Re: Small point
I believe a "flail mower" might be a wheeled, upscaled weed-whacker (UK: Strimmer).
The materials used in the flail might vary depending on the expected brush to be demolished.
All guess work.
Later
Completely wrong, except for the "materials used" bit. It's a small cousin to a mine flail. It appears it thrashes the brush into submission.
I approve.