Abstract: An optical nulling apparatus for testing an optical surface includes an aspheric mirror having a reflecting surface for imaging light near or onto the optical surface under test, where the aspheric mirror is configured to reduce spherical aberration of the optical surface under test. The apparatus includes a light source for emitting light toward the aspheric mirror, the light source longitudinally aligned with the aspheric mirror and the optical surface under test. The aspheric mirror is disposed between the light source and the optical surface under test, and the emitted light is reflected off the reflecting surface of the aspheric mirror and imaged near or onto the optical surface under test. An optical measuring device is disposed between the light source and the aspheric mirror, where light reflected from the optical surface under test enters the optical measuring device.

Abstract: Two formed sheet members secured together in face to face relationship by integral rivets together define a bracket with a central ball race and a plurality of drain passages radiating radially outwardly from the race. Leg portions formed along one margin of each of the identical pair of members define a saddle for seating the bracket on a pipe. An identical pair of wire straps are interconnected to opposite ends of a spring and at the other ends are hooked to the bracket, the straps having shape characteristics such that the spring force is applied in the plane of abutment of the two members.

Abstract: An improved wheel construction for agricultural apparatus, such as wheel-move irrigation pipe lines, has a hub and an annular rim joined by spokes releasably attached at their ends to the hub and rim in a manner such that the wheel may be knocked down or disassembled for storage and shipment and easily assembled at the point of use. The inner spoke ends are releasably joined to the hub by unique coupling structure which are engagable to firmly interlock the spokes to the hub and are releasable to separate spokes from the hub solely by relative movement of the spokes and hub between interlock and release positions.