Researchers in Finland Use FEA for 21st-Century Taxicab Design

	Researchers at Helsinki Polytechnic and the University of Art and Design in Helsinki, Finland, built a model of the CityCab taxi in Catia and Rhinceros and tested it in ALGOR. The above image shows stresses in the taxicab’s body and frame due to extreme static loading conditions.
	CityCab researchers wanted to know the absolute distortion of the frame under maximum-stress conditions. The above image shows the taxicab’s body and frame subjected to the maximum anticipated load -- a weight of 2250 kilograms (or over 5,000 pounds) placed on the left front wheel and on the right rear wheel.
	After modeling and testing the CityCab design using ALGOR FEA, researchers built a prototype of the taxicab to be showcased at the Paris Motor Show in September 2006. The above image is one of the three alternative graphic representations of the finished prototype.

Researchers at Helsinki Polytechnic and the University of Art and Design in Helsinki, Finland, are collaborating to design and produce “CityCab,” a next generation taxicab for the 21st century. CityCab will be a single-purpose vehicle for urban commuting and is designed for five passengers plus the driver, with an option for one passenger using a wheel chair. The CityCab project was inspired in part by earlier successful joint efforts between the two universities, namely the city-car Ibana (introduced at the Paris Motor Show in 1994) and two versions of the RaceAbout sportscar (introduced at the Geneva Motor Show in 2000 and 2005). Additionally, the need for more fuel-efficient, environmentally-friendlier taxicabs motivated researchers.

CityCab incorporates the latest hybrid powertrain, currently available in the Toyota Prius. In conjunction with the hybrid engine, a lighter, cheaper frame will allow the taxicab to use less fuel and to reduce emissions. Researchers in the project used ALGOR FEA to design an efficient frame and body. The goal of the design and testing was to find the lightest configuration of materials possible, while remaining within yield standards under maximum stress. With the help of ALGOR software, CityCab researchers are working to improve metropolitan transportation worldwide, while also working to improve the environment.

Modeling and Testing

Under the direction of their teacher, Markku Lavi, Team Manager Harri Santamala and students at Helsinki Polytechnic used CAD modelers Catia and Rhinoceros to draw the 3-D solid model of the frame and axles. The frame was designed using a combination of material properties, including steel, Alumina composites and carbon fibers. Most of the material properties were used directly from the ALGOR material library, with the carbon fiber and Alumina composite material properties from manufacturers’ data sheets. The use of more composites and carbon fibers and less steel makes for a lighter cab.

The CityCab researchers ran initial static stress tests on the taxicab’s frame in ALGOR. The researchers wanted to know the absolute distortion of the frame under maximum-stress conditions. The testing simulated the forces encountered by the vehicle on extremely rough terrain. Under these conditions, the researchers reasoned, the taxicab can bounce, putting the entire weight of the car and its payload on two wheels for very brief periods. The weight of the engine and maximum passenger weight were added to the load, for a total weight of 2250 kilograms or almost 5,000 pounds, applied to the frame around the wheels. The criterion for failure was the point of yield. The researchers went through three iterations of the model to arrive at one that optimizes the combination of materials.

Results and Future Plans

Through static stress testing, ALGOR software helped researchers at CityCab to reduce the weight of the taxicab frame by allowing them to virtually test a series of material combinations. The lab will soon put this design through ALGOR Mechanical Event Simulation (MES) crash test simulations, from which further iterations will most likely result. The tests will consist of 20 kilometer (or 12.43 miles) per hour collisions of the model against a solid crash wall. The researchers will look at the maximum deformation of the car and the final permanent displacement of the frame, especially at the passenger and driver seats, to ensure that these are within acceptable ranges.

In October 2005, a prototype complete with chassis and axles was built and the power train installed. Based on results from the MES crash tests, additional changes may be incorporated in the design. The finished prototype will then be introduced at the Paris Motor Show on September 30, 2006. The two-week presentation of CityCab in Paris will be an important trial period, when international automotive experts will analyze the vehicle and publish their findings in key periodicals and magazines worldwide. After incorporating relevant and critical changes from the expert evaluations, an additional six months of virtual testing in ALGOR will be conducted.

Finally, after making changes to the prototype suggested by the additional testing of the model, the resulting CityCab prototype will be used in actual, on-the-ground service as a research cab in the Helsinki metropolitan area, from Spring 2007 through September 2007. The taxicab’s performance will be evaluated from the standpoints of both passengers and drivers to gain valuable, empirical knowledge about how CityCab compares to the taxicabs now in use.

ALGOR software has been important for CityCab and its importance promises to increase as the project enters the upcoming critical phases of testing and production. “ALGOR is an absolutely essential tool for the ultimate success of the CityCab project,” said Helsinki Polytechnic Instructor, Markku Lavi. “With the help of ALGOR, we are working to design a cost-efficient, energy-efficient and environmentally-friendlier taxicab. ALGOR is helping to change automotive engineering for the 21st-century.”





Under the direction of their instructor, Markku Lavi (right),
Team Manager Harri Santamala (left) and fellow students
at Helsinki Polytechnic in Helsinki, Finland, used CAD
modelers Catia and Rhinoceros to draw the 3-D solid model
of the frame and axles of the CityCab and ran static stress
tests on the taxicab’s frame in ALGOR.