a means for holding said blades on {HEAD ~ a surface} of {TAIL ~ an imaginary horizontal circular cylinder} and rotating them about a horizontal axis of said cylinder in a closed cylindrical path, 
of
a means for holding said blades on { HEAD ~ a surface } of { TAIL ~ an imaginary horizontal circular cylinder } and rotating them about a horizontal axis of said cylinder in a closed cylindrical path ,
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH