This is a tricky one Wade. The despatch books usually state clearly whether the frame is rigid or spring but there is no mention of either for much of the 1946 year. There are two series of frame numbers though, one starting at about 1000 and the other starting at about 1800. Not until November 1946 (ie after the start of the 1947 model year) do we see a reference to a spring frame and when the first few appear, they are around the 890 series, so lower than the numbers used at the start of postwar Square Four production. At the same time, (Nov/Dec 1946) we get confirmation by reference that the series of frame numbers which began at about 1000 are in fact for rigid frames.
My conclusion is that I don't believe Ariel produced any spring frame Square Fours after the war until November 1946, all postwar Sq 4 production before then being in rigid frames.
As ever, I am happy to be proved wrong if some of you want to send me the appropriate engine and frame numbers!
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.