No. 1 Boiler / 4-row Superheater

[6892 Oakhill Grange]

Does anyone know if a 4 x 7 superheater was possible on a No. 1 boiler. For a long time I have thought not but a recent view of a picture of Lady of Legends boiler seemed to suggest that there was sufficient space on the tube plate.

 

Once you have pondered that one, could a King Boiler (is that a No. 9?) have a 5 x 8?

[DCB]

The King boiler was a S/12      9/10 /11 were boilers for the absorbed locos from the 1923 grouping  The S/10 being a short firebox short barrel version of the S/ 2 used on the MSWJR 0-6-0s and later used on 2251 and 94XX.  I think the no S/9 was an updated 2021 class domed parallel boiler, no idea what the S/11 was.

I don't think there is enough room in the S /1 smokebox for the 4 X 7 Castle/ County superheater. You could recess the front tube plate into the taper boiler so you would have essentially a straight throatplate County  or use the "half cone" arrangement of the early Saints and Black 5s/ Jubilees to get a larger front tube plate, and larger diameter smokebox but that would "Non standardise," the boilers making them unusable on the pre 1944 locos without new cylinders. The Modified Halls would just need County type smokebox saddles to take a larger smokebox while retaining their existing cylinders.

 

 All the GWR designed 4 row superheater locos needed new tube plates, the majority had new boilers, I think only the S/15 County boilers had new tube plates in an existing shell, 70 new 4 row Castle boilers and 34 new 4 row King boilers were built.  

However why would one want a larger superheater?  There is plenty of data on the improved performance of higher superheat locos when being thrashed, and plenty of anecdotal evidence that Superheater engines needed more time to "Warm up" than non superheated locos.  Very few no1 boiler locos were being used on long through runs by the 1940s, so where would be the advantage.  The King needed all the help it could get as it was built to the limit of the loading gauge, though some people suspect it was rather over weight when fitted with the 4 row boiler.

However when the limiting factor was weight then the advantage of superheating, let alone high temperature superheating is less clear.

For example, The original non superheated Saints and the later superheated Manors weighed almost exactly the same.  I don't think anyone would claim the Manor was the better loco.  But the Manors could have been better locos if they had had the non superheated No 1 boiler.  A non superheated Grange with the thinner weight saving footplating of the Manor (and King).    

[HowardGWR]

 

For example, The original non superheated Saints and the later superheated Manors weighed almost exactly the same.  I don't think anyone would claim the Manor was the better loco.  But the Manors could have been better locos if they had had the non superheated No 1 boiler.  A non superheated Grange with the thinner weight saving footplating of the Manor (and King).    

David, do you mean that a non superheated No 1 would have put the 78s in the blue line capability?  Excuse me if I misunderstood.

[DCB]

HowardGWR  

Yes. According to the Russel book the early 6'8"  2 cylinder 4-6-0 with the non superheated number 1 boiler were within the Blue 17 T 12 cwt  Blue Limits except they were 8 cwts over on the driving axle. They also had less weight on the bogie than the Manor.  So logically a non superheated No 1 boilered  5'8" 4-6-0 could have met the blue route criteria, especially as 5'8" wheels are lighter than 6'8" wheels.

Perhaps the side window cab and heavy screw reverser would have had to be sacrificed but it is pretty certain Churchward's 1902 4-6-0 updated with a long cone but non superheated no 1 boiler and fitted with the smaller 5'8" wheels would have been within the 17T 12 cwt Blue route restriction.