Recently, after facing questions from netizens about the material of the lower swing arm of the Ideal L9, the boss of Li Auto started to popularize science mode and "answered questions" about why a silver-like coating was used, but the inside was not made of aluminum alloy.

article: Cao Hao/Xu Bo

[Know Che Di’s original product] Recently, the boss of Ideal Auto started the science popularization mode again after facing netizens’ questions about the material of the lower swing arm of Ideal L9. I'm confused as to why it uses a silver-like coating but is not made of aluminum alloy inside. Then some friends may have questions: What is the difference between a steel or cast iron swing arm and an aluminum alloy swing arm? Is it a good thing to be made of aluminum alloy? Today, we are here to talk to you about the differences between different materials.

Li Xiang replied to netizens’ questions

Schematic diagram of double wishbone independent suspension

Before sharing the differences between different materials, let’s first take a look at what a swing arm is? It is a main component of the suspension system. Its scientific name is the control arm. It is located between the wheel and the subframe . One of its functions is to transmit force and moment between the wheel and the subframe or the body, and at the same time restrain the wheel up and down. The direction of movement ensures that the tires are as close to the ground as possible; another function is to form a soft connection with the shock absorber to ensure the comfort of the vehicle on bumpy roads. Regardless of whether the component is installed in the front or rear suspension system, as long as it is closer to the ground, that is, relatively lower, it is generally referred to as the lower swing arm.

Steel swing arm

Among the models currently on the market, the material of the lower swing arm is mainly divided into two categories: one is cast iron or steel lower swing arm, and the other is made of aluminum alloy material. The former has a higher usage rate. Basically, most models use cast iron or steel lower swing arms. The main reason is that its cost is relatively low, which can better control the cost of the entire vehicle.

Aluminum alloy swing arm

The characteristic of aluminum alloy material is that it is relatively lighter in weight. For cars, it is one aspect of lightweight design, but the cost will also be higher. However, its relatively lighter characteristics can bring smaller unsprung mass to the vehicle. In addition, due to the high manufacturing cost of aluminum alloy materials, when the vehicle needs to be replaced after a collision, the repair cost will be higher than that of cast iron or steel swing arms.

So what does reducing unsprung mass do? It mainly has two functions: first, it can make the rebound speed of the shock absorber faster, such as reducing the wheel volley when passing through a speed bump, thereby improving comfort; in addition, when the rebound speed of the shock absorber is increased, It can make the wheels stick closer to the ground on rough roads to provide better grip and improve the vehicle's control and driving quality.

The use of swing arm materials by various manufacturers:

After talking about the differences in the lower swing arms of different materials, we might as well take a look at how to choose the lower swing arm solutions for other models except the Ideal L9. Of course, considering that the Ideal L9 does not strictly have competing products of the same level and price in the market, so based on the car buying habits of ordinary consumers, we chose a model on the market with a similar price to the Ideal L9. Compare.

BMW X3

Mercedes-Benz GLC

Lexus NX

Cadillac It will have a certain improvement effect, but considering the suspension structure and force expectations, they believe that there is no need to use an aluminum alloy lower swing arm to meet the needs of the vehicle.

Moreover, these cars are also considered luxury brands in everyone's eyes. It seems that there is no need to consider too much cost control. It can only be said that the manufacturers still choose steel or cast iron rear lower swing arms. It is indeed based on actual needs. If It doesn't seem like a bad thing to be able to control the cost a little while meeting the usage needs.

Jaguar F-PACE

Cars such as Audi Q5L, Jaguar F-PACE, Lincoln Navigator use aluminum alloy lower swing arms. But the starting points of these cars are obviously different.For example, Jaguar is a loyal fan of the all-aluminum body. Its suspension system itself is derived from the sports car platform, so it will pursue more controllability. Its suspension also uses aluminum in many places, including the lower swing arm. Made of alloy, for a vehicle that focuses on sports and handling, it can indeed improve the vehicle's dynamic performance.

Audi Q5L

Although the Audi Q5L has reduced the proportion of rear suspension aluminum alloy in the new model, and the connecting rods are all made of steel, the lower swing arm is still made of aluminum alloy and uses a forging process, which is lighter in weight. The old model is lighter, so the suspension weight ratio of the new model does not change compared with the old model, and it can also achieve the purpose of reducing costs.

Lincoln Navigator

Most of the rear suspension of Lincoln Navigator is also made of aluminum alloy, and the lower swing arm has also been hollowed out, which not only has high strength but also further improves lightweight. After the Voyager's suspension uses a large amount of aluminum alloy materials, the effect can actually be directly reflected in the vehicle's control performance, driving stability, and comfort.

Ideal L9

So, let’s go back to the Ideal L9. Although the lower swing arm of the rear suspension is made of non-aluminum alloy material, it is certain that the current calibration state of the rear suspension of this car can meet the manufacturer’s requirements for comfort. Due to the requirements of safety and controllability, higher cost aluminum alloy materials are not used to control the overall cost of the vehicle.

And compared with many models made of practical steel or cast iron, the Lideal L9 also uses the anti-corrosion coating on the lower swing arm of the rear suspension, which reduces the chance of rust in this part and also improves the durability of the suspension. Got promoted. In addition, in terms of lightweight design, the car’s rear subframe and rear wheel horns are still made of aluminum alloy.

is written at the end:

actually uses a swing arm made of steel or cast iron. As long as it can meet the manufacturer's calibration requirements for vehicle comfort and maneuverability, it cannot be defined as "cutting corners." After all, controlling the manufacturing cost of the entire vehicle is also It can be reflected in the final selling price and bring benefits to consumers. Although aluminum alloy swing arms have the advantages of being lightweight and improving comfort and maneuverability, the cost of car purchase and subsequent maintenance is likely to be higher than that of models using cast iron or steel swing arms.

Generally speaking, if the cost of building a car is limited, the car company will definitely consider all aspects. Of course, cost is also one of the important factors, and relatively suitable materials will be used in the appropriate position. Let’s look at it from another perspective. For example, almost all models priced around 150,000 yuan use steel or cast iron chassis parts. At this time, if there is a car that uses a large number of aluminum alloy materials in the chassis parts, taking into account the cost control issue , there is a high probability that it will be "shrunk" in other configurations. So as a consumer, how will you choose?