Method of stress grading timber, and machine for stress grading timber

A timber stress grading machine which comprises:

• means for continuously moving a length of timber;
• means for stressing the moving length by applying a transverse load thereto, the length being supported by two supports between which the load is applied, to cause a deflection of the timber length;
• means for measuring said load and/or deflection;
• means for then stressing the moving length differently at the same position while supported in the same fashion to obtain a different deflection;
• means for measuring the different load and/or the different deflection;
• and
• means for relating the original load and original deflection to said different load and different deflection according to predetermined criteria, thereby to grade the timber length, the supports in each case acting freely to support the length as a simple beam during stressing thereof, so that the length is substantially unconstrained during stressing except by the load and the two supports between which the load is applied.