{HEAD ~ A chain grate} 8 is driven by {TAIL ~ sprockets} 10, 12 which rotate as denoted by the curved arrows 
is driven by
{ HEAD ~ A chain grate } 8 is driven by { TAIL ~ sprockets } 10 , 12 which rotate as denoted by the curved arrows
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH