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