Britannias & Derby design

Hi chaps just a query, interested Ivatt had decided upon 10 standard types for all LMS steam including Express Passenger all with just 2 outside cylinders. Just wondering if anyone here knows how much involvement he & Derby team(if any) had in the design of the Britannias, and if it was similar to any LMS proposals. Seems he had much work in the 2MT & 4MT tanks & tenders, not to mention maybe inspiring Caprotti valve gear on the 5MT. Thanks in anticipation.

 

Given that the three executives involved we're all ex LMS (Riddles, Bond, Cox) Derby and Horwich inflences we're very much to the Fore. E.S.Cox was definitely involved with the LMS Standards idea. The initial visuals of the standard Pacifics we're done by Frank Carrier the Derby office.
E.S Cox s books ) Locomotive Panorama, Standard Steam Locomotives, Speaking of Steam, will give you an insight, as will Bonds book ( a lifetime with locomotives ?)
or the RCTS books esp volume 1

 

I wasn't aware that Ivatt planned 2 cylinder Pacifics, very interesting. Tom Coleman did most of the design work under Stanier and he had his own list of LMS standard locos which would have included a 2-6-2 along that lines of the Gresley V2, another interesting 'might have been'. Derby was responsible for the Brits and Clans, and it was Coleman who suggested the Britannia boiler should have a greater barrel diameter at the firebox end to get better free gas area. According to Langridge there was 'no mutual respect' between Ivatt and Coleman, which is sad, but there we are!

Dave

 

Indeed, on further reading of the bond book and others the Planned LMS Standards are broken down into Existing (ivatt/stanier) and new (coleman and Cox designs) including the above mentioned 2-6-2, also a 4-6-4 and 4-8-4 class 9's ! but i dont recall seeing 2 cylinder class 7 or 6 Pacifics.
One suspects that Messrs Cox and Bond Loved the concept of the light Pacifics and 2-8-2's designed by Bulleid even if they we're flabbergasted by the over complex realisation of those ideas..
and both said in retrospect that the change from 2-8-2 to 2-10-0 was right, but that the 6/7 Pacifics would have been better as 4-8-0/ 2-8-2
... The British Standard Pacifics mixed in lots of good ideas and are decent engines but as finally built they are a little ' Confused' and fell short of what their designers originally intended.

Please whats the Langridge book ?

 

It's 'Under 10 CMEs' but I can't remember which of the two volumes.

Dave

 

As for the 5AT a compensated 4-6-0 would have been be a pretty solid starter...

 

Stanier pacifics did it day in and day out for over thirty years! There is no reason why a Bulleid couldn't do so also.

 

And if you drove one day in and day out for thirty years im sure you would get quite good at it...

 

Depends on the design specification ! The Duchesses were specifically designed for slogging up Shap and Beattock hence the loco weight (adhesion) of 105 tons whereas the unrebuilt BB/WCs were only 86 tons and the rebuilt ones aroiund 90 tons; even the MNs weighed only 98tons with consequent inferiority of the adhesion of the Bulleids

Many of us can still remember the fireworks of 34092 on the S&C but one could ask if that cascade was due to the power of the Bulleid or the fight for adhesion ?

 

I merely make the point that John Stewart's comment, with no disrespect to John intended, about pacifics IN GENERAL somewhat ignores the fact that they did go up Shap and Beatock regularly in all weathers, too many carrying wheels or not. This does not imply that there were never any adhesion issue, or that a Bulleid light pacific should be able to do the same. Its smaller size would mean that it could not be used on similar loads, but that does not preclude its use on loads comensurate with its size.

Pacifics do have adhesion issues, but give the advantage of a wide firebox and hence larger grate, which was essential for the work that the LMS (and LNER) had in mind. Substituting a 4-8-0 brings in the problem of a narrow firebox and limited range, while making it a 4-8-2 gives a very long loco which won't fit on an existing turntable, together with overlong boiler tubes or extensive combustion chambers and smokeboxes, not to mention additional weight; or very reduced wheel sizes giving high piston speeds and reciprocating masses to be balanced at the sort of speeds envisaged at the time .

A simple statement of 'it should have had eight coupled wheels' becomes a lot more problematical on the drawing board. A pacific it was then, and what we have now. If we cannot use a Bulleid on Shap because it's a pacific, it must follow that you shouldn't use a Lizzie also.

 

Perhaps both... without going into the physics adhesion will anly stand so much force and then its gone completely, which is why Clans we're supposedly better starters than moast pacifics
But factors other than the adhesion weight and potential starting TE factors are at work, namely the regulator type and how used to it the driver is...

 

Stainier pacifics had around 17% more adhesion than a light Bullied.

 

So what we need is a pacific that boils like a Bullied and clamps like a Clan!

 

Stop that before we get onto the 'Shouldnt the WC/BB'S have been rebuit as 2 cylinder machines ?' chat

The boiler for new Clan will be most likely be a welded take on the BR2 boiler, dont know that theres much that can be tweaked other than draught to make it 'boil llike a bulleid, though....

 

Some syphons maybe?

 

Not saying that they are a bad idea ... but Wasnt a bulleid Boiler 'de syphoned' and found to be none the worst ? or was that a V4...
Tube wall boilers anyone ?

 

In a thread I've seen on a board somewhere in the last day or two but cannotnow find, someone was putting forward the suggestion that the Gresley P2s were underboilered because they were 8-coupled rather than 6-coupled, and that rebuilding them as pacifics led to better matching of their boiler size with, er, the number of driving wheels! Discuss! (and if someone could find the post it would help!)

 

I'm struggling to see what the NUMBER of wheels has to do with it. The boiler must provide sufficient steam for however many cylinders of a given bore and stroke to turn the wheels of a given diameter. The number of these wheels is immaterial.