Durax cranks 

Readers may be puzzled by the references to "N.C.C.C" and "C.C.C". In the post-war period two lengths of cranks were produced for bread-and-butter roadsters. The shorter of the two was for non-gearcase machines. The gearcase referring to a built-in casing to protect the chain from water, grit and dirt, some had the facitity of holding oil in the lower section through which the lower length of the chain passed. The chainwheel had to be positioned further out to enable the inner side of the casing to sit between the chainwheel and the bottom bracket/frame. Hence "G.C.C." - gear-case clearance.  The shorter axles for machines without this facility were known as "N.G.C.C." - non-gear case clearance.

Strangely when double chainwheels were introduced into the UK for lightweights it was found that these two lengths matched up to the requirements for single and double chainsets and for some manufacturers this was the description used to define them.  Eventually a more technology-based description was used such as Campag's 109, 118 or 120 which listed the length in millimetres or in other cases imperial measures. Chater-Lea listed two lengths in the 50s, the single No. 1007 was to give the classic single-speed 1½" chain line. For double-chainset No. 1240 was listed - no measurements in either case (Aids to Happy Cycling, 1953).

Some 10 years later Chater were still using the same descriptions but Stronglight listed 127mm for single cottered and 132mm for the double.

The more I look into axles, the more I realise that this axle length subject should be teated as a project on its own as it gets more and more complicated which may explain why I have spent so many hours of my life putting axles in only to change them again when the instillation is complete with cranks.  Sometime more than once I must admit.