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