Project 10 Imperial Formula Racing

The Imperial Formula Racing Team is a multi-disciplinary, real world, student experience project within Imperial College London. Each year the team represents the university at Formula Student (FSUK), Europe's most established educational engineering competition.

This year, the aim was to support the development of EV21, a high-performance electric vehicle, to compete in this year’s competition. Several DMT team teams were assigned to meet the following goals:

  1. To implement the motor, mounting and cooling methods for the powertrain.
  2. To manage the interfaces for the entire vehicle, including the detailed design of brake and coolant lines, mounting brackets and the selection of appropriate vehicle sensors.

Additional teams were focused on research and development of future systems with the following aims:

  1. Design a battery module to optimize the power output, weight and cooling of the battery pack within the new chassis.
  2. Design a Quarter Car Dynamics Rig to use actual a suspension setup to measure outputs such as suspension forces, damping, spring coefficients and contact patch forces. This would also be useful for model validation of any simulation results obtained.

All the teams combined have made EV21 possible and we are proud to present it in the DMT exhibiton.

Click the arrow to show/hide an individual project.

DMT10A Powertrain

EV21 will be Imperial Formula Racing’s (IFR) most recent entry into the Electric Vehicle category of the Formula Student (FS) UK competition. This DMT project was to design and produce the drivetrain subassembly for EV21

The project involved choosing an appropriate transmission method, mounting to the rear section of a steel spaceframe, and ensuring integration with other subsystems. Additionally, it was required that a number of legacy IFR components must be used in the design; most notably, the EMRAX 228 motor and the Drexler differential. In line with research across other FS teams, a chain drive transmission was selected. Using the IFR dynamic simulator to produce lap time data and optimising this for acceleration, a transmission ratio of 3.53 was selected, producing a maximum rear wheel output torque of 811Nm. To reduce deflection and eliminate the risk of chain runout during operation, a double plate support structure was designed to house both the motor and differential in one structure, thereby keeping the majority of stresses within the plates rather than at mounting points. Finite element analysis using Solidworks and ABAQUS was carried out to ensure that all dynamic peak stresses could be managed by each component, even after mass optimisation has taken place. To allow for an integrated mounting design, the rear sprocket was bolted directly to the differential with a bespoke sprocket adapter. This moved the subsystem mass further inboard, minimising the compliance produced from the maximum chain tension. In order to appropriately tension the chain, an eccentric tensioning mechanism was designed. The differential was mounted off centre, relative to the bearing housings that supported it. The subsequent rotation of the housing within the mounting plates allowed horizontal translation of the rear axle; in turn, tensioning the chain. This tension will be applied by two people, using a C-hook spanner and notches at the outer circumference of the bearing housings.

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DMT10B Cooling

The project was to develop a complete and fully functional cooling system for the Imperial Formula Racing EV21 vehicle. Based on analysis, the system provides sufficient cooling for the motor and the motor controller in competition conditions and complies with all FS UK 2021 rules and regulations.

The water-cooling circuit uses the build-in coolant loops of the motor and the motor controller which are the only components that need active cooling. Radiator selection was based on NTU-method and CFD results ensured effective heat rejection from the circuit. The ducts and fans channel the air to ensure sufficient airflow across the radiator fins. Resistance to the flow was analysed to select a high-performance electric water pump that ensures the required coolant circulation. A dedicated LV battery was fitted to the system to supply electrical power to the fans and the coolant pump.

All major components are mounted to the EV21 spaceframe via sheet-metal mounting hardware and dedicated mounting points welded onto the steel structure. Flexible coolant hoses, electrical wiring, and the electronic control board are mounted via soft mounting.

The system meets the budget requirement of £1000 and will be ready for fitment to the EV21 vehicle before the FS competition scheduled for July 2021.

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DMT10C Vehicle Integration

The EV21 is a fully electric vehicle designed by the Imperial Formula Racing (IFR) team for the 2021 Formula Student competition. A recurring issue for previous IFR teams was the design of critical mounting components was often overlooked, which resulted in the sub-optimal integration of the car’s main sub-assemblies.

