The driving devices act into {TAIL ~ the ring gap}, and each of the driving devices has {HEAD ~ a separate drive} 
The driving devices act into { TAIL ~ the ring gap } , and each of the driving devices has { HEAD ~ a separate drive }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD