P2 Locomotive Company and related matters

I seem to recall David Elliott saying that another raison d'être for the P2 was that it could potentially accelerate to 75mph quicker than the A1.

 

I think he said 88mph

 

Why? My point is that it does not matter what speed path you give a steam train its accelerating charastics are dire in comparison to virtually any other train on the network. It is not about how fast you can run at but how long it takes you to get up to that speed. The only way that you can improve on that is by having a diesel on the rear to assist in getting up to that speed quite a lot quicker - and we are frequently told that that is not what people want. As the saying goes you can't have your cake and eat it.

Peter

 

That to me says that you are not allowed to exceed the lowest permissable speed of any vehicle in the train which in the case of steam is likely to be 75 0r 60 mph (or 45 mph if running tender first). There is nothing special about Mark 1 stock in this case as it applies equally to Mark2 and Mark 3 stock. I think that you are reading something into this that is not there.

Peter

 

That’s not what the document says though, is it? It clearly states that exemption is only granted "granted subject to the following conditions", which specifically restricts steam hauled stock to 75mph. If following your logic, why not just state the plated speed for any locomotive? After all, there are plenty of heritage diesels which operate at speeds less than the 100mph allowed for Mk1s.

The stock used with Bittern at 90mph in 2013 was specifically authorised to exceed the 75mph speed allowed in the regulation four exemption (quoting a June 2018 Steam Railway when "ORR spokesman Simon Belgard said that for the Bittern trips a Rail Safety and Standards Board standards committee "agreed to the proposals to run steam plus Mk 1 rolling stock at 90mph on a one-off basis"."). Specific reference to the Mk1 rolling stock would not have been required had the reg 4 exemption only been about the plated steam of the traction?

 

Look this is getting a bit silly don't you think? How can any stock be permitted to run in a train faster than the traction unit hauling it? In the normal course of events you don't need regulations to state that you must abide by the regulations. Surely the agreement here to run a steam loco plus stock at 90 mph "on a one-off basis" was not for the stock or the loco by itself but for the train as a whole. In other words, yes you can run your loco at 90 mph in this instance, but only if it has a train of Mark 1 coaches attached. What could be more strightforward?

Peter

 

For the Ebor Flyer, permission was for the train as a whole provided it did not include Mk I coaches, hence the substitution of Mk IIs. This was after Bittern had been allowed to take Mk Is at 90 mph and with the Mk Is themselves allowed to go at 90 mph behind a diesel or electric loco.
That made no sense at the time unless as an unintended consequence of how the rules had been written.
What also makes no sense is why we are discussing that trip on the thread for the P2, which we can be fairly sure will be limited to the same 75 mph as other express steam locos, regardless of what coaches it pulls.

 

I remember at one of the roadshows I attended, David Elliott was quite clear that the P2 was all about accelerating its load quickly to 75mph: it was never going to be a "flyer" like the A1 and wasn't intended to be.

 

Whatever the intended meaning was, the wording is terrible.
According to this, if I were to put my 1959 BR Conflat wagon on the main line (tare weight about 6T, from memory), it could be operated at 75mph as long as the engine at the front is a steam engine. Never mind that it would probably take off the first time it hit a dipped rail joint, assuming the wheel bearings didn't melt first!

 

Distance covered is distance covered. Cycles are what caused it to fail. It would have happened soooner or later with a sticky valve, speed is not the defining criteria in this one.

Incorrect. Stress is defined as Force over Area. The force is manifesting as a result of the stuck valve. The stress is not related to the speed.

Valve stuck - Range of motion restricted - expansion link goes in to bending - cycles eventually kill due to repeatedly cycling through plastic deformation. That happens sooner or later at 75 or 90, but it happens regardless.

Speed is not the defining criteria here. The range of motion/stuck valve is.

Correct.

If you sit down with a peper clip, and bend it back and forth until it breaks, it will take around 5-10 mins.

If you bend it once per day for a week, it will take about a week, but it will still break once it hits the same number of fatigue cycles.

There are very, very few places on the Aberdeen to Edinburgh line where that speed can be maintained for any length of time. On the old forfar route its a bit better bit even still.

 

deleted

 

deleted

 

Why would a BR conflat wagon be covered by regulations relating to passenger carry mk1 style rolling stock? The exemption wording only applies to mk1 style rolling stock, not goods wagons.

 

When it comes to a reciprocating motion, speed is a parameter as a reciprocating body is subject to a varying accelereation and deceleration and the faster it is going, the shorter the frequency and thus the higher the peak rate of acceleration, which occurs when its linear speed is zero. Acceleration x mass = force so the higher the acceleration the greater the force.
I'm not saying that this was the cause of the failure, merely that the applied force is related to speed in this case.

 

Barring any specific restriction (TSR, for example), the maximum speed of a train is that of the slowest vehicle. I don't know what that would be for a Conflat (Dia. 61 or 62?) but will hazard a guess at 45mph.
Pat

 

Speed of the slowest vehicle would be logical. The rule that would have applied for Tornado with Mk Is was not logical.

 

Of the steam locomotives I have travelled on a train being hauled by, the locomotives with consistently the fastest acceleration is 35028.

 

Yes of course. I could have quoted an 1870s 6-wheeled carriage, but I don't have one of those. The detail was unimportant, I was merely commenting on the quoted wording, which appears to omit the very important point below.

It's a newfangled one - dia. 69! Clasp brakes and all, so it will get wheel flats too. Probably would have been 45mph back in the day; these days, would it even be allowed? No idea.
(The question was purely hypothetical anyway, the wagon was withdrawn in 1981 and who knows when prior to that the vacuum cylinder was last overhauled. It's not a runner.)

 

If anyone in the West Midlands (Gloucester through to Derby) wants an easy way of getting up to the new Hopetown Depot for a visit, Pathfinder are running a tour up there on 5th April. Set down and pick up at North Road. I'll certainly be booking on it in the New Year.

 

Whilst trawling through the latest edition of the Trust’s Communication Cord news magazine, searching for some light in Tornado’s darkness, I was also stuck by the near absence of news dedicated to the P2 project.

On closer examination however, I came across this snippet which sadly reveals that the engineering misfortunes have now struck the P2 as well, with the revelation that pony truck cannon box will have to be be scrapped and a new one cast.

This is stated to be due to removal of the cracked managnese liners (who knew?) and welding in new ones, which has caused distortion which cannot be corrected by machining.

Components written off by welding distortion - ring any bells?

So that’s one cast and machined cannon box and two sets of manganese liners (8 in total).

Anyone estimate a value on that, plus labour?