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Could the W1 have beaten Mallard's speed record?

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Shaza

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Recently I’ve been looking into Gresley's planned developments of the A4 class and the re-built W1 class locomotives.

I know the W1, when rebuilt, wasn’t capable of developing high cylinder horsepower and due to having only 8" piston valves it was not as quick as an A4.

W1 locomotives tended to haul heavier, rather than faster trains.

I was wondering, if war hadn’t broken out, could a rebuilt W1 (with some modifications, like larger piston valves) have beaten the 125mph record set by Mallard?
 
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MarkyT

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I don't believe the A4 was short of steam at all when the maximum was reached, so Mallard might have even been able to beat Mallard's record if there had been a section of suitable track long enough to keep going, but the record-breaking run really was a one-off publicity stunt and no-one else (in UK at least) was close at the time so I don't think there would have been any desire to repeat the exercise with all its risks and uncertainties.

Getting back to the point, I'm not sure if the valve diameter alone is the key factor in the steam path. The size of the ports and the size and internal streamlining of the pipes, junctions etc would all have their parts to play.

In terms of steaming rate, the W1 with its 50 sq ft firebox grate should certainly have been able to easily outperform the A4 at 41.25 sq ft. though, both at 250psi, which contributed to the W1's appreciably higher tractive effort that made it so attractive for the heaviest trains.

The 50 sq ft grate was carried through into the later Peppercorn A1 design which was very free steaming and successful all-round with 10" valves, but never noted for particularly high speed running, although that was probably far more to do with the ongoing post war austerity climate not allowing the opportunity than anything else. Initially, the LNER had notions of applying an A4-style streamlined casing to the A1 design, but clearly that was dropped before production.

I think the most important thing to come out of Mallard's run was the demonstration of the double Kylchap exhaust, which significantly reduced the back-pressure from the blastpipe. Gresley was a great enthusiast for this continental technology, but he was not permitted to equip more locos before WW2 because the patent licensing costs were so prohibitive. Once the patent had expired during the war, Thompson and Peppercorn were free to use it widely on the largest locos.
 
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Spartacus

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I suppose properly prepared it could have done, but as MarkyT says, the same could be said for any of the other double Kylchap fitted A4s too, has the middle big end not overheaded. I don't kow if 10000 was similarly afflicted, but it was something that A4s were prone to.

Even Mallard's record probably wasn't a best possible one as she had to slow for a 15mph TSR at Grantham and restriction over the points at Essendine.
 

MarkyT

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I suppose properly prepared it could have done, but as MarkyT says, the same could be said for any of the other double Kylchap fitted A4s too, has the middle big end not overheaded. I don't kow if 10000 was similarly afflicted, but it was something that A4s were prone to. Even Mallard's record probably wasn't a best possible one as she had to slow for a 15mph TSR at Grantham and restriction over the points at Essendine.
That would have been impossible to pin down with a class of one. Although the A4 failures clearly happened, they were never exactly very frequent. The A3s never exhibited the problem at all, and they were an almost identical design mechanically apart from the cylinder dimensions, but they weren't used on the fastest accelerated diagrams routinely once the A4s were available.

A4s also had problems with the right-hand centre driving axlebox, which may have been linked to the big end issue and my father remembers visible frame distortions around this axle on many locos. Dad had a look at 60007 when first dismantled for its current overhaul at the NRM and it clearly has sections of new metal welded in around this area, presumably at a previous overhaul, possibly at Crewe after preservation. It was something that would not have been done at Doncaster in BR service as they would have replaced the frames if neccesary. With the middle crank, there was little room for extra bracing of the frames around the centre axle, so there could have been a systemic weakness that resulted in them flexing, causing problems for all local bearings, but I also suspect there may have been a gyroscopic component with this extraordinarily well balanced rotating element at speed. Dad solved both problems entirely in the 1950s by arranging for both centre driving axleboxes and the middle big end bearings to be changed routinely at 36k miles, just before the problem was expected to occur at the earliest from statistics. He told me that Royal Scots, another combined drive high power three-cylinder engine, also suffered from middle big end failures and they were even more hair-raising as the bearing design didn't have a rear strap so the brasses would be guaranteed to come adrift and the connecting rod would flail about between the frames!

