P2 Locomotive Company and related matters

More shiny bits are beginning to appear....

https://www.p2steam.com/2016/12/19/december-construction-update/



Foxy

 

Forgive me if this has been asked before.

Is the P2 Locomotive company co-operating in any way with the Doncaster P2 Locomotive Trust? Is there any mileage in sharing designs, patterns etc.?

 

I asked that question to the Doncaster outfit and was told.... no.... which I think is a bit sad

 

I believe that an offer to share some development and production costs was made, but the Doncaster team declined it.

 

I doubt if the Doncaster one will ever get built and wasn't really a sensible idea anyway. I want to see a P2 built as one of the most impressive machines ever to run in this country so who did I put my money with? A group I've never heard of or one that has successfully done it before?

 

Pity.

SFIK the projected locos would only have cosmetic differences, so why re-invent the wheel(s)? Not sure where the Doncaster trust expects to get its funding, but it would have far more chance of succeeding if it collaborated with the P2 Loco Company.

 

The Doncaster one will have the A4 type front end and that's about it. I'm not sure where they expect to get their funding but success breeds success and according to the last trust online newsletter, The Mikardo Messenger the Darlington one is coming on well on schedule.

 

The choice to build a P2 based on 2001 as built was not without potential major hurdles. The Lentz poppet valve gear was never satisfactory and so an alternative has had to be found. The alternative chosen is to be a version of Franklin B, as I understand it, but no details have been revealed as yet. The LNER did get good results from Caprotti gear and I wonder if this option was ever considered.

Building a P2 based on the rebuilt 2002 solves the valve gear issue. A standard Gresley/Walschaert application with acceptable clearance volumes which could benefit from Porta type valve design refinements if so desired with the advantage that no one would ever know from an external glance at the machine.

Leakage past poppet valves due to thermal distortion was part of the reasoning behind the return to piston valves. Tross designed elastic valve seats in order to try to overcome the issue. Porta found that his piston valve design was good for tens of thousands of close to leak free kilometres. Radial valve gears are well proven and reliable under railway operating conditions but doubts still remain with respect to poppet gear types.

Would I have chosen a RC gear fitted design? Probably not, though I would talk to the people responsible for 71000 and ask for some leakage testing when the gear is giving no further concern with respect to other mechanical functioning.

 

Poppet valve gear worked very satisfactory and successfully on many hundreds of locos in France, India, Malaya, Argentina...

 

....and a heck of a lot of work has gone into the complete redesign of the monobloc for No. 2007:

https://www.p2steam.com/design-study/


Foxy

 

I have to admit to preferring the look of the modified P2 with the A4 front end. It looks just a little more impressive and streamlined to me.

Please don't hit me.

 

Interesting that the Poppet Valves are in line with the cylinders, where they configured this way on 2001?

Cheers,

Alan

 

I would believe Chapelon and LDP they did the work and I as I understand it Andre Zavier Chapelon was French. 242A1 and 160A1 had piston valves. Want an arbitrator? 232U1. Designer; Marc de Caso. Valves? Piston.

Chapelon, in spite of the success of the rebuilt Pacifics and the subsequent 2-4-0s (4-8-0s), reverted to piston valves. Why? Maintaining a limited range of engines was one thing. The deleterious effect of leakage upon efficiency and hence power output was another matter.

 

That is the cylinder and valve monobloc. Not sufficiently detailed and absolutely no details of the valves and valve gear.

The view, to date, of those that have been involved in steam locomotive design is that there is little or no advantage to be gained from the adoption of poppet valves over modern piston valve practice. Look at the 5AT design and associated discussions. Then access some of the relevant Porta papers.

 

Covenantors have been kept abreast of all the thinking behind the adoption of the Lentz/Franklin gear and David Elliott has issued regular updates on the latest developments in The Communication Cord, the quarterly journal of the A1SLT. You can read about this process and the involvement of George Carpenter on Page 12 of the 2015 winter edition of the magazine:

https://www.a1steam.com/wp-content/uploads/2015/04/TCC37.pdf

Foxy

 

I like them both, but the original smokebox arrangement was quite unique and distinctive, so I'm glad that's what we're getting.

 

Brittish Caprotti was looked at ,but the way the cam boxes sit on top of the cylinders would mean the middle cylinder gear would be within (or at least need to be accessed though) the smokebox... which was considered to be asking for trouble .
The redesign of the cylinder monobloc was not done to accommodate a specific valve gear, but for ease of construction and solve a heat exchange related problem with the middle engine /steamchest
Piston valve engines are also subject to excessive steam leakage... if the packing/ glands / seals are not sound.
As 242 a1 has said development of design around Piston valves has continued and excellent results are possible in comparison with poppet valves( of the Chapeleon era) With Piston valves the system is simple and robust - an excellent starting point for refinement towards its maximum effectiveness
That isn't to say that even better results are not possible ( in theory) with Poppet Valves - but since he 1950's (Franklin B/Lentz British Caprotti ) there hasn't been much work done.
Poppet Valves still need some development towards being more simple and robust and this is what P2SLT are working towards on with the Franklin Gear.- remember America just don't do flimsy.

Appearance wise my favourite is the Pre streamlined Earl Marischal, the walschaerts valve gear allowed a more beautifully shaped running plate. The double deflectors needed a bit of tweaking bit they certainly added to the 'Grandeur'. as well

 

While I'm not personally that Interested in how many nuts and bolts each loco has and the engineering side of things as I'm far more interested in the £££££ side of things the Doncaster P2 group don't seem to be anywhere near the starting block to build the loco. If you start on the basis of the loco to cost around £5 million then say that your raising £50,000 per year then it's going to take you 100 years to achieve your target. The problem is that the Doncaster group are not even earning £50,000 as there current income is actually £5000. So that now pushes the completion date to 1000 years.

 

If that is the case it will certainly be destinctive at that point when it rolls out. Whether there is still a coal supply for it may be questionable.