 A driving factor behind the BSA/Triumph change was that Lucas had declared an intention to abandon production of motorcycle dynamos and magnetos, and instead produce only alternators.By contrast, Velocette, Matchless/AJS and Norton motorcycles continued to be pre-unit construction (the former machines with pressed-steel primary cases) until the end of production in the 1960s and 1970s respectively.In reality, the casings were not really "unitary", as the crankcase section was vertically divided in the middle and no oil was shared between the three portions.