Bulleid Pacifics - Past or Present

Best to keep it in the relevant power classes, methinks. I don't think we really know for sure (despite the 1948 trials) what a comparison between a 'Black Five', a B1, or a Std. class 5MT
would be like. A Bulleid would best be measured up against a 'Britannia' (although would the number of cylinders affect this?) or a 'Scot'.

 

There is a real danger of this part of the thread continuing ad nauseum. But I do feel obliged to point out that, as you can read in the original letter, the driver was put on an immediate charge of exceeding 120 mph. Not based on rumour, but passing times. The control office took strong decisive action on the day, and the driver was stopped, taken off the footplate, and relieved before he even reached the end of the journey. There aren't many examples of that happening.

One can discuss speeds and horsepowers endlessly, but the fact is that there is no actual fixed limit for the output of any steam locomotive. In fact the output capability increases with speed until the steaming capability becomes seriously challenged. The steaming limit, as on other classes of large engine, of the Bullied pacifics was never really determined simply because if the fire and everything else is right, put simply, the boiler can always deliver more steam than the engine can use.

The thought of an engine achieving speeds of over 120 mph does initially sound rather far fetched. But it is only 15 mph higher than the sort of speeds achieved in the last year or two by very run down engines, and of course there is the well known documented example of Mallard. That was my initial thought too, when I first heard this story very many years ago. But did hear it directly from the mouth of a very conservative driver who was based at the same depot as the people concerned, and who had himself been involved in pushing the limits of those engines. Having amongst other things fired one all the way to Inverness under observation. He was in no doubt at all about the accuracy of the story, and neither was anyone else I have heard talk about it that were around at the time. That's good enough for me.

 

I've said what a fanatic of Bulleids I am.

Yet the "exceeded 120 mph" on that route means that light pacific had to be a more powerful and faster machine, (and you just cannot separate speed from power at those speeds), than a Duchess and even Mallard, (which had the benefit of a long and at time steep downhill grade). Even in fact up to the standard of the A1 Atlantics and F7 Hudsons of the Milwaukee road. Two classes that exceeded virtually anything ever done in Europe including, possibly, (still not proven, may never be), the highest speed.

If anyone wants to believe that was the case for 21C160 then go ahead. You will not be alone in supporting a particular steam loco's high speed claim.

Join those who preserved a 19th century USA unsuperheated 4-4-0 because it reached 112 mph in 1893, (later tested by European timers as being capable of just over 80 mph) Join those who are adamant the PRR E2 Atlantic reached 127 mph in 1907, with that loco preserved as a the world steam speed record holder, (not in fact, they renumbered another of the same class and preserved that!). Join those who are adamant that the enormous PRR duplex reached 141 mph on a normal service train. It's supporters just will not believe the work done by one of the worlds leading experts on steam loco performance in proving it couldn't have generated enough hp to have got to that speed as a light engine. Then we have the PRR E6 4-4-2 No. 460, again preserved because it "reached" 114 - 115 mph" in June 1927, on a run where it also "exceeded 100 mph" several times. I am still searching out data on that run because there is a chance it may just got to 100 mph once on the journey. And so it goes on. The list is large. Now extended with 21C160's effort!

 

I'll get that done shortly. And you are spot on to use the word "achieve". It 's not just sustaining that speed, It's the enormous ihp needed to accelerate to that speed.

 

Oh dear! You just can't tell some people can you.

The BB/WC grate area is less than 10% different (by 3 square foot) from an A4, with a better steaming boiler, and the tractive power i.e. swept cylinder volume per unit distance travelled, is nearly 90% of the A4 - with better valve events - so very comparable. I'd say that makes it self evident that the potential maximum power output of either engine would not be all that different, and actually the Bulleid machine might even turn out to be the higher by virtue of the higher maximum boiler output. Yet someone seems to be saying on here that there is clear proof (from the size of the engine) that it is impossible for one of the Bulleid light pacifics to reach 120 mph. Well, most of the professionals that operated those engines on a daily basis disagree. I know which I go along with.

 

To get to 120 mph on the racing stretch Worting Junction to Farnborough on a reasonable length up Salisbury fast train would require in excess of 4,400 ihp. For the "exceeded 120 mph" we are above 4,500 ihp. Coal and water consumption over just that 16 miles stretch would have been circa 5 tons! And as it would have had to have been a superlative run up from Salisbury to have got up to a decent starting speed at Worting Junction there is a strong possibility the train would have needed to have stopped some way before Waterloo for the loco to fill up with coal and water! If the train had run lightly up from Salisbury to Worting to save on coal and water, then the extra acceleration needed after Worting probably takes us over 5,000 ihp!

No UK steam loco has ever got near 4,000 ihp. Not even the most powerful UK express steam locos ever, the four cylinder Duchesses. I believe there is a record of one of them having got to 3,500 ihp once.

The most powerful of the Bulleids, the Merchant Navy class, has only once been recorded at over 3,000 inhp. Then only marginally. There are several instances of fractionally under 3,000 ihp.

 

Well, if City of Truro can do 100mph... :-$

 

i wish i could answer you there SD as you have cut to the chase or thrash but a4's could certainly produce in excess of 2,100 ihp...
what we are all failing to agree on is that with 6 coaches down stoke bank a merchant navy could theoretically manage 120mph plus, but on the actual stretch of line with the train it had on the alleged '120mph incident' would have been physically impossible for the same loco ....or an A4, or a Duchess...even if a spinach enhanced popeye was firing.... (oil save you's Olive/Malachite/Brunswick/whatever... yachyachyachyach)

PS Which of the rebuilt bb/wc's is likely to go mainline first ?

 

With a six car train the ihp obviously comes down, but still needs to be way above the best a MN can pacific produce, let alone a light pacific.

Can't find the Mallard inhp in amongst my chaotic filing system! Somewhere I do have it tabulated over various parts of the descent of Stoke Bank. But from memory some way above 3,000 ihp. I cannot remember if that run was the peak ihp ever from an A4. On a light train and down a much longer and significantly steeper down grade than the LSWR racing stretches the London side of Worting Junction . Including 3 miles down at 1/178 and more than 4 miles at 1/200.

Not connected with your question Saggin' Dragon, but I'm going to stop responding on this thread to this issue now. Continuing here is going to achieve nothing. I have been in these sort of debates many times via email during my years of research where people see a speed number that gets printed for a particular loco. A speed way, way above the maximum hp capability of that loco. Yet they never let go of it, rarely accepting that hp has always been a limiting factor for steam loco performance, and always will be.

If the debate needs to go on it should be on the thread I opened recently for high speed steam locos, rather than clutter up this thread with posts that will take it increasingly off topic.

I will finish here with an example of how professional railwaymen in the USA recorded one of their high speed steam runs. No criticism of them. This is how people unused to the mechanics of using train passing times for other than their normal purposes can get so far off the mark when trying to calculate a maximum speed. This relates to the run I mentioned earlier with a PRR Atlantic 460, which was preserved for reaching 114 - 115 mph, (depending on which report you read). A flyweight train yes. But you do not get speed fluctuations with a steam loco over fairly short distances of a few miles each as shown by these successive section average speeds from the data used by PRR to calculate the maximum speed.

84 mph
108 mph
57 mph
76 mph
114 mph
84 mph
82 mph

This on a train running flat out with a clear road for a very special purpose.

My provisional analysis shows that the whole section covered by the above averages could have been done without speed exceeding 90 mph.

Yet the loco is preserved as a record holder!

All it wanted to get an idea of the maximum speed of that train was for someone on board to have recorded times to the nearest second at a fixed point on each main passing point for which a distance, (nearest tenth of a mile would do), was known or could have subsequently been calculated. Depending on the distance between timing points, (the further apart, the harder accurate maximum speed calculations become), that could have at least got the likely maximum speed range to within plus or minus 5 mph(ish), for that run where sustained fast running was the order of the day.

 

I realise you wish to withdraw from this thread but on the question of the peak HP ever from an A4, I have seen a log from a run by 60022 climbing Stoke Bank northbound. On this run it had gradually lost speed on the climb but then accelerated the train as the climb continued. The calculated HP was IIRC at least equal or slightly above that achieved by the same loco on its 1938 record run. Typically I cannot find the book so cannot quote the exact details.

 

As promised I've moved this part of the thread to the High Speed Steam Thread

 

Back to the thread, and apologies if this is mentioned already, certainly lots of interesting footplate anecdote from the past, but how do the guys running/ maintaining the unrebuilts find them today. Tangmere now and City of wells a few years back both seemingly strong, reliable engines, but is that down to;
'better than original' restoration, (weldings come on abit since the forties)
attentive servicing between runs,
TLC from support crews,
or even being driven differently ?
Are they more expensive to up keep than the Miscellaneous Staniers at Carnforth and are they really that heavy on coal ?
is Castrol magnatec the answer to all your prayers?


City and guilds in Metalwork
Qualified Vet'nary nurse

Cat needs Weldin ?.... im yer man

 

Bulleids were strong and reliable first time round. They were just more complicated than the maintenance staff of the time were used to.
City of Wells and Tangmere, like all current mainline steam locos, have/ had a dedicated maintenance team and support crew who know the loco inside out, and maintain it accordingly.

And, handled correctly, they are one of the most efficient steam locos ever built.

 

Bulleid fans will enjoy a visit to the High Speed Steam Thread now!

I had a long lost log I timed behind 35003 emailed to me tonight. Possibly only the second time a UK steam loco was recorded touching 100 mph twice on the same run. And maybe even the only time it is has ever been recorded on a Steam hauled normal service train in the UK. That is now being checked out by the email group I am in.

As mentioned on the other thread. I will tabulate and post on that thread the three runs I timed behind 35003 in 1967, (one from the footplate), where, in total, 4 separate 100mphs were logged!

 

And they did need handling correctly, but some of the crews loved them. I shall always remember the day we had original condition 34002 "Salisbury" on the up ACE. Quite a challenge for a light pacific on a train always booked for a much more powerful Merchant Navy. But it arrived from Exeter on time and Fred Hoare, who loved the original Bulleids, gave me a super run up to Waterloo. He had to make up several minutes in the schedule for a relaying slack, which he did. Only to catch a long signal stop near Woking! Very sad not to have pulled into Waterloo on time. Net time not much more than 76 minutes on the fast 80 minute Merchant Navy schedule. That was the day he "confessed" to me he had done 100 mph with an original Bulleid. Down through Broad Clyst, "So fast Bryan I could see right through the forest next to the track". A real gentleman and a driver who knew his craft so well. Especially when he got into the drivers seat of an original Bulleid.

 

Hence the nickname "Stopemall Junction".

 

Yes, Fred Hoare always used to say at Salisbury, "we'll be on time at Waterloo, apart from Stop All Junction"!

Us enthusiasts used to joke it was because the signalman were all photo enthusiasts, but only had a Brownie 125, (max shutter speed 1/25 sec). So to get sharp photos they had to stop every steam hauled train that went through!

Has it changed? LOL!