Abstract: A wheel mounting having a hub carried by a pair of axially spaced apart ball bearings carried on a spindle, the inner race rings of said bearings restrained against axial movement, and the outer race rings restrained against axial movement in opposite directions by hub carried snap rings. Elimination of hub shoulders previously required for positioning and restraining the outer race rings against axial movement caused by side loading reduces the casting and boring problems and facilitates simpler and more consistant assembly of the hub onto the spindle.

Abstract: By simultaneously illuminating an area of a hologram recording medium through an object transparency situated in substantially direct contact with the recording plane of the hologram recording plane with each of two angularly-displaced beams of coherent light, double modulation is achieved. The disclosed technique is particularly applicable to the serial recording on a single hologram of each of a stereo pair of object transparencies, which, on playback, provides a stereoscopic reconstructed image which is directly viewable by an observer.