A flyer is a balanced U-shaped arm of wire or stamped metal that turns around the bobbin, carrying the yarn through an eye so that one revolution inserts one twist and, if the bobbin lags, winds the yarn on. Its outward pull is mass times the square of angular speed times radius, so doubling the speed quadruples the force on each arm, and an unbalanced arm shakes the whole row of spindles.
Part of Spinning Frame
The rotating guide arm that inserts twist and lays yarn onto the bobbin at the same time.
One Revolution Of The Flyer Is One Twist In The Yarn
The overview describes the path: yarn leaves the front rollers, passes through the hole in the top of the spindle, then through a hook or eye on the flyer arm. The flyer turns around the spindle; each turn twists the yarn once and, because the bobbin turns slightly slower or faster, winds it on. The twist per inch is flyer rpm divided by inches delivered per minute (Twisting). Hand-wheel flyers have hooks along one arm, spaced 1-2 cm, to guide the yarn along the bobbin (Spinning Wheel). A frame cannot have a spinner moving the yarn from hook to hook, so either the flyer eye or the bobbin must traverse up and down to lay the yarn in even layers.
The Force On An Arm Rises With Speed Squared
For an arm of mass m whose centre of mass sits at radius r, the outward force is F = m × ω² × r, with ω in radians per second (standard mechanics, recalled). Take an assumed arm of 20 g (0.02 kg) with its centre of mass 50 mm out, at the assumed spindle speed of 2,000 rpm used elsewhere in this tree:
- ω = 2,000 × 2π ÷ 60 = 209.4 rad/s, so ω² = 43,865
- F = 0.02 × 43,865 × 0.05 = 43.9 N, about 4.5 kg-force on one arm
- at 4,000 rpm: ω² is four times larger, F = 175 N
If the two arms are balanced the forces cancel at the spindle and only bend the arms. If one arm is heavier by 2 g, an unbalance of 0.002 × 43,865 × 0.05 = 4.4 N at 2,000 rpm acts on the bearing and turns once per revolution. In a row of twenty spindles, twenty such shakes fall on the same rail.
What You Need
- Wire or sheet metal that holds its shape: mild steel or hard brass wire, or stamped iron.
- A balance for weighing each arm.
- A polished eye or hook (a groove or burr cuts the yarn).
- A bearing and a seat on the spindle (Bearings and Bushings).
Method: Making And Balancing A Flyer
Step 1: Form the two arms to the same shape and length with the same bends. Make them as a pair from one length of wire if possible.
Step 2: Weigh each arm. The overview does not set a limit; aim for equal to the resolution of your balance, and file the heavier arm at its tip.
Step 3: Polish the eye with fine abrasive and a leather strop, then draw a length of yarn through it and watch for fuzz or snags.
Step 4: Spin it on the spindle by hand, then under power with no yarn. A flyer that shakes the table is out of balance or bent.
Step 5: Check after a week of running for bending, loosened seats and grooves in the eye.
Worked Example
Two arms weigh 20.0 g and 22.0 g with centres of mass 50 mm out. The mass difference of 2 g at 2,000 rpm gives 0.002 × 43,865 × 0.05 = 4.4 N, as above. Filing 2 g from the heavy arm’s tip removes it, but check that the centres of mass still sit at equal radii: balance is mass times radius on both sides, not mass alone.
Common Mistakes
- Balancing by weight alone with unequal arm radii.
- Raising the spindle speed for output without refiguring the force, which grows with the square.
- An eye with a burr, which frays yarn and breaks ends.
- Letting a bent flyer run because the frame “mostly works”.
Safety
A flyer strikes whatever reaches into its circle
At the assumed 2,000 rpm the arm tip passes any hand within reach many times a second, and it throws a broken wire or loosened part outward with the force above. Fit a guard along the row, tie back hair, and never pass a hand near a flyer until it has stopped. The stop and the coast time are discussed in Drive System; children do not work near running flyers (Task Assignment by Age).
What’s Next
- Learn next: Bobbin and Whorl — the speed difference that does the winding
- Combine with: Spindle Construction — the spindle the flyer rides on