Riddles Quote

https://imgur.com/EXrS9kg
https://imgur.com/dGiNqYc
https://imgur.com/ccTqN1w
https://imgur.com/lUU9woG
https://imgur.com/wX7g9cz

 

Not easy site to follow.

However, the problem of 9Fs and the like doing 90 mph and its attendant piston speed is that the valve and piston rings don't last very long.

 

Very interesting. There's something almost Thompsonesque about the 4-8-0 and I love the double edged compliment regarding the Bulleid pacifics!

The comment about shallow fireboxes and adequate grate areas is interesting, when you recall some of our threads about early 4-6-0s.

 

No trouble.
Not very many steam trains drove many minutes at 90.
Seconds rather.

 

I think you’ll find quite a few LNER Pacifics were capable of sustained 90mph runs. That was the entire point of building them in the first place.

Granted on the routes they ran there were few places to do such speeds - but they all proved rather capable of doing so.

 

The Bulleids were no slouches either. As with all front line express locos, it was line speed limits that hindered them, not the inability to run fast.

 

Quite educational, thankyou. The ads were a bit....err................wierd

 

Thank you for posting this. I especially liked the last one. Iwas present when Mr Riddles attended IMLEC in Bristol in 1971. Somewhere I have the programme signed by him. Many years later I competed in an IMLEC at Bristol with my BR Class 2 2-6-0. At one point I was travelling at a scale speed equivalent to 135 mph for the full size loco. I wonder if hope he would have approved?

 

I use adblock and was not aware of being a Trojan horse.
Can pictures be hosted otherwise less offensive?

 

I would have loved being at the IMLEC 74 and have given free advice how to win next IMLEC.
A 2-10-0 compound with a big midframe LP cylinder and two outside HP cylinders.
Pure Webb from Crewe where Riddles learned his trade.
Have removed pictures from Imgur.

 

Deleted

 

That explains why I can see them. But why post something interesting and then remove it?

 

I do not understand copyrigth laws and Imgur carries a lot of trash.
Sources are:
Pacific Steam.Martin Evans.Percival Marschall 1961
Steam World issue 144 from 1999
Model Engineer 3495 from 1974

 

The nearest to the proposed 4-8-0 is presumably the GWR 4700 2-8-0? Wasn't it quite a long wheelbase and presumably restricted as a result?

 

The GWR thing had a narrow firebox between frames that sit so close to backside of wheels as possible.
With a wide firebox over driving wheels a la WD 2-10-0 and 9F frames can be closer to each other and this makes sideways movements of coupled wheels possible.

 

Possibly a daft question, but when so many pre-grouping attempts to exceed four coupled wheels failed due to inadequate firebox grate and/or draughting, what design feature made the GER/LNER S69/1500/B12 Class so much more successful than many other contemporary designs? It certainly wasn't bags of space!

 

Probably because they received a new larger boiler in the 1930s and at much the same time (perhaps more importantly) got new redesigned cylinders and valve gear in line with the then current practice and thinking.

 

I've mused on this somewhere on the forum before, but I think there are two facets to this. The 1500 design is undeniably smaller than some of the contemporary failures; easier to get reasonable proportions in terms of firebox depth to grate area if your firebox simply isn't as big. The grate on the original 1500 is smaller than a lot of 4-4-0 designs at only 25 sq.ft, but the B12/3 is much more in keeping with later 4-6-0 practice at 31 sq.ft, so that can't be the whole story.

The big difference, IMO, is that the design is a very different configuration to a lot of the failures and most of the later successes. Take the Drummond 4-6-0s, which were notably troubled by their (large) shallow grates. The firebox sits over both the trailing and centre coupled axles, rendering the ashpan very shallow there and thus prone to choking the front and rear of the grate. The dampers are actually between the axles, so incoming air has to do a neat U-turn to get the extremities of the grate, no doubt packing any ash in nicely. The worst variants had an enormous barrel too, so the front of the brick arch was forced lower. The fireman then has to be be very adept at maintaining a thin, shallow, hot fire over the whole grate without developing any holes. I think it's possible that a lot of the early unsuccessful 4-6-0s shared this undesirable configuration.

On the GER 4-6-0, the firebox simply straddles the centre coupled axle, the trailing axle is behind the backhead. It's basically a big 4-4-0 with an extra axle shoved in the middle. So the only bit with a restricted ashpan depth below is the centre, which air can reach from ahead or behind. Ash can shake down either side of the hump over the axle and the whole grate should get a good supply of air most of the time.

Most later successful 4-6-0s have a sloping grate over the trailing axle, but having nothing to do with the centre axle. Again, there's a hump in the ashpan somewhere along the grate, but air tends to come in ahead of and behind the hump. The front of the firebox can be suitably deep, allowing plenty of depth of fire under the brick arch. Some of the larger designs (Castles, Lord Nelsons, Kings etc) have a split grate, where the rear portion is roughly horizontal and the bit ahead of the trailing axle slopes down. This ensures the sloping grate doesn't make the firebox unduly shallow at the back end.

 

@8126 Thanks for the comprehensive info. Your comments on airflow beneath decks were illuminating, though as you say, it doesn't seem the whole answer. The B12/3 rebuild (which undoubtedly prolonged the life of the class in numbers) with larger boiler and firebox was evidently quite a masterful achievement and re-equipping the rebuilds with long travel valves certainly seems to have improved their performance.

There's a possibly telling comment in the 'LNER Ecyclopedia' entry concerning poorer quality coal in the postwar period, as much as train weights, being the driving force behind Gresley's development of the B17. If that is correct, perhaps in original condition, they were as close to the success / failure line as the LNW 'Claughtons', just that the S69 came down on the right side of that line. Perhaps it's a mischievous thought, but given his success with the B12's, I can't help wondering what might have been if Thompson had been let loose with the Bowen-Cooke design!

All things considered, it's surprising the layout which made them so useful over lines with axle load isues wasn't copied by any other railways, many of which had routes every bit as tricky as their GER stamping grounds. The LNER deployment to the former GNoS rather bears this out and they certainly 'got about' during the WWII period of government control.

These locos have been a firm favourite since my days of chasing Hornby locos around the carpet (probably why my knees are shot!). The story of how the survivor survivied ("Yes, of course we'll send it for scrapping when we can get it out of the shed"!) only served to further endear this unique class to me.

Sorry 'bout the thread drift folks, but the Riddles firebox considerations changed the points!