The set of {HEAD ~ wheels} is arranged substantially on {TAIL ~ a line} extending through the arbor 
The set of { HEAD ~ wheels } is arranged substantially on { TAIL ~ a line } extending through the arbor
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH