Is a Minimum of 9 Teeth for a Gear Acceptable?
2 Answers
Gear minimum of 9 teeth is not acceptable. Below are relevant introductions about gears: 1. Concept: It refers to the gearbox. The transmission is one of the most critical components in a vehicle's drivetrain system. 2. Function: It enables a wide range of adjustments to the vehicle's driving speed and the torque on the driving wheels. Due to varying driving conditions, vehicles require significant variations in speed and driving torque. For instance, when driving empty on a straight highway, the driving resistance is minimal, whereas when fully loaded and climbing a slope, the resistance increases substantially. However, automotive engines have a relatively narrow range of speed variation, and their torque variation range is even less capable of meeting the demands of actual road conditions.
I encountered this issue when working on gear design before. A 9-tooth gear sounds aggressive, but the practical risks are significant. The standard minimum number of teeth for gears is generally recommended to be 14 or more to prevent undercutting—where part of the tooth root is cut away, making it weaker. I've used 9-tooth gears before; they barely function in models or under light loads but are noisy. Under heavy loads, such as in automotive transmissions, they jam and break due to poor meshing, which accelerates wear. When designing, it's crucial to calculate the module and pressure angle correctly. With a 20° pressure angle, a 9-tooth gear will definitely undercut; at 25°, it might work but with a short lifespan. Additionally, gears with fewer teeth have poor strength and can easily cause cascading failures in engine transmission components. In short, for durability and safety, it's best to choose 12 teeth or more—don't risk saving a little space for much greater hazards.
