Does a large gear driving a small gear increase or decrease speed?
2 Answers
A large gear driving a small gear reduces torque while increasing speed. Gear ratio principle: When two gears with different diameters mesh and rotate together, the larger-diameter gear will rotate slower than the smaller-diameter gear. Their rotational speed ratio is inversely proportional to their gear diameters. Inverse relationship between speed and output force: When power remains constant, speed and force are inversely proportional. A small gear driving a large gear decreases speed but increases output force; conversely, a large gear driving a small gear increases speed but reduces output force. A small gear driving a large gear achieves speed reduction and torque increase, while a large gear driving a small gear results in torque reduction and speed increase.
As an enthusiast who frequently tinkers with engines, I've observed that when a large gear drives a small gear, it indeed results in acceleration. Simply put, for every full rotation of the large gear, the smaller gear, having significantly fewer teeth, will rotate at a doubled speed. It's similar to when you switch to a smaller front sprocket on a bicycle—your legs push more slowly, but the wheels spin much faster. In a car's transmission, this principle is used to increase speed in higher gears, albeit with reduced force, thereby lessening the engine's load. However, it's important not to overlook the change in torque—when speed increases, you might feel a lack of power when climbing hills or accelerating. I've used similar setups in DIY modifications, where selecting the right gear ratio is crucial to balance performance. The key takeaway is that excessive gear clearance or insufficient lubrication can lead to noise or wear during high-speed rotation.