Aerodynamic & Safety Development of Open Cockpit Helmet Design

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Aerodynamic & Safety Development of Open Cockpit Helmet Design

Thomas Urry (10004753)

Supervisor: Debi Roberts

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Abstract The purpose of this project is to analyze the aerodynamics of a helmets used in karting, the choice of why karting was chosen is explained in the report. Various wings which are designed improve performance are analyzed and also the aim to investigate the safety aspect of helmet design and to look into the materials used within in them and how they are tested for strength. To achieve this aero tests are done on three helmet designs (plain, solid wing, slot gap wing) in stand-alone tests and also in karts. Each helmet will also be tested up right and tucked down as this is what kart drivers to streamline their bodies, which meant having to design two kart setups so that the helmet was tucked in one and un-tucked in the other. During the testing it was discovered that for karting a plain helmet with no attachments seemed to be the best in terms of overall aerodynamic performance. However due to the time limit of the project the domain size and mesh tightness; the testing was accuracy may not be 100% accurate. However it has still enabled the analysis of the helmets as the airflow is still visualized and gives an idea of what the air is doing around each design. When looking at the helmet safety section it proved tricky to find out about helmet construction as manufacturers keep their processes secret. Also within this project there is research into the helmet industry and the theory of aerodynamics to give readers a basic understanding of what is occurring in the testing.

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Contents .................................................................................................................................................................................... 1

Abstract ................................................................................................................. 2

Introduction ........................................................................................................... 6

Objectives .............................................................................................................. 7

Background Research & Literature Review ............................................................. 7 Primary Research Helmets ............................................................................................................................ 9 Arai SK-‐5 GP5 Shell: -‐ ........................................................................................................................................ 9 Vemar Bike Helmet: -‐ ..................................................................................................................................... 10

Schuberth SF1 (A Current Helmet Used in F1) ................................................................................... 10 Arai Helmets; Venting & Ducting .............................................................................................................. 11 Why Karting? ..................................................................................................................................................... 11 Nassau Panels & Karting Bodywork ........................................................................................................ 12 M4 (Kosmic, Tony Kart, Fernando Alonso Karts) .............................................................................. 12 New Age 2 (Maranello, CRG, Old Intrepids) ......................................................................................... 13 Freeline (Birel) ................................................................................................................................................. 13 Bigfoot Nassau Panel ..................................................................................................................................... 13

Safety Aspects & The Materials Used In Helmet Construction .............................. 14 Fibers Used in Helmet Construction ........................................................................................................ 14 Helmet Strength Testing ............................................................................................................................... 15

Initial Ideas & Designs .......................................................................................... 16 Basic Helmet ...................................................................................................................................................... 16 The Kart ............................................................................................................................................................... 17 Helmet Wing Attachment 1 (Solid) .......................................................................................................... 17 Helmet Wing Attachment 2 (Slot Gap Wing) ....................................................................................... 18

Aerodynamic Testing Details & Setup .................................................................. 19

Testing of Helmets ............................................................................................... 20 Basic Testing and Setup of The Domain and .STL File ..................................................................... 20 Basic Test Setup Simulation for Domain: -‐ ........................................................................................... 20

Stand-‐Alone Helmet Tests (Up-‐Right) ................................................................... 22 Basic Helmet Up-‐Right ................................................................................................................................... 22 Velocity ................................................................................................................................................................. 22 Pressure ............................................................................................................................................................... 23

Helmet Wing Attachment 1 (Solid) Up-‐Right ...................................................................................... 23 Velocity ................................................................................................................................................................. 23 Pressure ............................................................................................................................................................... 24

Helmet Wing Attachment 2 (Slot Gap) Up-‐Right ................................................................................ 24 Velocity ................................................................................................................................................................. 24 Pressure ............................................................................................................................................................... 25

Stand-‐Alone Helmet Tests (Ducked Down) ........................................................... 26 Basic Helmet Ducked ...................................................................................................................................... 26 Velocity ................................................................................................................................................................. 26 Pressure ............................................................................................................................................................... 26

Helmet Wing Attachment 1 (Solid) Ducked ......................................................................................... 27

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Velocity ................................................................................................................................................................. 27 Pressure ............................................................................................................................................................... 27

Helmet Wing Attachment 2 (Slot Gap) Ducked .................................................................................. 28 Velocity ................................................................................................................................................................. 28 Pressure ............................................................................................................................................................... 28

Stand-‐Alone Helmet Testing Data ........................................................................ 29 Pressure Data .................................................................................................................................................... 29 30 MPH (13.41 M/S) ...................................................................................................................................... 29 60 MPH (26.82 M/S) ...................................................................................................................................... 30 90 MPH (40.23 M/S) ...................................................................................................................................... 30 120 MPH (53.64 M/S) .................................................................................................................................... 30

