Why is the clutch pedal in a manual transmission car the heaviest of the three pedals?
I saw this question: The clutch pedal is the heaviest of the three pedals in manual cars, so why don't manufacturers design the clutch pedal to be lighter? In fact, this problem is very simple. We can analyze it from the following points:
Why is the clutch pedal so heavy?
The clutch pedal is definitely the heaviest on a manual-shift car, and that has to do with how it works. When you press the clutch, do you know what you're driving? This is a huge spring.
Since the clutch is transmitted by friction and the engine torque is so large, the clutch pressure plate must be clamped to ensure that the clutch does not slip. Therefore, there is a huge diaphragm spring on the pressure plate, which can generate a large clamping force to ensure that The clutch can transmit large torque normally without slipping. But when you press the clutch, you have to overcome the force of the spring to disengage the clutch. So the clutch pedal is the heaviest.
Moreover, the accelerator pedals are very light because they drive the accelerator. The biggest resistance on early pull-type accelerators is the return spring, but its elasticity is extremely limited and can only be stepped on by one toe, let alone the whole foot. Many cars are now equipped with electronic throttles, which make the pedal lighter.
Although the brake pedal is very light to press, because it is vacuum-assisted, if it is not assisted, the brake pedal will definitely be much heavier than the clutch pedal.
Why not lighten the clutch pedal
There are three main ways to reduce the weight of the clutch pedal:
The first is to reduce the spring force of the pressure plate, but obviously this is impractical. Because the reduced elastic force means that the clutch is not strong enough, the clutch can easily slip.
The second is to increase the lever ratio of the clutch pedal, because the clutch pedal itself is a lever structure, and increasing the lever ratio can make the pedal lighter. But unfortunately this is not practical, because as the leverage ratio increases, the rear clutch pedal travel will also increase, affecting driving. After all, you don't want to have to lift your leg when you press the clutch.
The third is to increase the power of the clutch, which is achievable. For example, many heavy trucks are equipped with power clutches. But the problem is that truck engines often have thousands of kilometers of torque. In order to ensure that the clutch does not slip and the spring force is too large, it is not necessary to fully apply the power, but also to use power. Moreover, the strength of the clutch pedal of a family car is acceptable to most people, so there is no impact without help.
More importantly, increasing power will increase costs, not only the cost of power equipment, but also the structure of the clutch and transmission must be changed. Moreover, the resistance characteristics of the clutch pedal are different at different positions. If you simply increase a constant power, the clutch will be lighter, but the pedal feedback will become very vague. And if you want to maintain the original characteristics of the clutch, the cost will continue to increase, so manufacturers might as well go directly to automatic transmissions.
Reasons for abnormal clutch weight
Some faults or minor problems can also cause the clutch to become heavier. The most common situations in daily car use are the following:
1. The clutch cable is damaged
Many of today's manual gears are hydraulic clutches, using brake fluid to transfer power. However, some car clutches still use cables to transmit power. In some cars, after a long period of use, the friction between the cable and the wire wall creates a gap, causing the cable to be caught in the gap and increase the movement resistance. At this time, the clutch will become heavier.
2. Clutch plate wear
Worn clutch plates can also cause the clutch pedal to become heavier, which is a problem that many people don't realize. Because after the clutch plate is worn, the diaphragm spring of the disc deforms greatly, and more force is required to push the diaphragm spring away when the clutch is stepped on.
3. The pressure plate diaphragm spring is worn
Worn disc diaphragm springs can also cause the clutch to become heavier. Since there are many diaphragm springs on the pressure plate, under normal circumstances, when the clutch is stepped on, the release bearing pushes all the diaphragms together to separate, so that the entire spring body is evenly stressed and easy to separate.
4. The separation bearing seat has large resistance
When the clutch is depressed, the release bearing moves forward and backward. Some people like to apply butter on the bearing seat when replacing the release bearing, so that the release bearing movement can be better lubricated. In fact, this approach is superfluous. Since the rotation speed of the release bearing is very slow and the friction between the bearing and the bearing seat is very small, it is difficult to wear even without lubrication. However, applying butter will increase the movement resistance of the release bearing and make the clutch heavier. In particular, the clutch plate will wear off a lot of dust during use, and sticking to the butter will make the butter thick and hard, which can only further increase the resistance to the movement of the release bearing.
Therefore, when replacing the release bearing, there is no need to apply additional butter on the bearing seat, otherwise the clutch pedal will become heavier and heavier after a period of use.