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Showcasing the Brakes

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Name: Jack Dunlop

Sub-team: Chassis & Dynamics

Part: Braking System

The braking system encompasses the hydraulic circuit and its components which is used to slow down and stop the vehicle. It needed completely redesigned for our new 10” wheels and UGR-19 sees the use of 4 custom Disc Brakes with two separate hydraulic circuits for front and rear. The system uses lightweight callipers and minimal reservoirs along with a bespoke pedal box optimised for driver use. The Stainless-Steel discs are designed to maximise pad bite, have optimal thermal efficiency and be as lightweight as possible. This was the first time I had ever used FEA simulation software, so it was a challenge to set this up however mechanical stress testing was carried out on the brake discs, image below. This system is lighter than UGR-18’s and effectively works with the new 10” Wheels.

Scrutineering

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Today the team took UGR-19 down to the University Garage to be scrutineered. The guys who work in the garage kindly do this for us every year and it allows us to be insured. They were very pleased with how the cars looking and so we’re now all ready for testing!

Showcasing the Front and Rear Wheel Hubs

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Next up in our Showcasing Series we have the Front and Rear Hubs!

Name: Finlay MacNeill

Sub-Team: Unsprung Mass

Parts: Front and Rear Wheel Hubs

What is the purpose of the components? The wheel hubs are designed to safely connect the wheels of the car to the rest of the unsprung mass assembly and because of this, the rest of the car. The front hubs do just this, whereas the rear hubs have an extra function of transferring the power from the drivetrain and engine into the wheels.

What are the specific features of your design? This year myself and the rest of the USM team made the decision to use different sized wheel bearings at the front and rear. Because we had chosen smaller front bearings this meant we could reduce the size of the front hub axle and reduce its weight significantly when compared to previous designs.
There is a lip feature on both the front and rear hubs that acts as a centering spigot for our wheel so that when the wheels are assembled onto the hubs, the important act of centering the wheel is done by this lip feature, rather than the wheel studs.
Ease of assembly was very important to the team for this year’s hubs and I decided to incorporate a stepped axle into the hub design so that when it came to pressing the hubs into the wheel bearings, there wouldn’t be any unwanted pushing or pulling on unsupported bearing faces that could potentially lead to damage.
Weight saving was also very important for this year’s USM team, especially with our change down to 10” wheels. To ensure that the hubs were as light as possible I introduced some very nice weight saving pockets into both the front and rear hubs. This was done by simulating the hubs using ABAQUS FEA and iteratively deciding where material was at its lowest stress and removing this from the final design.
This photo below is an example of the sort of simulation I was undertaking to remove material.

How did you test the parts? As shown above, the main bulk of the testing and validation for the wheel hubs comes from the FEA conducted during the design stage. There are initial simulations that I completed to see where material could be taken out of the hub designs and then closer to the end of the process, final simulations were completed to see what sort of factor of safety and fatigue life my designs had and if they were adequate enough for the team.

What were the challenges to overcome? The main challenges that I faced when designing these front and rear hubs were mainly down to complexity of working within one of our larger subassemblies on the car. Since we were moving down to 10” wheels this year it required a complete re-design of the USM assembly and that involved a lot of time and effort from everyone in the sub-team to make sure that our parts all worked together seamlessly and prevent any problems with contacting parts, assembly difficulties etc. Thankfully we have a very strong USM team this year and through a lot of double and triple checking as well as countless meetings, we manged to prevent any major problems from arising.

What are the main improvements from last year? The main improvements from this year’s hub designs must be the weight saving. I did manage to reduce the number of components in the hub assembly as well as make them slighter easier to fit together, but with this year’s hub assembly being 30% lighter than the previous one I feel very pleased with that result. That 30% along with the other weight savings in our wheels, brakes and uprights meant that the USM sub-team have saved our car approximately 15 kg for UGR-19!

Final thoughts? I would like to thank Hague fasteners for their outstanding job on the wheel studs for this years’ 2019 hub assembly, the money saved on purchasing these components as well as the strength and security they provide is invaluable, and we are incredibly pleased to have them onboard as part of the UGR-19 team!

Showcasing the Silencer

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Over the next couple of weeks we’ll be showcasing various different parts of the car! The designer of each part will talk you through their design decisions, helping you understand the process. First up, it’s Ryan and his Silencer!

Name: Ryan Clark

Sub-team: Powertrain

Part: Silencer

What is the purpose of the component? The purpose of the silencer is to make sure the car is quiet enough to pass the noise test. The rule regarding this states that the maximum permitted sound level is 110 dB(C) an 11,000 RPM, so the silencer aims to attenuate enough of the noise produced by the engine so this value is not exceeded.

What are the specific features of your design? The main change this year was the change of the geometry inside the can. Instead of having a straight pipe through the can, the perforated pipe has two bends in it. This was done in order to increase the sound attenuation of the component, whilst not being restrictive enough to limit the power very much. An image of this, in the software package, and the product received from the manufacturer, can be seen below.

What were the challenges to overcome? The largest challenge faced was the lack of knowledge within the team; this was the first year that someone was specifically tasked with designing the silencer.  As it was now being considered with larger importance, it was challenging to teach myself not only how to use the software package to its full extent, but also the theory behind the acoustics involved in the problem.

Which simulations did you carry out? So far, many simulations have been carried out which pointed towards the bent tube design, with a screenshot attached below.

The graphs plot engine speed, in revolutions per minute, against measured sound level, in dB(C). This curve was produced by the software Ricardo WAVE, and shows the sound level produced by the car as the driver revs the engine higher. The blue line is the sound profile of the silencer used by UGR-18, last years car, and the green the so called “bent tube” silencer. Although the graph does not predict it will be 110 dB(C) or less when it reaches 11,000 RPM, WAVE has not been 100% accurate in its predictions. To combat this, a sound drop of 6 dB was aimed for, as UGR-18 was 6 dB over the permitted level. This bent tube achieves a drop of 8 dB, which should put it below the maximum level. The next step is to test the design on the car and see how closely the results tie in with those achieved in the simulations.

What are the main improvements from previous years? The can is made from aluminium rather than stainless steel, meaning it is significantly lighter. The can is attached to the endplates by rivets, rather than the welding used last year, making it far easier to dismantle the silencer if we need to. The bent tube design discussed earlier will help the silencer attenuate more noise than previous years.