To solve this issue, the Vehicle Integration Team’s role was to design the mechanical and hydraulic interfaces and routings between various EV21 subsystems. These included the steering column mounting, pedalbox mounting, and hydraulic brake lines system. In addition to that, a set of sensors for car telemetry were selected, and mounted to the car. The VIT team also ensured good communication and coordination between IFR sub-teams, using a team-wide Gantt chart, to ensure optimal integration of sub-assemblies. A visual map was also created to show all sub-systems, detailing every interface between sub-systems.

The steering column mounting consists of two steel plates, welded using five support tubes to the EV21 spaceframe. The pedal mountings are welded to the chassis and are designed to be adjustable to accommodate various drivers’ heights. The hydraulic brake lines design consisted of stainless steel fittings and braided stainless steel hoses to ensure high braking performance and re-usability for future IFR vehicles.

A set of sensors was selected from the AiM Sportline. The EVO4S data logger was selected to be mounted on the same channels as the motor controller at the rear of the car. Two wheel-speed sensors were also chosen to be mounted on the front wheels, along with a camera to be mounted above the driver’s head on the spaceframe and connected to the data logger to have in-sync sensor data with the video feed. The sensors can also be used on a go-kart for the Automotive Design with Motorsports course.

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DMT10D Battery Module

Imperial Formula Racing (IFR) strive to design, build and test electric racing vehicles that compete in the Formula Student (FS) competition at Silverstone every year.

With the concern that the current battery pack will overheat, as well as rapidly growing EV cell technology, we decided to focus our DMT on the design of a new, optimum FS car battery module.

After understanding the limitations of the current module as well as developing a detailed module design specification, we first decided to optimize the cell selection and configuration at a pack level. We achieved this by processing the electrical and physical properties for a vast number of cells and used a search algorithm that output the minimum mass configuration by finding the optimum pack operating voltage. Together with several other considerations and constraints such as the power and capacity required, an optimized pack level configuration of 126s3p operating at 450V nominal was obtained. The selected cell was the cylindrical Sony VTC6A 21700 which yielded a lowered cell mass of 26kg whilst conserving a sufficient pack capacity of 5.54kwh. We hope this pack sizing matrix and algorithm will be of future use for IFR.

Since physical prototyping was limited due to the COVID19 pandemic, our team developed and validated a heat transfer model that enabled us to gain an insight on the thermal response of concepts in event conditions. The unsteady heat equation was first solved on MATLAB and then implemented into SIMULIA to observe spatial thermal distributions. The highest performing thermal management concept was then developed into a full module design, where weight was minimized further, saving another 1.4kg on a pack level. Furthermore, the devised thermal management is flexible, able to accommodate both pumped or stagnant coolants for which we considered phase change materials or water due to its high specific heat to density ratio and availability.

Further design considerations to ease assembly and manufacturing were considered and implemented. This included standardization of parts as well as selecting UL94-V0 materials to conform to the strict fire-retardance safety requirements. Spot-weldability and AWG standards were considered to design reliable electrical connections which were isolated at best from the expected car vibrations.

Finally, a precise assembly procedure was put together to safely guide the remote assembly of the module. Subsequent testing is also planned to test the module under race conditions to ensure it behaves as expected.

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DMT10E Quarter-Car Test Rig

Vehicle shakers and test platforms are used throughout the automotive and motorsport industry to evaluate noise, vibration, and harshness (NVH), performance metrics and to test component durability. Testing of race car suspension and chassis components focus almost solely on assessing handling performance, as well as tuning suspension to optimise the cars dynamics capabilities rather than minimise NVH. Quarter-car rigs are used to measure theresponse of a single isolated wheel and suspension system and form an integral part in validating suspension models and design.

The rig has been designed to interface with the EV3 race car suspension from Imperial Formula Student. It incorporates a module design to ensure adaptability for use with a range of different suspension types and geometries. The design allows for quick adjustability of suspension motion ratios and other key suspension parameters enabling the user to investigate the sensitivities these parameters have on vehicle performance. The frame consists of bolted aluminium extrusions which enabled the design to be disassembled easily into a compact form for storage. The test rig has been designed to easily integrate an actuation system, which would enable more extensive testing in future iterations.

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Maintained by Richard Silversides r.silversides@imperial.ac.uk