P2 Locomotive Company and related matters

A scale model will need to account for scale wear and tear. Its imperitive to understand the forces and stresses on the individual components.

As mentioned above, FEA and motion studeis, potentially even fluid dynamic study, would be a wise, and prudent, move by the trust if there are any doubts about the Valve Gear. £50k would actually pay for this quite comfortably.

If the gear was wearing or failing in service, it is crucial to understand why that was, before metal is cut and precious capital is expended. If metal gets cut before the engineering is understood, that is the definition of poor project management.

From the P2 page.

The target for 'The Valve Gear Club' is £300,000, with supporters making donations of £1000 as a lump sum or in monthly installments of £100.

We hope to raise the initial £50,000 in the first half of 2024 to allow for the manufacture of a prototype cam box and test rig, with the intention of the prototype then being fitted to the locomotive. Please sign up below using the online form, or download forms to print and return to the Darlington Office.

If it were me, id be taking the £50k, or less, and employing some engineers to actually do engineering first, not testing, and iron out any bugs on the computer. Id much rather see areas onf high stress on screen, adjust the geometry, on screen, re-run my studies, on screen and then create a design that is fit for purpose, on screen, before cutting a gram of steel. That way, when i do get to curring steel im going to be confident in what im making.
Why would you fit a prototype to the locomotove?

Further, why was it the case that these designs didnt survive the rebuilds? Waht was it that put off the engineers at the time? If it is an underdeveloped design, that needs refinement, then it makes no sense whatsover to build one of the same design just to test what you know is deficient. Thats a waste of time and money. Do the engineering first, figure out the issues, then build a prototype of that design and see if the results match the engineering analysis.

At a first glance, and it is a glance, the likley issues here wont be in the worm drive box, or the drive shafts, but almost totally in the valve drive and return. In the era of internal combusion valve technology has come on leaps and bounds. Do the valves need to be driven mechanically by a shaft? Why not use hydraulics to control valve events? VTEC on a steam locomotive anyone? Why persist with a design which clearly didnt last in serivce without going through the engineering of it with a fine tooth comb? Why? That would be a mistake.

Trawling the web for info, delivered the below.

Never ceases to amaze me what can be found on the internet.

Dockstader Valve Gear Simulations

An unusual valve gear ill tell you that : r/trains

PRR #5550 Running Gear - B2 Rotary Cam Poppet Valve

The more reading I do, the worse this gets. LNER Encyclopedia: A History of Lentz Valve Gear on British Steam Locomotives

Mono-bloc valve box as fitted to No 8280

The September 1927 issue of 'The Locomotive' reported that "The goods engine which we fully described in our issue of February 1926, has been in continuous service for upwards of two years, and the poppet valve gear has not, we are informed, given the slightest trouble, nor have any repairs or renewals to any part of it been required". (9)

No 8280 was converted back to conventional piston valves in September 1937.

What do you mean its fine but we are still remving it? WHAT?!

In his 1947 paper to the Institution of Locomotive Engineers, Spencer noted that "As originally turned into traffic No 2001 had continuous cams, but, after approximately 10,000 miles' service, trouble was experienced owing to point contact of the follower rollers breaking down the case-hardened surface of the inlet cams. Stepped cams were therefore fitted, but the valve events were consequently restricted to six ranges of cut-off in fore gear. … On an engine of such high tractive effort the large difference in power between each cut-off position proved inconvenient and was not conducive to economical working". (15)

For various reasons Cock o' the North was not a success on the route it was designed for. A major criticism was the high coal and water consumption. Bulleid defended the engine in the discussion which followed Spencer's 1947 paper, saying "the fundamental reason for this was that she was not properly used. Instead of working trains well up to her capacity over long runs she was employed in a service such as Edinburgh to Dundee, went to Aberdeen and hung about there, and did very poor mileage per day, with the result that she showed a heavy coal consumption, most of the coal being burnt through misuse rather than in working trains".

Ah ok so blame the crews, but dont look at the engineering. Got it. Great work!

Clearly, this design needs work. Do it now, before pressing in to service something which is evidently not fully understood. It can be understood and remedied through the application of good engineering.

What is the exam question here? Control valve events.
Nowadays there are multiple means by which that could be done. It doesnt have to be mechanical. The whole rotary thing is nice, but if you are unprepared to do the engineering to get it right, then why not have a hydrualic system. The worm drive drives a pump, that pump delivers fluid to the valve servos, there is an intermediate control box that is electrically controlled.... See where im going here? Its just as smart to clean sheet the whole design if you are unwilling to actually figure out the mechanical issues leading to why lenz was eventually dropped.