Velocity Data ...................................................................................................................................................... 32 30 MPH (13.41 M/S) ...................................................................................................................................... 32 60 MPH (26.82 M/S) ...................................................................................................................................... 32 90 MPH (40.23 M/S) ...................................................................................................................................... 33 120 MPH (53.64 M/S) .................................................................................................................................... 33

Pressure Coeffients/Gradients ................................................................................................................... 34 30 MPH (13.41 M/S) ...................................................................................................................................... 34 60 MPH (26.82 M/S) ...................................................................................................................................... 34 90 MPH (40.23 M/S) ...................................................................................................................................... 35 120 MPH (53.64 M/S) .................................................................................................................................... 35 Pressure Gradients Basic Helmet (Un-‐Tucked) .................................................................................. 35 Pressure Gradients Basic Helmet (Tucked) .......................................................................................... 36 Pressure Gradients Wing 1 (Un-‐Tucked) .............................................................................................. 36 Pressure Gradients Wing 1 (Tucked) ...................................................................................................... 36 Pressure Gradients Wing 2 (Un-‐Tucked) .............................................................................................. 37 Pressure Gradients Wing 2 (Tucked) ...................................................................................................... 37

Stand-‐Alone Helmet Testing Discussion ............................................................... 37 Un-‐Tucked ........................................................................................................................................................... 37 Tucked .................................................................................................................................................................. 38

Kart Testing ......................................................................................................... 39

Kart Test (Empty Kart) .......................................................................................... 39

Kart Testing Data (Empty Kart) ............................................................................. 39 Pressure Data .................................................................................................................................................... 40 Velocity Data ...................................................................................................................................................... 41 Empty Kart Pressure Coefficients & Gradient Graph ....................................................................... 43

Empty Kart Testing Discussion .............................................................................. 43

Kart Testing With Helmets Tucked & Un-‐Tucked .................................................. 44 Basic Helmet ...................................................................................................................................................... 45 Pressure Un-‐Tucked ....................................................................................................................................... 45 Velocity Un-‐Tucked ......................................................................................................................................... 46 Pressure Tucked ............................................................................................................................................... 46 Velocity Tucked ................................................................................................................................................ 47

Wing 1 ................................................................................................................................................................... 48 Pressure Un-‐Tucked ....................................................................................................................................... 48 Velocity Un-‐Tucked ......................................................................................................................................... 49 Pressure Tucked ............................................................................................................................................... 49 Velocity Tucked ................................................................................................................................................ 50

Wing 2 ................................................................................................................................................................... 50

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Pressure Un-‐Tucked ....................................................................................................................................... 51 Velocity Un-‐Tucked ......................................................................................................................................... 51 Pressure Tucked ............................................................................................................................................... 52 Velocity Tucked ................................................................................................................................................ 52

Kart Testing With Helmets Tucked & Un-‐Tucked Data .......................................... 53 Pressure Data .................................................................................................................................................... 53 30 MPH (13.41 M/S) ...................................................................................................................................... 53 90 MPH (40.23 M/S) ...................................................................................................................................... 53

Velocity Data ...................................................................................................................................................... 54 30 MPH (13.41 M/S) ...................................................................................................................................... 54 90 MPH (40.23 M/S) ...................................................................................................................................... 54

Pressure Coefficients/Gradients ............................................................................................................... 55 30 MPH (13.41 M/S) ...................................................................................................................................... 55 90 MPH (40.23 M/S) ...................................................................................................................................... 55 Un-‐Tucked 30 MPH (13.41 M/S) .............................................................................................................. 55 Tucked 30 MPH (40.23 M/S) ...................................................................................................................... 56 Un-‐Tucked 90 MPH (13.41 M/S) ............................................................................................................... 56 Tucked 90 MPH (40.23 M/S) ...................................................................................................................... 56

Helmet in Kart Testing Discussion ........................................................................ 57 Un-‐Tucked ........................................................................................................................................................... 57 Tucked .................................................................................................................................................................. 58

Nassau Panel Testing ........................................................................................... 60 M4 Based Design .............................................................................................................................................. 60 Lipped Nassau Panel (Un-‐Tucked) ........................................................................................................... 61 Velocity ................................................................................................................................................................. 61 Pressure ............................................................................................................................................................... 62

Lipped Nassau Panel (Tucked) .................................................................................................................. 63 Velocity ................................................................................................................................................................. 63 Pressure ............................................................................................................................................................... 64

