I owned/operated a King Kutter Rotary Harrow for several years primarily for pedestrian trail grooming.
Ground powered, too often it did not spin, just acted like a short tine Spike Tooth Harrow. Teeth snagged trail exposed tree roots. Rotary Harrow acts on the surface only, though short tines will rip out some vegetation as long as those highly stressed short tines hold up. I does not cut/penetrate soil to disrupt weed roots, like a Disc Harrow.
Relative to VIDEO, I rate a Disc Harrow with 22" diameter pans a more effective and versatile implement.
Ingenious tool; limited applications. Limited to horse arena
sand grooming, I think a Rotary Harrow would be very useful.
King Kutter no long produces Rotary Harrows. Orders must have been few.
I sold my KK Rotary Harrow on eBay to a customer in Texas, who wanted to experiment with it, as I did and you do.
MORE: http://www.tractorbynet.com/forums/attachments/271517-king-kutter-60-rotary-harrow.html?highlight=
Now, I use an ETA Landscape Rake or an ABI Attachments TR3 'Command Series' Rake for trail and farm road smoothing, mostly the TR3 Rake. I have the extra heavy Landscaper's "Command Series" model TR3, with standard hydraulically controlled scarifiers.
Ratchet Rake bucket attachment also quite useful in woods work. Superior to a Landscape Rake for debris collection. Also good for "opening" small areas to 1/8 acre, as in the VIDEO. (Photo #5)
I have never groomed an arena. TR3 Rakes may be the best arena groomers out there, but EXPENSIVE new.