Lightcar Challenge Written Explanation
Lightcar Challenge Written Explanation Executive Summary The Leaf automobile has been designed to address many of the challenges that are holding the automobile industry back from the next evolution in the light-weighting of passenger cars. Current production lines are not suitable to make a car such as this commercially viable so next generation vehicle manufacturing techniques must be implemented. With a light, carbon fibre frame, electronic drivetrain and maximized usage of waste power, the leaf is the candidate to take us into the new era.
Components Chassis The chassis is made from carbon fibre members which are attached together using aluminium joiners. These main structural members run the length of the car. The members are 3D curves that effectively join together multiple elements of a regular space-frame design. The elements could be 3D printed with advanced rapid techniques or plastic molded and used as a core structure to weave the carbon fibre over. Having this internal structure will also increase the buckling strength of the member by adding internal support. Using slender shapes like these space-frame type members without any forks a fibre wrapping process could be used as in the lexus LFA (shown below in Figure #).
The connecting members would be round hollow carbon fibre sections that are more easily mass produced and joined using aluminium lugs. Using this joining technique maintains the modular nature of the design which allows for ease of assembly and in-service parts replacement. Another major advantage of having a modular chassis is the ease of disassembly. All recyclable materials within the car can be removed easily and the space-frame components can also be broken down into single sections to refit into another new or used model. Drivetrain The Drivetrain of the Leaf consists of two in-hub, direct drive brushless motors mounted to each of the rear wheels. The motors are powered by battery cells that are located under the front and rear seats, the proportion of front/back placement is a variable that can be used to optimise the weigh
distribution. Power electronics behind the rear seats provide the means of powering the motors, recharging the batteries when plugged in, regenerative braking via a KERS system and allows the solar cells to assist with charging.
Concept Validation The carbon fibre space-frame chassis lends itself to a lightweight structure. Aluminium space-frames can weigh as little as half that of a conventional steel uni-body design [1]. Aluminium has the advantage of being more easily extrudable than steel, custom profiles can be created reasonably cheaply have a relatively small up-front cost when compared to steel forming tools. For aluminium space frames the disadvantage is in the cost of the material and the speed difficulty of assembly. Carbon fibre reinforced plastics are currently in their infancy, like most young technology the cost of the raw material and that of forming them is large. New Zealand currently has more than 30% of its energy needs being met by renewable methods. Although it may be hard for other counties to achieve this figure the amount of renewable energy production is on the rise. Future trends show that prices for solar power systems are decreasing. Solar power can be implemented locally in housing and to the surfaces of the car using faceted or flexible solar cells. Cars parked outside will charge when sitting; and while plugged in at the owner’s residence the solar panels of the house can feed straight into the vehicle decreasing resistive heating and therefore energy loss of power cables. A total paradigm shift of the automotive sector is needed to allow cars with a carbon fibre chassis to become a viable option in the future. The cost of such a car is prohibitive with today infustructure, however as the demands and desires of the automobile industry and its clientele shift to a more sustainable outlook then we will see these large and revolutionary changes how our cars look and are made. Even with future technologies it will be very difficult to compete with the build speed and cost of a conventional uni-body chassis. The
Potential issues The potential issues with this design are as follows
The price of carbon fibre would have to drop a considerable amount to make this design commercially viable. Once damaged, the structural members would have to be replaced. Ease of disassembly and repair would have to be maximized through modular design to alleviate this issue. The Car may not be suitable for long distance travel due to the reliance on the electrical system. Although a KERS system and the solar elements help, the range of this vehicle may not be that of petrol cars and energy filling will take much longer. To improve the range extra cells could be temporarily installed by the user or the use of a small heat engine could assist in charging the battery.
The infrastructure in much of the automotive industry would have to change. This is a large issue and is said to be why the next evolution has not been made in light-weighting cars.
[1] http://www.technologyreview.com/featuredstory/400002/a-practical-road-to-lightweight-cars/
Components Chassis The chassis is made from carbon fibre members which are attached together using aluminium joiners. These main structural members run the length of the car. The members are 3D curves that effectively join together multiple elements of a regular space-frame design. The elements could be 3D printed with advanced rapid techniques or plastic molded and used as a core structure to weave the carbon fibre over. Having this internal structure will also increase the buckling strength of the member by adding internal support. Using slender shapes like these space-frame type members without any forks a fibre wrapping process could be used as in the lexus LFA (shown below in Figure #).
The connecting members would be round hollow carbon fibre sections that are more easily mass produced and joined using aluminium lugs. Using this joining technique maintains the modular nature of the design which allows for ease of assembly and in-service parts replacement. Another major advantage of having a modular chassis is the ease of disassembly. All recyclable materials within the car can be removed easily and the space-frame components can also be broken down into single sections to refit into another new or used model. Drivetrain The Drivetrain of the Leaf consists of two in-hub, direct drive brushless motors mounted to each of the rear wheels. The motors are powered by battery cells that are located under the front and rear seats, the proportion of front/back placement is a variable that can be used to optimise the weigh
distribution. Power electronics behind the rear seats provide the means of powering the motors, recharging the batteries when plugged in, regenerative braking via a KERS system and allows the solar cells to assist with charging.
Concept Validation The carbon fibre space-frame chassis lends itself to a lightweight structure. Aluminium space-frames can weigh as little as half that of a conventional steel uni-body design [1]. Aluminium has the advantage of being more easily extrudable than steel, custom profiles can be created reasonably cheaply have a relatively small up-front cost when compared to steel forming tools. For aluminium space frames the disadvantage is in the cost of the material and the speed difficulty of assembly. Carbon fibre reinforced plastics are currently in their infancy, like most young technology the cost of the raw material and that of forming them is large. New Zealand currently has more than 30% of its energy needs being met by renewable methods. Although it may be hard for other counties to achieve this figure the amount of renewable energy production is on the rise. Future trends show that prices for solar power systems are decreasing. Solar power can be implemented locally in housing and to the surfaces of the car using faceted or flexible solar cells. Cars parked outside will charge when sitting; and while plugged in at the owner’s residence the solar panels of the house can feed straight into the vehicle decreasing resistive heating and therefore energy loss of power cables. A total paradigm shift of the automotive sector is needed to allow cars with a carbon fibre chassis to become a viable option in the future. The cost of such a car is prohibitive with today infustructure, however as the demands and desires of the automobile industry and its clientele shift to a more sustainable outlook then we will see these large and revolutionary changes how our cars look and are made. Even with future technologies it will be very difficult to compete with the build speed and cost of a conventional uni-body chassis. The
Potential issues The potential issues with this design are as follows
The price of carbon fibre would have to drop a considerable amount to make this design commercially viable. Once damaged, the structural members would have to be replaced. Ease of disassembly and repair would have to be maximized through modular design to alleviate this issue. The Car may not be suitable for long distance travel due to the reliance on the electrical system. Although a KERS system and the solar elements help, the range of this vehicle may not be that of petrol cars and energy filling will take much longer. To improve the range extra cells could be temporarily installed by the user or the use of a small heat engine could assist in charging the battery.
The infrastructure in much of the automotive industry would have to change. This is a large issue and is said to be why the next evolution has not been made in light-weighting cars.
[1] http://www.technologyreview.com/featuredstory/400002/a-practical-road-to-lightweight-cars/
