A whacker packer. If you've ever been on a construction site you seen places where dirt has been back filled. Most of the time you'll see a rolling machine packing the dirt. It has to be at a certain measured firmness to be deemed okay. Then you have area that the rolling machine can't go. That where you'll see device that is about 3 1/2 feet tall. It has about a 1 foot square pad on the bottom. The is sorta like an accordian in that the foot goes up and down. One tube slide inside another. It's driven by a gasoline engine mounted on top. The operator holes onto a handle and just guide it by directing the machine on the bounce.
The ones we had were made be a company by the name of Whacker Packer.
Ive run both, the hand ones are kinda fun. The real big diesel compactors do the job, but man, what a boring job...back and forth, all day long.....I did the pad for the haybarn here, I think it was close to 8 feet of dirt compacted down to around 2 feet. Inside that barn is like sandstone, like rock. Cant tell ya how many dump truck loads of dirt, non stop for two days. Boss rented that thing for me to operate and he brought the dirt in the big dump truck, dug it up other side of the farm with the excavator..
I also own a non machine one, just biodrive. Steel handle with a square plate on the bottom. This is NOT fun, freaking hard to use after around 100 good whacks, but it will pack dry clay dirt pretty darn hard, if you do it in thin layers, pack, add more dirt, pack, etc. for along time.... I pack around RxR ties set as gate posts with it, mostly.