Discussion in 'Steam Traction' started by Ian White, Oct 31, 2017.
Put a king boiler on it and name it Roxanne...
(Well, what else would you name a Sting...?)
This is precisely why I can't read Tuplin's work - Far too much of the "Here's what they should have built" - I have tried to complete one of his books, but gave up and donated it to the VCT.
Paint it blue and name it Gordon...
I guess if you read Tuplin's "here's what they should have built ..."
maybe you arrive at "and here is one very good reason why they didn't!"
(Fantasy loco design is lots of fun, if only you ignore those pesky constraints of loading gauge, axle load, material properties, operational requirement, drawing office capacity, available components and patterns ...)
Tuplin's works today would be well suited for internet forums with his might have been locomotives and amazingly detailed verbatim conversations from many years past except he didn't devote page after page to what colour the may have been's should have been painted.......
For a professional engineer Tuplin could be surprisingly amiss on the detail. He says, for example, that even though the Castle had to have a lighter boiler than the Std 7, a Std 7 boiler should have worked on the Saint, because the Saint was lighter than the Star, missing the fact that the difference in Star and Saint weights was, predictably, on the front bogie, and the driving wheels carried the same weight on both.
Well it’s green so you might get away with Henry
I find Tuplin's books readable and informative, but am conscious that he can be over-strident in putting forward his pet viewpoints and that some of his alternative design suggestions are "top of the head" and not fully thought-out. Even the most competent engineers may of course drop clangers, but these would usually be challenged and corrected in the real world before damage is done. Many CMEs must have issued instructions for designs to incorporate features X/Y/Z only for the Chief Draftsman or other subordinate to come back with "We have a problem ......"
I notice that, just like with amateur enthusiasts, Tuplin's fantasy designs are mostly for express passenger types. I don't recall Tuplin redesigning an 0-8-0 or 2-8-0 goods engine.
Tuplin described Midland Red as magnificent but I think his preference was for LNWR black, which he described as having "stately dignity". He reviled the colours of the Bouch/ Fletcher-era NER locos that he saw in York Museum ("Garish colours and blatant lining .... flaunted Victorian taste at its lowest level ...."). I'd better not go any further off-topic!
This was something I never had heard about before. So thanks a lot for interesting reading and the illustration bluetrain!
It must be another interesting project for modellers (I wish I was some of them)
Although the design rationale for the Hawksworth Counties has been questioned, one consideration that has been suggested was to provide about the same tractive effort as the Castles. To achieve that while keeping the same width over the cylinders as the Halls required both increased boiler pressure and the new driving wheel diameter of 6'3". I am wondering whether a Super-Saint with a no. 7 boiler would have had any higher TE than an original Saint, and if so how that would have been achieved.
Well given that the only attribute of a boiler that contributes to tractive effort is the boiler pressure (TE = No of Cylinders x ((Cylinder Diameter squared x Cylinder Stroke x 0.85 x Boiler Pressure)/ 2 ) I don't think you'd be able to increase the tractive effort by putting a no 7 boiler on top of a Saint chassis and changing nothing else, as I believe the no 7 and no 1 boilers both run at 225psi.
What this might have been able to do is increase the steaming capability of the boiler, meaning you could increase the cylinder diameter as there would be an increased steam supply to meet the increased demand of larger cylinders, and increase the tractive effort that way. You'd also need to make sure things like there was optimum draughting built into the design to get the most out of it (although I think Swindon were, on the whole, pretty good at getting this spot on)
Driving Wheel diameter also play a role in tractive effort.
For two cylinder locomotives the general rule in Europe was that five revolutions per second was max legal speed
So for a GWR Saint-class with 2.045m (6ft 8½in) drivers, that formula gives us 2.045 x Pi x 5 = 32.1m/s x 3.6 = 115km/hr (72mph).
The usual (steam-era) British practice was in fact to assign specific speed limits only to routes rather than engine classes. The two-cylinder versions of the German Class 01 and 03 Pacifics, with 2.0m (6ft 7in) drivers, seem to have been given speed limits slightly higher than the formula indicates - 120km/hr (75mph) for the early batches and 130km/hr (81mph) for the later batches (which had larger bogie wheels).
Back on the GWR, I believe that the 4-cylinder Star and Castle classes were normally preferred to the Saints for high-speed duties.
The two-cylinder 01 and 03 classes were designed for 120 km/h and later allowed to run 130 kmph.
The very high maintenance costs when running that fast , caused the building of three cylinder 01.10 and 03.10 (and streamline as well ) after 1937 and allowed 140 kmph.
It was measured that steam economy was 6% worse for three instead of two cylinders doing same job .
The 01,01.10 and 03.10 had 1000 mm bogie wheels and the 03 had 850mm.
Of course, how could I forget that?
My guess is that the advantage of a larger boiler would have been seen primarily just in terms of enhanced sustained steaming rate. Though it is interesting that a significant, though largely invisible, trend between say 1920 and 1950 was changing boiler proportions so as to have more superheater area (and concomitant reduced tube heating surface) - i.e. higher superheat was a better route to sustained power output than higher sustained steam production.
There are a couple more Tuplin "fantasy" designs at Post #63 on this thread:
You will be amused to see the Tuplin version of a Chapelon 240P! This has four 20½in (520mm) diameter cylinders, supposedly within an overall width of 8ft 8in (2640mm). The LMS Stanier "Black 5" 4-6-0 was carefully designed to fit just within this width - but it only has 18½in (470mm) diameter cylinders. The Tuplin 4-6-0, with a 3-cylinder layout similar to North Eastern S3 (LNER B16) and Prussian S10.2, is more plausible, but connecting rods may need to go inside the coupling rods to bring the cylinders closer and keep within width limit.
I've acquired several Tuplin books from second-hand sources. I do like his writings, but need to be careful not to believe everything that I read! There is an assessment of Tuplin here:
First Saint seen on the mainline since 1953 today!
I see that she is so beautiful that she has been stopping traffic in its tracks in Bridgnorth today (or just arrived unfortunately during the school run!)
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