Large Lipped Plate Nassau Panel (Un-‐Tucked) .................................................................................. 65 Pressure ............................................................................................................................................................... 65 Velocity ................................................................................................................................................................. 65 Large Lipped Plate Nassau Panel (Tucked) .......................................................................................... 66 Pressure ............................................................................................................................................................... 66 Velocity ................................................................................................................................................................. 67 Nassau Panel Variations Discussion ........................................................................................................ 68

Conclusion ........................................................................................................... 69 Testing Conclusions ........................................................................................................................................ 69 Project Limitations & What Would Be Done Differently Next Time? ........................................ 72

Appendices .......................................................................................................... 72

Works Cited ......................................................................................................... 72

Figures ................................................................................................................. 72

Tables .................................................................................................................. 74

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Introduction The safety of a driver’s head and the aerodynamic performance of the driver’s helmet are becoming an increasing factor of concern for designers. A team will try to gain as much performance out of the car as possible whether it’s the design of an aerodynamic rear wing or getting their drivers to wear helmets that increase performance aerodynamically. An area of motorsport where helmet performance is the most sorts after is karting; this is because the entire drivers head is exposed to the airflow therefore minimizing drag around the head would be a big help for performance. Aswell as aerodynamic performance the karts can achieve high speeds therefore increases the risk of accidents where the drivers head will be subject to large impact forces from parts of karts and the tarmac as the driver is completely exposed. This means drivers head safety is of high importance and rules are

in place to manufacturers to abide by to make sure the helmets are safe enough to compete with in motorsport. This project therefore looks into how these performance benefits can be gained in order to increase competitiveness. It will also look at modifications which can be made to the area around the driver to increase performance and if it is possible to direct air over the helmet in a controlled way to reduce drag. In terms of safety a there will be a look into the various materials and construction methods that are used in the construction of helmets and how they are checked for safety and the laws that they are controlled with. It is also important to look into a method used in karting to increase aerodynamics called ‘tucking’ where the driver tucks down to make the kart slicker through the air, and if this can be used with helmet designs to have a more profound effect to the overall performance of the kart down straight similar to a DRS system.

CAD and CFD software will be very important as it means all the tests and designs can be done on the computer and not in real life. This will save time, as it will mean many tests can be done in quick succession testing different designs. Also it means that after a test the helmet can be imported back into CAD software and altered the re-tested. The CAD software being used is called Creo Parametric; it allows a user to design a part or object in

Figure 1 http://www.shoei-helmets.com/Safety_ActiveSafety.aspx

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3D and export it as an .STL file which can then be tested in a variety of software’s. The CFD software that is being used is called Cham Phoenics, it is computational fluid dynamics software that simulates fluid flow on an object allowing the user to change many variables such as turbulence, and it also lets a user import a .STL file from Creo Parametric to test which is the main reason for choosing this software.

Objectives

The key aim for the project is to increase the overall aerodynamic performance of a standard motorsport helmet that would typically be used in karting along a straight. It will be designed in CAD software (Creo Parametric) and then tested in aerodynamic software (Cham Phoenics) to analyze and seek conclusions from. Firstly a basic helmet will be designed and this will be the base helmet which

parts will be formed onto and tested to see if there are benefits gained. Aswell as just the helmet being tested the helmet will be tested with a kart designed in CAD to see how the airflow around the helmet is affected when in a racing scenarios I.E. in a kart and following another kart etc. Investigating the effects of tucking is also important as this position in the kart can be used with an efficient helmet design to massively increase performance down straights. Aswell as the aerodynamic performance the research will take place to look into the helmet construction and the materials that are used in the construction of a helmet. Also it is important to look at the purpose of helmet ventilation and benefits that can be had from a good ventilation system.

Background Research & Literature Review

This project looks into the aerodynamic capabilities of helmets and how various aero devices can be used and altered to improve the aerodynamic efficiency of the helmet. A good book to start with is Race Car Aerodynamics: Designing for Speed by Joseph Katz as it provides an overview to the main aerodynamic theories and devices employed in motorsport today. In order to undertake this study a look into the aerodynamic theory surrounding motorsport is required and how different devices are used in motorsport to achieve aerodynamic efficiency and to gain an understanding of the various

Figure 2 http://www.schuberthnorthamerica.com /categor ies/motorcycle/s2/

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challenges that need to be overcome when designing an aerodynamically efficient part. It is also important to gain the understanding of these theories and how these devices react in order to understand the CFD results which are achieved through Cham Phoenics.

The principal theory to gain knowledge of before studying more advanced aerodynamics and the various devices is the different ways in which air flow and pressure exert forces onto a vehicle. “The first is pressure, which acts normally (perpendicular) to the surface and is responsible to the vehicle’s lift and part of the drag. The second force is shear force (eg. friction) which acts parallel to body’s surface and contributes only to drag.

The resultant force due to these contributions can be divided into

various components. ” (Katz, 2006) these forces are lift drag and side forces illustrated in Fig. 3 below. Simon Mcbeath describes drag and lift in a different ways that is simpler and described using examples to give the reader an easier understanding. “A COMPETITION CAR, like any vehicle, is a highly complex aerodynamic device. Unlike an aircraft in normal flight, a car is always in close proximity to the ground. This complicates the airflow around it, and makes understanding what’s going on even more difficult. But aircraft and cars have one thing in common – in travelling through air they both generate substantial forces. Both have to overcome aerodynamic drag, a force that opposes forward motion. An aircraft has to generate a lift force equivalent to its own weight in order to maintain level flight. A car however has no such perquisite, and in fact it is greatly preferable that it stays on the ground so that its tyres can generate grip to provide tractive forces – that is, accelerative, braking and cornering.” (McBeat, 2006) This description of basic drag and lift theory is much more simplistic than the Joseph Katz one which is much more scientific, however the Joseph Katz one is accompanied by a diagram which describes the theory

Figure 3 (Katz 2006 Fig 2-20)

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well with not a big description required, but the description that is there is thorough and in depth providing good research material for the project. The Competition Car Aerodynamics book is an easier read than the other making it easier to understand the first time around however the Race Car Aerodynamics Book takes several readings to gain an understanding of the text. A final example to examine and compare back to these two is Road Vehicle Aerodynamics by R H Barnard which looks at the various aspects of aerodynamics in road cars form small cars all the way to articulated vehicles. It gives a good insight into the technologies and designs used by modern manufacturers in today’s car market to create an aerodynamically efficient car which is not for just power but for fuel efficiency. This book also has explanations of lift and drag forces but unlike the other the explanations for lift and drag are split into different section which makes it easier to read and understand. “The total force resisting the forward motion of a road vehicle comes partly from the rolling resistance of the wheels, and partly from drag” “the aerodynamic drag dominates at speeds above 65-80 km/h (40-50mph) and there are considerable economic and performance advantages to be gained from drag reduction” (Barnard, 2009). The first of these two quotes describes the two factors that can cause a cars drag, and the second describes the benefits that can be gained from a good aero package. Finally it also shows the speeds in which aerodynamic drag starts to affect a cars performance; this allowed a base to start doing Cham Phoenics tests at 60mph as this is just above the lower drag range.

Primary Research Helmets

Arai SK-‐5 GP5 Shell: -‐ This is a typical helmet used in karting to protect the driver’s head and for performance. It has several not standard features which were purchased of Arai and stuck onto the helmet these are the wing on the top rear of the helmet and the chin piece just below the visor.

The wing on the top of the helmet is there to allow air to flow smoothly off the back of the helmet

and to reduce the drag leaving flowing off of the back of the helmet. The second non-standard part is the chin piece this is designed to reduce buffeting on the drivers head at high speeds. The driver who’s helmet this belongs too said “With the chin piece attached I could keep my head up and I was able to keep my head stead when I reached fast speeds.”

Figure 4 - Self Taken Photo Arai SK-5

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There are also several small vents around the helmet these are for driver cooling; two are located on the top of the helmet and two larger ones above the chin piece.

Vemar Bike Helmet: -‐ This particular helmet is used predominantly for motorcycle riding and can be used in karting, it is however mainly used by drivers with lower budgets, as it is the sort of helmet found in most basic motorcycle shops. In the design of helmets it is important to balance the strength of the helmet with the weight of the helmet because it would be pointless having a very strong helmet but is extremely heavy so the user can’t keep their head up. On the rear of this helmet there is a set of vents that can be opened or closed at the drivers will, which vents the drivers helmet out cooling them. There is also a similar vent on the front, which will allow cool air to flow into the helmet, and the rear vents would there for exhaust the hot sweaty air from the helmet giving the rider more comfort.

