Abstract: A vibration system for concrete pipe making machines which system utilizes a precisely manufactured inner mold core that contains mounting surfaces for two coupling shaft bearings and two electric vibrators. The bearing mounting surfaces are accurately located with respect to the electric vibrator mounting surfaces to allow the mold core to become the vibration structure. Jaw-type coupling hubs are keyed and fixed to each end of a coupling shaft with each electric vibrator also having a jaw-type coupling hub fixed to one end of its eccentric weights. The eccentric weights of both electric vibrators are aligned upon assembly in the core.