A treadle loom is driven by two foot pedals that turn a crank on a 20-30 kg flywheel belted to the loom, and one person can keep it at 40-60 picks a minute. That flywheel holds only 17-26 J at 50 revolutions a minute, about the same as a single 12.5-28.1 J throw of the assumed 0.25 kg shuttle, so the treadle works the shed and the beat while the weaver throws the shuttle by hand, and the loom stays a person’s tool, not a small power loom.
Part of Power Loom Construction
Human-powered operation for smaller looms, what a person can supply, and where a treadle drive stops being enough.
What The Overview Describes
For places without water power the overview uses two treadle pedals driving a crank by connecting rods, a heavy flywheel of 20-30 kg at 0.5 m diameter to smooth the pedalling, and a belt from the flywheel to the loom crankshaft. One person can sustain 40-60 picks a minute, slower than water power but 5-10 times faster than hand weaving. The mechanism is the one in the treadle lathe and the flyer spinning wheel (Treadle Lathe, Spinning Wheel), with its dead-centre problem: the crank cannot be pushed when the rod is in line with it, so momentum must carry it through.
Check the claim: at 40-60 picks a minute and 20 picks per cm the cloth advances 2-3 cm a minute, 1.2-1.8 m an hour, 9.6-14.4 m in 8 hours, against the 1-2 m a day of an experienced hand weaver (Weaving): 5 to 14 times.
The Flywheel Cannot Carry A Shuttle Throw
For a ring-shaped flywheel the corpus uses I ≈ m r² and E = ½ I ω² (Flywheel). Take m = 20 kg and 30 kg at r = 0.25 m, turning once per pick at 50 rpm (ω = 5.24 rad/s):
- 20 kg: I = 20 × 0.0625 = 1.25 kg·m²; E = 0.5 × 1.25 × 27.4 = 17.1 J
- 30 kg: I = 1.875 kg·m²; E = 0.5 × 1.875 × 27.4 = 25.7 J
The throw of the assumed 0.25 kg shuttle takes 12.5 J at 10 m/s and 28.1 J at 15 m/s (Picking). That is 12.5 ÷ 25.7 = 49% to 28.1 ÷ 17.1 = 164% of the energy the wheel holds. A flywheel that gave up 12.5 J in one pick would slow by a large part (E falls from 17.1 to 4.6 J, and speed with the square root, to 52% of its value). The weaver’s foot would have to deliver the throw in the instant, which no one can do at that rate. So a treadle loom throws the shuttle gently or by hand: by Kay’s fly-shuttle cord (hand-jerked, which the overview credits with doubling weaving speed), or with a lighter shuttle and slower throw, since energy scales with speed squared (at 5 m/s the assumed shuttle needs 3.1 J).
What A Person Can Supply
The corpus gives about 50 W as what one person can steadily add with an arm (Hand-Cranked Centrifuge). Legs sustain more; a figure near 75-100 W is recalled and not from the corpus. The overview’s loom needs 375-750 W at 100 picks a minute. If power scaled with speed (an assumption), 40-60 picks a minute would need 150-450 W, more than a person gives, so the treadle drives either a narrower loom or only part of the work. The power per metre of width is also assumed proportional; the practical test is to run a loom from the treadle with a spring balance on the pedal and see what the weaver sustains over an hour.
The Person Is The Plant
A treadle loom needs no water, no line shaft and no spinning room, but it needs a weaver who treadles, throws, ties broken ends, changes bobbins and fixes the loom. Its yarn must come from hand spinners: the corpus estimates 3-4 spinners per weaver for worsted-weight wool cloth (Weaving), or from a frame whose output is far larger than one treadle loom needs. The step from here to a power loom is a step in plant, not in mechanism (Power Drive System).
What You Need
- Two treadles, connecting rods, a crank and a flywheel (20-30 kg at 0.5 m).
- A belt to the loom’s crankshaft (Belt and Pulley Systems).
- A loom with a hand-thrown fly-shuttle cord, or a light shuttle.
- A seat and a clear floor.
Method: Setting Up A Treadle Drive
Step 1: Build the flywheel and crank with the crank pin offset set for a comfortable stroke.
Step 2: Fit the connecting rods to the treadles, and set the belt so the loom turns once per pick or as the weave needs.
Step 3: Balance the wheel (Flywheel Design).
Step 4: Try it unloaded, then with the loom, watching for dead-centre stalls.
Step 5: Add weight to the rim opposite the crank pin if it stalls on dead centre.
Worked Example
A weaver treadling at 50 picks a minute moves a 1 m wide cloth at 20 picks per cm by 2.5 cm a minute, 1.5 m an hour, 12 m in eight hours. The same loom at 100 picks a minute from water power makes 24 m, twice as much. The treadle’s gain over hand weaving, 12 ÷ 2 = 6 times at the hand weaver’s upper figure of 2 m a day, is real; its limit is the weaver’s power and attention.
Common Mistakes
- Trying to throw a heavy shuttle from the treadle.
- A flywheel too light for the dead centre.
- Judging the loom by pick rate and not by what the weaver can sustain for hours.
- Ignoring the yarn supply.
Safety
The flywheel and belt keep turning after the feet stop
A 20-30 kg wheel has a stored energy of 17-26 J at 50 rpm, enough to drag a hand or hair into the belt before it halts. Guard the belt and wheel, tie back hair, keep children away from a running treadle drive, and never reach into the loom while pedalling or while the wheel coasts (Task Assignment by Age). Brace the frame so the stroke does not tip it.
What’s Next
- Learn next: Power Drive System — the water-powered step beyond
- Combine with: Shuttle Mechanism — the throw the treadle cannot supply