at least one turn assist cylinder, each said {HEAD ~ turn assist cylinder} coupled between said frame and {TAIL ~ a corresponding said caster wheel assembly}; and 
coupled between
at least one turn assist cylinder , each said { HEAD ~ turn assist cylinder } coupled between said frame and { TAIL ~ a corresponding said caster wheel assembly } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH