Two sets of gears. z<sub>1</sub>=14 (red); z<sub>2</sub>=42 (blue); z<sub>3</sub>=14 (yellow); z<sub>4</sub>=28 (green).
<a href="//commons.wikimedia.org/wiki/User:Jahobr" title="User:Jahobr">Jahobr</a>
2016-12-05
<span class="int-own-work" lang="en">Own work</span>