At the end of the flat tank era, Walter Moore not only designed a cammy engine; he also designed the first cradle frame to be used by Norton and the pics above show some of the first cradle frames that were made.
What makes this collection of frames very interesting is that all of them were designed to use the Royal Enfield rear hub. Not many of these were made, from 1932 on Nortons own rear hub was used that combines the rear sprocket and drum in one casting and the frame was changed accordingly.
From top to bottom:
a 1928 CS1 frame; containing the three stay rear frame and designed for the Moore OHC engine.
a 1929 ES2 frame; production CS1 and ES2 frames from the end of 1927 up to (approximately) the end of 1930 were all the same and entirely interchangeable.
a 1931 CS1 frame designed for the Carroll OHC engine; still containing the three stay rear frame but lower than the previous frames and using a bigger diameter front-down tube (the dolls-head Norton box as fitted is not correct; a Sturmey-Archer box should be fitted).
a 1931 CS1 frame, also designed for the Carroll OHC engine but now with the two stay rear frame. The bottom frame tube is no longer made from smaller parts that are connected by the bolt that also fixes the bottom of the gearbox. This frame looks very much like the cradle frame to be used on Inters and ES2 models throughout the thirties, however, it's still designed to be used with the Enfield rear hub.
Finally, it is worth mentioning that vintage CJ/JE models (the 350cc versions of the CS1 and ES2) also used the two stay frames and which also took the Enfield rear hubs. These frames are different again from the later CS1 two stay frames.
