{HEAD ~ A chain drive system} within {TAIL ~ each} of the pair of trollies mounts a support arm assembly on which a fire proof cab is removably mounted 
within
{ HEAD ~ A chain drive system } within { TAIL ~ each } of the pair of trollies mounts a support arm assembly on which a fire proof cab is removably mounted
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH