edge whereby only one or two significant vibrations or jars occur per rotation of mass 104 thus the engagement surfaces may not be completely smooth a relatively larger number of protrusions may be utilized to produce higher frequency vibrations irregular vibrations may be produced by spacing the cams at irregular or non symmetrical spacing accordingly the arrangement of protrusions and recessions may allow the vibrations to occur at a continuous frequency or at irregular frequencies e g several quick beats and or pauses and one beat or the like depending on the spacing of the cams for example with only one camming element then only one beat might be produced per revolution of mass 104 in another example multiple and or irregular beats may be produced per revolution of mass 104 accordingly the number of protrusions recessions and the spacing therebetween may be selected to create a desired frequency of vibration and motion in one embodiment the camming surfaces such as protrusions 116 and or recessions 118 and or camming surfaces 120 may be interchangeable to change the vibration frequencies in one embodiment corresponding camming surfaces 120 are provided on engagement end 122 of mass 104 which is the upper end as shown in fig2 camming engagement surfaces 120 may be of various types shapes and the like in one embodiment roller bearings may be but are not required to be utilized as camming surfaces 120 fig3 which is cross section 3 3 of fig2.