The lengths of the links comply with the conditions: A͞B=O͞C=A͞P and A͞O=B͞C=C͞Q. Figure AOCB is a parallelogram linkage. Link 1 rotates about fixed axis D and is connected by turning pair P to link 4. Links 2 and 3 turn about fixed axis 0 and are connected by turning pairs A and C to links 4 and 5. When link 1 rotates about axis D, point P describes circle p-p of radius D͞P and point Q describes circle q-q of radius E͞Q=D͞P. Therefore, by adding link 6, shown by dash lines, the mechanism can be made to transmit rotation with a mean t ransmission ratio between links 1 and 6 equal to i₁₆=ω₁/ω₆=1. Links 1 and 6 rotate in the same direction. Angle ∠ POQ is always equal to α.
$688$LW,GI$