The other two articulated joints of {HEAD ~ blade} 2 follow circular orbits around axle 4, since these are kept at {TAIL ~ a constant distance} from axle 4, which is equal to the length of a blade arm 3 
The other two articulated joints of { HEAD ~ blade } 2 follow circular orbits around axle 4 , since these are kept at { TAIL ~ a constant distance } from axle 4 , which is equal to the length of a blade arm 3
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH