extending the expansion link upwards would have caused clearance issues, whereas there's definitely a bit of room for redesigning with a longer slot in the lower half without fouling the eccentric rod pin. Or Doncaster just thought that pulling trains in reverse was beneath the dignity of an A4.

There are quite a few bits of interesting technical information in Locomotive Adventure that never really crop up elsewhere; a fine reminder that quite significant changes are not always obvious, or even visible from the outside.

 

See my signature

 

It's wrong though.

 

I've never looked at the expansion link on an A4 that closely but that is what I have always understood was done; a slightly longer link with slightly longer levers on the reversing shaft and a simple re-calibration of the reverser scale wouldn't be a major job. As you say, A4's would rarely have to do much real work in reverse so it wouldn't be a problem. What I don't know is whether Gresley applied the same 65% philosophy to his other 3 cylinder locos.

 

Broken ones, and Windsor Castle had those silly side things on royal train duty

 

DoC is a good example, I remember seeing her at Shildon when she first arrived and it looked the proverbial life expired machine from the 1960's, very realistic, but nothing like museum exhibit finish, looks a million times better now.

 

Is that the version people refer to as 'semi's' IE semi streamlined?

 

In short yes. Another give away is that both 6235 and 6229 don't have the connecting curved footplating at the front end, that links the bufferbeam to the running board that runs along the top of the frames, where as 6233 does as she'd ran from new unstreamlined.

 

Here here. Radical fleet redesigns as opposed to the incremental improvement favoured post Churchward would have risked throwing away the key commercial advantage Churchward won for the GWR, that of standardisation. The fact that small components such as manifolds and valves were shared across the entire fleet, pretty much, was an early example of something which has been an industrial "holy grail" since. Cost goes down and availability goes up. Since the base designs were essentially good (a result of a very scientific approach) there was until at least 1950 no advantage that could be gained by changing radically the design of the next loco that was sufficiently large (and during the war no money anyway) to justify such a move.

 

The GNR 1000 class originally had the maximum cut-off of 75%. The conjugated gear gave rise to overrunning of the inside cylinder valve whilst the engines were coasting at high speed. The solution taken was to reduce the maximum cut-off to 65%. The range of drifting techniques used by the various railway companies varied. Drifting in full gear, mid gear anywhere in between gear, with or without some steam being applied. With anti vacuum valves fitted or without, with them fitted upstream of the superheater, with them fitted downstream. By-pass valves could be fitted, or not. The correct drifting technique will not result result in any damage to the locomotive. It should not give rise to cooling of the cylinders or adversely affect the lubrication. Ideally both steam consumption and work done by the cylinders should be zero. The list goes on but it is the first item that is the important one here. It makes it obvious that the drifting technique being used was wrong but this was not addressed and the outcome was that the 65% restriction carried over into later designs. This was quite unnecessary. As for correct drifting technique mid-gear with a trace of steam to prevent negative work, no anti vacuum valves fitted and no by-pass ones either has been found to meet the many requirements.
On the subject of the GW the argument could be made that it stagnated because of an obsession with standardisation. It becomes very hard to financially justify change, the numbers involved make it prohibitive. You cannot say that the "scientific approach" taken by the company was good, the alarm bells should have been ringing in the early 1930s. The real scientific advances had, and were continuing to, take place elsewhere.