Abstract: A railroad track ballast tamper, operating on-track, having a workhead resiliently and pivotally supporting a pair of platforms on each side of each rail with tamping blades pivoted on each platform and vibration motors fixed to each platform. Lowering the workhead tilts the blades toward the rail because of the platform pivot locations, and actuators coupling the blades squeeze the blades toward the tie so as to tamp, with vibration and squeezing action, that region beneath the ties and under the rail.