 

Do not think there is any doubt that a full virtual, and then and then a real, model would be money well spent.
Some of your your history snippets are not really pertinent.. the design of gear intended for the new P2 is 25 years of development beyond anything the LNER ever used.

 

Appreciated. Im going in to this cold. What is the design they are proceeding with and why is it flawless?

 

The Locomotive, as an industry journal reliant on industry adverts, was inclined to be enthusiastic/uncritical in its descriptions. As to why a valve gear was removed or not adopted more widely, I think it is equally likely to be an issue of critical mass i.e. unless there were enough locos with the gear to justify the investment in skills/facilities etc then the safe choice is to go with the tried and tested technology, even if theoretically inferior. As to non-mechanical solutions, I am sure I read somewhere that compressed air was used in the Cossart system (presumably a very reliable valve gear in view of its use on the Paris suburban services) but perhaps it was used to close rather than open the valves, as the loco had mechanically driven camboxes.

 

the design is the Franklin type B ( rotary drive) poppet valve gear... is it Flawless ? afaik it was never taken off a loco it was put on... but that might be just a time and place thing.
IIRC the American T1 New build also intends to use Franklin B
Patent docs which have general arrangement diags here:
http://www.trainweb.org/tusp/patents.html

 

I suspect, as @huochemi says, "The Locomotive" is being uncritical (don't bite the hand that feeds) but it is in any case worth noting that there is ten years between that article and conversion back to conventional piston valves.

You have to look at the capacity of a drawing office and workshop to do work for locos that fit into the "flawed, but not outright dogs" class, particularly unique / one-offs. If 8720 was still basically doing a job, even if not as well as the more conventional members of the class, then you might defer a rebuild until some other reason required it. For example, the time to rebuild along conventional lines might have best made sense if the entire cylinder block needed replacing anyway. With an experimental design, only if it is drastically inferior to the original (either in coal cost or availability) might it be worth removing the modifications once any trial running is complete. If it is just so-so, you wait until rebuilding would be due anyway.

To be fair to Bulleid, coal consumption on locos - and particularly big locos - is dependent on how they used. Get the diagramming wrong and, if you measure total coal consumption (rather than just what is used on the run) then it will look poor due to standby losses.

Tom

 

If your prototype is full size, made of the same material and you can satisfy the fact that it has not suffered undue or irreversible wear as a result of testing, what would be the justification for not fitting it? The original statement might be better presented as 'the first of the assemblies will be subjected to final confirmation testing before fitting to the locomotive'?

Leaving a unique loco that was capable of 10 years useful (but not groundbreaking) work alone and making it standard at a convenient opportunity seems sensible to me? 10+ years of service out of an experiment that would require its own specific maintenance and inspection regimes is pretty good going for a one off in what was already a small class of locomotives.

Were the crews being blamed, or the rostering? I don't think you would argue with the statement; 'Per delivery, the overall efficiency of this HGV has been disappointing while it has been used for the village post round'. I wouldn't need to get it in for testing to inform you the work being done with the machine is biasing the data against it. I think it's generally accepted that one of the reasons the P1's were considered 'uneconomic' is because they weren't able to be used on the weight of trains that they were capable of shifting.

 

Correct. They were intended to haul a 100-wagon coal train. It's therefore a pity that there were no refuge sidings on the ECML that could hold a train that long...

 

You can see that all on FEA, wear and tear, material analysis. A design of mine, of a high speed oscillating mechanicism, required wear rates for low friction "plastic" bushing. They're still running after 25 years use ..one of my successes among "failures"...

 

Interesting from that piece in The Locomotive that the loco had six positions of forward gear, assuming these were in the range of 25-75% cut-off, that gives you steps of 10% each time, was that really so inefficient?

 

The Tay Bridge situation of only working there to Ferryhill is odd to me, im guessing part of that was the constraints on MPDs in and around Edinburgh, that aside, there is little about the Aberdeen-Edinburgh run that is post round, its a tough route.

I suppose drilling down in to this, the place to start is on the numbers. What are the valve duration events like, compared to piston valves? How are the volumes, compared to piston valves? Are the gas paths comperable? All the issues around mechanical wear, which does seem to factor, can be resolved through careful design and upkeep. Gears wearing is going to have a disproportionatly larger effect on the valve operation here, when compared to piston valves.

