Inside cylinders

[Pyewipe Junction]

Can someone explain why British locomotive designers remained faithful to inside-cylinder designs until well into the 20th century?

Even Bulleid used them on the Q1s as late as 1940/1. I would have thought that inside cylinders actually presented problems for maintenance as the valve gear would be hard to get at. And, as we know, the J39s were dogged by problems that basically related to their inside cylinder configuration.

Any views?

[stembok]

Pyewipe Junction: good question, particularly as Gresley had built outside cylinder moguls for the GNR and LNER before the 289 J39s of 1926 and there was also Collett with the GWR
0-6-0s of the 2251 class in 1930.
Of all the mainline engines built in the UK over half were 0-6-0s most with two cylinders. Despite the problems of access - not a concern of many CMEs." I've built it you maintain it!" - the inside cylinder layout proved to be reliable and presumably cost effective, as well as providing valuable spacing and bracing at the front end of the locomotive. The limitation was of course the space available between the frames and thus the need for outside or multi cylinder designs for more powerful locomotives. Initially, also, many Victorian engineers probably had a preference for the neatness of the inside cylinder design with motion hidden away. Another reason for moving away from inside cylinders was the greater difficulty of using Walschaert's valve gear inside the frames, not however insurmountable -the GWR did it - and again problems of access as boilers grew larger. It is likely that Gresley would initially have liked a 3 cylinder 2-6-0 based on the K3s instead of the J39s, but according to FAS Brown financial considerations intervened and the need for a new design was urgent, hence the 0-6-0 based on the ex NER P3/J27 class. Of course the J39 engines were often used on fast freight and excursion work, but were not best suited to this and maintenance tended to be heavy together with problems with axlebox wear and with the motion. Perhaps, as 0-6-0s with 5'2" coupled wheels they were not really suited to these classes of work.

[richard]

Some times the inside cylinder design was more preferable - eg. in the J94 which was an industrial design adapted for wartime shunting work. The inside cylinder arrangement was considered better - less vulnerable to damage, and better suited for poor quality track (I'm a bit doubtful as to whether inside cylinders were much better for poor quality track).


Richard

[Belvoir]

I believe that in the early days of outside cylinders there were problems with cylinders working loose from the frames - with unenviable results - and this prolonged the use of inside cylinders. Also the inside cylinder block also helped to stiffen the forward frames. We need not discuss the aesthetic values of late 19th. century designers as they appear self-evident.........