It is technically possible to build even smaller operating steam engines. Hand-made examples, as small as Z scale (1:220), with a gauge of only , have been produced. These are fired with a butane flame from a burner in the engine's tender. AA Sherwood of Australia, an engineering lecturer, produced some miniature scale model live steam engines in the late 1960s and early 1970s. His smallest live steam engines were 1:240 scale which is smaller than the 1:220 of Z Scale. The smallest scale Sherwood worked in was 1:480, though that was not live steam.