Drawing and twisting in spinning cotton, wool, etc
Drawing and twisting in spinning cotton, wool, etc. The front drawing-rolls, B, rotate faster than the back ones, A, and so produce a draught, and draw out the fibers of the sliver or roving passing between them. Roving passes from the front drawing-rolls to throstle, which, by its rotation around the bobbin, twists and winds the yarn on the bobbin.
Only the input is driven; every other part of this model moves by physics (MuJoCo), and its ratios are measured. Run it live, change its parameters, or switch the friction off to see the output stop.
- Modelled as
- Seen from the side. Only the front rolls B are driven (6 rpm, by their line-shaft pulley); gears (12, 14, 18) turn the back rolls A slower, and bevels and spur gears (40 to 10) turn the flyer. The top rolls rest on the bottom rolls under their own weight and are not geared. The yarn is a lumped friction model (new yarns: in the compiler, under OpenSpec add-yarn-nip): at each nip a lump of yarn slides along its path and is gripped by both rolls only by friction (mu 0.5 times the top roll's weight); the roving and the spun yarn are tension-only springs; between the nips the fibres slip once their tension passes their yield, and the spun yarn is taken up at the bobbin's radius by the flyer turning faster than the bobbin, which is dragged round by the yarn against its own friction.
- Measured
- The top rolls are turned by the yarn at 1.0001 (A) and 0.9999 (B) of their bottom rolls; the roving is delivered at 0.667 of the speed of the drawn yarn (the 12 to 18 draught); the bobbin lags the flyer at 0.816 of its speed (0.814 expected from the take-up). No step callback: native MuJoCo bodies and tendons only.
- Notes
- The yarn is drawn as a cord through sites posed from the simulation each frame, its twist sliding by the simulated travel. Brown shows no gearing; a train is added so that only B is driven.
Film (MP4) · Still (PNG) · Spec (YAML) · Model (MJCF)