Schuberth SF1 (A Current Helmet Used in F1) Schuberth are one of the top suppliers of helmets in the world they supply helmets for several Formula 1 drivers and also produce helmets for other industries such as police, fire fighters and the military aswell as motorsport. Their main helmet is the SF1, which has a carbon fiber shell and costs approximately 5000 Euros to buy. This helmet must meet the highest FIA specifications to be used in Formula 1. The SF1 is constructed using 19 layers of carbon fiber and carbon-aramid fibers and fabrics that are then all compressed and processed using an autoclave. The visor is also made from high impact materials to prevent an object hitting the driver’s face, which is why it is made from 3mm bulletproof polycarbonate to meet the stringent FIA rules. An example of how strong the Schuberth helmets are was at 2009 Hungarian grand prix where a spring came off of the back of Rubens Barichello’s car and struck Felipe Massa just above the left eye causing him

Figure 5 - Self Taken Photo Vemar Helmet

Figure 6 - http://racinghelmetsgarage.blogspot.co.uk/2012/04/schuberth-sf1-falonso-2012-by-jens.html

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to be knocked out but ultimately alive which shows how strong these helmets are. Schuberth have their own private wind tunnel that they use to test the performance of the helmets aerodynamically helping them to achieve the best aerodynamic performance available. The SF1 generates neutral uplift, which means the driver’s head can stay stable at high speeds. Unlike the Arai SK-5 helmet there is no spoiler on the rear, which is mainly because there is a roll hoop directly behind the drivers, head meaning airflow would hit that immediately after flowing over the helmet; whereas in karting the air flow off the back of the helmet into open space. The ventilation on the SF1 can allow 10 liters of air per second to pass through the helmet through 10 inlets and then back out through 6 exhaust outlet giving the driver fresh air and venting out the sweat and hot air.

Arai Helmets; Venting & Ducting Ventilation is a very important part of helmet construction for several reasons; firstly the flow of air through the helmet reduces fogging in the helmet, which would impair the driver’s vision and cause them to crash. Secondly a good ventilation system will provide airflow into the helmets interior and will then flush out the warm damp air out of the helmet, this will give the driver more comfort and therefore the drivers ability to give maximum performance for longer and they can concentrate on the race rather than the discomfort of a sweaty helmet. Aswell as this the ventilation system can reduce noise in the helmet by creating turbulence to eliminate the vacuum at the rear of the helmet; also it will lower the buffeting on the helmet. Combining inlets to let air in and exhaust outlets to vent the air out and to get the positioning correct for maximum effect will achieve a good helmet ventilation system.

Why Karting? Karting was chosen was because the drivers heard is completely exposed to the element meaning aerodynamic modifications can be much more effective in karting compared to other forms of motorsport. Also the fact the drivers head is do open means that safety is of high importance to karting drivers as it very easy for a kart driver to ejected from the kart and be struck by another kart. In karting there is a maneuver used by drives where the tuck down to the steering wheel to increase performance of the kart by allowing air to flow

Figure 7-Self Taken Photo Untucked Kart Figure 8-Self Taken Photo Tucked Kart

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over the drivers back rather than hitting the drivers torso and facial area. It may be possible therefore to design a feature for the helmet to make this more effective and to act as a form of DRS (drag reduction system), which is used in Formula 1 to give the car a boost of speed for overtaking. However before karting was chosen research was done into what different areas of motorsport could the helmet be designed for. Areas that were looked at included Formula series, LMP open top cars, motorbikes, road cars and hill climb cars.

Nassau Panels & Karting Bodywork A Nassau panel is the piece of bodywork on karts that covers the steering column and has the driver’s number. There are various designs for these; they direct air towards the driver therefore making it the ideal piece of bodywork to re-design to assist in directing air over and around the driver. The main constraint to designing a Nassau panel is the steering wheel has to be the highest point on the car with no driver in the kart. Nassau panels and body work are designed by different manufacturers but are generally a standardized set of panels which are chosen by teams, that is why you often see different chassis manufacturers using the same bodywork. Below is a selection of bodywork kits and what teams use them.

M4 (Kosmic, Tony Kart, Fernando Alonso Karts)

Figure 9 - M4 Design (www.spellframe.co.uk)

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New Age 2 (Maranello, CRG, Old Intrepids)

Figure 10 - New Age 2 (www.spellframe.co.uk)

Freeline (Birel)

Figure 11 - Freeline (www.kartdavid.co.uk)

Bigfoot Nassau Panel

F igure 12 - Bigfoot Nassau Panel (www.kartdavid.co.uk)

