P2 Locomotive Company and related matters

Dunno what is currently flavour of the month. It used to be BS 1452 grade 12 but the flaked graphite which gives it self lubrication properties is replaced by spheroidal graphite in SGI which I'm not certain is as good. However, I'm no metallurgist so can easily be shot down here. It runs in my mind that 6024 has had SG iron cylinders fitted but has liners. I'm sure Aberdare can give chapter and verse on this if he is willing.

 

The ex Polish Class 52 Kriegslok that was (is?) on the Nene Valley Rly had at least one fabricated cylinder block on it.

 

And the Poles can't weld! At least, that's what Richard Greenwood once said when talking about the Worth Valley's S160 boiler repairs.

 

I too thought of the NYMR's effort and wondered! Was the 76079 cylinder stress relied as often as the P2 one is planned to be, though, in fact was it stress relieved at any stage? One saving grace may be that the P2 cylinder has much greater mass to dissipate any build up of heat through.

 

More mass means more weld, which is more heat in to the structure and therefore greater residual stress which needs to be removed.

 

I'm not a metallurgist either, but I've often wondered about that particular question (is SG iron as good as grey iron as a liner material) and the answer appears to be that from a wear resistance point of view, no it doesn't establish such a good graphite lubricating film. It's one of those awkward questions where there's lots of "as is well known" but not much "this is the fundamental mechanism" out there in the internet searchable literature. In theory, for any cross section through the material (which a surface nominally is) you should get the same percentage graphite regardless of microstructure, if the overall percentage of free graphite is the same.

My best hand waving guess is that the graphite flakes have a structure aligned to the flake direction, whereas in the nodules it's random. So with a flake structure, the majority of graphite surface will be in flakes parallel to the surface, which happily spread a film out, whereas with SG iron the graphite structure can be oriented in any direction in any given nodule exposed. That or the nodules are effectively torn out by the cutting process, leaving a graphite-poor surface, whereas the metal preferentially peels away from the parallel flakes even when they're slightly below the desired nominal surface, leaving a graphite rich surface.

Either way, I seem to remember Wardale writing that pearlitic grey iron was the material of choice for liners and rings, which seems to match with current automotive thinking, since the extra hardness of the pearlite matrix (over a purely ferritic matrix) improves wear resistance. Compacted graphite and SG irons are used in automotive applications where the surface stresses are considered too high for grey iron, like some piston rings, or liners in extreme applications, but in steam locomotive applications I'm sure grey iron mechanical properties are adequate (and therefore overall properties superior) for liners.

 

You should have tried being a mechanic at an FSO (formerly Polski-Fiat) garage! Before that I was at a Skoda dealers, but they were the old Skodas; every service came with a list of faults filling a toilet roll.

 

Next time i am in a hot bath i shall think of all my weld stresses being relieved..

 

You know it just occurred to me recently, just how both crazy and incredible it is that in the time it's taken many of these other new build projects to now draw close to finishing (seeing as a good number of them are at the advanced stage now or recently have been completed), the A1 trust is not far off the completion of there SECOND loco as well as solid plans in the works for at least 3 more after!

P2 seems only a year or two away now, and they've technically already had parts made of the next project after being a V4, which if I'm right should in turn provide commonalty in parts for a new V3 Tank after that should it not?

Got the impression that the V4 was essentially an improved tender version of the V3, having pretty much the same type of boiler and general parts.

Really have to hand it to the trust/company's continued professionalism and great thinking in getting to this point, when looking back at how far they've come.

 

It’s still not complete yet!

 

Not entirely sure what your point is seeing as I didn't say it was c0mpleted yet...

 

I’m just saying that there’s still a way to go before we see it with a fire in its belly, wasn’t 35006 perpetually ‘only 2 years away from steaming’ from the mid nineties?

 

True but I think there are quite a few crucial number of differences between the two, and I don't see why it is you seem to assume the P2 is one of those projects that'll keep on getting delayed years upon years, as so far the company has been pretty much on schedule to completing the locomotive roughly around the time they said they would.

I think they deserve the benefit of the doubt here at least, seeing as they have already built a whole engine and operated successfully for some years now.

 

And It has been achieved WITHOUT having to dismantle any existing/surviving locomotives for parts, unlike so many other so-called 'New Builds'

 

Think when they produce the item, it will make for a great engineering update.

 

Agree entirely. They seem to be mastering the "difficult second album" phase well.

The interesting bit will be succession-planning. At the moment they have an incredibly effective team, keeping that consistency will be key

 

Apart from the same number /size of wheels...not really

 

They've already had some turnover of personnel without apparent ill effect.

 

Ah well was given the wrong impression then. Thought if they shared the same boiler size/type that would fit the trust/company's tactic of having locomotives that share the same boiler and other critical parts, such as with the A1 and P2.

 

V3 looks like a parallel boiler onto a narrow firebox, max dia 5 foot, grate area about 23sqft, v4 taper boiler to 5ft 4 max dia onto a wide firebox 28sq feet. Maybe the front section /smokeboxes are similar ?

Initial Sketches for a Tank engine version of the V4 a 2-6-4 ? were produced (the only wide fire box tank i can think of) At first glance its easy to imagine its just a V4 / L1 cut and shut, but my investigations into building a 2-8-2 based on Brit -Clan and 9F Components quickly informs that this is anything but simple... i dont think anyone is brave/ foolhardy enough to produce a new loco design from an initial sketches nowadays...