Development of the car:
To start our development we went down the more traditional F1 car style with the wide front and rear wing. This created a really aerodynamic car but was completely impractical to make as it wasn’t ‘designed for manufacture’ which our next iteration was as we learned from this.
To improve our design from version 1 we wanted to keep the main body style of the tapered wedge design, as this gave great aerodynamics. The double wing design was great as the front wing allowed us to funnel air under the car to create and air cushion for it to ride on making it appear lighter, and the double wing allowed us to funnel the air that went over the front wing to be pushed over the wheels meaning that they would be of minimal resistance to the air when spinning. What we kept alongside the wedge design for the body was the side-pods as they were great in the CFD testing as they cause the air, that has passed over the front wheel, to be deflected over the back wheel as well as pushing any air that would come in the side to be pushed out the side and not interact with the wheel, slowing us down. The rear wing however had to go, the traditional F1 style wing is designed to provide down-force and this isn’t wanted for this competition as there is a guide string and no corners meaning down-force will only slow the car down.
Version 2 of our car implements all the good bits of version 1 and removing the unnecessary parts. Starting off: the front wing splits the airflow, this allows us to scoop a lot of air under the car to create the same cushion as version 1 but allowing us to have a simpler wing design (which can be manufactured), the air that goes over the top is then channeled around the wedge and up the ramp and over the side-pods causing the air to go over the rear wheels. The side-pods keep their design as it works great causing the air to be completely diverted from the wheels. However we have left the front wing in the middle and not in-front of the front wheel as this allows the air to get under the front wheel and lift the front of the car up slightly adding to the air-cushion effect. The wheels are also slightly staggered from the front view to allow the air to hit the side-pod and be deflected outwards rather than hitting the wheel and causing vortexes to be sent into the rear wheels which would slow the car down.
We have filleted all of the trailing edges of the car body, including the sidepods and rear face to reduce the trailing vortexes that would be left behind by having sharp edges as these would slow us down by creating low pressure behind the car.
The rear wing has a traditional “wing profile” on the outside which provides stabilisation but is lofted into a spoiler shape for over the body to provide downforce. The loft that creates the twisting shape will induce a corkscrew shape into the air which will make it easier to mix with the gas coming out of the “powerpack” creating more thrust.
The sidepods are flared out at the back to push the air around the back wheels to reduce drag as, if the wheels sucked air under them at the back that would result in lifting up the back which isn’t good as the gas canister is already doing that as it is above the axle line, the flare doesn’t reach the magnitude of the width of the wheels as the air will follow the trajectory and go around, this means we can save weight by keeping them tucked in and only interrupt the airflow where it is essential. The sidepods are also curved in in the middle to allow the air that was forced around the front wheels to join back smoothly and promote laminar flow which will keep the car moving at its full potential. The draft angle on the sidepods also creates a skirt of air around the bottom as the flared base of them keeps the air under the car “lightning it up”.
The front wing is inspired by the ocean and nature, this has resulted in a “hammerhead shark design” which links back to our logo of the blue waves representing the oceans. This has created a strong and aerodynamic shape; this is why we based the design off a hydrodynamic and powerful shark. This design also adds a “mean” look to the car which makes the colour scheme pop. By integrating the front wing into the foam we are allowing the front to be as light as possible which helps with our aim of getting air under the front, by making it pivot on the back axle. This can be seen by the centre of mass in the screenshots. As the front wing is integrated into the foam, which is nowhere near as strong as 3d printed wings, but it is over 6 times lighter, this means we can have a much bigger wing and still save a massive amount of weight. We have filleted the stress points behind, where the wing joins the body to allow it to be a strong as possible and not snap off when it hits the brushes.
The body of the car was kept as close to the “no-go zone” as possible as this allows the axles to be shorter and as they are metal and heavy this will save a noticeable amount of weight. This is why the body is only 2mm wider than the “no-go zone” and the bushings are sunk into this 1mm shell by 0.5mm each side as this allows the wheels to get closer to the foam which allows the airflow to get around the wheels and not get funnelled into the cavity in them as this will cause compression inside the wheel and slow the car down as the wheels will be pushed outwards and cause extra friction. The body also follows the curve on top of the sidepods as this allows the air that is getting pushed out to also go up and over the wheels.
Testing
Wings:
After combining components for a track test, results found first wing type to be too heavy. Attributed to incompatibility between the new 3D printed front wing and the unchanged back section of the car, originally designed for an integrated front wing. We would later discover that a 3D printed front wing works better with an integrated back wing. Three different shapes of front wing were tested:
- Shorter with square edges – fastest performance
- Longer with square edges – slowest performance
- Longer with curved edges – mid range performance
Were Predictions Matched?
Interestingly, yes. Although the first car was slower than we expected due to unforeseen weight issues. The speed of the car wasn’t as critical for this test. Instead, we were looking at the changes in speed relative to each individual wing design. This is similar to discounting background radiation in a Physics Practical or discounting a systematic error.
Car:
What we wanted to test was the difference in race time between our new car and our older iterations. In total we tested 5 cars (2nd, 3rd , 4th and 5th iterations including another teams car who we competed against at the regional finals. We started off by testing the 4th iteration (regionals car) to check if the time is similar to the time recorded at the regional finals which it was. This allowed us to conclude the track time data was accurate with the tracks used at the competition. Upon recording the data from track testing by testing each car three times and excluding anomalies we were able to come to a conclusion that the 5th iteration was the fastest car which led us to the conclusion to start manufacturing the second car. This entire testing process allowed us to gather extremely valuable data that could not be gathered using any other testing methods.
Iterations
Two key alterations – throughout our design and iteration process we kept detailed records. Post track test results, we re-visited our development timeline to review any design elements that had previously performed well in CFD but had not yet been utilised. These were assessed from a different perspective and used as inspiration for the next car.
- Separate back wing swapped for an integrated version. Reducing the total weight of the car and shifting centre of mass further forwards.
- Top cone reduced in size to reduce weight.
- Based on track tests – installation of the short square-edged front wing. The fastest of the three.
Both cars have been fully tested in CFD throughout their many iterations, to ensure that everything works as it should – keeping laminar flow over the car.
Testing (Again)
As we are changing the front and rear wing designs from regionals, we were worried about the strength of it. To work out whether they would survive the racing, we decided to test the car with the wings and shorten the track so that the car had less time to decelerate, and it would hit the brushes at a greater speed resulting in a greater impact force, this would test whether the wings would stand up to the racing or not. We also tested multiple wing iterations with different profiles and densities. Since they all survived, we feel confident that they will not become damaged whilst racing as they will not reach the same speeds as this impact testing. This was extremely useful data as it allowed us to decide on using the lighter wing iteration which should help us save weight whilst not compromising car structure.