If there is one single thing about spinning wheels that seems to generate confusion, it is ratios, understanding what they are, what they do, and how to figure them.

The key to understanding ratio is knowing how a spinning wheel works. Here�s what happens: Every time the spinner treadles the wheel, the drive wheel turns one time. For each time the drive wheel turns, the flyer turns X number of times. The ratio is the number of times the flyer rotates for each rotation of the drive wheel. If the flyer turns 5 times for each turn of the drive wheel, then the ratio is 5 to 1 and this is written 5:1. It�s important to know how many times the flyer is turning per treadling as each time the flyer turns one twist is being inserted into the fibers. So with a wheel ratio of 5:1, each treadling action inserts 5 twists. If the spinner drafts 1 inch of fibers with each treadling, there are 5 twists per inch (tpi) being inserted into the yarn.

The fastest way to determine the ratio of your wheel is to simply mark one arm on the flyer and mark one spot on the drive wheel. Line the marked spots up at the 12:00 position and then turn the drive wheel while counting the number of times the flyer rotates. Stop when the drive wheel is back at the 12:00 position. Note that ratios are not always even numbers so your wheel may well have a ratio of 8.5:1 or 6.75:1.

The most accurate way to determine your ratios is to take a few measurements and do a bit of math. For this you need some non-stretchy cord, a measuring tape, a scissors, pencil and paper, and, if your math ability is as bad as mine, a good calculator.

Since spinning wheels have axles mounted right in the center of the drive wheel, it�s not possible to get an accurate measurement of the diameter without totally tearing the wheel apart so we�ll start with the circumference.

Step 1 in all cases is to measure the circumference of your wheel. If your drive wheel has grooves, measure down inside the groove. Use the cord, wrap it around, cut it to the correct size and then measure the cord. Write that number down and then divide it by 3.14. The answer is the diameter of your wheel.

Step 2 in all cases is to measure the circumference of your whorl or whorls.
For a single drive bobbin lead wheel, measure the whorl on your bobbin.
For a single drive flyer lead (Scotch tension) measure the whorl on the flyer shaft.
For double drive, measure both.
Again, use the cord for measuring the circumference and measure down inside the grooves. Divide by 3.14 to get the diameter.


Single drive bobbin lead: Divide the drive wheel diameter by the whorl diameter. The answer is your ratio.

Single Drive flyer lead (Scotch tension): Divide the drive wheel diameter by the whorl diameter. The answer is your base ratio. If the bobbin is less than half full, your effective ratio is about 85% of the base ratio; if the bobbin is over half full the ratio is about 95% of the base ratio.