We used to build these all the time, but the ones we made had old 1 ton truck axles really low geared around 6.5 to one ratio . made full decks on then like a proper shredder with a 24" disk and swing blades By mounting only 2 of the duel wheels turned outboard it allowed for a full 6 ft shredder. the deep gear ratio meant the dixk spun faster they would cut not just beast the brush.
This thing he built is a pretender.