Force optimization on grain cleaning drive system of combine harvester

A grain cleaning system for a combine harvester, the combine harvester including a chassis and a header for harvesting agricultural material, said grain cleaning system comprising:

• a chaffer sieve configured to be supported for movement relative to the chassis between a chaffer sieve front dead point (FDP) and a chaffer sieve rear dead point (RDP);
• a shoe sieve positioned below at least a portion of the chaffer sieve, the shoe sieve configured to be supported for movement relative to the chassis between a shoe sieve FDP and a shoe sieve RDP;
• a first link including a first end and a second end coupled to the chaffer sieve;
• a second link including a first end and a second end coupled to the shoe sieve;
• and
• a drive shaft driven to rotate about a shaft axis, the rotation of the drive shaft driving the first link to reciprocate the chaffer sieve and driving the second link to reciprocate the shoe sieve,
• wherein either (i) when the shoe sieve is positioned at the shoe sieve FDP, the chaffer sieve is positioned at a location between the chaffer sieve RDP and a chaffer sieve midpoint (MP) position that is defined between the chaffer sieve RDP and chaffer sieve FDP, or (ii) when the shoe sieve is positioned at the shoe sieve RDP, the chaffer sieve is positioned at a location between the chaffer sieve FDP and the chaffer sieve MP, and
• wherein either (i) the second end of the first link is coupled to the chaffer sieve at a point on the chaffer sieve that constitutes a center of gravity of the chaffer sieve, or (ii) the second end of the second link is coupled to the shoe sieve at a point on the shoe sieve that constitutes a center of gravity of the shoe sieve.