Queen's University Shell Eco-Marathon Design Project

The scope of the project is defined by the rule book provided by Shell, which dictates certain requirements for each system. The scope is reasonably open, and mainly requires a steering system and front suspension system that function and fit with the chassis. The functional requirements of each system are based heavily on cost, ease of installation, and weight. The goal of each system design is to optimize each requirement to best meet the team’s needs. The Shell rulebook shows basic requirements for the entire care, such as height, weight, and other specifics. For this project the rules being considered are those in the steering and suspension sections, which are all quite standard and leave room for creativity.

Before selecting each type of system, alternative ideas were explored. For the steering system, a rack and pinion design, an arm joint design, and a ball joint design were considered. After evaluating each idea with a weighted matrix, the rack and pinion design was selected due to its light weight, cost and dependability. The final steering design uses the rack and pinion, but also explores spindle, control arm, wheels, hubs and brake designs.

For the suspension system, leaf and coil springs, as well as driver seat and air suspension were considered. Using the same matrix system as a selection tool, the driver seat suspension system was selected, due to its simplicity. Although not a typical system seen in full size cars, for the scope of this project and the Eco-marathon event the suspension seat suits the car’s needs. In addition to the seat, rubber pucks have been added between the spindles and the frame to dampen the vibration from the motor. Due to the smooth nature of the track, a full front suspension system is not required, the combination of the seat and pucks fit the needs of the vehicle.

The car will experience various forces during the race, the largest sum of forces possible being the dynamic loading from hitting a large bump in the track, the dynamic loading from braking, and the dynamic loading from turning all occurring simultaneously. To ensure the steering system will not fail under these conditions, a thorough ANSYS analysis was done on the spindle mounting column, replicating the worst-case scenario with an additional 1.5 times factor of safety to represent the lower strength of the welds. The design passed by a large margin because of the combination of aluminum beams and steel bolts.

The original budget for this designed system started at $1500 CAD, as the project progressed that became less and less feasible to meet the client’s needs. After a meeting with the eco-marathon team, the total cost came out to $3900 CAD, which was accepted by the team. The closing of this project comes with four main deliverables in addition to this report: a detailed CAD drawing of each design, a parts list, an economic analysis (which has been included in this report), and full assembly instructions for the designed system

Figure 1: The steering system.
Figure 2: The spindle.
Figure 3: The hub and brake assembly (from external source - see references in attached pdf)
Figure 4: ANSYS analysis of a designed member used to mount the spindle - forces
Figure 5: ANSYS analysis of a designed member used to mount the spindle - stress
Figure 6: ANSYS analysis of a designed member used to mount the spindle - deformation
Figure 7: The given chassis

Note: The given chassis, created by a team a year prior, was initially not supposed to be changed. It ended up being partially changed to accommodate the steering system. It was also recommended that the given design should not be used as it was determined that there was concern for the design's safety due to the nature of the small connectors, set screws, carbon fiber tubes, and minimal analysis done in the initial design. If the chassis design is decided to be used, it was recommended that the entire bottom layer of members in the chassis be made from aluminum.