How do manual cars work?


Why do we have to switch gears to go faster? Why weren’t cars originally made to automatically do that?

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A car’s engine only works at a very limited range of speeds. So limited that your car (with only one gear) would be stuck between (for example) five and twenty miles per hour.

By having different gears, one gear could be 5-20, the next 10-40, then 25-100. Suddenly our car can go a much wider range of speeds.

If we want our engine to be *efficient*, the window gets even smaller. Instead of 5-20, it’s maybe 5-10. More gears also lets us get more efficiency by keeping the engine speed where it will be the most efficient.

A manual gear shift is super simple. Really no more than a few fixed gears and a few sliding gears. Automatic the transition requires some sort of computer to control it, which was really the only thing fundamentally preventing us from making automatic transmissions from the getgo. Of course price would be an issue and it wasn’t really deemed worth all of the extra complexity.

You only need to change gear to increase the speed if the engine handles higher RPMs, the same is the case for automatic transmission cars the question is just how the gear changes.

The internal combustion engine has a limited RPM range the can work in and an even smaller one that they are efficient at so they can rotate too fast or too slow. The solution for a car that can drive at a large speed range is to have gears that change how fast the engine rotation relative to the wheel.

So if you are with the RPM range you can change speed by changing the amount of fuel you give to the engine but if you route it you need to change the rearing ratio.

The difference between an automatic and a manual gearbox is fundamentally how a gear change is initiated. A manual change is initiated and performed by a human moving a lever. In an automatic, it is most of the time because of a control system build on hydraulic.

An automatic gearbox is more complicated than a manual and historically there has been quite a large difference in cost. There has also been a difference in how many gears were common, automatic had fewer an the result is they were often less efficient.

How the gearbox is connected to the engine with a torque converter or a clutch is another difference in how is built.

The result was manual gearboxes were verrry common because of the cost and efficiency difference. Today both differences are quite small so it is primarily a question of what people are used to and what the prepared to use.

It is not the case that automatic transmission system are new, the first on car was made in 1904 and mass produce in 1939.

Electric cars do not need to change gears, a electric motor can operate in a lot larger RPM range. A major part is a work from 0 RPM. There are also Continuously variable transmissions that do not use gears but they are a lot less common

Did you ever ride a bike? To start moving you want a short (or light) gear, so that you can gain speed with a relatively low force on your pedals. A short gear, however, means that you’ll be spinning your pedals crazy fast at relatively low speeds already.

You also want to be able to move at a decent speed, so you’ll also want a long gear, which allows you to avoid having to spin the pedals too fast and still ride much faster than with the short gear you used to start.

Car’s combustion engines are the same, they don’t produce enough “force” to be able to make the car start moving with a very long gear. If you make one gear suited to start from a standstill, the engine will be spinning as fast as it can at a low speed. So you have several gears to make the best use of the range of “spinning” speeds that the engine works best with.

As with everything, simpler solution to problems are found and refined first. It took another couple of decades for manufacturers to master the added complexity of automatics and mass produce them. At that point, market specific needs caused the automatic transmission to become more or less widespread.