<a href="https://en.wikipedia.org/wiki/Four-bar_linkage" class="extiw" title="w:Four-bar linkage">Four-bar linkage</a>, <a href="https://en.wikipedia.org/wiki/Antiparallelogram" class="extiw" title="w:Antiparallelogram">Antiparallelogram</a>; red: speed vectors
<a href="//commons.wikimedia.org/wiki/User:Jahobr" title="User:Jahobr">Jahobr</a>
<span class="int-own-work" lang="en">Own work</span>