What Transmissions Do Continued

Part 2 of 6     April 10th 2017

That brings us to our second problem: cars need more or less torque in certain situations.

For example, when you’re starting a car at a standstill, you need a lot of power, or torque, to get the vehicle going. If you floor the gas pedal, you’re going to make the engine’s crankshaft spin really fast, causing the engine to go way above its power band, and possibly destroy itself in the process. And the kicker is you won’t even move the car all that much because torque drops off on an engine as it goes above its power band. In this situation, we need a lot more torque, but to get that, we’ve got to sacrifice some speed.

Okay, what if you just press on the gas a wee tiny bit? Well, that’s probably not going to cause the engine to spin fast enough to get into its power band in the first place so that it can deliver the torque to get the car moving.

Let’s take a look at another scenario: Let’s say you’ve got the car moving really fast, like when you’re cruising on the freeway. You don’t need to send as much power from the engine to the wheels, because the car is already moving at a brisk pace. Sheer momentum is doing a lot of the work. So you can let the engine spin at a higher speed without worrying as much about the amount of power being delivered to the wheels. We need more rotational speed going to the wheels, and less rotational power.

What we need is some way to multiply the power produced by the engine when it’s needed (starting from a standstill, going up a hill, etc.), but also decrease the amount of power sent from the engine when it isn’t needed (going downhill or going really fast).

Enter the transmission.

The transmission ensures that your engine spins at an optimal rate   (neither too slow or too fast) while simultaneously providing your wheels with the right amount of power they need to move and stop the car, no matter the situation you find yourself in.

It’s able to do this effective transmitting of power through a series of different sized gears that leverage the power of gear ratio.

Next Week, Gear Ratios

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