For me, its about the numbers. It has to start there, and thats before cutting a gram of steel. There is no excuse not to use the tools at hand, FEA etc, and get the design right from the outset.

 

Was half way through a lengthy explanation of Lentz varsible vs stepped vs Caprotti when yet again the ******* site fell over. Will try again later, draught off line then post ….

 

A tough route certainly, but is a 92 mile slog conductive to presenting a large and heavily loaded locomotive with the opportunity to produce and use steam efficiently in the same way a longer, sustained sprint along the ECML would be? An interesting read from this afternoon is that one of the reasons the feedwater heater was dropped from 2001 is that it required the throttle to be open for it to operate and that the Aberdeen - Edinburgh route did not require the throttle to be opened often enough for it to be useful. I'm sure someone more experienced can better inform, but I would guess that your fire is not burning at it's most efficient when there is nothing coming through the blastpipe?

As to the second point (and much of the original post), have the trust said anywhere that they were going to go blindly into specifying and ordering full sized valve gear without doing the basic maths? It can't be that far stretched to believe that might at the very least be in the 'brain dump' David Elliott left behind?

 

There is a fairly comprehensive account of the use of Franklin-Lentz valve gear in the late Bill Withuhn's book American Steam Locomotives Design and Development 1880-1960. He was a licenced steam driver and also Curator of Transport at the Smithsonian. It's main application was the Pennsylvania Railroad's T1, including two prototypes. The gearboxes were very reliable, only failing when neglected through lack of lubrication. The valves themselves were designed for a maximum wheel rpm of 550. The T1s were 4-4-4-4 duplexes with a rigid frame and were thus prone to slipping, not only at starting but also at speed. The duplex arrangement was used to allow the use of lighter rods. The main problem was frequent valve breakage, due to overspeed; the valve material used made little difference.

https://www.amazon.co.uk/American-Steam-Locomotives-Development-1880-1960/dp/0253039339/ref=sr_1_4?crid=2R6337336PU3A&dib=eyJ2IjoiMSJ9.owt3zldQ5cgyEz-35Knsklsi9iHnq8w7evbdYlSVmpLGjHj071QN20LucGBJIEps.cGdAl4qBDq7XCw0ay9d7YKnQ6h1ha_uld7MiuMNkv9M&dib_tag=se&keywords=william+withuhn&qid=1742407475&sprefix=william+withuhn,aps,90&sr=8-4&ufe=app_do:amzn1.fos.95fd378e-6299-4723-b1f1-3952ffba15af

 

Work started on K4 5399 in 1939 and it showed an increase in drawbar power of from 20 to 40%, the figure increasing with speed!

 

Having been failed by the iPad / Safari / NP gremlins in my last attempt to post, I took the opportunity to do a bit of Googling , and found this excellent page penned by David Elliott 6 years ago. It details the P2 design philosophy, including problems to be overcome with the cylinders, valve gear and the computer modelling of the chassis riding qualities. Sadly, in a rather damning inditement of today’s Trust, there’s a rider added that the page is no longer maintained ……

https://www.a1steam.com/educational-resources/prince-of-wales/design-study

 

Thank you so much for this... I've only read a few lines and realised it needed much more deeper reading. If this is being cast aside by the trust.. I'm flabbergasted.. it's engineering at it's best combining 20C technology with today's 21C technology, absolutely fabulous....

 

I’d forgotten it existed - six years is a long time … since it was written I think the only solid progress has been the fabrication and machining of the cylinder block (plus progress on the tender, but there’s nothing very challenging there, and no doubt like Tornado’s re-plated tender, will now have to be butchered to fit the ETCS cabinets).

 

K4 was constructed before 1914.

In 1929Chapelon tested a modified pacific from 1907 and achieved more.

Anno before Chapelon or after Chapelon is the only sensible way to index years.

 

I suspect you are both adding 2+2 and making 5. It doesn’t say the design study is being discarded, it says a web page is no longer being maintained. That’s not uncommon with pages of archival value, particularly if a site changes the platform it is hosted on but wishes to digitally preserve old information of interest. I could point you to pages on the BBC site with a similar disclaimer. Quite likely it is a configuration in the legacy platform to put the same wording in as a standard header on old pages that haven’t been migrated.

I don’t think it says anything about whether the Trust have faith or not in the information contained as a resource.

(Disclaimer: I’m not an engineer. But I do run the web platform for a large organisation with a very complex and multi-headed public web presence …)

Tom