Safety cages are mandatory safety equipment in open racing cars, as they are the only thing protecting the driver’s head if the vehicle rolls over. Unfortunately they also tend to be heavy, as they are made of steel—and the high position of the driver’s head moves the centre of gravity upward, affecting handling. Engineering student Jesper Kjær Jørgensen decided to do something about the problem.
While completing an engineering internship at FORCE Technology in 2016, he came into contact with the company Agile Automotive which required an analysis of the design of a steel roll cage they had developed for their track racer, Agile SCX.
While analysing the safety of the roll cage, he came up with the idea for an entirely new construction:
“Regardless of steel cage design, it has to be heavy in order to be strong enough to support the vehicle’s weight when it rolls over at high speed. This impairs the car’s acceleration and negatively affects road handling. So I decided to explore whether it was possible to construct a roll cage in a lighter material without compromising on safety,” he says.
Throughout his studies, Jesper has specialized in construction and design—in particular composite materials. And because carbon fibre is frequently used everywhere where low weight and high strength are important, it seemed only natural to try to design a roll cage made of carbon fibre:
“Carbon fibre has much higher tensile strength per unit weight than steel, and it can be shaped in a variety of ways. This allowed me to develop much lighter cages—something I definitely wanted to try out,” says Jesper.
Good sparring fixed issues
The opportunity came when he had to choose his final project and returned to Force Technology in order to realize his idea. However, this was easier said than done—not least because the roll cage had to be cheap to produce and easy to install in the cars.
A great challenge in working with carbon fibre composites is that the material is extremely difficult to process once it has been cast—placing demands on both design and production.
“Every time you get a new idea, you have to consider how it can be produced and whether it is realistic to do in a single step,” says Jesper.
Because the project is one of the first of its kind, Jesper had to find solutions to many challenges without being able to refer to ‘standard’ or ‘best practice’.
However, using his supervisor at DTU Diplom—Christian Kim Christiansen—and FORCE Technology as a sounding board, Jesper was able to find an effective way of solving problems, and six months after the start of the project, he had designed an entirely new type of roll cage.
The customer, Agile automotive, is extremely pleased with the project:
“We are always look for new and innovative approaches to our racing car thinking—whether it’s something that makes the car lighter or stronger. And the design of the carbon fibre roll cage is a great example,” says Tim M. Hansen, CTO at Agile Automotive.
The results are tangible. Jesper succeeded in reducing the cage weight by approximately 50 per cent, and if the customers are willing to accept a slightly higher price tag for the carbon fibre cage than its steel counterpart, there is every chance that Agile Automotive racing cars will be even faster in the future.