A down-the-hole vibratory unit for a drilling system includes a casing comprising a fluid inlet. The vibratory unit can also include a plurality of eccentrically weighted rotor assemblies positioned at least partially within the casing and in fluid communication with the inlet. The eccentrically weighted rotor assemblies can be unbalanced relative to a central axis. Additionally, the eccentrically weighted rotor assemblies can be configured to rotate in response to a fluid flow directed thereto to apply centrifugal forces to the casing.