Picking launches the weft-carrying shuttle through the open shed with a leather picker on a swinging stick, once per revolution of the loom, at 10-15 m/s. An assumed 0.25 kg shuttle then carries 12.5-28 J, which is a projectile and not a tool, so the loom needs a guard along the front and the weaver stays out of the line of flight.
Part of Power Loom Construction
Throwing the shuttle through the shed once per pick, what it needs and what it can do to the weaver.
The Pick Is A Short, Hard Blow
The overview describes picking: a picker, a leather pad on a stick, strikes the shuttle from one side; the shuttle flies across the warp through the shed; a matching picker and box catch it at the other side (Shuttle Box and Checking); and the picking motion is driven by cams on the crankshaft. The power loom shuttle travels at 10-15 m/s. The design of the shuttle and its launch is in Fly Shuttle Design.
The picker has about 0.067 to 0.10 s of flight to deliver (1 m at 15 and 10 m/s), within a pick of 0.6 s at 100 picks a minute (Weaving Mechanics). The blow must be early and short enough to leave the shed open while the shuttle crosses.
The Energy Behind One Pick
The overview gives the shuttle’s size, 250-350 mm long, 40-50 mm wide, 30 mm tall, hardwood and hollow, but not its mass. Assume 0.25 kg with a loaded bobbin; weigh your own.
- At 10 m/s: E = ½ m v² = 0.5 × 0.25 × 100 = 12.5 J
- At 15 m/s: E = 0.5 × 0.25 × 225 = 28.1 J
- Average power at 100 picks a minute (1.67 a second): 12.5 × 1.67 = 20.8 W to 28.1 × 1.67 = 46.9 W, a small share of the loom’s 375-750 W.
To reach that speed over an assumed picker stroke of 0.15 m the acceleration is v² ÷ 2d = 100 ÷ 0.3 = 333 to 225 ÷ 0.3 = 750 m/s², and the force on the shuttle F = m a = 83 to 188 N, about 8.5 to 19 kg-force. The picker, stick and strap all carry that load on every pick. Their strength sets how fast the loom can be run.
What You Need
- A shuttle (Fly Shuttle Design).
- Pickers of tough leather, which wear and are replaced often (Leatherwork).
- A picking stick and its drive from a cam on the shaft that turns once per pick.
- A guard at the front of the loom and a weft stop so that a missing weft does not weave on (recalled practice, not from the corpus).
Method: Setting The Pick
Step 1: Weigh the shuttle loaded, and compute the energy at your intended speed.
Step 2: Set the stroke and timing so the shuttle leaves while the shed is nearly open and arrives before it starts to close.
Step 3: Test at low speed by turning the loom by hand and then at a slow belt speed. Confirm that the shuttle runs straight and enters the far box fully.
Step 4: Raise the speed in steps, watching the picker and strap, and stop where the shuttle begins to rebound or fly out.
Step 5: Inspect pickers and straps daily.
Worked Example
At 100 picks a minute, a shift of 8 hours has 48,000 picks. Each one strikes the picker and the receiving box with the energy above. No source gives picker life, so log the number of picks each picker survives, and replace it at a fraction of that. Keep a spare set in the loom shed, so that failure happens on the bench and not as a shuttle leaving the loom.
Common Mistakes
- Raising loom speed without checking the shuttle’s rebound.
- A shuttle with loose tips, which come off in flight.
- Weft slack in the shuttle, so the thread flies out and fouls the shed.
- Standing in line with the shuttle’s path.
Safety
A shuttle is a projectile
The overview records frequent shuttle injuries in historical mills. At 10-15 m/s and an assumed 12.5-28 J a shuttle leaving the loom can break bone or put out an eye. Fit a guard along the front, keep the line of flight clear, check the shuttle tips and race every day, and stop the loom if a shuttle fails to seat. The loom’s stop is at the belt and the plant’s at the gate (Power Drive System); children keep away from running looms (Task Assignment by Age).
What’s Next
- Learn next: Beating Up — pushing the weft into place
- Combine with: Shuttle Mechanism — the whole shuttle system