I recently got into cars.
In: Engineering
Gears have teeth. Each tooth on one gear fits into and corresponds to a tooth on the other gear[s] it is connected to along those teeth. So the first thing you do is count how many teeth are on each gear. For the sake of a simple example, we’ll look at where one gear has 10 teeth and the other has 20. We connect the engine to the gear with 10 teeth and the wheels (well, the path towards the wheels) to the gear with 20.
When the engine done one full turn, 10 teeth of the gears have been spun through. For the engine side gear that’s 1 full rotation, but for the wheels side gear that’s only half a rotation. So by the same physics rules as using levers (ie a see-saw) to assist in lifting a heavy object, you have only turned the wheels gear half a rotation, but you have applied double the force (torque, or “muscle” as it were) upon it. Or alternatively, the torque required by the engine was much lower in exchange for the fact that you didn’t travel very far.
So that’s a 20:10 ratio, or rather 2:1. Typically ratios are written as x:1 no matter what, even if it means x is a fractional number.
In a real car, 1st gear is probably something like 3.5:1 ratio, your top gear might be something like a 0.7:1 ratio (the engine gear is bigger than the wheel gear this time!), and the path to the wheels goes through a differential or similar device that likely also provides a permanent gearing ratio of around 3.5:1 again. All numbers are approximate of course, and vary by car. Use these numbers are guides only.
Latest Answers