The Prototype vehicle is a three wheeled, single-passenger vehicle meant to push the limits of fuel efficiency. It competes in the Shell Eco-Marathon, and SAE Supermileage competitions. This competition class has very few limits on design, allowing a number of creative solutions in order to achieve extremely high fuel mileage. This year, UBC Supermileage is developing a monocoque version where the shell and chassis are integrated in one piece.
The Urban Concept Car is a slightly more practical vehicle meant to bridge the gap between the prototype vehicle and the vehicles you see on the road today. It only competes in the Shell Eco-Marathon. Teams are required to design the vehicle with a minimum of four wheels, larger stance, headlights, tail lights, turn signals and other practical considerations that the average city vehicle requires today.
The engine used in our Prototype vehicle is a Briggs & Stratton Junior 206. This engine is standard for all teams in the SAE Supermileage Competition. This stock engine is 205cc’s with a maximum horsepower rating of 8 horsepower and a torque of 10 ft-lb. This year, a custom cylinder head has been designed to increase the compression ratio from 8.5:1 to 12:1. This will achieve a decreased displacement from 205cc to 120cc, resulting in a greater thermal efficiency.
The engine used in our Urban Concept vehicle is a Honda GXH 50. It is a 50cc, 1-cylinder, 4-stroke engine with a net power rating of 2.1 horsepower and a torque of 2.0 ft-lb. For comparison, this engine is similar to those used in lawnmowers. To maximize our fuel efficiency, a fuel injection system is also used for this engine.
Our current Prototype vehicle uses a carbon fibre - Nomex sandwhich where 1.5" of lightweight Nomex honeycomb is sandwiched between carbon fibre and Kevlar reinforced polymer on both sides. The use of thicker Nomex than the Urban Concept is to compensate for the narrower chassis, which is reduced in size to minimize weight. Kevlar is used to allow rivets to be installed on the chassis. The total weight of the chassis (including all components except the engine) is less than 100 lbs.
Our current Urban Concept vehicle uses a carbon fibre-Nomex sandwich where 1" of lightweight Nomex honeycomb is sandwiched between layers of carbon fibre reinforced polymer on both sides. The wider width of the Urban Concept chassis allows for the chassis thickness to be reduced without compromising rigidity. The total weight of the chassis (including all components except the engine) is approximately 120 lbs.
The newly innovated powertrain is configured as a two-stage, fixed-pulley reduction system. As the name implies, there are two pulley reductions from the engine to the wheel. The flexible drive of the powertrain has been switched from roller chains to carbon fiber timing belts to optimize weight, while maintaining a high strength. In addition, timing belts can deliver comparable efficiency to a roller chain system, however, there is less maintenance associated with timing belts. By designing our vehicle to run at a maximum speed of 50 km/hr, this system allows our engine to transmit power at its optimal speed.
The drive-train includes a planetary gearbox and a 2-gear box. The engine transmits power to the planetary gearbox through a gear reduction, and from there to the second gearbox. The default position is a 2:1 reduction gear set, and when the clutch is engaged, the 1:1 gear set “overdrives” the 2:1 set, putting the vehicle in second gear.
The Prototype vehicle steering system is similar to that of a motorcycle, where there are two handlebars for steering, a throttle, and braking handlebars. The space inside for the driver is very limited and the driver drives lying down, so this design allows us to use the confined space efficiently. Steering for this vehicle is operated through the front wheels.
The Urban Concept steering system is based on Formula 1 style steering. The steering wheel operates like those found in regular cars, and switches for controls such as the starter motor, lights, and windshield motor are situated in the centre area of the wheel. Steering for this vehicle is operated through the front wheels.