The Thompson Pacifics; what were their strengths and flaws?

[john coffin]

Oh silly me, I obviously should not believe anything that is written in books by many of the doyen of LNER locomotive history and knowledge.

The RCTS I think can stand up to scrutiny, since many of the co-authors were existing railway men who had close links with the Doncaster Drawing
office and works, including many of the pertinent people in the affairs mentioned from page 182 in vol2A of Locomotive of the LNER.

The last batch of A2/2's Peppercorn were built with Kylachap, BUT NOT Self Cleaning smokeboxes, because the space was not there.

Simples to paraphrase the meerkats!!!!

Paul

[Paul_sterling]

According to the relevant "green book" the drawing office at Doncaster was unable to fit both the kylachap and the self cleaning
smokebox gear in the same space, during the design stage.

Since the loco was designed at a time when they knew that ongoing staff problems, the less cleaning that was needed the better.

Paul

That makes absolutely no sense, given Bronzino was later fitted with the kylchap, and all of the multi valve ones were too. And the fact the smokebox isn't that much shorter than the Thompson equivalent. They managed it in Humorist which has the smallest smokebox of all of the kylchap fitted types - so what on earth was it really about?

There were issues with the A2's and steaming quality when used with single chimney and self cleaning screens. In the initial design phase they couldn't fit self cleaning and the double kylchap. The indifferent steaming I suspect led to them favouring Double chimney and a better operating engine needing its smokebox cleaning out, than a an indifferent steaming one with a clean smokebox!

Its also possible that Peppercorn wasn't a big supporter of the Double Kylchap, though I doubt it, as its wholesale adoption on the A1 might suggest he learned quickly from the A2.

If you tabulate the Pepp A2's, Thomp A2's, and Gresley A3's, considering three factors, Self Cleaning Screens, Doubly Chimney, and Multi Valve regulator, i'd be reasonably confident that you won't find a loco in that list with Double Chimney and Self-cleaning screens, and MVR.

Paul.

[Paul_sterling]

Oh, I almost forgot
the OP question was about strengths and flaws.

Thompson A2's, well, the A2/3's, were well known for their speed abilities. HCB Rogers did dismiss this as not being a Thompson thing, but I think that a little unfair, in terms of steam circuit, and ability to run fast was a reflection on the efficiency of their cylinder and valve design, a free flowing circuit, and an ability to raise an abundance of steam.

Paul.