The Taber® Torsional Stiffness Apparatus - Model 108 has been
employed to measure the relative stiffness of gloving leathers.
Based on the design described in ASTM D2821 (Standard Test Method
for Measuring the Relative Stiffness of Leather by Means of a
Torsional Wire Apparatus), this instrument is useful in measuring
the flexibility and stiffness of a leather or other bendable
specimen.
Description
The Torsional Stiffness Apparatus incorporates a torsion head and
wire that translate a twisting motion to a 1/2" wide x 4 1/2"
long specimen. Mounted to a rigid base and support post, the
torsion head includes a dial protractor graduated from 0 to 360°.
Made of 0.010 inch diameter tempered stainless steel wire, the
torsion wire passes through the center of the torsion head in a
loosely fitting sleeve gripped by a friction bearing. A fixed
index pointer indicates the degrees of twist introduced to the
torsion wire.
Specimens are secured to the Torsional Stiffness Apparatus by two
clamps. The upper specimen clamp is fastened to the lower end of
the torsion wire and is able to rotate as the torsion wire is
twisted. The lower specimen clamp holds the specimen in place
which allows the twisting action to occur. To accommodate the
twisting action, the lower specimen clamp can slide up or down
guide posts mounted to the base.
To operate the Torsional Stiffness Apparatus, the torsion head is
rotated in a plane normal to the torsion wire. As the torsion
head rotates, the torsion wire twists the test specimen. Mounted
to the top of the test specimen upper clamp assembly is an
indicator that measures the twist applied to the specimen until
the specimen has been twisted 90°.
An optional Finger Control Knob provides an ergonomic design that
allows for two-hand operation of instrument, permitting a smooth
twisting action of the specimen.