Anspach Denny <danspachmd@...>
I do not have a dog in this particular hunt re: Gresley valve gear motion. However, In his recent pretty definitive book on the SP’s five coupled steam locomotives, Bob Church has elegantly laid out his findings on 3-cylinder valve gearing, citing a host of both primary and secondary sources, not excluding personal interviews with those who worked on such steam motive power. I personally know of any other sources of such credibility on this subject. In this regard, I feel that those that would -with standing- like to challenge Bob’s views and findings in this matter had better have their own data and sources at the ready.
IMHO, this same book (Signature Press) is one of the most important books published in long time on steam locomotives, and steam locomotive development culture during the standard era. The value lies in the book being so much more than just the narrow focus on several fairly uncommon classes of locomotives of a single railroad; In the telling the stories, and the overview, Bob really covers in fascinating detail how railroad management made motive power decisions; how the needs and abilities of maintenance facilities tilted their sails to accommodate these new locomotives, or in turn, how the new locomotives had to be altered to meet the requirements of existing facilities; and just how changing requirements, technology, and traffic, and assignments over a lifetime caused a railroad to significantly alter or modify a locomotive so that we learn how photos of “as delivered” may have little in common with photos “in use”, etc.
The value is that the reader in his mind can just substitute any other class of locomotive from railroads A, B, or C to get a good picture about how things probably really would have been on any other railroad besides the SP.
Denny S. Anspach MD