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
Because your transmission can only operate within the perimeters of what an engine can do.
If an engine can only turn at 1,000 rpm. It can only cycle 1000 times in a minute. the moving parts can only do so much work in those 1,000 rotations. You use your transmission to either lengthen the distance/time of the work to be done (taller gears) or you shorten the distance (smaller gear) but make the work “harder”
The glory of modern transmissions is we have multiple gears.
The REALLY large drive gears and really short output gears. This means the bigger gear has to move a bigger distance, over a longer period of time to achieve the same work as the shorter gear. But this work is accomplished easier. The problem is, that big gear takes a lot of RPM’s to do one full cycle. So in a low gear, you’d have a lot more “torque” or power, but a lower top speed. since it takes longer to turn that big gear.
so you shift into 2nd, now you have slightly less torque, because the drive gear is a touch smaller, and the output gear is a touch bigger. You give up torque and gain a higher top speed.
Then you eventually get to your final gear, you have a lot less torque, but a much higher top speed. This is why you’ll probably stall your car if you try moving from a stop outside of a low gear like 1st or 2nd. To get moving, your engine needs the gear advantage. But once you start moving, and you’ve ramped up some speed, it’s easier to maintain a speed than it is to get there. so you can give up some of the torque once you’re moving.
Source: I’m a motorsports tech who specializes in Porsches.
Latest Answers