Why Brisith Locomotive seldom use new wheel arrangement

[MarlowDonkey]

One reason suggested for the Midland small engine policy is that larger engines were too heavy for many of the bridges and culverts etc

Was it not also suggested that much of their passenger network was on routes where shorter trains were adequate? Much like British Rail with DMUs and Sprinters in later years or even Voyagers and similar today.

 

[Gostav]

One reason suggested for the Midland small engine policy is that larger engines were too heavy for many of the bridges and culverts etc, and the they couldn’t afford to/wouldn’t spend the money to upgrade them.

And an important infrastructure for steam locomotive is the turntables if they were built in the early days would be too small for large locomotives.

 

[341o2]

when Oliver Bulleid proposed his first design for a 4-8-2 Southern Railway locomotive, this was one of the objections to it

 

[geoffk]

The LNER was a "big engine" railway, by British standards. Many Gresley designs were the largest/most powerful of their wheel arrangement, e.g. K3, O2, N2, V1/V3, D49, J38/39, and of course it was well supplied with Pacifics and V2s. The Great Eastern section had to wait for the Britannias before it got the
power it needed, previous designs being restricted in size by short turntables.

The LMS never had enough class 8 passenger locos and too many heavy expresses were in the hands of Black 5s and Jubilees.

The Southern ended up with more pacifics than it needed and they could be found trundling round North Devon with one or two coaches. The Lord Nelsons
were few in number so that the trains they handled needed to be within the capacity of the smaller King Arthurs.

The GWR did things it own way. They had plenty of Castles, which were capable of fine performances but were not really heavy-haulage machines, while the axle-loading of the Kings restricted the routes they could use, hence only 30 were built.

The largest freight 2-8-0s, although classified 8F, had boilers no bigger than those used on 4-6-0s of class 5. Eventually the 9F 2-10-0 provided what was needed at the top end of the power range but, by then, steam development was over.

 

[Cowley]

The LNER was a "big engine" railway, by British standards. Many Gresley designs were the largest/most powerful of their wheel arrangement, e.g. K3, O2, N2, V1/V3, D49, J38/39, and of course it was well supplied with Pacifics and V2s. The Great Eastern section had to wait for the Britannias before it got the
power it needed, previous designs being restricted in size by short turntables.

The LMS never had enough class 8 passenger locos and too many heavy expresses were in the hands of Black 5s and Jubilees.

The Southern ended up with more pacifics than it needed and they could be found trundling round North Devon with one or two coaches. The Lord Nelsons
were few in number so that the trains they handled needed to be within the capacity of the smaller King Arthurs.

The GWR did things it own way. They had plenty of Castles, which were capable of fine performances but were not really heavy-haulage machines, while the axle-loading of the Kings restricted the routes they could use, hence only 30 were built.

The largest freight 2-8-0s, although classified 8F, had boilers no bigger than those used on 4-6-0s of class 5. Eventually the 9F 2-10-0 provided what was needed at the top end of the power range but, by then, steam development was over.

A good summary there.
One thing I would say about the GWR 4-6-0s is that once they got west of Taunton they were eminently suitable for hill climbing.
All that weight put on the rear driving axle of a 4-6-0 meant minimal slipping up Dainton/Rattery etc, and in that sense they were very well designed.

 

[Bevan Price]

One reason suggested for the Midland small engine policy is that larger engines were too heavy for many of the bridges and culverts etc, and the they couldn’t afford to/wouldn’t spend the money to upgrade them.

Yes - Derby built 2-8-0s for the Somerset & Dorset Railway, but coudn't use them on its own routes. Things only started to change when LMSR got some Beyer Garratts for use on the main line out of London. Unfortunately they were badly flawed due to Derby insisting that Beyer Garratt used unsuitable Midland standard components where possible....

 

[RLBH]

The Southern ended up with more pacifics than it needed and they could be found trundling round North Devon with one or two coaches. The Lord Nelsons
were few in number so that the trains they handled needed to be within the capacity of the smaller King Arthurs.

Could the one not be the cause of the other? It would make some sense if, having had the experience of not being able to use the performance of the Lord Nelsons lest a King Arthur have to substitute, the Southern Railway overcompensated the next time they ordered top-link passenger machines. In any case, I believe a fair chunk of the 'Pacifics working North Devon branches' problem was that once you'd sent a big train from Waterloo to the South-West shedding coaches at every junction, the big engine on the front had to go somewhere, and it was more cost effective to work all the way down the branch than to go on shed and warm a second, smaller engine up to take over the final portion.

The GWR did things it own way. They had plenty of Castles, which were capable of fine performances but were not really heavy-haulage machines, while the axle-loading of the Kings restricted the routes they could use, hence only 30 were built.

One wonders if an eight-coupled passenger locomotive might have been beneficial to the GWR in allowing King or Pacific-type performance with lower axle loads.

 

[Cowley]

Could the one not be the cause of the other? It would make some sense if, having had the experience of not being able to use the performance of the Lord Nelsons lest a King Arthur have to substitute, the Southern Railway overcompensated the next time they ordered top-link passenger machines. In any case, I believe a fair chunk of the 'Pacifics working North Devon branches' problem was that once you'd sent a big train from Waterloo to the South-West shedding coaches at every junction, the big engine on the front had to go somewhere, and it was more cost effective to work all the way down the branch than to go on shed and warm a second, smaller engine up to take over the final portion.

One wonders if an eight-coupled passenger locomotive might have been beneficial to the GWR in allowing King or Pacific-type performance with lower axle loads.

Re the ex Southern Pacifics working west of Exeter, the West Country's based at Exmouth junction would've replaced (for example) a Merchant Navy at Exeter Central before heading down to St David's and into north Devon/Cornwall etc.
So they would've already had (in some cases) lighter loads.
The Plymouth expresses would've been longer though and they would've been worked harder on those trains I believe.

As for the (ex)GWR routes, the eight coupled express freight 47xx class did some excellent work on summer Saturday passenger services to the south west. As I think the odd BR 9F did at times too?