"Insights Of Exploring Technology"

Are frameless car doors really advanced?

By, CoolMotor

• 2023-11-16
• 43 View

Indeed, frameless car doors have nothing but good looks. This brings about reduced NVH performance, reduced rigidity, higher failure rate, higher cost, etc., all of which are exchanged for improved appearance. Let’s take a closer look at what sacrifices frameless doors have made in order to look good. For comparison, the same model naturally has both frameless and traditional door versions, which is more representative. Therefore, I chose Volkswagen Magotan (traditional doors) and CC (frameless doors). The two can be said to be the same car, because overseas, Magotan is called Passat, and CC is called Passat CC, which means a bit of coupe. Similar operations include Mercedes-Benz C and C coupe, the same model positioning, the same Wheelbase, same interior, almost the same body, the only difference lies in the shape of the rear and the use of frameless doors. Since I couldn't find any data on the B6 Magotan, I now use the B7, and there's not much difference between the two.

Let's focus on the car door and take a look at the exploded view of the components. What are the differences? If we exclude all door interior trim and wiring harness factors (which have nothing to do with frameless doors), as well as differences in exterior trim parts, among the many differences in parts, there are the following three parts that are directly related to whether there are frames or not.

1: The shape of the door sheet metal is different.

2: Glass shapes are different.

3: The sealing strips are of different lengths.

Next let’s look at them separately.

Sheet metal:

As the name suggests, the frameless door means that the upper half of the door is completely made of glass. The traditional door has a Japanese-shaped structure, while the frameless door has a square-shaped door. But from the perspective of the door, the rigidity of the frameless door will be slightly worse unless reinforced in other ways. Just like a convertible is certainly not as rigid as a traditional cage body, without the support of the upper part, it is prone to deformation when subjected to torque and bending moments. In order to enhance the rigidity of the door, CC chose to add an additional reinforcement member to the door and at the same time enlarge the depth of the inner door panel to obtain higher overall rigidity. In comparison, Magotan's doors appear relatively thin, simple and plain, and the goal is achieved.

Glass:

I believe it can be clearly seen from the picture that the glass size of the CC is significantly larger than that of the Magotan, although the door lengths of the two cars are almost the same. The main difference is in the longitudinal length.

The reason is that when the glass rises to the top, the frameless door glass almost completely protrudes from the door. There is no Y-direction support at the upper end, and it will shake if it is stressed. Therefore it is necessary to lengthen the lower glass to provide a longer moment and utilize window rails to stabilize the glass. On the other hand, Magotan is much simpler. The right end of the glass is always in the guide groove of the door frame, so the lateral force can be directly transmitted to the door. The glass itself does not receive too much force, nor does it shake.

After looking at the glass, let’s look at the guide rails. In order to better fix this piece of glass that is prone to shaking, the guide rails have also been reinforced accordingly. The fastening points used to hold the glass in place are significantly larger and wider to prevent the glass from wobbling. In addition, the guide rail itself is also thicker and provides greater resistance to bending moments. However, the overall structure is relatively consistent. They are all double-track structures. Some models will use a single-track structure. On that model, the glass needs to rely on the window frame to assist in positioning, so it cannot be used on frameless doors.

Sealing:

Traditional car doors have two seals. On high-end cars, there are even three seals to improve NVH performance. On frameless doors, it is lowered to one and a half steps. There is a full ring of seal on the car body, the upper half ring forms a seal with the glass, and the lower half ring forms a seal with the door sheet metal. On the door, there is another half-ring seal that seals with the door sheet metal.

On the Magotan, the body sealing strip is a whole piece, which is directly sealed with the door sheet metal. Similarly, the sealing strip on the door is also a whole, forming a seal with the body sheet metal.

In fact, in frameless car doors, different car companies have different solutions for sealing the half circle between the glass and the body. Some convertibles have the glass drop a little before you pull the door handle, others don't move at all. These are two different sealing methods. The type of glass that can move uses the vertical movement of the glass to insert the top section into the door frame sealing strip to achieve a better sealing effect. However, if you open the door too quickly, pushing the door before the glass has lowered will cause jamming. Therefore, you need to wait patiently for the glass to finish moving before pushing the door, which is somewhat inconvenient.

Summarize

Therefore, frameless car doors are indeed as the author said, a lot has been sacrificed for the sake of appearance. But I have to say, the frameless doors are so cool!