Choosing a Spinning Wheel Drive Ratio: The Ratio at Which Take-Up, Not Twist, Sets the Pace

Most spinning wheels are sold with two or three drive ratios, selected by moving the drive band between grooves on the whorl, and most instruction treats the choice as a matter of taste: a high ratio for fine yarn, a low ratio for thick. That advice is incomplete in a way that costs output. The ratio sets the spindle speed for a given treadling rate, and spindle speed sets both how fast twist can be delivered and how often the yarn breaks or faults. This paper computes finished yarn per hour across the usual range of ratios for one stated yarn, charging each ratio for its breakage downtime and its under-twist faults, and identifies the ratio at which output peaks. In the computed results, the best ratio is 13; the best spindle rpm is 715; the best metres per hour is 48; the best grams per hour is 1.44; the low ratio metres per hour is 17.8. Set the drive ratio so the spindle runs near the computed peak for the yarn being spun, and treat any ratio well above the peak as a repair-time purchase: it buys revolutions the spinner cannot keep. The study is simulated, not measured; all inputs are stated assumptions, printed in the accompanying computation, which readers may replace with their own values and re-run.