The engagement of the spring and {HEAD ~ the stop} with the drive lever yields {TAIL ~ lever arms} of different lengths 
The engagement of the spring and { HEAD ~ the stop } with the drive lever yields { TAIL ~ lever arms } of different lengths
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH