P2 - Progress

[drmditch]

An interesting update on the P2 website ....here....

The analysis of the number and causation of crank axles failures is most interesting.
I still suspect that these failures were the major trigger for the rebuilding as Pacifics.

(I did look for an existing thread to post this on, but couldn't find an appropriate one.)

[Seagull]

I still suspect that these failures were the major trigger for the rebuilding as Pacifics.

To me that would make more sense for them being rebuilt as pacifics than just about any other reason I have seen.

It also suggests why they were not bought south during the war to work the heavy trains.
A crank axle failure of an engine that size would have caused serious disruption on the busy southern mainlines and be difficult to clear.

It's interesting that the starting point of the failure seems to have been at the keyway. I wonder if the other failures were the same.
If that were the case a simple change to the design (possibly larger radii to the corners) of the keyway slot may have prevented further failures.

Unfortunately the science of stress analysis was in it's early infancy at this time.
Probably Gresley and Bullied did not appreciate the 'built in' failure path they had designed.

Makes you wonder if Bert Spencer had been asked to look for an answer to the failures that maybe Mr. Thompson may never have had a reason to rebuild them.

Alan

Awaits the flying paperweights

[Hatfield Shed]

Cheap and dirty engineering solution. Replicate the design of the crank axle of the UP 9000 class 4-12-2. Although they had their troubles, I don't believe broken crank axles featured.

[mick b]

Heritage railway current issue has a article on the Vitry tests.

[ahardy]

The article about 2001 in France was published in The Railway Magazine, written by yours truly!

Its stimulated a little bit of interest, something I had hoped for.

Progress on 2007 is whizzing along. I regularly give talks on the original P2's and the project to build 2007. I gave a talk last Wednesday and am about to set of for the SLS at New Barnet to give them one tonight. Even in the space of 8 days things have move forward with tonight's show containing more than the last.

Andy

[Sir Nigel Gresley]

Everything on the continent with more than six coupled wheels (and even the FS 625 and 640 2-6-0s) used the Krauß-Helmholz "bogie" configuration, and whilst most were 2-cylinder locos, crank axle failures were not prolific. This may have saved the P2s, and given the 9Fs a greater radius of action (pun intended). Whilst we're on continental lines, why no more than a cursory trial of the Giesl ejector; and what about Marcotty fire-doors?

[Bill Bedford]

Actually the originally P2s were effectively 0-8-0s. Just having a pony that worked as advertised, to guide the loco into curves, would have been as effective as any of the other suggested expensive solutions.

[drmditch]

Actually the originally P2s were effectively 0-8-0s. Just having a pony that worked as advertised, to guide the loco into curves, would have been as effective as any of the other suggested expensive solutions.

Actually, if my reading of the P2Steam.Com website is correct, and subject to correction by Mr Hardy above, this is exactly what is proposed for No.2007.

The problem with any kind of Krauß-Helmholz or Zara truck was that the middle cylinder got in the way, and as Gresley himself said, there was enough innovation in No.2001 anyway. In any case, the information quoted above suggests that the crank axle failures may have been more to do with more power and more 'sticktion' on basically the same crank axle and bearings as the 4-6-2s. Where a Pacific could relieve torque by slipping, the Mikado couldn't and wasn't intended to.

It's just a shame that no-one was able and/or permitted to resolve some of these problems in the 1930s/40s.

Never mind - it's going to be done at last!