تماشای ویدئو Reductor with gears of equal number of teeth 1 از آی-ویدئو
A result once generally supposed impossible.
The cranks rotate two times slower than the red gear.
For details see:
http://meslab.org/mes/threads/21452-Bien-toc-bang-cac-banh-rang-co-cung-so-rang?p=121995#post121995