Hi Ray,
Many thanks for that info,………….
Recently, I was looking at some Big Bertha drawings that a club member had produced via CAD etc and in particular the very narrow valve heads typical of the Midland Railway at that time…..He was concerned that with so small amount of "lap" he wouldn't get any expansive working and was considering re-designing the whole of that part of the cylinder / valve area……
I have an inkling that at some time in the past I've both read about the full-size one in our ME mag. and seen a 5" model in action but for the life of me I can't remember the details !! …… My brain cavity also acts as a spare GWR 30" Vac. cylinder I think !!
It would certainly save my friend a lot of wasted research time if we could get some drawings for a known working engine and / or have access to that loco and its' current owner, if only for a chin-wag as to its' performance etc…
Any help from any source would be most welcome….
Best regards from}—
Alan R