and Universal Electrical Test Stand
Manufactured by The Electric Machine Corporation of Indianapolis Indiana, in the United States, the Elmco lathe was available in two forms: the 24A as an ordinary plain, non-backgeared or screwcutting type or as the rather different 34A, in which case it was combined with the maker's Universal Electrical Test Stand. With two patents granted in November and December 1921 - and so production presumably having started well before then - the test stand was entirely self-contained and marketed to small garages and repair shops as a one-stop solution for testing the electrical equipment of automobiles and light trucks. With their relative unreliability and need to be regularly serviced, such items as generators, magnetos, commutators, armature windings, field coils, distributor points and condensers, etc. provided garage owners with a profitable sideline. However, the test stand also had the advantage of incorporating a simple, compact, motorised and self-contained lathe that could be used not only to rotate generators and skim armatures but undertake simple turning jobs.
Although they used the same bed, carriage and tailstock, the 24A and 34A were very different, the former being a simple device with a rather lightly constructed, open headstock with the spindle running in annular ball bearings and fitted with a wide, 3-step cone pulley for drive by flat belt. A separate, traditional-type countershaft was offered, this being recommended by the makers to run 260 r.p.m. and so provided lathe spindle speeds of 152, 286 and 550 r.p.m. However, at a time when almost all other small lathes were delivered without a drive system or motor (and so had to be coupled up to an expensive wall or ceiling-mounted remote countershaft) the test stand lathe was delivered ready to run, being fitted with a variable-speed drive of the friction type. This transmission system - although not capable of handling very heavy work - had the advantage of allowing the whole assembly to be not only compact, but also able to be located in any convenient position - and not necessarily against a wall. Bolted to the bench at the back of the lathe, at 90° to the spindle, was a large 1 h.p. electric motor by General Electric - model 20672, Type RSA, Frame 465, Form A, 110/220-Volt - fitted with a large cast-iron disc that pressed against the friction-material-lined edge of a second disc keyed and sliding on the headstock spindle. By turning a handwheel on the left-hand face of the headstock, the spindle disc could be moved to and fro causing it to slide across the face of the motor disc and so, as it moved nearer to the centre or closer to the periphery, change the ratio of the drive and hence the spindle speed. What was the friction material? Well, almost unbelievably, it was a form of compressed "paper", a material with exactly the right characteristics and commonly used for smaller pulleys on all sorts of machine-tool "friction", variable-speed and ordinary flat-belt drives. Even today its use continues with one company specialising in the system, paperpulleys.com who have made replacements for not only industry but also the owners of such vintage cars as Metz, Carter Car, Guery & Bourguinon, Sears, Trumbull, and Orient Buckboard.
Supplied with a 6-inch faceplate, two drive dogs, a lantern toolpost, a set of wrenches and various small fittings and casting to hold armatures and other components, the maker's also offered, as an extra, a 3-inch diameter, 3-jaw chuck.
Although unique in its combination with a test stand, the Elmco was not the only friction drive lathe on the American market aimed at the automobile trade for another maker, or agent, ''The General Radial Drill Co.'' of Cincinnati, Ohio, U.S.A. offered the interesting Schaffner ''9-inch'' bench lathe, rather over-optimistically described by them as "Beyond Competition". While the Schaffner had a drive using three (later six) separate pulleys of the ingenious (and patented) "Gibbs V-Disc" with the motor sliding and pressing against the edge of each, the Elmco enjoyed the advantage of being instantly variable and used the same basic arrangement as fitted, for example, to some pre-1914 lightweight European "cycle cars", the English "Nearacar" motorcycle and the American-made "Cartercar".
Although many machine tool makers have fitted their products with some form bought-in, self-contained swash plate (friction cone) drive (such as the Kopp fitted to Colchester Chipmaster lathes), others have built their own, sometime unique systems, these including some versions of the vintage American Onan; the Bulgarian-made Mashstroy from the 1970s and 1980s; the English EXE Company's foot-pedal-controlled mechanism offered during the 1920s as an option for their lovely little 2.5-inch lathe and the much heavier industrial-class German Robling made from the 1940s until the 1960s.
If you have an Elmco lathe and can provide some better pictures than those below, the writer would be pleased to hear from you..