Lots of recent interest in tillers and tilling so ... I have an old Mantis (very small, called the "20 pound tiller) that I bought used for $20 a few years ago. I guess it's 20 to 30 years old. I found it was fun to use to cultivate in close spaces and to till our six 2' by 8' garden boxes. So when I saw a new (repaired) Toro similar machine at Lowes on clearance for $100 last fall, I picked it up. Same usage. btw, the Mantis is 2 cycle and the Toro is 4 cycle.
Also have (for many years) a couple very old Wards front tine tillers (bought used, one free)(must be 3 or 4 hp I guess) and I've used them to till previously worked small garden areas and flower beds - and tore up a few compost piles by letting it climb right up and over. One is continuously loaned out.
A couple years ago I bought a used 5 hp (?)Craftsman rear tine tiller - light weight and not very powerful. Again, only useable on previously worked ground - but easy to load and off-load on the pickup. One forward speed.
My workhorse is a 25 yo Sears 8hp bought new (end of year clearance for $600) that is heavy, has variable speed and can break new ground if you only take a light bite - and hang on cause these things are powerful and can jump. It does have the swinging handles which allows you to avoid making footprints in newly tilled earth. I wouldn't bother to try it on "rock hard clay". It would continuously try to walk across the surface and be a bitch to hang on.
We have a lot of clay - gets hard and opens cracks so wide you can shove your fingers in them in this hot weather. I use a 14" moldboard plow on a
1950's IH Farmall Cub when breaking new ground - and sometimes even first thing in the spring on previously worked ground to turn previous growth under. Sometimes just dragging a small disc harrow around with a 1970's 8hp Wheelhorse is enough to get started with the previously worked area.For someone who insists on tilling "rock hard clay" I would suggest using something heavy - a farm tractor with down pressure on the hitch and a pto driven tiller. I suppose a high end garden tractor might do the job but I would rather spend $2000 on an old farm tractor than $6000 on a garden tractor with questionable ability to do the job.
Anybody else ?