Science, Technology and Engineering
Geralt
CC BY-SA 4.0
Wheel_on_âPeggy,â_a_Lima_Shay_Geared_Steam_Locomotive_(SN_2172)
Steven Fine
CC-BY-SA 4.0
Clock gears
Przemek Pietrak
CC BY-SA 3.0
Science,_Technology_and_Engineering
CC0 1.0