Hollow Tine Aerator Design

I want to convert a manual hollow tine aerator to a motorised one. I have experimented with electric motor, 3000 rpm, with an eccentric load, mounted on the hollow tine aerator framework. It did not work. I don't have a suitable gearbox. I don't know what a suitable output speed should be. I guess about 100 rpm. I tried mounting an industrial hammer drill. Unlike brick or concrete, the soil did not have sufficient resistance to make the hammer device operate. I think hammer drills have two opposed undulating disks, one stationary and the other spinning that produce the hammer action. I remember when, many years ago, I hired a commercial motorised hollow tine aerator it was extremely heavy and very large. It had a revolving cylinder onto which hollow tines were attached – not suitable for small gardens. Comments on potential designs, with approximate parameters, would be appreciated. I have noticed in the forum detailed information is often requested. The detailed information I have provided does not imply I am asking for complete designs. Design approach or ideas is what I seek. Thank you. Manual hollow tine aerator parameters: 5 hollow tines at pitch 2.6 inches (66mm) Tine diameter 0.63 inches (16mm) Tine length 4.5 inches (114mm) Tine wall thickness 0.08 inches (2mm) Tines welded to a 1 x 1 x 0.12 inch (25 x 25 x 3mm) steel angle Load spreader 1 x 1 x 9.4 inches (25 x 25 x 240mm) Angle/ Load spreader 2 screws, 0.24 diameter (6mm) at 7 inches (178mm) pitch Superstructure 0.75 inches (19mm) outside diameter Forms an inverted 0.68 inches (17mm) inside diameter U and welded to the angle. Operation of the manual hollow tine aerator needs the user to stamp on the angle for the tines to penetrate the soil thus filling the hollow tine with soil. The next stamp forces the tines into a new soil location. The soil entering the bottom of the hollow tine expels the previous cylinder of soil out of the top of the tine. Believe me this requires a lot of effort even when the soil is moist.