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