Draughting of Jubilees

I understand that when the Jubilees were first introduced, as essentially a taper-boilered version of the Patriots, they steamed very poorly, so it was a matter of urgency to improve the draughting. How would the LMS have decided when they were good enough? Presumably when they became about as good as Patriots. Then, considerably later, BR tried some further tweaks, including double chimneys, presumably giving some further improvement in performance so that (in BR's opinion) no further work was justified.

The effects of optimum draughting would certainly be of interest, but couldn't the same be said of almost any steam locos running now?

 

Fascinating stuff, in looking for further details of the revised system on the King I also found a link to Mr Koopmans book here.... https://www.camdenmin.co.uk/product...ter-second-edition-to-be-published-late-april

 

So, would fitting 2 x 4-nozzle blastcaps to Bahamas help?
i.e a total of eight nozzles

 

yes …….and no !
the Jubs rarely if ever ...really lived up to their true potential . they were not the advance on the Claughtons and Pats that they should have been .

Rooke managed 1650 idhp or thereabouts but that was streets ahead of the normal standard for the class , and no improvement at all over a nominally less powerful 1913 design .
if nothing else , a decent performance should have been more readily accessible in day to day running than it actually was.

Connaught and Pheonix had the 1st two 2A boilers which gave excellent results , but even these two kept the smaller cylinders rather than get the 18 x 26" fitted to the Scots .---and no more were converted . maybe the work available did not justify another 190 loco's of class 7. or had the LMS spent a lot of dosh getting the 6P boilers to perform and wanted a return on that investment . Staniers early work on LMS boilers must have cost a packet to put right

 

Hard to say, if the blast pipe is not wide enough to support wider orifices it is a useless exercise.
kind regards
Jos

 

Steaming with a 3-cylinder locomotive was not really understood, it needs a smaller orifice. Also the earlier boilers had problems with preferential drafting, the combustion products preferred the tubes instead of the flues,
so superheat went down. Playing with the front-end is a problem under those conditions. If preferential drafting is an issue, the vacuum has to be maintained and the backpressure decreased, they did not look further than a double chimney.
kind regards
Jos

 

from what I saw of the Jubilees , which was quite a lot , they always seemed to give better results when being flogged . is that just an uninformed view or is there a reason for that ?

 

Someone on this or another thread stated that 6023 re-draughting was a "resounding success". I am not sure whether that was based on measurable evidence or was simply based on the observation that the loco could haul a lengthy train uphill and still have steam to spare. If you look say at or , 45699 is taking 11 coaches over Shap summit with steam feathering from the safeties. Prima facie therefore it is making sufficient steam on what is perhaps one of the more testing stretches of mainline, so I wonder what problem improving the draughting would overcome?

 

Apparently, the LMS worked out that they needed 91 Class 7 (BR power rating) locos post war. The seventy parallel Scots were already at that, the Baby Scots were coming up for major boiler work, while the Jubilees, whatever their problems, were still newish engines with newish boilers, and it's inconceivable that so many boilers would be withdrawn at such a young age. Simple mathematics then dictated the rebuilding of 18 Baby Scots with the 2A boiler was the answer.

 

6023 was not making steam at all, getting it to work was already a small victory. Then the choice of the orifice size appeared successful as the crews are unanimously in their praise. So it is not based on measurements. As for 45699 over Shap, any locomotive can steam if the orifice is small enough. What CMO's in the past wanted was the largest possible orifice so that the smallest part of the effort of the locomotive went into exhausting. Imho that should be the case in heritage also, since most of the locomotives are 60+ years of age and could use a little extra care.
Kind regards
Jos

 

Well put. In Campbell Highet book All Steamed UP ,he was in charge at 27A Bank Hall MPD , Liverpool. I quote from the book, The cream of the Bank Hall stud was with-out doubt the three 6P Jubilees,45698 45717 and 45719, They were mainly employed on York and Leeds services and of the trinity 45698 was outstanding .Their reliability was a by word among the staff. .The staff found it a pleasure to work on these loco's. Un quote. The 3B Bushbury Jubilees that worked the Wolverhampton -Birmingham to Euston 2 hour trains were also held in high regard. Bristol to York and later thro' to Newcastle with 22A Bristol Jubilees was no small run, Manchester -Glasgow similar. Any one know on what regular trains they didn't perform admirably ?

 

Probably not. Outstanding performances tend to be recorded; indifferent or worse ones less so. I always remember a driver telling me at Liverpool Exchange station in April 1968, 'Unless it's an express job, I'd rather have a Black 'un than a 5X any day.' This is probably a true record of the situation although a little unfair to the 5X. These were designed as express types while the Fives were true mixed traffic engines. But the 5Xs were used on a lot of goods workings.

 

Jubilees are fitted with Ross pop valves They don't t feather. They are either open or shut. They can leak, though, but that can be the case at any pressure.

 

Good point.

 

This isn't about saying that Jubilees are bad machines but that there is potential for Improvement, clearly BR thought so, but BR's attempted improvement might also have been short of the mark .

 

As I understand it, the main front end issue with the Jubilees were simply due to Stanier not having three cylinder experience, and adopting Swindon practice for the blast cap, etc. Being a great man, not afraid to learn from his mistakes or from others' experience, he let Coleman et al sort them out.
It should be remembered regarding their boilers that Derby (or Crewe, or especially Horwich) had never had trouble getting boilers to steam, the problem was they were horrendously expensive to maintain. The Swindon type boiler was much better on maintenance, but wouldn't steam at first, until they replaced the tubes with a Horwich type arrangement.
I'm afraid that's were SGC's argument is flawed - Claughtons may have put in good performances (although I don't think they did often enough, love them though I do), but their original boilers wouldn't steam, and with the larger replacements their frames couldn't take it. On maintenance costs the Claughtons and even the Patriots were not so good.

 

I can't agree with that Andrew . the early performances of the Claughtons' verged on phenomenal . they were double manned with picked crews . Driver Button ,of Jeanie Deans fame finished his time on one.
like many new types , crews took time to learn best practice . with a crew who knew their business - and in LNWR days top link crews did- they could produce all the steam the cylinders could shift

the problem the Claughtons had was steam leakage past valves and pistons as a result of the single piston ring required by the Schmitt patent as a condition of the use of his superheater .
this was only resolved in the late '20s when the Webb type multi ring pistons were fitted .
the Scots had the same problem - and the same solution

 

I'm looking forward to seeing how well Bahamas goes.

 

Derby (Midland) boilers were not the best steam producers and they generally got away with it by the railway being a little and often line with lots of short trains. The S & D 2-8-0's were good at dragging heavy loads over the Mendips but the further up the hill they went, the lower the boiler pressure got. Experience of 53809 on the NYMR was no different. All this is getting away from the Jubilees, though.

 

Of course GWR boilers steam just fine, so obviously something went badly wrong in translation. I think someone mentioned Midland standard tube sizes?