The LNER Encyclopedia

Just a quick question, were the P1s built with long travel valve gear? If not were they ever converted to such?
Just a thought I had whilst looking at a marvellous kit built one.

To quote from the RCTS green book;- The layout of the valve gear was based on the O2 2-8-0s .... with .... 5.5" travel at 75% cut off.

In other words they were short travel valves.

While many express passenger and mixed traffic locomotives were altered to long travel valves I have never seen anything to suggest that any of the slow running goods engines were altered. This makes some sense as the greatest benefit would derive from altering the faster running classes.

The green book does mention that Gresley considered fitting long travel valve gear to the O2s in 1927, the cost of alteration being £228 per engine.
This apparently was never authorised so I would suggest that the P1s were also never altered and the green book makes no mention of valve gear alterations to them. The later batches of O2s from 1932 onwards were fitted with long travel valves giving 6.625" travel in full gear.

Alan

Seagull wrote: ↑Sun Apr 04, 2021 11:36 am ...The green book does mention that Gresley considered fitting long travel valve gear to the O2s in 1927, the cost of alteration being £228 per engine.
This apparently was never authorised so I would suggest that the P1s were also never altered and the green book makes no mention of valve gear alterations to them. The later batches of O2s from 1932 onwards were fitted with long travel valves giving 6.625" travel in full gear.

Moreover, short of waving your measuring stick over the valve rod travel, there would be no significant external evidence of this change, because the lower position of the expansion link on the smaller wheeled freight locos would not have required any modification to the footplate above the cylinders, and thus no 'giveaway' clue of the altered casing on the long travel valve equipped pacifics.

Plenty else in variant country on the P1s though at various times, superheater changes, boosters removed, A3 boiler and banjo dome, and - fiction alert - they would look a lot sexier with a double Kylchap exhaust too...

Not sure I agree with the comment there would be no visible difference. The O2/3s which had long travel valve gear had a higher centre section of footplate to accommodate the longer expansion link compared with the O2/2s which had short travel valve gear.
Andrew

Keeping in mind that this fitting of long travel valves to the P1 is hypothetical; there would be more vertical height to play with on the P1 compared to the O2, because of the extra 6" of wheel diameter on the P1, had this modification been carried out. As such, my feeling is that a revised motion bracket for the longer expansion link probably would be all that was necessary, and thus no need on the P1 to raise the footplating between the ogee curves.

All we need now is the engineering design draftsman experienced in the LNER's Walschaerts layout to see what's possible...

I don't rule it out but I'm not convinced that the space would be there under the un-altered P1 running plate. I'm bearing in mind that compared to the short-travel early O2s, the P1 cylinders (which need to align with axle centres) would be raised by 3", and with them the slidebars, motion brackets and expansion links. In addition, the running plate of the P1 does not appear to be any higher relative to the wheel centres, compared to the early O2s, being a very noticeably closer fit over the wheels.
Ignoring aesthetics and ease of access, had alteration to long-travel been decided, a D49 style box over the top of the expansion link and rear of the radius rod might have been a cheaper option than an alteration to the longest part of the running plate.
None of this seem a crucial matter of course.

It isn't crucial at all, because it is hypothetical: but I would want an aesthetically pleasing result.

The comparison I would suggest is with the K4, on the same 5'2" wheels and built with long travel valves. I can see no objection to this arrangement on the P1, other than less efficient events when at or near full back gear due to increased angularity of the radius rod, by the valve chest centreline being higher on the P1 than on the K4. Since there would be no question of running the mightiness any distance under load in reverse other than by occasional force of circumstance, this should be acceptable.