SPINLAB Stelometer 654

Author:  Jarren Ray

Overview of Instrument

    The Spinlab Stelometer is an instrument that tests a flat sample of cotton fiber for tenacity and elongation. The instrument breaks a flat bundle of fiber and indicates the force required to break the fiber on a graduated scale. The elongation is determined on another graduated scale at the breaking point of the fiber sample. A simple calculation is used to determine the tenacity of the sample. The calculation uses the breaking point number (which is indicated on the graduated scale) and the known weight of the sample to determine tenacity. A precision balance is needed in conjunction with the stelometer to get the weight of the sample.

Theory of operation

    When evaluating the quality of raw fiber, Tenacity and Elongation are two physical properties of great importance. They are also important for the suitability of fiber for yarn making. Information produced by the stelometer is essential to the yarn spinner making clothing and the researcher developing new varieties of cotton with higher quality fiber traits.

    The stelometer determines the force that is required to break a small, flat sample of fiber. The broken sample is then weighed. Both the breaking force and weight are plugged into an equation to determine the tenacity. Elongation is how far the fibers will stretch before they break. To briefly describe the mechanism by which breaking force and elongation are determined for a sample, a picture of the stelometer is shown below


In the first picture you can see that the loading arm is up and locked, while in the second picture the loading arm has rotated to the left.  

A sample is loaded in the top part of the loading arm. As the trigger is depressed, the loading arm will pivot to the right at the pendulum if you were looking at the stelometer from the front. The rate at which it pivots is determined by the dashpot adjustment. The pendulum is pivoted in such a way from the loading arm that its motion at first is gradual, but as it rotates further the range of motion exceeds until it stops against a rubber stop. 

As it rotates, the sample in the top part of the arm is held tightly in a clamp. The clamp comes apart as the loading arm rotates stretching the fibers until they break. As they are being stretched, the force indicator and stelometer indicators move along with the clamp until the fibers break. At this point the indicators stop, leaving them on the scale at a particular number.  

Instrument Components

Standard Operating Procedure for Sample Preparation

Standard Operating Procedure for Sample Calculations

SOP short version

Calibration and Literature