The two forms of car wiper blades arms are shown in the following figure. The left one is the tandem method (two wiper arms wiping in the same direction), and the right one is the opposed method (two wiper arms cross left and right).

So what is the difference between these two systems?

First of all, no matter what kind of wiping method the car wiper arm adopts, in accordance with the requirements of the national standard, it must reach 98% of the wiper coverage directly in front of the driver (zone A), and 80% directly in front of the co-pilot (zone B). % Scraping coverage. Therefore, the selection of the sweeping method is based on this standard.

Usually, the following points should be considered in the design of whether to use tandem wiping  or opposed wiping:

1.Glass aspect ratio.

If the glass aspect ratio is greater than 0.7, it is recommended to use opposed wiping arms, otherwise the coverage requirements of zone B may be difficult to meet;

2.Flow trough space.

Generally the wiper arm for opposed wiping is about twice as long as the tandem wiper arm, and a larger flow trough space is required to install;

3.Cost.

Generally, a larger wiper arm and a longer windshield wiper blade are used for opposed system, so the cost of opposed wiping is higher than tandem wiping.

Analysis of the advantages and disadvantages of tandem wiping compared with opposed wiping:

1. The cost of tandem wiping is lower;

2. When tandem wiping, the coverage of area B is relatively small, generally around 80% to 90%, and it is generally easier to achieve 90% for opposed wiping;

3. The water trough space occupied by the tandem wiper arms is small;

4. Since the tandem wiper arm and wiper blade are shorter, the load is correspondingly smaller. You can use a smaller motor to save a little energy;

Generally speaking, in the case of meeting the coverage requirements, it is generally up to the car manufacturer to decide whether to use tandem wiping or opposed wiping according to the shape and space of their own models.