Abstract: A method and apparatus for balancing rotatable members whereby a member to be balanced is rotated first in one direction about an axis at a selected speed and then is rotated in the opposite direction about the same axis and at the same speed. A sensor determines the circumferential apparent location of greatest imbalance or runout of the member in each of the directions of rotation, following which any imbalance of the rotatable member is compensated for by adding or removing weight to or from such member at a circumferential zone which is equidistant between the apparent locations of greatest imbalance.

Abstract: A portable seam tester is provided for testing the seam strength, on the job site, of large sections of flexible sheet material formed by seaming together smaller size panels. The tester has a piston and cylinder mechanism carrying spaced toggle action clamping means adapted to receive and retain folded double-thickness portions of the material at opposite sides of a seam. Pressurized fluid is controllably supplied to the cylinder to force the clamping means away from each other, thereby placing the material in tension so as to impose a predetermined stress on the seam.