Abstract: The non-destructive testing of materials, particularly coarse grain materials such as the carbonaceous materials used in the anodes and cathodes of an aluminium smelting furnace, using longitudinal compression waves employs a waveguide to apply the waves to a specimen, the and specimen having a cross-sectional dimension Dg of between 3 and 5 times the material average grain size Dg. Alternatively, or in addition, the waves used preferably are of effective wavelength from about 30Ds to 50Ds. Alternatively, or in addition, the effective wavelength of the waves is preferred to be approximately equal to the length of the sample; the necessary very long samples may be obtained by connecting a plurality of smaller elementary samples end-to-end. The apparatus may include a controllable furnace for cycling the sample to determine the change with temperature of the physical characteristic that is being measured.

Abstract: A ski suspension strut for a snowmobile comprises: upper and lower telescopically arranged members guided for a predetermined range of relative axial movement but constrained against relative rotation. The lower member is of cylindrical profile and is rotatably supported in a fixed generally upright orientation by mounting means in the snowmobile. One end of the lower member is connected to a snowmobile ski and the second member is connected to a steering mechanism in the snowmobile to be rotated thereby in effecting steering movement of the ski. Damper means is located interiorly of the lower member and operatively connected to both members to dampen relative axial movement thereof. Linear bearing means are mounted in the lower member in sliding engagement with a section of the upper member that is of constant square profile over a suitable length.