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Elon Musk Explains Repair Solution for Tesla’s Single Cast Frame in Case of Collision

Tesla has always been a benchmark for other automobile companies since its inception. Its rapid rise to become the world’s most valuable carmaker could mark the start of a new era for the global auto industry, defined by a Silicon Valley approach to software that is overtaking old-school manufacturing know-how. On the similar lines was the mega event on the 22nd of September, the “Battery Day”.

Elon Musk Explains Repair Solution for Tesla’s Single Cast Frame in Case of Collision

Battery Day is simply the shareholders’ annual meeting. In line with the year, the meeting was equally unusual with the event being held in an open space at Freemont, California. For the shareholders that attended the event live seats were replaced by their Tesla’s and clapping was replaced by honking. The event was divided into two parts: Company Update and Year-in-Review and the Battery Day Keynote.

During the Battery Day Keynote Elon Musk briefed about two major updates in the upcoming models:

  1. The upgraded 4680 battery.
  2. Single piece cast underbody

What is the single-piece cast underbody?

Battery packaging and structural rigidity are the two points Elon Musk’s Tesla could optimize. Tesla wanted to address this issue and address it they did. On the battery day, Tesla announced that the upcoming models will have a Single piece cast underbody. The Single piece casted underbody directly addresses the above mention issues. It is an ingenious idea. The underbody essentially acts as a structural part of the car and simultaneously integrates and protects the battery package efficiently.

Tesla Giga casting Innovations

The above image is of the Single piece cast rear underbody. The reason why it’s a thing of beauty is that Tesla ideated and delivered the largest in-house part casting machine the automobile sector has seen. The manufacturing of this underbody is already underway at Tesla’s California factory.

What is the genius behind this casting machine?

Model Y Gigacasting

Basic information about casting for the people unaware of it; in casting molten metal is given the desired shape by settling the metal into a mold. This molten metal is then cooled in a controlled environment. The metal solidifies after it cools down to a certain temperature. After the metal solidifies, it is released from the mold and further processes such as heat treatment and finishing to obtain a working piece are carried out on it. Thus, casting eliminates multiple hours of machining required for intricate parts. However, a casted piece is brittle and requires post-manufacturing treatments i.e. heat treatment to provide the piece with adequate strength.

Now, Tesla manufactured a custom casting machine to deliver this single piece underbody. The reason why this machine is a thing of beauty is that Tesla was able to achieve all the above 5 to 6 steps in a single shot.  Normally the major questions will pop up in one’s mind. How does the piece achieve the required strength? The answer is Material Science. Tesla’s R&D department has successfully delivered an Aluminium Alloy which doesn’t require post processes like Heat treatment and extra coatings.

The objective of the Single piece cast underbody

As I said before, Battery packaging and structural rigidity are the two points Elon Musk’s Tesla could optimize. Tesla was able to achieve both with this invention. Sandy Munro in his video explained that this arrangement of cells with the help of system integration will lower the battery overheating problems which will increase the range by a staggering 14%. The cells and underbody stand to reduce 10% mass of the existing Model Y. The packing ensures that the battery pack moves towards the center of the car. This helps to improve the polar moment of Inertia which in turn increases the structure’s torsional rigidity. Furthermore, Tesla reduced approximately 400 parts by replacing the orthodox housing by this single piece cast underbody.

Tesla Single Body Structure

Elephant in the room

It’s a fact that castings without heat treatment are brittle. Everyone tip their hats to how Tesla mitigated this issue by developing their secret alloy. Inventions and ambiguity around them go hand in hand. One such ambiguity around the single-piece cast underbody was; how does Tesla plans to repair the damages caused to the underbody. It is a fair and excellent question. Every piece of the car must have an easy option when replacement or repairing is required. Tesla hasn’t overlooked this possible problem. In a tweet, an account with the handle “Tesladri” asked how Tesla plans to repair rear end damage with frame involvement if everything is just one piece. Elon Musk briefly explained Tesla’s solution to it.

Tesla Tweet

The solution is simple and shrewd. The initially delivered Models will have a crash absorption rail attached to it. These rails on failure will be replaced by a bolted part for collision repair. Refer to the attached photo for better imagination.

The image on top shows the current underbody and cell packaging. The image at the bottom is what Tesla proposed a single piece cast underbody looks like. The future underbody has a crash absorption rail as indicated by the red arrow. This rail acts as a safety net for the packaging. If a crash were to take place, the rail will fail first to safeguard the battery packaging.

Tesla’s engineering concerning safety, performance, range, software, or manufacturing is astonishing. Yet, perhaps what is most astonishing is that the company was able to pack all of this into each car it builds–and still, produce a product people love.

Ritwik Shah
Ritwik Shah
Aspiring Mechanical Engineer and Formula Student. An automotive and sports enthusiast who is always up for a discussion.


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