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Safety Aspects & the Materials Used In Helmet Construction Back in the early days of Formula 1 there was a higher emphasis on speed rather than driver safety. Juan Fangio preferred to race with no head protection at all just a balaclava to protect his head, However in 1953 helmets were made compulsory for all Formula 1 drivers and in 1963 drivers were made to wear full face helmets with visors which is has now involved into the current helmet see in Formula 1. The FIA set standards that all manufacturers must follow strict laws for example in Formula 1 helmets must meet the FIA 8860-2004 advanced helmet technical specification. These regulations were developed over eight years at the Transport Research Laboratory (TRL) based in the UK, and the three main Formula 1 and open cockpit racing series helmet manufacturers (Arai, Bell, Schuberth) have to adopt this criteria. The compositions of the materials used by helmet manufacturers are generally kept a secret by the manufacturer. However the outer layers of it are generally the same and are a fiber-reinforced resin over carbon fiber and under this s a layer of aramid which is often used in the manufacturing of bulletproof vests and finally a layer of polyethylene covered in a flameproof material used in the drivers overalls. Formula one drivers have their helmets custom fitted to ensure maximum comfort and the best possible hit, this is done by taking the a scan of the drivers head and then creating a model of the head. This model is then wrapped layer by layer with 120 mats of carbon fiber; each layer is then bonded together using an autoclave which hardens the carbon fiber under pressure at 132 degrees celcius to create a shell. Due to the huge loads that can be faced by a helmet parts such as the visor cut out and around the neck where there are weak points are reinforced by aluminum or titanium. The visor of the helmet is also a key part of the helmets integrity and is made from a three millimeter thick piece of polycarbonate which provides impact protection and is also fire resistant. The visor is tested by having projectiles launched at it at speeds of 500KM/H (311MPH) and the visor must not show marks that exceed 2.5mm deed.

Fibers Used in Helmet Construction Various fibers are used in the construction of helmets such as carbon fiber and aramid fibers. “Fibers consist of thousands of filaments, each filaments having a diameter of between 5 and 15, allowing them to be producible using textile machines; for example, in the case of glass fiber, one can obtain two semi products as shown in Figure 1.2. These Fibers are sold in the following forms:

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• Short Fibers, with lengths of a few centimeters or fractions of millimeters are felts, mats, and short fibers used in injection molding.

• Long fibers, which are cut during time of fabrication of the composite material, are used as is or woven.

Principal Materials are

• Glass • Aramid or Kevlar (very light) • Carbon (high modulus or high strength) • Boron (high modulus or high strength) • Silicon carbide (high temperature resistant)”

(Tsai, 2003) (Placeholder2)

Figure 13 (Tsai, 2003)

Helmet Strength Testing At the TRL test facility helmets undergo many tests to ensure that they meet the FIA’s 8860 laws which require a helmet to withstand an impact of 9.5M/S (21.3MPH) and at this speed mustn’t display a deceleration more than 300g’s while 225 joules of energy must be dissipated all of which are measured on sensors placed all around the helmet. Each helmet is fitted onto a metal head analog which is rigged with sensors to show the readings of forces not just on the helmet but what goes through the driver. The helmet and head is then place on a sled which is mounted onto a 15.5M high tower which can accelerate objects to 17M/S (38MPH) from top. The helmet is then dropped onto various surfaces to simulate impacts which can include a flat surface, a sharp edge, a half sphere and even objects such as springs or wheels. Aswell as impact tests helmets must also undergo several more tests which test

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deformation and procedures which test the HANS device to ensure that it doesn’t fail and cause the drivers head to hit the steering wheel. There is also a fire test which is to ensure that the fireproof credentials of the helmet are true. The helmet is subject to 800 degrees celsius for approximately 45 seconds and the interior of the helmet should not exceed a temperature of 70 degrees celcius.

Initial Ideas & Designs

Basic Helmet For the control test a basic helmet is needed so that the results from modifications made to the helmet can be compared back to this basic model. This will be a way to draw up conclusions whether or not an attachment is a benefit to the aerodynamic performance of the helmet. There are two basic helmets which have been designed firstly a blank helmet which has not features such as a visor which will be used for the aero test as it is more simple and will make fluid flow smoother over the helmet which will give better results for analyzing modifications. The second model has a visor cut out so the interior of the helmet can be seen this is more for aesthetics and presentation purposes. To create the basic helmet a swept blend is used in Creo, this work by sketching a straight line up the center of the helmet, which is essentially like the spine of the helmet. Along this line points are derived where later on sketches can be drawn for each layer of the helmet. The swept blend works by drawing layers along a line and the software fills in the gaps in a solid form. Getting the number of points to sketch on is key as too many means too much detail and can result in a rough bumpy surface and two less an unrounded helmet. The interior of the helmet was done by creating a sphere within the helmet, which is then set to remove the material that is where the driver’s head would be. Once this was done the openings are extruded into the helmet and remove the material that was there. These models are then converted into .STL files that can be then inserted into Cham Phoenics.

