The coupler preferably comprises a compliant belt and pulley drive, {HEAD ~ a worm and gear drive}, or {TAIL ~ a bevel gear drive} 
The coupler preferably comprises a compliant belt and pulley drive , { HEAD ~ a worm and gear drive } , or { TAIL ~ a bevel gear drive }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL