I added a shadow to each gear. It looks like a papercraft. This original image was donated by Pearson Scott Foresman, an educational publisher, to Wikimedia Commons, and is thereby in the Public Domain. you can see the source URL in the below comment. This is a gear -animation which depicts a normal gear and a epicyclic gear. For the url of the reference I referred to ,see the comment below. This animation is implemented by attributeName="transform" function of SMIL.
Gear-animation-02混音
animateTransform、animation、gear、Gears、Pearson-Scott-Foresman、remix 228417、remix 230238、SMIL.attributeName="transform"、type="rotate"、yamachem
animateTransform、動畫、齒輪、齒輪、皮爾森 - 斯科特 - 福爾斯曼、混音228417、混音230238、SMIL.attributeName =“改造”、類型=“旋轉”、Yamache米
資料來源：openclipart ( https://openclipart.org/ )