Hi Myra,
The flyer whorls are different sizes. Which one you use depends on how much twist you want in your yarn.
It works like this: Every time you treadle, the drive wheel turns once and the flyer turns X number of times and each time the flyer turns it puts that number of twists into your yarn. So, If your flyer turns 10 times every time the drive wheel turns once, then 10 twists will go into the yarn. This is the ratio of your wheel. If you draft 1" of yarn each time you treadle, you will have yarn spun at 10 twists per inch.
Now, each flyer whorl has a different diameter so your wheel has 2 different ratios. The larger the diameter of the whorl, the less twists go to the yarn; the smaller the diameter the more twists go into the yarn.
Here's how to find your ratios: Tie a sting around one flyer arm and another around one spoke of your wheel. Line things up so both strings are marking the 12:00 position. Slowly turn your drive wheel and count the number of times the flyer arm string goes past the 12:00 position until the marked drive wheel spoke is back to the 12:00 position. That will tell you the ratio for that particular whorl. Then move the drive band and do the same for the other whorl.
But it sounds to me like you need to adjust the tension of your wheel as the bobbin fills. This is normal. Simply adjust the tension (tighten it) in small increments as the bobbin fills and all should be well no matter which ratio whorl you are using.
