You might think of the humble gear as a relatively modern invention, but did you know that the history of gears may date all the way back to the 27th century B.C.? Experts have found gears in everything from ancient chariots to devices used to measure the movements of the stars.
Today, you’ll find both metal and plastic gears in everything from cars to watches to conveyor belts. We can’t live without them!
Wondering how gears work their way into your favorite devices? Let’s take a look at some of the most common types of gears you might find today.
Among the most popular types of gears, these varieties have teeth that are parallel to the shaft access. When one spur gear moves, it transfers power to a parallel gear.
Spur gears tend to appear in a huge range of materials and a variety of gear applications. They are often used when a slower speed is necessary, as they grow loud at higher speeds.
As their name suggests, helical gears move in a sort of helix pattern. In contrast to spur gears, whose teeth are parallel to the shaft, the shaft of a helical gear slants at an angle. This allows helical gears to carry more load than spur gears can.
Double Helical Gears
Double helical gears have, as you might expect, two different slants across their surface. These identical but opposite helix angles have a small gap between them.
Using a double helical gear puts even more teeth in contact with each other, which allows these gears to withstand even greater loads. It also helps to distribute vibrations by distributing the load.
This gear variation looks similar to the double helical gear. However, there’s no space between the helical faces, meaning that the gear has a closed “V” pattern.
Herringbone gears are great for applications that create high vibration and shock. Because of their high production cost and the difficulty of manufacturing them, however, they can be expensive and uncommon.
Where the gear types above are circular, bevel gears are more conical in shape. It’s possible to find them in a range of angles, though 90-degree angles are the most popular option. Like herringbone gears, bevel gears tend to be expensive.
There are two sub-varieties of bevel gears.
Straight bevel gears are the most common. These matched gears engage all of their teeth at once during rotations instead of interacting with another gear’s teeth little by little.
Spiral bevel gears have teeth that curve, making them more efficient than the option above. They’re also known as “skew bevel gears.”
Worm gears consist of two parts: the “worm” and the “worm wheel.”
The worm is a narrow shaft with a screw-shaped cut. The worm wheel is the matching gear. Together, they transmit power at a right angle, making them great for high shock loads and low horsepower uses.
Like spiral bevel gears, hypoid gears operate at a 90-degree angle. However, their shafts do not intersect. You’ll find hypoid gears in a range of industrial uses, but they’re most common as automotive gears.
A Modern Marvel
No matter when humans first used gears, it’s safe to say that they’ve become a modern marvel that we’ve all come to rely on. The next time you power up a drill or use an elevator, thank the gears above for their service!
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