30—YARN HAIRINESS: A SURVEY OF RECENT LITERATURE AND A DESCRIPTION OF A NEW INSTRUMENT FOR MEASURING YARN HAIRINESS

This paper is intended to supplement one published in 1966 containing a survey of the literature on yarn hairiness, and the review of the literature is brought up-to-date at the time of writing.

A new electronic instrument for measuring yarn hairiness is outlined. This apparatus enables three parameters to be obtained directly and simultaneously, these being hairiness, hair length, and yarn diameter.     

Characterisation of shock absorber deformation by optical surface digitisation

Abstract

The performance of shock absorbers has been tested in specific regulatory drop tests onto an unyielding target at the BAM drop test facility. Optical surface digitisation methods have been used to measure, analyse and evaluate permanent deformations of shock absorbers more systematically. The measurement principle of the used fringe projection technique and its technical application to shock absorber investigations is explained in detail. Furthermore, examples of shock absorber testing results as well as final data visualisation are given in the present paper.     

33—A GRAVIMETRIC TECHNIQUE FOR DETERMINING THE MEAN FIBRE DIAMETER OF WOOL

A method is presented for determining the diameter of wool gravimetrically by using fibre snippets instead of full-length fibres. A quantity of the snippets is weighed and then counted with an electronic particle-size analyser (a Coulter Counter). The average length of snippets is obtained by measuring the length of a small random sample. The product of the average snippet length and the number of snippets present in the weighed sample provides an estimate of the total length of the weighed snippets. Hence their mass per unit length can be calculated, and, if the fibre density is known, the r.m.s. diameter can also be determined.

For continuous-filament nylon, the method gives excellent agreement with diameter values obtained by a conventional gravimetric technique. For combed wool, the snippet gravimetric diameter is always less than the projection-microscope diameter, corrected to r.m.s. Some of this difference is attributed to reentries in the wool-fibre surface.     

The Calibration of Air-flow Apparatus for the Determination of the Fibre Diameter of Wool

There is a general algorithm for the determination of practicable starting allocations of colours to the two sides of a 4 × 4 box pick-at-will loom, but its convenience in use varies greatly. An improvement is indicated, but a simpler and more efficient algorithm is suggested for the one-empty-box case, for which the general algorithm is least satisfactory.

Two of the constraints of weft patterning on such 4 × 4 box looms are examined, largely by using the general algorithm. First, the maximum number of practicable starting allocations is determined for any given number of weft colours and any smaller number of box-pairs. Next, it is shown that there is a possibility that a weft repeat may be unweavable with one shuttle per colour if the number of picks in the reduced repeat is not less than the number of shuttle boxes in use.

In contrast to the genera! case, if there is only one empty shuttle box, the box plan that minimizes the number of large box movements for a given weft repeat can rapidly be determined by using a microcomputer.     

43—THE AIR-FLOW DIAMETER OF WOOL TOPS: THE EFFECT OF COEFFICIENT OF VARIATION

Differences between the results obtained for the fineness of wool tops measured by air-flow and projection-microscope methods can arise because the coefficient of variation of the measured top is different from that of the tops used to calibrate the air-flow meter. The validity of some assumptions implicit in the air-flow calibration is examined and a correction table for precise use of the air-flow meter calculated. The corrections range from ?2% at 16 μm to zero at 36μm.     

34—WITHDRAWAL FORCES IN THE PROCESSING OF WOOL SLIVERS: PART II: THE INFLUENCE OF VARIATIONS IN GILLING ON THE WITHDRAWAL FORCE

An account is given of the use of withdrawal-force measurements to determine the extent of fibre alignment in slivers. It is shown that a direct relation between withdrawal force and percentage noil exists. Several variations in the preparation of slivers were investigated, namely, the number of gillings, the draft during gilling, and the direction of feed.     

35—AN AIR-FLOW PROCEDURE FOR DETERMINING THE FINENESS OF RAW WOOL

A satisfactory procedure has been found for determining with an air-flow meter the mean fineness of greasy wool sampled from bales by pressure-coring. A wool-model Shirley Analyser is used to remove dirt and vegetable matter from the washed wool cores. The Analyser also intimately mixes the wool fibres of a sample, which substantially improves the precision of the air-flow measurement. The effect of the Analyser on the measured value of fineness is investigated, and possible methods of calibration of the air-flow meter for use on wool cores are considered. A series of measurements on greasy-wool cores by both air-flow and projection-microscope methods is used as a basis for the suggested procedure. The precision of measurement is evaluated, and a particular calibration method is recommended. The mean fineness of a sample of greasy wool in core form can be found with a precision of ± 0 5 μm.