A model of the effect of orienter design and operating variables on the mean angular deviation of oriented wood strands

A model has been developed of the effects on the mean angular deviation of oriented strands of orienter design variables, such as the choice of discs or vanes, the width of the lateral gaps between discs or vanes, operating variables such as strand length, strand flow rate, and the free fall distance between the bottom edge of the orienter discs or vanes and the strand mat surface. The mean angular deviation of strands on the surface of a mat is the sum of the orientation arising from the interaction of strand length and gap width and the disorienting effect of free fall distance between the bottom edge of the orienting vanes or discs and the mat surface. The mean angular deviation of strands falling freely at production flow rate through the gaps between discs or vanes can be estimated as close to half of the maximum angular deviation possible for the given gap and mean strand length. The mean angular disorientation of strands during free fall can be estimated as a linear function of the strand length and the free fall distance. Use of these relationships in a previously published model of strength development in oriented strand products (1) predicts that a 1-inch decrease in gap width, with a height above the mat of 1.5 inches, will increase the modulus of elasticity (MOE) of a 3-inch strand product by approximately 0.58 Mpsi and that a 1-inch decrease in height above the mat, with a gap width of 0.750 inch, will increase edge MOE by approximately 0.21 Mpsi.

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