How to solve the geometry problems of the Shelby Cobra body using the RangeVision Spectrum 3D Scanner

Task: To evaluate the accuracy of manufacturing and assembling a replica Shelby Cobra car. Check the geometry of the body for symmetry and get the data necessary to align the body parts and adjust them to size so that the joints of the parts are smooth and all the car doors open freely.
Solution: RangeVision Spectrum, ScanCenter NG, Blender
Summary: The Shelby Cobra car was scanned by the RangeVision Spectrum universal 3D scanner. The resulting 3D model of the car was used to check the symmetry of the left and right sides of the car. As a result, several defects were identified, which were subsequently eliminated during bodywork. All the body parts were sized, the geometry of the body was aligned according to symmetry and painted.

We will never know the name of the person who first decided to create a replica of the coveted car in his garage, which was not possible to buy. Over time, this activity began to spread with tremendous speed. Now the construction of car replicas excites the minds of thousands of enthusiasts around the world.

The replica is a self-assembled car, maximally repeating the appearance and layout of the original model. Car parts can be found at car disassemblies, in garages, or supplied in a separate set of the "assemble yourself" format. Recently, the latter option has become very popular. Many companies create their own kits for building replicas of legendary cars and expensive supercars. On average, it takes 1.5 years of slow work to build a replica car.

You must admit, it sounds tempting: you can buy a kit car kit and build the desired car for almost a penny compared to the price you are asking for the original. But there is another side to the coin. During the construction of replicas, problems often arise with the body: the gaps may be uneven, the attachments often cannot be installed without fitting, and the edges of the glass may not match the opening. To solve this kind of problem, you need to involve professionals.

Ildar, a well-known blogger on the Runet, who is working on a project to create a replica of the iconic Shelby Cobra 427, faced similar problems.

The Shelby Cobra is one of the most replicated replica cars. This legendary racing car was created by engineer Carroll Shelby and was produced from 1962 to 1967. In his short life, he managed to collect a huge number of awards and trophies. In 2016, the first copy of this car was sold for an incredible $ 13 million and became the most expensive British car in the world. The film "Ford vs Ferrari" tells just about the history of this car. It is worth noting that the film has raised a new wave of Shelby Cobra popularity in the world.

In September 2020, Ildar asked our good friend Maxim Tereshchenko, a blogger and head of the Machinator workshop, for help in leveling the body of the replica. His team specializes in this kind of specific work and has already been involved in similar projects. The machinists were faced with the task of identifying and correcting all the shortcomings of the car body in just 1 month.

During the initial inspection of the replica, the machinists noticed that some body parts did not fit together: the left door was installed with a large gap, and the trunk lid was slightly wider than the opening.

However, the eye often does not see all the flaws in the geometry of the body, because the car has many symmetrical points. Without measurements, it is impossible to identify all the places with asymmetry and correct all defects. To see the full picture of the asymmetry of the body, it is necessary to make accurate measurements.

One of the options for obtaining complete body data is 3D scanning. As a result of digitization, a 3D model of the object is obtained, which is used to check the symmetry of the parts and identify all the flaws in the geometry of the body.

To perform the 3D scanning, the Machinators used a RangeVision Spectrum 3D scanner. The scanner combines features such as high accuracy of scanning objects, portability, large capture area, and affordable price. It is great for auto-tuning tasks.

Machine operators have been familiar with 3D scanning technology for about two years. Previously, to digitize individual parts of cars, the guys used an inexpensive handheld scanner of another brand, which turned out to be insufficiently accurate. But to scan such large objects as a car, they needed a more suitable tool for this. The machinists chose RangeVision Spectrum: "We got acquainted with Spectrum when we took the order to create a body kit for Geländewagen. It was necessary to scan the bumper. We turned to our friend Ivan Moskvichev (Plastmaska), who had this scanner. We looked at how it works. And we decided that we need such a scanner. It’s quite suitable for our purposes."