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Figure 14 - Basic Helmet Design

The Kart The kart is simple design that will help to see how the helmet is affected by airflow over the kart and if any modifications can be made to better airflow hitting the helmet making it cleaner and smoother flowing or redirecting airflow efficiently to reduce drag. The key part of the kart which affects how airflow hits the driver’s head is the nassau panel, the design for the nassau panel on this kart is based on the M4 bodywork kit as seen in the research section on bodywork on karts. This was chosen because the karts which use them are usually seen at the front of most grids therefore are of high quality. With this in mind modifications will be made to hopefully boost overall aerodynamic performance.

Helmet Wing Attachment 1 (Solid) This is the first aerodynamic attachment designed to fit onto the basic helmet. It is designed similar to the wing designed by Arai and is seen on the Arai SK-5 looked at during research. The aerofoil shape flows off the curvature of the rear of the helmet to allow smooth airflow over the helmets rear wing.

18

Figure 15 - Solid Wing Helmet Design

Helmet Wing Attachment 2 (Slot Gap Wing) The second wing design for the helmet is a bit more radical the theory being that as air flows over the helmet it will maintain its path over the top of the wing. However when the driver ducks down it presents a large gap in the wing which is to allow airflow to pass through it like when a Formula one car has its DRS open. This helmet will therefore be tested at the ducked position to see if this theory is true.

19

Figure 16 - Slot Gap Wing Design

Aerodynamic Testing Details & Setup For each helmet design it is important to make sure that appropriate tests are done which are relevant to what is being achieved in this project as not to waste time with results that do not allow for conclusions to be drawn up from them. The first point to look at is what speeds the test should be done and how many different speeds can be done? It is important to have a range of speeds to look at so results can be analyzed over a range to see how the helmet is affected throughout the range in order to see if the helmet performs well throughout the range of speed. This is because it would be bad to design a helmet that only works at low speed but has terrible drag at high speed. Therefore the speeds that the helmets are being tested at are 30 MPH (13.41 M/S), 60 MPH (26.82 M/S), 90 MPH (40.23 M/S) and 120MPH (53.64 M/S). This range of speeds is to simulate a kart coming out of a slow bend and onto a long straight accelerating to 120 MPH before braking. These speeds would

20

allow a full range of speed tests to show how the helmet would fare at most areas of the kart circuit. Once a helmet design has been made which is efficient and an improvement over the standard design it will be time to move onto the next set of tests that involve using the kart model and a body simulate. This will be where the helmet is tested with a kart to help redesign the nassau panel to Improve performance. But also to test the theory of ‘ducking’ which is used by drivers to make the kart slick through the air by reducing drag. This will also help to see if aero parts used for the helmet when the driver is sat up impede the airflow and increase drag when the driver is ducked. The domain where the tests are taking place has to be big enough to allow the airflow to settle after passing over the helmet and before hitting it therefore the domain is 25M long and the helmet is positioned 3M from the inlet. Also another key factor is when a driver is sat in the kart there head is angled forward slightly and therefore the helmet is rotated 10 degrees forward in the domain to replicate this.

Testing of Helmets

Basic Testing and Setup of The Domain and .STL File It is important to make sure that all the designs and test domain are all working correctly before they are fully utilized for testing so that the results are correct when it comes to the real tests where the data is vital. It also allows testing the .STL files to make sure there are no holes or errors in them that could affect airflow and influence results. Also setting up the domain in this part of testing means that when testing begins it is a case of swapping the .STL for another and changing the airflow speed to save as a different case study, this will save time creating a new domain each time a test needs to be run and will allow for simultaneous tests to take place on different pc’s. A key part of setting up the domain for testing is to set a mesh and a number of iterations that will run. The mesh is a grid of squares or rectangles within which the iterations take place the tighter the mesh and the more iterations the more accurate the results will be at the end of it however this can result in extremely long tests and large file sizes. For this project a mid-sized mesh has been used and 1000 iterations will take place in each square of the mesh. It is also important to note that the mesh needs to setup on all axis to get high quality three-dimensional results. After all this is setup it means the tests take approximately three hours each to complete which is an acceptable balance between test length and accuracy.

Basic Test Setup Simulation for Domain: -‐

21

This test takes place at 60 MPH (26.82 M/S), which is a good mid-range speed to gain an idea of if the .STL works and how it reacts to the airflow. From what can be seen in the tests the helmet file works well and gets consistent results throughout the domain with no anomalies appearing at the inlet and outlet. We can also see a boundary layer appearing on the floor of the domain which can easily be eliminated by changing settings However from this test it is possible to see that the domain is too short and should be made longer for the actual test to see what happens further downwind of the helmet. From this basic test we can also see how the helmet will react in a wind tunnel and the basics of what to look for when testing properly, for example you can see high pressure build up at the front of the helmet where the air makes first contact with the helmet. There is then lower pressure over the top of the helmet where the air speeds up and finally the lower pressure and velocities behind the helmet representing the drag following the helmet.

