The original Royal Enfield 500 Twin came into being in England in 1948 as yet another British export twin. Like Edward Turner's 1937 Triumph Speed Twin, the Royal Enfield was a parallel twin with 360-degree firing order (both pistons moving, and therefore vibrating, together) and only two rolling-element main bearings. This was a pushrods and rockers engine whose crankcase was vertically split like that of a single. To reduce shaking force, like Turner's Triumph, it was given lightweight aluminum connecting rods, at first running directly on the crankpins, and later on bearing shell inserts. A separate four-speed gearbox was bolted to the back of the crankcase, driven in English fashion by a primary chain enclosed in a chaincase.