My apologies to everyone who's been waiting patiently for things to progress on 171.
I've been experiencing a frustrating year trying to track down drawings, photos and information about no.171's inside motion and leading driving cranks. I finally had a reply from the RPSI and its Locomotive Officer about a month ago, after offering a donation to 171's Overhaul Fund, but it all seems to have gone dead again. I know that the RPSI are constantly busy, and even more so with "Q" class no.131 potentially coming to life next year, but I do sometimes wonder whether they tend to leave honest enquiries hanging in the air. 'tis difficult not to feel neglected.
Working inside motion was always going to be something I wanted to install in my model of no.171; it is visible between the frames and - in 21mm gauge, at least - there is plenty of room to fit it in.
However, it turns out that, being originally built by Beyer Peacock & Co., "S" class drawings are held in the archives of the Manchester Museum of Science and Industry. I discovered this by pure accident when a small JPEG image popped up during a Google search. Following the link took me to MMSI, and a larger image which is clearly the "S" class engineering drawing. Praise the Lord, it is a cross-sectional view and even shows the inside motion and cranks in some detail.
One thing that was also clarified was that the frame outlines of the SSM kit are very close to the original drawing - previously I had thought the kit frames were weak - so a lot of care will be needed to install the mounts for the sprung suspension.
I am now going to have to invest at least fifty quid in an A0-size working copy, supplied by the Museum - assuming of course that they can scan one...... That's almost as much as I paid for the kit!!