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