The Black Ratio
Myah Doakes
Celeste Byers

Gear Ratios and Mechanical Advantage

By Celeste Byers and Myah Doakes

Understanding the concept of gear ratios is easy to grasp if you understand the circumference of a circle (the circumference is equal to the diameter of the circle multiplied by Pi). If a gear has half the circumference of another gear, it would have to complete two full rotations in order to do as much work as the larger gear. This explains why two gears, one twice as big as the other, have a gear ratio of 2:1. Most gears have teeth. Teeth make it really easy to determine their gear ratios because all you have to do is count the teeth of both the gears and divide those two numbers by each other! For example, if one gear has 100 teeth, and the other gear has 20, the gear ratio when these two gears connected together would be 5:1. Teeth on gears are helpful because they make it so slight imperfections in gear circumference don't matter and also keep the gears from slipping. The number of teeth on the gears ensure that we always get integer ratios. The gear ratios are controlled by the number of teeth on the gears even if the diameters are a bit off! As you can see, although it takes more effort to rotate the larger gear, the weight moves up at a faster speed! When you rotate the smaller gear, it is easy to move, but it takes more time to pull up the weight. All of this is because of gear ratios and mechanical advantage. Mechanical advantage is the factor by which a mechanism multiplies the force put into it. Assuming that the friction of the axle and gear are small, the mechanical advantage is simply the gear ratio.