As {TAIL ~ the bars} 24 rotate around {HEAD ~ a sprocket}, as shown in FIGS 4 and 5, the bars reverse direction, going from pointing up to pointing down or vice versa 
As { TAIL ~ the bars } 24 rotate around { HEAD ~ a sprocket } , as shown in FIGS 4 and 5 , the bars reverse direction , going from pointing up to pointing down or vice versa
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH