A projection 18 is provided in the chains 17 to push {HEAD ~ the rear end} of {TAIL ~ the base frame} 5 
of
A projection 18 is provided in the chains 17 to push { HEAD ~ the rear end } of { TAIL ~ the base frame } 5
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH