How Do You Run a Machine With Your Feet? Keep Your Hands for the Work

Any machine that shapes material needs power and needs guidance, and a worker with two hands cannot easily supply both. An early lathe required one person to turn the work while another cut it, which doubles the labour and separates the judgement from the control. Moving the power source to the feet solves that completely, since legs are strong, can work rhythmically for long periods and are otherwise idle while somebody sits at a bench. The worker then supplies power continuously with the lower body while both hands do the skilled part, which is why the arrangement appears wherever a craft requires sustained rotation or repetition.

The same mechanism drove a wide range of trades:

• •The pole lathe, springing back on each stroke via a bent sapling
• •The flywheel lathe, giving continuous rotation in one direction
• •Loom shafts, raising and lowering sets of warp threads
• •The spinning wheel, freeing both hands to draw out the fibre
• •Grindstones and polishing wheels in metal and glass trades
• •The sewing machine, from the middle of the nineteenth century

Converting a foot's up and down movement into continuous rotation has a mechanical catch that had to be solved. A crank at the top or bottom of its travel lies exactly in line with the connecting rod, and pushing at that moment produces no turning effect at all, which is called dead centre, so the machine can stall in that position and refuse to start. A heavy flywheel carries the motion through it, which is why treadle machines have one and why starting usually requires a push by hand to set the wheel turning in the right direction. Two cranks set apart, or a two-part treadle worked by both feet alternately, also remove the problem.

Supplying power with the body for a working day has physical consequences that the records document. Sewing machine operators in nineteenth century workshops worked long shifts at high speed, and contemporary medical writing describes leg, back and pelvic complaints attributed to the work, some of it reliable observation and some of it the period's assumptions about women dressed up as medicine. Pole lathe turners developed asymmetric wear patterns visible in skeletal remains, since one leg does all the work. The introduction of motors was welcomed by workers for exactly these reasons, well before it was justified on grounds of output.

The arrangement survived the arrival of electricity by decades in many trades, and the reasons are practical rather than nostalgic. It costs nothing to run and needs no supply, which mattered enormously in rural areas where electrification arrived late, and it still matters where supply is unreliable. It gives extremely fine control of speed, since the operator feels the load directly and can slow or stop instantly, which is difficult with an early electric motor. It is nearly silent and has almost nothing to break. Those qualities keep a market alive today, with hand-operated and foot-operated sewing machines still manufactured and widely used.

Moving the power source to the feet lets legs supply sustained rhythmic effort while both hands do the skilled work, which is why lathes, looms, spinning wheels and sewing machines all adopted it. A crank in line with its rod produces no turning effect, so a flywheel is needed to carry the motion past that point. The arrangement outlasted electrification because it costs nothing and gives instant control.