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South Bend Lathe Silent-chain Drive
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1918 South Bend "Silent Chain Motor Driven Lathe"
Until the 1920s, and in some cases for very much longer, most machine shops had what would today be called an "Integrated Power System". At the heart of the system was a lovingly-cared-for large steam engine or electric motor that drove, via a convoluted run of belts and ropes through a labyrinthine maze of pulleys hanging from bearings attached to girder work inside the roof of the building, each of the factory's machine tools. The drive assembly in the roof was referred to as 'line shafting'.
Each machine was attached to the overhead shafting by a wide, flat belt, usually with some sort of ancillary control system which involved "fast-and-loose pulleys" where a belt, idling on a "loose" or free pulley could be flicked across to a "fast" or connected pulley which, being fastened to (or part of) another pulley next to it, provided drive to a machine on the floor below. Other more complex systems were also used that involved such intricacies as bevel-gear drives, built in split-ring clutches, foot-operated belt throwers and automatic lubrication systems. Once an overhead drive system had been expensively installed in a specially-prepared building, the nightmare of maintaining and constantly overhauling the multitude of bushings and hangers, inconveniently and dangerously located ten or twenty feet in the air, could begin. No wonder Works Engineers clocked-off dreaming of a better solution; their salvation eventfully came in the form of the small, high-speed electric motor that was able to provide each machine with its own, independent, power source. The tricky installation of a drive system could be delegated to the machine maker and now, if you fell out with your landlord, it was possible to pull the machine tools out of their Victorian dungeon and move across the road, or town, to somewhere both more convivial and cheaper - to say nothing of enjoying the other advantages that individually powered machines brought to the workshop and production process,.
South Bend were early in the market with a self-contained drive system, although at first it was only offered as a very expensive extra that added over 50% to the cost of the smallest machine and 27% to the largest - plus the cost of the motor itself..

The claims for the "Silent Chain" drive system were impressive. South Bend maintained that the lathe, installed in an office, would run so silently that the occupants of the next room would not hear it run - even if  they would, in reality, have certainly heard and smelt it working.
The countershaft was mounted on oil-immersed, self-aligning roller bearings and provided with an over-centre tensioning device which, maintained the makers, allowed the belt tension to be released and the belt moved from pulley to pulley whilst the lathe was running - not an action likely to calm the countenance of today's safety inspector from the Nanny State.. The motor speed was recommended to be 900 rpm and a reversing switch was provided  complete with a long operating bar which stretched the full length of the lathe bed; the attachment of this extension to the switch can be seen in the photograph above.
By 1933, with lathe production having topped 55,000, the same system was still in production, mounted in an identical manner above the headstock of the lathe but with the massive (and expensive) inverted-tooth chain  having been replaced by a conventional V belt - and the system naturally renamed the "Silent V-Belt Drive"..

email: tony@lathes.co.uk
Home   Machine Tool Archive   Machine-tools Sale & Wanted
Machine Tool Manuals   Catalogues   Belts   Books  Accessories

South Bend Lathe Silent-chain Drive
South Bend literature is available
Pre-1920    1920-30     8" & 9"    Light Ten    Heavy 10"    Clones   The Factory   
South Bend Home Page   9-inch "Workshop"    Accessories    Silent Chain Drive
      South Bend G-26-T    The Rarest South Bend Lathe Of All   Series 20 Toolroom