Transmit rotation with fixed ratio; involute teeth maintain constant velocity ratio.
Involute gear teeth give constant velocity ratio and tolerate centre-distance errors. Module m=d/N sets size; mesh requires equal module and pressure angle (typically 20°). Types: spur, helical, bevel, worm. Contact ratio should exceed 1.2.
A 20-tooth pinion with module 3 mm has a 60 mm pitch diameter.
Gears transmit rotation with an exact speed ratio, which is why they are used in almost every power train from clocks to wind turbines.
Transmit rotation with fixed ratio; involute teeth maintain constant velocity ratio.
Gears transmit rotation with an exact speed ratio, which is why they are used in almost every power train from clocks to wind turbines.
The velocity ratio stays constant even if the centre distance changes slightly, which makes manufacture and assembly tolerant.
The small clearance between meshing teeth that allows slight movement. Too much causes noise and position error, while too little causes binding.
Typical applications include selecting a gear pair to reduce motor speed for a conveyor, designing a differential that lets two wheels turn at different speeds and checking the tooth strength of a gear in a gearbox.
Study "Cams and followers" first (topic 85 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
Pitch diameter d=mN. Helical gears are quieter. Worm gears can self-lock.
A 20-tooth pinion with module 3 mm has a 60 mm pitch diameter.
The next topic is "Gear trains", which builds directly on this one.
It is classed as Advanced in Engineering Mechanics (topic 86 of 106). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Engineering Mechanics.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.