Improving on A4's

[John B]

Does anyone have any ideas on how the Gresley A4 could have been improved?

It's a big question I know but my mind has been working on it for a short while and I wanted to share my ideas. Which direction would Gresley have taken next? there are just so many ways he could have gone.

When I started thinking about these ideas I thought of adding the query to the "new build" section but I realised other stages have to be gone through before ti would reach a firm proposal stage.

What form would an improvement constitute, more speed, more power, faster acceleration from a standing start, better fuel economy or greater reliability between services?

Generally speaking I would have liked to have seen all of these factors incorporated and adequately dealt with in the final product.

How would this be achieved? that is the main question.

More cylinders - maybe four with a slightly smaller cylinder size.

Bigger wheel diameters - say 7' 6", faster running speed for less effort.

Bigger boiler with higher pressure - say 300 - 350lb.

Mikado wheel arrangement to carry the bigger boiler.

Improved draughting (polishing of and increased dimensions) of the steam/exhaust passages.

Bigger valves and ports for more efficient valve events.

Modified Walscaerts valve gear on all cylinders.

Additional cab comforts - bigger and better cab seats, all controls easily in reach, access to quality cold and hot water for tea brewing, personal lockers and adequate toilet provision. More enclosed cab for winter running but easily opened right up for summer running. Electric generation for communications, lighting and signalling etc.

Bigger, through corridor tender

Could the Kylchap double chimney and blast pipe be improved upon?

Finally, and here's the biggy, I would want the engine none streamlined and looking just like a big A3 but hopefully with the smoke drift problem cured, preferably without the deflectors.

Anyone else got any thoughts on all this?

[jwealleans]

Hello Richard,

Isn't there a diagram in Top Shed of a proposed 4-8-2 which was in his thoughts before the war?

It may (I'm struggling to remember) have been based on the A3 shape, although the A4 styling seems to have been in favour at that time (P2, W1...).

I'm not sure he would have gone for 4 cylinders - he seems to have been a bit evangelical about the 3 - and I'd have thought anything with wheels that large might have struggled on the banks out of the Cross. I'm with you on the draughting and steam ports. I don't think anything better than the Kylchap arrangement came up. I'd like to think that the improvements when Swindon style optical alignment techniques came in in the 1950s would also have been adopted.

This all supposes that the trend was towards heavier trains rather than faster; there are only so many streamlined trains which can be accommodated. It would be interesting to know what forward thinking was at the time ; Gresley was at his best when building for a very specific purpose. Electrification might have spread far more widely and we might have had something totally different pulling the '10 O'Clock'.

[Colombo]

The streamlining was really unnecessary in ordinary service, a pair of smoke deflectors would provide sufficient up draught to clear the exhaust. Maintenance costs would be reduced without the streamlining. Rather than the derived motion on the middle cylinder, three sets of Walschaerts valve gear would have required less setting up. Perhaps an increase in cylinder diameter from 181/2" x 26" to 19" x 26" might have been accomodated, increasing the tractive effort from 35,455 lbs to 37,400 lbs.

Roller bearings on the tender would have reduced friction.

In fact Peppercorn did build this loco, it became his class A1.

Colombo

[Tom Quayle]

I suppose a Garret style 4-6-2-2-6-4 is just being silly

[richard]

Colombo, my thoughts exactly!

Although the RCTS books do describe various "sketches" that might have been, World War 2 and Gresley's death made sure that none ever saw the light of day. I believe Gresley would have kept the conjugated gear. Otherwise, it would have been very similar to the Peppercorn A1 in detail but final wheel arrangement (4-6-2/4-8-2) and streamlining (A1/A4) would be matters of conjecture.

Richard

[John B]

Thanks guys for all your inputs.

I am curious, would Gresley have been satisfied with the Peppercorn A1 if he had designed it? What could this engine do that an A4 could not?

They were known as powerful engines but heavy coal users. As far as I know they were fast express engines but were nothing startling in the speed department with 100 mph being towards the top end of their range. They were however capable of hauling heavy 15 coach trains at consistently high speeds so in that regard they more than did the job they were built for.

Gresley I believe, would have expected more from these engines in terms of free steaming capabilities, top end speed and economy. I agree with J Wealleans that the need for absolute speed had decreased during and immediately after the war so my guess is he would have expected this engine to pull trains anywhere up to 120mph + speeds but with much heavier payloads. Gresley was always responsive to the needs of the times in which he lived and I am sure he would have satisfied those needs with his exceptional design flair – I would have expected something unexpected from him