Types of Gears Used in Aircrafts
Gears are an imperative part of many motors and machines, where they do things like increase torque output by providing gear reduction and alter the direction of rotation like in automotive vehicles. They are used for far more applications than just these two, and therefore come in many different types. The most common gear types are spur, helical, bevel, rack, and worm. In this blog we will discuss each type and how they differ from one another.
Spur gears are toothed, cylindrical shaped gears used within industrial equipment to transfer mechanical motion. They are the most commonly used type of gear and are frequently aligned in series for large gear reductions. The teeth in these gears are straight and mounted parallel to one another on differing shafts. Areas where spur gears are used include washing machines, screwdrivers, windup alarm clocks, and other devices. The advantages of spur gears are that they are efficient and easy to assemble, have straight teeth that are easy to align, and minimize power loss due to slippage. Their disadvantages include that they are very loud at high speeds, must be used in parallel, and are not as strong as other types of gears.
Helical gears feature a diagonal tooth profile that makes them smoother and quieter than spur gears. They can be mounted parallel or crossed, but when crossed, the same handed gears must be used (both left or both right). While their diagonal teeth allow the gears to engage more gradually, they also cause more slippage and therefore a decrease in efficiency. In turn, this slippage leads to increased axial thrust on the shaft, making it important to choose a bearing that can withstand the added thrust generated by the gears.
Bevel gears are used in intersecting shafts and have a changeable operating angle due to their unique shape. One disadvantage of bevel gears is that their variable operating angle makes them more difficult to assemble than other gears. The shafts of these gears also experience a large force, so similar to helical gears, it is important to ensure the bearing is capable of withstanding the force. There are two types of bevel gears: straight and spiral. Generally speaking, the type will depend on the manufacturer, though many will offer both. Straight type bevel gears are similar to spur gears and therefore prone to suffering from backlash and excessive noise. Adversely, spiral bevel gears share similarities with helical gears due to the orientation of their teeth. Always remember to buy spiral bevel gears in pairs as they are only guaranteed to work with a gear from the same manufacturer.
The final two types of gears are rack gears and worm gears. Rack gears can be found in two styles: flat and round. When paired with spur gears or pinions, rack gears can transfer rotary motion into linear motion. Worm gears feature two pieces, the worm wheel and worm gear. These gears are quiet and self-locking but suffer from high power loss and high thrust loads. Whatever application your gears will be used for, know that there is a wide selection of options to help you find exactly the gear you need.