polyurethane is carried on the end of arm 26 pad 27 is impacted by spur 24 when armature 20 rotates clockwise it is desirable that pad 27 have a visco elastic property substantially matching the rebound characteristics of the print medium 31 in that event armature 20 and the hammer head 29 will begin rebound at substantially the same time when impact with stop pad 27 and print medium 31 occur concurrently extending upwardly from armature 20 is stem 28 which carries a hammer head 29 the forward end of hammer head 29 terminates in an impact face 30 for striking medium 31 against type characters on a carrier such as a belt not shown the tab 32 above hammer face 30 distributes the mass of the hammer to make the center of the effective impact and stem mass more nearly coincident with the center of impact this desensitizes the hammer to double impacts tail 33 behind hammer face 30 provides guidance for hammer head 29 stem 28 has a substantially reduced width compared to armature 20 stem 28 is also tapered slightly from the point of armature 20 to the base of hammer head 29 thus stem 28 is made flexible to allow bending about the pivot axis of armature 20 the amount and degree of flexure can vary depending upon the operating parameters of the hammer system in accordance with this invention the degree of flexibility is such that the impact mass i e hammer head 29 follows the armature 20 in a delayed fashion and in addition oscillates relative to armature 20 the period of oscillation of the resonant frequency of the hammer stem impact mass is chosen such that there are n 1 2 periods of oscillation during the.