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