Engagement between the worm screw 167 and the helical wheel 168 is maintained by {HEAD ~ the action} exerted by {TAIL ~ the pinion} 151 
Engagement between the worm screw 167 and the helical wheel 168 is maintained by { HEAD ~ the action } exerted by { TAIL ~ the pinion } 151
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH