Spinning wheel drive options
On a spinning wheel the flyer adds twist, and the bobbin “takes-up” or “winds-on” the twisted fiber, aka yarn. Both the flyer and bobbin spin, but they have to be able to spin at different speeds. This allows you, the spinner to control how much twist is added before the yarn is wound on to the bobbin. There are three general ways to control how twist is added, and yarn is taken up: Double drive, single drive flyer lead (Scotch tension), and single drive bobbin lead (Irish tension).
What’s the same
Double drive spinning wheels
Double drive wheels have one drive band wound around twice, or two drive bands: Both the flyer and the bobbin are spun by the band, using whorls (pulleys). The whorl size can be changed to adjust the speed of the flyer and bobbin. Smaller whorls mean faster spinning (see “ratios” section below).
For double drive, the bobbin spins faster (has a smaller whorl) than the flyer to take up yarn. However, the whorl for the bobbin has a “U” shaped groove, which allows the drive band to slip when tension is applied to the fiber being spun. Slipping slows the bobbin, so that extra twist can be added to your yarn before take up. The flyer whorls have a “V” shape, which grips the drive band and does not slip easily. Sometimes two drive bands are used: no-slip elastic on the flyer; cotton or hemp on the bobbin which slip more easily.
Single drive flyer lead spinning wheels: Scotch tension
Scotch tension is a very common single drive spinning wheel configuration. With Scotch tension the flyer is driven/spun by the drive wheel. The flyer always spins and adds twist when the drive wheel is spinning. The bobbin can either spin with the flyer, which adds twist without taking up yarn, or can spin more slowly than the flyer (or stop) to take up yarn.
An adjustable brake on the bobbin is set so that applying tension to the fiber with your hand will make the bobbin spin, but releasing the tension on the fiber will allow the brake to stop the bobbin, and take up yarn. Since the bobbin tension can be set very light, you can have very light tension while still adding twist: scotch tension is great you want to spin very light yarns.
Single drive bobbin lead spinning wheels: Irish tension
Single drive bobbin lead, aka Irish tension, is similar Scotch tension, just flipped; in this case the drive band goes around a pulley on the bobbin. The flyer has an adjustable brake that allows it to spin faster or slower depending upon the tension applied to the fiber being spun. Because the bobbin is driven, take-up can be very strong with Irish tension, and this makes it a great wheel for bulky yarns. They also tend to treadle easily.
Drive options: the differences
Double drive offers consistent take-up. They are a joy to use for spinning fine and medium yarns. Some beginning spinners find it finicky to adjust a double drive spinning wheel, but it’s easily learned. The flexibility of using two different drive bands to control tension and slippage of the bobbin whorl add a great deal of flexibility. Additionally, many double drive wheels can be converted to Scotch tension. All in all, this is a very versatile set-up, though if you know you’ll be spinning either very fine (cobweb) or lots of bulky yarns, wheels optimized for that might give you a head start.
Scotch tension (flyer lead single drive) are great all-around performers. The tension on the flyer can be set to be very light, which is great for super fine yarns. Tension is relatively easy to adjust, and can span a very wide range, contributing to this being one of the most versatile systems. However, it will take some trial and error to make the minute tension adjustments required.
Many beginners like Irish tension: working with a strong pull makes it easier to get the “feel” of controlling tension. The strong pull also means that they are great for bulky yarns. They may require a more finesse and practice for fine yarns. Super fine or cobweb yarns may be difficult on Irish tension. Finally, Irish tension spinning wheels tend to treadle the easiest, which some people prefer.