The 3D scanning process consisted of the following steps:

• Calibration of the scanner
• Preparing the body for scanning
• Applying markers
• Scanning in marker mode

Before the 3D scanning, the machinists carried out preparatory work. The scanner was assembled and calibrated. For better results, the shiny chrome parts of the car were coated with a matte film, and the rubber on the wheels was treated with a matting powder. To increase the accuracy of scanning an object in this project and speed up the process, the Machinators used the marker scanning mode. To do this, the markers were applied to the surface of the car body.

The marker scanning mode is in high demand when digitizing large objects. Markers allow ScanCenter NG software to automatically combine model fragments based on markers applied to the surface of an object, which increases the speed of obtaining results and allows for greater accuracy.

It was the first time that the guys scanned the car completely. The scanning speed of the entire car was about three hours with all the preparations, which pleasantly surprised them. Maxim admitted that using the Spectrum 3D scanner has led to a reduction in time spent on obtaining measurements and increased work efficiency by obtaining more accurate results in less time.

Before using scanners, machine operators performed measurements using a laser level, which was time-consuming, and the accuracy of the readings left much to be desired. This method allowed us to obtain data for 7 days of work by two people. Obviously, using a 3D scanner can significantly save time and human resources. The time spent by the Machinists on making measurements and obtaining a processed 3D model was reduced to just a few hours.

After scanning, the Machinators received a high-precision 3D model of the car. It was exported to the Blender program for further processing. The specialist cut the model in half, selected the reference half and applied one part to the other by mirroring to see the correspondence in symmetry, diagonals and planes. According to the 3D model, the left wing of the car was 1.5 cm lower than the right one, the holes on the wings were of different sizes, the gaps between the parts were different, and the trunk lid was slightly larger than the opening.

The machinists received the final reference model of the car, which had the necessary symmetry and had all the necessary dimensions, which greatly simplified further work.

Now the machinists have started bodywork to correct all the body defects. First of all, the specialists dismantled all the doors and the trunk lid in order to properly install the main body and the front fenders.

The machinists carried out the following types of bodywork:

• Reduced the trunk lid
• The left wing was raised
• The gaps between the parts were exposed
• The planes of the body surface were leveled
• All openings have been processed
• The hinges were installed
• The excess materials were removed from the door so that it could close freely.
• The body was prepared for painting
• Painted the body
• White vinyl decorative lines were applied

The machinists coped with their task brilliantly! Thanks to 3D scanning, the specialists carried out accurate measurements and fixed all the body defects in a fairly short time! Maxim admits: "We have gained a lot of experience working with this car, with the scanner. This is the first time we have scanned such a large-scale object. With the help of scanners, we found that the body was really uneven. It was not visible to the eye. Without the scanner, we would have spent a very long time tinkering and looking for the reason where something went wrong, or would not have been able to cope at all. The project is now completed. Everything has been successfully assembled. We are pleased with the result. It was interesting!" The owner of the replica has already received it back and is engaged in further assembly of the car.

It turned out that Maxim and his team use the RangeVision Spectrum 3D scanner not only for geometry control tasks of automobile parts and bodywork. One day, they were approached by a client with a request to make a complete copy of the car’s mirror, but so that its dimensions were 30% larger than the original. The guys scanned the mirror, zoomed in on the 3D model, and printed the part on a 3D printer. The client was very pleased with the result. The guys also use the scanner to solve various car tuning tasks, for example, such as creating improved body kits based on individual car parts.

The example of this project shows that a 3D scanner is an important 3D technology for a company engaged in car tuning, restoration and repair. The 3D scanner allows you to significantly reduce time and costs at the stage of preparatory work, and improve the quality of work performed. In fact, the scanner removes many of the limitations of conventional measuring devices. The measuring instruments familiar to this industry are inexpensive, but they have a high subjectivity of the data provided and are not suitable for complex measurements. Thus, 3D scanning helps to optimize the entire process of the automotive industry, which is very important in an ever-changing reality.

RangeVision would like to thank Maxim Tereshchenko (Machinators) and Ivan Moskvichev (Plastmaska) for their help in preparing the material.