The drum is what all second stage fans are spinning in. The rotating drum simply rotates the drum off of the chute and to the side. Unless the equipment is used, or you're a commercial operator, or somebody with a special snow consideration, rotating drums aren't worth the extra expense, in my mind. Wet snow will stink with just about any snowblower. Consider these two videos. Same equipment, just different conditions:
The first video and the snow is flying because the snow is dry.
The second video and the snow isn't moving very well because it is wet and heavy. Yet, it is a same equipment and this is a monster of a rotating drum blower. oldafretired, thank you for the compliment on my videos! My used McKee 720 SnowLand'r is 86" wide, 30" tall, with twin 13" augers, and a 27" fan rotating in an 8" drum. The drum is fixed and sends everything up the chute. My tractor has something around 49 PTO hp. The blower is a good match for my PTO hp Even so my blower is of little use in wet and heavy snow, but is great for blowing back snowbanks, sleet-snow, and dry snows. McKee invented the modern 2 stage blower and sold them as McKee, John Deere, New Ideal, and some other brands. McKees are a good blower and there are a
zillion different variations, but you can spot the McKee manufactured blowers by their distinctive auger design. I thought about an inverted blower but then realized that an inverted blower wouldn't be good at blowing back banks and high snow drifts unless I had a larger-framed utility tractor. At the end of the day, a plow will out-perform a blower every time until the snow gets so deep that your plow cannot plow it, then it is blower time.
Too bad you're not in Minnesota as we have a pile of 3PT snowblowers for sale on craig's list.