Yarn Twist Liveliness, Snarling & Residual Torque

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 6 inputs are read from the form on every keystroke: Yarn Linear Density, Twist, Yarn Bulk Density, Test Loop Length, Twist Released as Snarl and Setting Efficiency.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Snarls in the Test Loop together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Twist Multiplier (Ne basis), Surface Twist Angle, Twist Still Free to Release, Twist per Inch, Snarls per Metre of Loop, Yarn Diameter, Yarn Count and Twist Energy Index — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

Substituting

A hundred and forty snarls in a metre of yarn is why single jersey knitted from unset ring yarn spirals. The fabric is not being knitted badly - it is being knitted from a spring, and the loops rotate until the torque is balanced by the fabric structure.

How to use it

1. Work through the input groups in order — Yarn & Twist and Snarl Test & Setting. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Snarls in the Test Loop in the dark results panel — that is the headline figure, expressed in turns.
4. Check the supporting rows underneath (Twist Multiplier (Ne basis), Surface Twist Angle, Twist Still Free to Release, Twist per Inch, Snarls per Metre of Loop, Yarn Diameter, Yarn Count and Twist Energy Index) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Snarls in the Test Loop before a trial is booked, so machine time and material in Spinning, Winding & Yarn Package Engineering are committed against a calculated figure rather than an estimate.
• Costing and quotation — Snarls in the Test Loop is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Yarn Linear Density) shows how much of the gap in Snarls in the Test Loop each variable explains.
• Teaching and study — the accepted ranges bracket normal Spinning, Winding & Yarn Package Engineering practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• The snarl prediction is semi-empirical: the geometry is exact but the released fraction is a measured input that varies with fibre, moisture, time since spinning and the test method, so the snarl count should be treated as a comparison between yarns rather than an absolute prediction. Moisture matters more than most people expect - the same yarn tested at 45% and 75% relative humidity gives noticeably different liveliness, which is why the test belongs in a conditioned laboratory. Setting efficiency is entered as a single figure but real setting is time, temperature and moisture dependent and partially reverses on ageing, so a yarn set weeks ago is livelier than the same yarn set yesterday. The twist energy index is a ranking device with no units, not a physical energy.
• Every input is bounded to the range normal practice occupies (Yarn Linear Density 4 to 200 tex, Twist 100 to 2500 tpm and Yarn Bulk Density 0.3 to 1.3 g/cm3, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Standards and further reading

• ASTM D1423 - Twist in Yarns by the Direct-Counting Method.
• ASTM D1422 - Twist in Single Spun Yarns by the Untwist-Retwist Method.
• ISO 2061 - Determination of twist in yarns, direct counting method.
• AATCC 179 - Skewness Change in Fabric after Home Laundering, the downstream consequence.

Questions people ask