Things You'll Need
Instructions
Find an old washing-machine motor. It can be purchased inexpensively at a junkyard or an appliance-repair store. Washing-machine motors are excellent for building a vibrating plate because they are used to running with uneven ̵1; vibrating ̵1; loads; they almost always have a flywheel, which you need; and they're designed to run in a closed container without overheating. Be sure you get the mounts and the stiff industrial springs that connect the motor to the frame.
Drill one of more holes in the flywheel of the motor; all the holes should be in one quarter of the flywheel. This will cause the motor to vibrate at a steady rate as it runs. Start with one hole and drill more of them to increase the vibration. Cheap, and therefore soft, metals are used to make flywheels, so they're easy to drill holes in.
Build a wooden frame to contain the motor; use the boards to build wooden steps on one side. Use the same axel mountings that the motor had when it was in a washing machine to attach it to the floor and to the center of the large plastic or wooden platform. Attach the edges of the platform to the wooden frame with large springs ̵1; you can probably get them from the same washing machine.
Wire up the ̶0;dead man's switch̶1; so that the user can hold the switch to activate the vibrating plate, and release it to deactivate the plate. The switch is serving the same purpose it did on the chainsaw, snow blower or jet ski it was originally designed for. It's also a safety measure, because it automatically shuts off if anything goes wrong.