The pivot mechanism 20 permits pivoting about a vertical axis, and permits {TAIL ~ limited relative motion} between the front and rear frame sections 16 and 18 about {HEAD ~ a horizontal axis} 
The pivot mechanism 20 permits pivoting about a vertical axis , and permits { TAIL ~ limited relative motion } between the front and rear frame sections 16 and 18 about { HEAD ~ a horizontal axis }
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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD