I understand the basics of how the clutch/gears work and that if the input speed is too high for the gear, you shift to the gear that can handle the higher speed. But what makes that gear able to withstand that? Isn’t the gear smaller, which would make it spin faster?
Hope this makes sense to car people.
In: Engineering
Think about it like a geared bicycle.
What matters is the interaction between *two* differently sized gears. This is called the gear ratio.
The first gear on a bike is smaller than the pedal gear, so the pedal gear rotates more times than the drive axle.
As the gears grow larger, the ratio changes so that the pedal gear – or motor’s output shaft – turns the drive axle more than once. The further away from 1:1, the more energy it will take to turn the drive axle, since the output shaft is rotating it more times with the same amount of revolutions.
To answer your question, the gears use the momentum of the flywheel, the clutch, and synchros to match the rotation of the trans input shaft with the rotation of the next gear in sequence. The gears are connected to the input shaft through shift linkages.
At the top of the first gear on a bike, you are pedaling very fast. Shift up to second, you are pedaling slower again. The change in gear ratios allows that energy to be maintained but with a lower RPM. Because the gear got larger, I have to put more energy into turning it. This is why when you shift into a higher gear, RPM go down.
It works exactly the opposite when downshifting. Think of going down a hill on a bike. I am in 6th gear, pedaling at a mild pace. I shift down one gear, I am pedaling like a madman. One more gear down, I blow my knee out. This is because the input energy stayed the same (or increased), but the force required to turn the axle decreased. On a bike the knee blows out, on a car this will destroy the engine.
To avoid this, you want to let the RPM go down so that when you downshift the RPM doesn’t exceed the redline. Preferably nowhere near the redline. If you aren’t a fan of downshifting, just throw it in neutral and apply brake! Just like an automatic.
Hope that answers your question!
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