Each bobbin hangs on a peg under a small trolley. The trolley has rollers that run inside the steel box rail. Trolley to trolley is joined by a short link that pivots, so the chain bends round the U-turns in storage but cannot stretch or bunch. Two hundred of these, 165 mm apart, make one 39 m train.
A rubber wheel on a motor presses on the chain from above through a slot in the rail. Turn the wheel, the whole train slides. Reverse the wheel, it slides back. Drive stations sit closer together than one train length, so some wheel always has grip. That is why no loop is needed anywhere.
| Motor current | Grip plus drag. Rises when rollers wear or the rail gets dirty. |
| Slip | Wheel turning, train not moving. Needs a pulse sensor on the wheel or the rail. |
| Chain stretch | Worn pivots make the train longer. Shows as a slowly growing start-to-end sensor time at the same speed. |
| Hanger faults | A bent peg drops or jams a bobbin. Shows as a repeat fault on one train id. |
Schematic, not to scale. One storage track of each kind is drawn; the real layout has two of each, and three ring frames with two working tracks each. Frame names follow the I/O list. The mill later renamed R13 to 14 on the drawing. 20 seconds here stands for about 25 minutes, and the creel phase in real life is hours.