Must the steering shaft of the tractor be fitted with a disc brake axle?

Owners who have run through the transportation understand that more brakes are used on the trailer to count drum braking, but when buying a car, you can always hear the sales staff introduce the design of the "front disc and back drum".

The so-called "front disc and back drum" refers to the disc brake used by the front wheel of the vehicle and the drum brake used by the rear wheel.

In fact, in 2019, the Ministry of Transport issued the relevant standards for tractors and trailers, which made clear instructions on the restrictions on the installation of braking devices on tractors and trailers, requiring that all steering wheels of the steering shaft of traction vehicles with a maximum speed of more than or equal to 90km/h should be equipped with disc brakes. In other words, most of the newly produced models need to be equipped with at least 1 axle disc brakes.

Why is that? In fact, this also starts from the different characteristics of the drum brake and the disc brake.

1. Drum brake

The drum brake is composed of the brake drum, brake shoe, brake pump, friction plate and return spring. When braking, the brake shoe rotates outward under the action of the actuating device, and the friction plate on the outer surface presses against the inner cylinder of the brake drum, generating friction torque on the brake drum.

The most obvious advantage of the drum brake is the strong braking force. It produces friction through the friction plate and the inner wall of the brake drum for braking, the greater the friction area, the greater the friction, and the braking force is naturally larger.

However, due to the closed wrapped brake drum, the heat dissipation of the drum brake is poor, and it is easy to gather a large amount of heat energy during the braking process, resulting in the friction plate and the brake drum being heated and deformed, causing brake recession and jitter phenomenon, affecting the braking efficiency.

In addition, the drum brake structure is more complex than the disc type, and the brake needs to respond one by one with multiple components such as the pump and the adjusting arm, so the brake response speed is slow.

2. Disc brake.

Disc brake by hydraulic control, the main parts include brake disc, pump, brake caliper, oil pipe, etc., brake disc is fixed on the wheel, with the wheel rotation, pump is fixed on the bottom plate of the brake, brake caliper on the two friction pieces are installed on both sides of the brake disc.

Its working principle is that when the brake pedal is pressed, the pump piston is subjected to the liquid pressure conveyed by the oil pipe, and the brake caliper is pressed to clamp the brake disc, and the brake disc is brake dead. When the brake pedal is released, the pressure is released and the piston returns to its original position.

The biggest advantage of disc braking is the fast response speed, according to the relevant experimental data, when the three-axle tractor chooses the overall braking, the emergency braking at a speed of 60km/h, the braking distance can be shortened by about 10 meters than when using the drum brake, and then it also plays a good role in reducing the vehicle's own weight.

In addition, the relevant data show that the braking force of the left and right wheels of the vehicle using the drum brake is about 30% different, and the vehicle using the disc brake is less than 10% because of the self-adjustment function, which can improve the comfort of the vehicle when driving.

Compared with the drum brake, the disc brake, brake calipers, etc. are fully exposed in the air, and the heat dissipation performance is excellent, especially when the wheel is rotating, the air flow speed around the disc brake can be accelerated, and the braking effect is not easy to be affected by overheating.

Even after the vehicle wades in water, the brake disc is shaped like a vertical dish, which is not easy to appear water phenomenon, and when the brake disc is rotating, there is a large centrifugal force, and the water between the brake disc and the brake caliper is easily thrown out, so the water reliability of the disc brake is relatively high.

Of course, the disc brake is not completely without shortcomings. Due to its structural problems, the strength of the disc brake is weak, which limits its use environment and transportation conditions, and is not suitable for extreme transportation environments such as heavy loads. At the same time, compared with the brake drum, the brake disc area is smaller, the heat capacity is worse, and the heat generated by the disc brake will be larger than that of the drum brake under the same braking force.

It can be seen that whether it is disc brake or drum brake, each has advantages and disadvantages, and can play a better effect if it is properly applied. Therefore, even if the upgrade to the disc brake does increase the investment cost of the car company and the owner, the installation of the disc brake on the steering shaft of the tractor may also be a choice under the combination of safety and economy.