Perhaps Thompson and Peppercorn were correct to split the drive on the later pacifics, but I don't think the underlying problem was the Gresley 2 to 1 valve gear, as Stanier had claimed. The concept could still have been incorporated on a split drive three cylinder engine using the technique applied on the B17, with the conjugation levers between the forward and rear cylinders instead of being in front of them all in the classic Gresley configuration. In maintenance and reliability terms generally, the 2 to 1 gear was a boon, as there were far fewer bearings and other components to inspect and oil between the frames, and thus no failures attributed to them. It exhibited no problems at all on the many hundreds of other LNER engines it was fitted to.
 

Spamcan81

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I don't believe the A4 was short of steam at all when the maximum was reached, so Mallard might have even been able to beat Mallard's record if there had been a section of suitable track long enough to keep going, but the record-breaking run really was a one-off publicity stunt and no-one else (in UK at least) was close at the time so I don't think there would have been any desire to repeat the exercise with all its risks and uncertainties.

Getting back to the point, I'm not sure if the valve diameter alone is the key factor in the steam path. The size of the ports and the size and internal streamlining of the pipes, junctions etc would all have their parts to play.

In terms of steaming rate, the W1 with its 50 sq ft firebox grate should certainly have been able to easily outperform the A4 at 41.25 sq ft. though, both at 250psi, which contributed to the W1's appreciably higher tractive effort that made it so attractive for the heaviest trains.

The 50 sq ft grate was carried through into the later Peppercorn A1 design which was very free steaming and successful all-round with 10" valves, but never noted for particularly high speed running, although that was probably far more to do with the ongoing post war austerity climate not allowing the opportunity than anything else. Initially, the LNER had notions of applying an A4-style streamlined casing to the A1 design, but clearly that was dropped before production.

I think the most important thing to come out of Mallard's run was the demonstration of the double Kylchap exhaust, which significantly reduced the back-pressure from the blastpipe. Gresley was a great enthusiast for this continental technology, but he was not permitted to equip more locos before WW2 because the patent licensing costs were so prohibitive. Once the patent had expired during the war, Thompson and Peppercorn were free to use it widely on the largest locos.

Reportedly Sir Nigel wanted a crack at 130 but the antics of the Austrian Corporal put paid to that.
 

hexagon789

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Recently I’ve been looking into Gresley's planned developments of the A4 class and the re-built W1 class locomotives.

I know the W1, when rebuilt, wasn’t capable of developing high cylinder horsepower and due to having only 8" piston valves it was not as quick as an A4.

W1 locomotives tended to haul heavier, rather than faster trains.

I was wondering, if war hadn’t broken out, could a rebuilt W1 (with some modifications, like larger piston valves) have beaten the 125mph record set by Mallard?

Mallard's driver always thought she could've gone faster given the chance and there are a number of anecdotes/tales of Mallard's record having been exceeded by other A4s let alone other locomotive classes or companies...
 

Bevan Price

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Given suitable lengths of good quality straight track, and favourable gradients, I think there were several UK steam classes that could have equalled, or bettered Mallard's speed record. So I would suggest the Peppercorn A1, Stanier Duchess and Rebuilt Merchant Navy Pacifics.
The W1 was a bit of a "fragile" beast, as were the unrebuilt Bulleid Pacifics, and less likely to beat any records.
 

MarkyT

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Given suitable lengths of good quality straight track, and favourable gradients, I think there were several UK steam classes that could have equalled, or bettered Mallard's speed record. So I would suggest the Peppercorn A1, Stanier Duchess and Rebuilt Merchant Navy Pacifics.
The W1 was a bit of a "fragile" beast, as were the unrebuilt Bulleid Pacifics, and less likely to beat any records.
I think effective streamlining really starts to make an appreciable difference once you climb significantly above the 100mph mark, so assuming they were equipped with that, those other locos might very well have had a chance. Equally important though was the internal streamlining of the steam path and exhaust passages, and as far as Gresley, his successors and my dad were concerned, the Kylchap really was the Rolls Royce in the exhaust department. Each advanced feature adds that extra little bit of power, reduces the air resistance, etc. They all combine to produce the ultimate peak in performance. Some of the Peppercorn A1s for example, including the modern replica of course, used roller bearings for instance to reduce rolling resistance appreciably; these were very rare in the UK. As 7Ps of course the A4s were technically less powerful than all of those 8Ps. Don't know about 'fragile' but it's certainly possible that as a rebuild there were some not entirely desirable compromises involved in the W1s conversion from a former four-cylinder compound. Without detailed drawings and descriptions of the time its impossible to know how much of the original engine was reused. Perhaps the fairly small piston valve diameter was a legacy of that for instance.
 

