Can the roof trunk really hold a lot of things? It's really big. In terms of volume, the trunk of the roof can really hold a lot of things.
The trunk volume of mainstream cars on the market is generally between 400 and 700 L. For example, the trunk volume of Angkor Vesela is 420 L；; "Sales King" Sylphy, 5 10L.
Of course, larger SUVs, such as Haval H6, have a regular trunk volume of 808L.
In contrast, the roof trunk is almost as big as the trunk, and the common specifications on the market range from more than 400 liters to more than 800 liters.
Installing a trunk on the roof is equivalent to directly adding a trunk to hold things.
But there is a weight limit, but the load weight of the roof is limited. The trunk itself has a maximum load limit, and the car also has a maximum load limit on the roof. When loading things, the two limits cannot be exceeded.
Just like: there is also an upper limit for horse-borne goods. If the load is too heavy, the horse will fall, right? The horse fell down and couldn't walk.
The maximum load of the trunk itself is generally in the product manual, and the maximum load of the roof will be indicated in the car manual.
For example, Audi Q7, the user manual says: the maximum load of the roof 100kg.
Except for the trunk of the roof of the car, it can only hold dozens of kilograms of luggage, which is almost as heavy as an adult, lying on the roof.
Some smaller cars will have a smaller load, which is easy to understand, just like: small horses carry small goods and big horses carry big goods.
So the suitcase looks big, but it can't hold heavy things. Luggage that can't fit in the trunk is ok. If necessary, buy one.
But if you want to take everything and touch anything heavy, it is basically not feasible.
What are the side effects? The trunk on the roof is convenient and contains a lot of things. Let's talk about the side effects first and weigh the pros and cons. The first side effect is: affecting manipulation.
Doesn't the trunk affect the control of the roof, and it is buckled on the roof like a boat?
When driving at high speed, the speed of airflow passing through the upper surface of the curved surface will be faster than that of the lower surface, which will lead to a pressure difference between the two sides and produce something called "aerodynamic lift".
You don't seem familiar with this thing. Let's start with the conclusion: it will have a negative impact on driving stability.
What is the reason? How do you feel? What is its principle? Like the wings of an airplane.
In other words: the faster you drive, the whole car will float up like an airplane. Okay, the more you float on it, the worse the tire grip, okay? Right?
I found a paper in the magazine "Automotive Practical Technology" to share with you, which was mentioned in "Aerodynamic Analysis and Test of Loading Device of Roof Rack".
The aerodynamic lift of automobile will directly affect the handling stability and dynamic performance of automobile. Excessive aerodynamic lift will reduce the adhesion between the tire and the ground, resulting in high-speed "floating". This is always easy to understand, high-speed "floating".
This paper also uses this model for simulation analysis. The results show that the aerodynamic lift increases with the increase of vehicle speed, and reaches 160N at the speed of120km/h/h.
Have no idea? As we said in the previous video: When the family car is driving, the aerodynamic lift is mostly within100 N.
After loading the suitcase, although it will not roll over directly, the aerodynamic lift will be more than doubled, and the control will also have a feel impact.
Higher fuel consumption not only affects control, but also consumes fuel and increases fuel consumption.
In Jilin University, I also found you a paper "Study on the Influence of Roof Box on Vehicle Aerodynamic Drag Reduction", which said that it was a wind tunnel experiment directly.
The experimental results show that the aerodynamic drag coefficient of the whole vehicle increases by 1 1.4%, and the aerodynamic drag of the whole vehicle increases by 20. 1% and 20% after the roof trunk is added.
Take the test scores as an example, which is the difference between 100 and 80.
We also found a paper in "Automotive Engineering" magazine to share with you, which was mentioned in "Aerodynamic Performance Optimization and Verification of an SUV".
The speed is 60km/h, is it common? Air resistance accounts for about half of vehicle resistance. The faster the vehicle speed, the greater the proportion of air resistance to vehicle resistance, and the greater the influence of roof trunk on fuel consumption.
We assume that the aerodynamic drag accounts for half of the total drag, and then take the data of 20. 1% in the paper just now for a rough calculation.
There is a suitcase on it. It's cool. It's from Shuai Shuai, isn't it? When the fuel consumption is greater than 1%, 10L engine oil becomes 1 1L engine oil.
Moreover, the extra load itself will also increase fuel consumption. That was air resistance and aerodynamics, right? It has weight, doesn't it?
When things are put in, there are often dozens of pounds in the car. It is also possible that the fuel consumption per 100 kilometers is 1 2L compared with before.
A good suitcase can reduce side effects.
Of course, if you choose your luggage better, there will be fewer side effects. Otherwise, how can the price be different and the shape be different, right?
Just now, the paper "Research on the Influence of the Roof Box on the Aerodynamic Drag Reduction of the Vehicle" said that the installation position of the trunk will have an impact on the aerodynamic drag, and the biggest impact is called "angle of attack".
To put it simply: if there is a deviation in the height of the front and rear suitcases, the resistance will increase.
Inferior or poorly designed suitcases may not only have quality problems, but also increase the resistance due to insufficient installation accuracy, making the resistance even greater.
"Oops" is very simple, just shoes: the height of shoes is different before and after, so it is more difficult to walk.
If you can't understand it yourself, ask the girl in high heels which feels better, running in sneakers or running in high heels, right?
Therefore, when choosing a suitcase, you should try to choose qualified products from big brands.
There is a standard in the automobile industry called "roof loading device", which stipulates that each set of roof loading device must be inspected by the manufacturer before leaving the factory, and the product quality qualification documents are attached.
I really bought the "three noes" product because I was greedy for cheap. It may really be worth the loss.
I searched casually on the e-commerce platform, and even found that some merchants' factory real shots were made of 3D renderings or P, and the quality problems may be worrying.
You can install a roof trunk when you travel frequently. Generally speaking, if you travel frequently or have a certain demand for storage space, it is good to install a roof trunk.
But if it's just for beauty, or if you want to put something heavier, it doesn't make much sense.