The conventional rapper design is improved to provide longer service without maintenance and easier access at less cost when service is required by, among other things, redesign of the hammer assembly, hammer shaft and lever assemblies, and the hammer assembly housings. Design improvements include the provision of access panels on the housings, a guide and lock mechanism for removing and inserting the hammer assembly out of and into the hammer assembly housing, providing the hammer with a removal, and keyed engagements of hammer shaft assembly components.