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