COMPUTERMATIC TIMBER-GRADING MACHINE — LABORATORY EVALUATION OF PERFORAAANCE WITH RESPECT TO FEED SPEED AND THE DYNAMIC/STATIC DEFLECTION RELATIONSHIP

Timber of various stress-grades was passed a number of times through a Computermatic stress-grading machine running at 60 m/min and 150 m/min in a laboratory. The deflection of all the tested points on each stick was recorded, and deflection at each of the points was also determined statically for com-parison. The range of dynamic deflection values for each point (termed repeatability) and the mean deflections were also calculated. Data from tests on verification sticks were used to determine differences between deflection measurements taken statically and those taken in a Computermatic machine. There were no consistent differences in mean deflection measurements at the two feed speeds. A mean increase in repeatability error of one-half of one machine measuring unit found at the higher feed speed was considered to be of little practical significance in industry. The modulus of elasticity as determined by the Computermatic machine on the verification sticks at the point of least stiffness was on average slightly lower than the same property determined on the static machine. Three percent of the sticks had modulus of elasticity differences greater than the 10 % allowed by the current Australian Standard