Patent ID: 7974803

Claim:
An apparatus for calibrating a wood testing machine with a first bending section means and a second bending section means each with a bending span defined by two end-span rollers, one in each of two clamp roller groups and a load sensing roller located at or about a center of the bending span with a force measurement means that produces output values proportional to a force applied by the load sensing roller when said roller bends elongate material by a predetermined deflection whereby the predetermined deflection in the first bending section means is a first predetermined deflection and the predetermined deflection in the second bending section means is a second predetermined deflection and the first predetermined deflection is in a direction substantially opposite to the second predetermined deflection, comprising: a. A test bar that can be positioned within either the first or second bending section means such that the test bar will bend in one direction in one bending span and in an opposite direction in the other bending span such that a first test bar reading and a second test bar reading are produced equal to output values from a first and second force measurement means, respectively, said test bar having an EI value equal to a product of a modulus of elasticity (E) of a test bar material and a moment of inertia (I) for a cross section of the test bar, and; b. a calibration shim of predetermined thickness that can be introduced between a load sensing roller and the test bar when the test bar is bent in the first bending section means or the second bending section means, such that a shim reading equal to a change in output value is produced for each bending section means with said readings proportional to the thickness of the calibration shim and the EI value of the test bar whereby a first shim reading is produced for the first bending section means and a second shim reading is produced for the second bending section means, and; c. a first calculating means that determines a shim scale factor for each bending section means such that a product of the first shim scale factor and the first shim reading equals a product of the second shim scale factor and the second shim reading, and; d. a second calculating means that determines an overall scale factor such that a sum of the product of the first shim scale factor and the first test bar reading and the product of the second shim scale factor and the second test bar reading, multiplied by the overall scale factor is at a predetermined relationship to the EI value of the test bar, whereby the first shim scale factor, the second shim scale factor and the overall scale factor together are the calibration of the wood testing machine.