The angle α shows that the retainers 1 0 and 11 can be pivoted in the tension less state to allow {TAIL ~ an increase} or {HEAD ~ reduction} of the angle α 
The angle α shows that the retainers 1 0 and 11 can be pivoted in the tension less state to allow { TAIL ~ an increase } or { HEAD ~ reduction } of the angle α
OTH OTH 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 OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH