Bulleid Pacifics - Past or Present

Probably because there's not a lot of need for class 6. Class 5s are good for most slower passenger services, anything faster or heavier use a class 7.

The main purpose seems to have been to produce a Pacific with a wide firebox but with an axle load of less than 20 tons. A Brit is about half a ton over that limit so can restrict their usage. A Clan is still heavier than a WC/BoB though.

 

Thought I’d posted this the other day but evidently not - I always assumed the Clans were intended to replace the likes of the Jubilees and Scots.

 

Clan - Class 6. Scot - Class 7. Hardly a like for like replacement.

 

Also the Scots had been recently "rebuilt" with largely new major components, so would not have been due for replacement for a fair while. If the Clans had a potential role it was as replacements for elderly Class 6 locos but with wide fireboxes to deal with poorer quality coal. Weren't even the Standard Class 5s originally going to have wide fireboxes? However, if steam had remained in service long enough for a lot of the pre-nationalisation loco stock to have been withdrawn, there can't have been many, if any, potential Clan duties that could not have been worked by either Britannias or Class 5s.

BTW, shouldn't this discussion be on the Clan thread?

 

Rather than build the Clans,, why didn't BR, just relocate some rebuilt light Pacific's to Scotland, didn't they have a lower axle loading compared to the clans? and with electrification in full swing, by then, not so many would have been needed for the SW div's needs

 

Thank you for (a) a good question and (b) bringing this thread back to its proper subject. We will probably never know what went on the minds of Riddles and his team on this particular might-have-been.

 

That was a consideration for doing the same on the Eastern Region, I do think things like familiarity amongst crew’s and engineering staff comes into consideration, don’t forget it’s another load of spares to have in the stores, I know the 1st 10 Merchant Navy boilers were built in Glasgow but how familiar would ex LMS or LNER workshops familiar with things like welded steel fireboxes at the time?
For another example were the 16xx tanks allocated to far north for working the Dornoch Branch still sent south for overhauls?

 

Some did go to the GE section when the Britannias were withdrawn after some cases of axle movement were discovered. I think they were quickly returned!

 

Some went before the Brits were introduced IIRC in order for ER to assess what a class 7 could achieve. There’s a bit about it in Gerry Fiennes book.

 

A day with 34081 in a temporary guise. Support it if you can as the NVR wagon group are a great bunch.

 

https://www.bulleidsociety.org/News/Latest_News.html

21C123 being stripped in preparation for overhaul. Boiler to Leaky Finders at some point, rest to be done at Bluebell.

 

Saw some postings over on FB about this happening but didn't want to post about it till it was confirmed by Bluebell/ Bulleid Society.

 

Sir Keith Park has left the building

Sunnie

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There were in fact big problems with the boilers through until about the late 1950s with wholesale firebox replacement and lowering the boiler pressure from 280 psi to 250 psi was presumably an attempt to solve this.

The solution was to adopt the hugely successful Treatment Integral Armand - 'TIA" - as developed by Louis Armand for the SNCF and rolled out across France during the war under the occupation. This treated the water in the boiler and enabled the French Railways to practically close all their boiler maintenance shops, the post war American built 141R 2-8-2s never had replacement boilers.

Both the Bulleid Pacifics and the 141Rs had steel fireboxes which were common abroad - indeed standard in North America. At 300 psi boiler pressure which was used in American and German locomotives you must have steel fireboxes - copper does not retain enough strength at the higher temperature that goes with the pressure - but the steel fireboxes do require good water treatment.

 

North British certainly supplied the first 10 inner fireboxes and it seems they very probably had some design input: steel fire boxes are stiffer than copper and the stays need to be twice as long - which the Merchant Navy boilers had - round the inner firebox. This was apparently made smaller to go inside the outer firebox and the grate area was 48 square feet - if you do the calculations for how big the grate area would have been with a copper firebox and shorter stays you get 50 square feet. As Bulleid had had quite a lot to with the Cock of the North on the LNER before he came to the Southern and the original scheme for what became the Merchant Navies was for a 2-8-2 with poppet valve gear likely it had a 50 sq ft grate too
Invaluably making them for export North British knew the tricks with a steel firebox and presumably explained to Cocks who was recruited for the design of the Merchant Navies that the extra stay length was needful. There were problems with the Merchant Navy fireboxes before the water treatment was fixed but not quite the stay and cracking problems that have happened with the steel firebox on the boiler for Tornado.

Whether North British supplied anything more to Eastleigh than the inner fireboxes I am not sure but would be glad to know if they did.

NB The fire boxes of the Light Pacifics did crack in the rear corners of the outer fire boxes. Their boilers had a light weight foundation ring made of bent plate and not a solid ring like the Merchant Navy ones. It had not helped the Merchant Navies which were over their design axle load that with the extra width in the water space the wider foundation ring was distinctly heavier.

 

So true...
THE big difference between copper and steel fireboxes is that scale bind to steel just like concrete to rebar. Thus a thin layer of scale leads to lower efficiency and slightly thicker scales to overheat of the steel in the boiler. The scales on a copper firebox can be washed away, but not on a steel firebox.
Water treatment prevent scales from forming and then steel fireboxes are more economical and just as efficient as copper.

 

When the original boiler from Meiningen for Tornado was delivered it had been explicitly made clear that if there were any claims against Meingen works should the boiler prove unsatisfactory they would be dismissed if the water treatment had not been good and thorough.

 

34081 dressed up as 34111 ‘Royal Auxiliary Air Force’ at Wansford for their centenary special. Note the Royal headcode ready for a VVIP on the footplate.

 

Sir Keith Park at Corfe Castle first test run photo Graham Froud

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