Solar Racing Basics: Chassis

Click to zoom / Image credit: American Solar Challenge

Continuing the analysis of my Solar Racing Basics Poster (see this tag), solar cars have to keep their driver safe and the vehicle in one piece. There are two basic ways of doing this. First, a car can have a carbon-fibre-reinforced polymer body over a metal chassis. For example, Bochum’s thyssenkrupp blue.cruiser (below) is supported by a tubular frame of ultrahigh-strength steel. Second, a car can have a load-bearing “monocoque” body, possibly also of carbon-fibre-reinforced polymer. Carbon-fibre-reinforced polymer is strong for its weight, and this is significant, since a noticeable amount of energy in a solar car (though less than aerodynamic drag) is lost in rolling resistance. The rolling resistance of a car is proportional to its weight (it also depends on the quality of the tires), and so reducing weight makes the car faster. In 2019, the lightest solar car (from Western Sydney) weighed just 116.8 kg without the driver.

Cars may include a “roll bar” or “roll cage” to protect the driver in addition to the monocoque body. This “roll bar” or “roll cage” may be made of metal tubes, or it may also be made of carbon-fibre-reinforced polymer. A close look at unpainted carbon-fibre-reinforced polymer shows the “chequerboard” pattern of carbon-fibre “cloth” embedded inside transparent epoxy polymer (as in the body and roll bar of Durham’s Ortus, also below).

 
Click to zoom / Image credits: Anthony Dekker (Bochum’s thyssenkrupp blue.cruiser and the interior of Durham’s Ortus)

To read more, see see this post about car body and chassis by Nick Elderfield of the University of Calgary Solar Car Team, this Instagram post about composite materials by MIT Solar Electric Vehicle Team, and this UMNSVP wiki on Composite Chassis Design.

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