What is a Gear Ratio?
by Karim Nice Worm Gears If you want to create a high gear ratio, nothing beats the worm gear. In a worm gear, a threaded shaft engages the teeth on a gear. Each time the shaft spins one revolution, the gear moves one tooth forward. If the gear has 40 teeth, you have a 40:1 gear ratio in a very small package. Here’s one example from a windshield wiper.
Any two gears will have a ratio. If your car has a 20-tooth (20T) pinion and a 100-tooth (100T) spur gear, that’s a 20:100 ratio; however, we need to go one step further and divide the number of teeth on the spur gear (100) by the number of teeth on the pinion (20). It’s easy: 100 20 = 5 The gear ratio is 5:1 (say five to one), and that means that the pinion must make five revolutions to turn the spur gear one revolution. It’s that simple. Once you know the gear ratio you want, you can use any combination of tooth counts to get it. For example, a 5:1 gear ratio could be achieved with a 100T:20T, 105T:21T, 110T:22T, or 115T:23T combinations.
A gear ratio is the relationship between the number of teeth on two gears which are meshed. This relationship is expressed mathematically. For example, if one gear with 13 teeth is driven by a gear with 21 teeth, the gear ratio is 1/1.62, or 1:1.62. Almost all types of mechanical machinery, such as vehicles, farm equipment, and industrial machines, use gears in some way, and gear ratios are used to help define the machine’s performance. The idea of a gear ratio is based on the circumference of circles. When two gears with different circumferences are connected by teeth on the outer edge, the movement of the one is translated into greater or lesser movement by the other. If a gear with a large circumference is turning one that is only half as big, the smaller gear will spin twice as fast as the larger one. The same concept works in reverse. Gear ratios are specifically tailored by manufacturers of engines and other machinery, to achieve a certain result. In some contexts, such as automo
A gear ratio is the ratio of the number of teeth on a pair of gears that are meshed together. Here is a gear with 40 teeth meshed with a gear with 8 teeth. The gear ratio is 40 to 8. We can simplify thisi to a ratio of 5 to 1. This means that the 8 tooth gear must rotate 5 times for the 40 tooth gear to rotate once. This also means the 40 tooth gear has 5 times as much torque as the 8 tooth gear. How do I compute a gear ratio for more than one pair of gears?
