Wool combing cyclically feeds a fringe, clamps it in nippers, combs the projecting end, inserts a top comb and uses detaching rollers to withdraw and piece the combed fibres into a continuous sliver. Any roller drafting comparison must use circumferential surface speeds, not RPM alone.
Roller Motion in Wool Combing Interactive Calculator
Compare circumferential surface speeds for selected feed and draw-off roller pairs.
Equation Used
- Each entered diameter is the effective working diameter of its selected roller.
- Roller speeds are constant and surface speed is πDN with no slip or deformation.
- The displayed ratio compares two steady circumferential speeds only.
- Nipper, comb, detaching reversal, piecing, fibre mechanics, loads, quality and ratings are excluded.
The secondary figure uses the same selected roller diameters, speeds and surface-speed ratio in a simplified fibre-band comparison.
How rectilinear wool combing works
A short fringe is fed through open nippers; the nippers close while a circular comb passes through the projecting fibre ends. The top comb then enters, and detaching rollers withdraw the combed fibres and piece them onto the previously formed web. The rollers can reverse during the piecing cycle.
The visual on this page is a bounded surface-speed comparison for selected feed and draw-off roller pairs. It does not reproduce nipper, circular-comb, top-comb, carriage-reversal or piecing timing.
What this calculator demonstrates
Select feed-roller diameter and speed, draw-off-roller diameter and speed, plus a target surface-speed ratio. The calculator returns both circumferential surface speeds, their ratio and the draw-off RPM required to meet the selected target with the entered diameters.
It does not calculate fibre extension, combing draft, feed per nip, piecing, noil, top yield, fibre length, sliver mass, roller pressure, timing, production or product quality.
Roller surface-speed arithmetic
For roller diameter D in millimetres and rotational speed N in rpm, circumferential surface speed is v = πDN/1000 metres per minute. The selected speed ratio is R = vdraw/vfeed = DdrawNdraw/(DfeedNfeed).
For a selected target ratio Rt, required draw-off speed is Ndraw,req = RtDfeedNfeed/Ddraw. RPM ratio alone is valid only when the compared roller diameters are equal.
Default selected example
With a 50 mm feed roller at 4 rpm and a 40 mm draw-off roller at 40 rpm, surface speeds are about 0.628 and 5.027 m/min. Their ratio is 8.0:1, not 10:1, because the roller diameters differ.
To reach a selected target of 10:1 with those diameters, the draw-off roller would require 50 rpm. That arithmetic does not establish an appropriate machine setting for wool.
Scope and correction boundary
Woolmark and Australian Wool Education Trust training material show that actual combing is a timed intermittent sequence involving nippers, circular comb, top comb and reversing detaching rollers. A single steady roller ratio cannot represent that sequence.
The removed page used RPM ratio while its own formula required diameters, and then attached universal settings, tolerances, forces, yields, fibre damage, materials and mill examples. The replacement is only a transparent roller surface-speed comparison.
Questions
Why are roller diameters required?
Linear surface speed is circumference times revolutions per minute. Two rollers at the same RPM have different surface speeds when their diameters differ.
Is the surface-speed ratio the full combing draft?
No. The combing head feeds intermittently and detaching rollers reverse and piece fibres. This steady comparison omits those cycle details.
Does a higher ratio improve fibre separation?
The calculator cannot answer that. Fibre behavior and product quality require the actual machine sequence, settings and material.
Can the required-RPM result be used as a machine setpoint?
Not without manufacturer documentation and the complete drive, timing, roller and fibre-processing constraints.
Primary technical references
- The Woolmark Company, Worsted Top Making Facilitator Guide — feed, nipper, circular-comb, top-comb, detaching and piecing sequence.
- Australian Wool Education Trust, Combing Theory — rectilinear-comb components, feed and detaching sequence.
- US4703431A, Sliver Drawing Apparatus — feed and front rollers, surface feeding speeds and a predetermined drafting speed ratio.
- US5509179A, Autoleveller Draw Frame — circumferential-speed ratios of sequential roller pairs and controlled draft context.
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