Clarence Yard

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I started at KX in the 1970's in the Depot Managers Office in West Side Offices, sharing an office with the daughter of Arthur Taylor, who took Silver Link on it's first trip and she reckoned he could have got a lot more out of it. Several old time drivers (and former steam fireman) used to wax lyrical about the ability of a Kylchap fitted A4 to "kick on" at relatively high speeds. I remember one saying, "even the worst ones were good after Mr Townend and that chap from the Western (presumably K.Cook) sorted them out!"

I did ask about the W1 and those of them that worked it liked its pulling ability but it was an "oddity" & "bit slow". I suspect being a one off with some "history" didn't do it any favours. Several drivers said that they or their mates regularly got well over the ton on their A4 and not by "doing a Bill Hoole" either, i.e. by thrashing the fireman. There were claims about Mallard's record being beaten but it would seem that 105mph & a bit more was not unknown, when the situation demanded it.

The two classes I would have liked to seen have a real crack at some fast running on the ECML would have been the rebuilt Merchant Navy's and the Kylchap fitted 71000. The former has that same ability to "kick on" and I have experienced some phenomenal acceleration at higher speeds behind 71000 and it is fairly obvious that the Kylchap makes a real difference to that loco's performance.
 

MarkyT

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Surely the A4s were class 8P? The A3s were 7P.
Sorry my mistake. You are quite right, they were 8P, but at the lower end of that band, with a smaller tractive effort than all those other 8Ps mentioned.
So it seams like the rebuilt W1 would have been unlikely to beat Mallard’s 126mph, although Mallard could have given a second chance.
Partial plans for a production rebuilt W1 'super A4' apparently are supposed to be with the NRM archives. It was proposed to use the W1 frame and most of the A4 components (with some minor improvement based on lessons learnt) and a larger grate area than even the W1. Could this 'super A4', less like the W1 and more like the A4, have been theoretically faster than an A4 even on its best day?
If there had been no war and Gresley had not died, then a production LNER Baltic/Hudson may indeed have been the next development, but higher top speed on special test runs, however feasible, would never have been the primary objective. The ability to haul larger trains over long distances at marginally higher routine speeds (i.e up to around 100mph) while minimising coal consumption would have been the business incentive. The problem with ever-larger grates would also have been the limits of human firing capability; for the largest locos in the US, mechanical stoking became a necessity for that reason and it could be argued that the most powerful UK locos like the Duchesses were already closely approaching that limit. It should be noted that Kylchap efficiency helps to mitigate this, bearing in mind that proven coal saving alone was the business case used for retro-fitting this exhaust technology to the entire Gresley pacific fleet post WW2. It also improved performance of course and ensured even the least experienced firemen could maintain excellent steaming in all conditions. That became very important in maintaining service quality towards the end of steam and during the difficult transition to modern traction when pacifics sometimes had to relieve failed new diesels at short notice, often managing to match diesel performance on those faster diagrams. Right at the very end of their ECML careers, as timetables were accelerated, Gresley Pacifics turned in some of their most impressive routine performance feats ever, despite their age. They truly went out with a bang. The same can be said for the rebuilt Bulleids on the South Western a few years later of course.
 

Taunton

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There was no real commercial demand for speeds of 126mph, so no need for a design that achieved it. Improvement in running times would come from better acceleration from rest, and better climbing of long gradients that did not wind the loco. This requires different characteristics, but I'll leave the steam engineer experts to describe. Oh, and better brakes than vacuum.
 
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