What is the relationship between gear speed ratio and tooth ratio?
3 Answers
The speed ratio of two meshing gears is inversely proportional to the tooth ratio. For example, for two meshing gears, if the larger gear has 40 teeth and rotates at 100 rpm, and the smaller gear has 20 teeth, then the smaller gear will rotate at 200 rpm. That is, the number of teeth of the driving gear × the speed of the driving gear = the number of teeth of the driven gear × the speed of the driven gear. Additional information is as follows: 1. Speed: For two meshing gears, the more teeth a gear has, the slower its speed. In other words, among meshing gears, the gear with more teeth rotates slower, while the gear with fewer teeth rotates faster. 2. Gear transmission is one of the most widely used forms of mechanical transmission: It offers accurate transmission ratio, high efficiency, compact structure, reliable operation, and long service life. Current gear technology can achieve the following indicators: circumferential speed v=300m/s, rotational speed n=105r/min, transmitted power P=105KW, module m=0.004~100mm, diameter d=1mm~152.3mm.
When I was young, I played with model cars, where the gear speed ratio and the tooth count ratio were inversely related. Simply put, if one gear has more teeth and the other has fewer, the smaller gear spins faster while the larger one spins slower. The specific formula is that the speed ratio equals the number of teeth on the driven gear divided by the number of teeth on the driving gear, or the reciprocal of the tooth count ratio. For example, if the large gear has 20 teeth and the small gear has 10 teeth, the small one spins twice as fast as the large one. This principle is common in car transmissions and affects acceleration and climbing performance: a high tooth count ratio provides high torque at low speed, while a low tooth count ratio does the opposite. When modifying cars, I adjust the gears to balance the tooth count ratio for optimal fuel efficiency, and I also pay attention to gear wear, which can affect precision—otherwise, the drivetrain may produce unusual noises or vibrations. Regular maintenance helps maintain the ideal ratio.
Last time I modified my off-road motorcycle, I personally experienced the close relationship between gear speed ratio and tooth count ratio. The principle is that with a larger tooth count ratio, such as fewer teeth on the front sprocket and more on the rear, the rear wheel turns slower but with greater torque, making it suitable for climbing. Conversely, a smaller tooth count ratio results in higher speed and faster rotation. The speed ratio is inversely proportional to the tooth count ratio. During chain maintenance, I often check if the tooth counts match to avoid chain slippage or overheating. If the tooth count design is unreasonable, the engine load will increase, and fuel consumption will rise. I tested different tooth count ratios while riding on mountain trails, recorded data to compare speed changes, and found that this is crucial for off-road performance. Simply changing a sprocket can enhance the handling feel.
