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