Take-up advances the finished cloth by a fixed length each pick, which sets the picks per centimetre: 0.5 mm per pick for 20 picks per cm. If a ratchet turns the cloth beam by a fixed angle each pick, the cloth piling up on the beam enlarges its diameter, a 90 mm beam reaching 144 mm after 20 m of 0.5 mm cloth, and the advance per pick grows by 60%, so the cloth must be pulled by a fixed-diameter roller and stored on a separate, loosely driven beam.
Part of Power Loom Construction
Pulling the cloth forward by a set amount per pick and winding it up without changing the weft density.
The Rate Is Set Per Pick, Not Per Hour
The overview: finished fabric winds onto the cloth beam at the front, and a ratchet advances the beam by one weft spacing after each pick, driven by the loom. For the reference loom at 20 picks per cm the weft spacing is 10 mm ÷ 20 = 0.5 mm, so the cloth moves 0.5 mm per pick, 5 cm a minute at 100 picks a minute (Weaving Mechanics). Change the advance and the cloth changes: fewer picks per cm is a lighter cloth. The beat does not set it (Beating Up).
A Growing Roll Defeats A Fixed Angle
Take the overview’s beam, 8-10 cm in diameter (Floor Loom Construction gives 8-10 cm), here 90 mm. One revolution advances the cloth by the circumference, π × 90 = 283 mm, which is 283 ÷ 0.5 = 565 picks. As cloth wraps on, the radius grows. For an assumed cloth thickness of 0.5 mm and 20 m (20,000 mm) of cloth, the area added is the length times the thickness: π(R² − 45²) = 20,000 × 0.5, so R² = 2,025 + 3,183 = 5,208 and R = 72.2 mm, a diameter of 144 mm. Now one revolution takes in π × 144 = 453 mm, 60% more than 283 mm. With the ratchet turning the beam by the same angle each pick, the advance per pick has grown from 0.5 to 0.8 mm and the picks per cm have fallen from 20 to 12.5. The cloth gets thinner as the roll fills.
The fix is to separate the two jobs. A roller of fixed diameter pulls the cloth, and the finished cloth is wound on a second beam turned by a slipping drive that takes up the slack. The fixed roller needs a rough surface to grip the cloth (a sand roller, a roller dressed with coarse abrasive; recalled design practice). The advance is then π × D per revolution of the roller, whatever the cloth roll has grown to.
Setting The Gearing
For a roller of 80 mm (assumed): circumference π × 80 = 251 mm, which is 251 ÷ 0.5 = 503 picks per revolution at 20 picks per cm. A ratchet of 20 teeth advanced one tooth per pick makes one revolution in 20 picks, so the reduction to the roller is 503 ÷ 20 = 25:1. Change-gears alter the ratio for other densities: picks per revolution = circumference × picks per cm ÷ 10, so 15 picks per cm gives 377 and 25 gives 628.
The storage beam grows too. To store 100 m of cloth of 0.5 mm: R² = 45² + 100,000 × 0.5 ÷ π = 2,025 + 15,915, so R = 134 mm and a diameter of 268 mm. Leave room in the frame, or remove the cloth in lengths.
What You Need
- A take-up roller of fixed diameter with a gripping surface.
- A ratchet and pawl, pawl-lifted once per pick, driven from the slay or a cam.
- A reduction gear train with change-gears (Gear Ratios).
- A cloth beam driven through a slipping clutch or friction band.
- Guards over gears and ratchet.
Method: Setting The Take-Up
Step 1: Decide picks per centimetre and compute the advance per pick.
Step 2: Compute picks per revolution of the take-up roller from its diameter.
Step 3: Choose gears so the ratchet step gives that advance.
Step 4: Weave 10 cm and measure the picks per centimetre; trim by changing a gear.
Step 5: Re-measure after 20 m to confirm the density has not drifted.
Worked Example
Without the fixed roller, the picks per cm over a 20 m piece falls from 20 to 20 ÷ 1.6 = 12.5, a visibly thinning cloth that takes (20 - 12.5) ÷ 20 = 37.5% less weft per metre at the end than at the start. With the roller the density stays at 20.
Common Mistakes
- Driving the cloth roll directly.
- A ratchet pawl that skips, leaving a band of thick weft.
- A smooth take-up roller that slips.
- No room for the finished roll.
Safety
Ratchets and gears pinch, and the roll gains weight
The ratchet, pawl and gear train move with every pick and close on fingers; keep them guarded. A full cloth roll is heavy and pulls on the frame; lift with a team. Clear the beam only with the loom stopped and locked, and know where the stop is (Power Drive System). Children keep away from running machinery (Task Assignment by Age).
What’s Next
- Learn next: Power Drive System — what turns the whole loom
- Combine with: Warp Beam — the other end of the warp