22

Stand-‐Alone Helmet Tests (Up-‐Right)

Basic Helmet Up-‐Right

Velocity

Figure 17 - Basic Helmet Velocity Stand-Alone Contours & Streamlines (Un-Tucked)

23

Pressure

Figure 18 - Basic Helmet Pressure Stand-Alone Contours (Un-Tucked)

Helmet Wing Attachment 1 (Solid) Up-‐Right

Velocity

Figure 19 - Solid Wing Velocity Stand-Alone Contours & Streamlines (Un-Tucked)

24

Pressure

Figure 20 - Basic Helmet Pressure Stand-Alone Contours (Un-Tucked)

Helmet Wing Attachment 2 (Slot Gap) Up-‐Right

Velocity

Figure 21-Slot Gap Wing Velocity Stand-Alone Contours & Streamlines (Un-Tucked)

25

Figure 22-Airflow through the Slot Gap Design

Pressure

Figure 23-Slot Gap Wing Pressure Stand-Alone Contours (Un-Tucked)

26

Stand-‐Alone Helmet Tests (Ducked Down)

Basic Helmet Ducked

Velocity

Figure 24-Basic Helmet Velocity Stand-Alone Contours & Stramlines (Tucked)

Pressure

Figure 25-Basic Helmet Pressure Stand-Alone Contours (Tucked)

27

Helmet Wing Attachment 1 (Solid) Ducked

Velocity

Figure 26-Solid Wing Velocity Stand-Alone Contours & Streamlines (Tucked)

Pressure

Figure 27-Solid Wing Pressure Stand-Alone Contours (Tucked)

28

Helmet Wing Attachment 2 (Slot Gap) Ducked

Velocity

Figure 28-Slot Gap Wing Helmet Velocity Stand-Alone Contours & Streamlines (Tucked)

Pressure

Figure 29-Slot Gap Wing Pressure Stand-Alone Test Contours (Tucked)

29

Stand-‐Alone Helmet Testing Data

Once a set of testing is completed the data needs to be input into spreadsheet in order to keep an accurate log of data and tests as they happen. The spreadsheet contains all the relevant data from the testing to draw up conclusions from, using the F1 ground setting in Cham Phoenics it is possible for the solver to generate the lift and drag figures for whatever is in the domain these figures are logged at the top of the table. These figures will let us see any patterns which could appear and also quickly compare results between tests. The second part of the results tables is the generation of pressure coefficients and pressure gradients which are a key part of fluid flow analysis. In order to generate a pressure coefficient first of all we must take a pressure reading from eight points around the object being test or in this case the helmet. There must be four points around the top of the helmet and four below the helmet which will produce two lines on a graph. These two lines will be a similar shape for the different speeds being tested but the scale of the graph will change. Once these data points have been collected it is now possible to calculate the pressure coefficient using the formula below which has been input into excel.

𝑪𝒑 = (𝒑− 𝒑∞)

(𝟎.𝟓×𝑨𝒑×𝑽𝟐

This equation involves taking the pressure from the point chosen for

testing (𝑝) and then to minus the atmospheric pressure (𝑝∞) from it. This figure is then divided by half of the air density (𝐴𝑝) multiplied by the air velocity squared (𝑉!). Below is a table indicating the co-ordinates being used in the stand-alone helmet tests for both tucked and un-tucked tests.

Pressure Data

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH

Tucked 30 MPH Above Basic Wing 1 Wing 2

Above Basic Wing 1 Wing 2

1 38.50706 38.27239 38.61656

1 -‐14.7238 -‐30.4387 -‐15.5184 2 83.34644 85.34308 84.86957

2 3.162778 -‐3.52912 2.42671

3 -‐92.0731 -‐80.3871 -‐90.1739

3 74.60942 80.93491 71.22896 4 46.39919 36.80982 43.40814

4 -‐65.6141 -‐39.2597 -‐52.3132

Below

Below 1 -‐77.6605 -‐76.8455 -‐75.2095

1 -‐4.35698 -‐19.93 -‐3.55875

2 -‐30.3008 -‐29.491 -‐27.3879

2 -‐23.3058 -‐26.6041 -‐22.4084 3 -‐19.0319 -‐22.4782 -‐19.0916

3 5.315559 -‐22.4539 3.520688

4 1.296342 -‐1.2493 4.655514

4 24.85949 -‐30.7486 16.63789

30

Table 1-Stand Alone Pressure Data 30MPH

60 MPH (26.82 M/S)

Un-‐Tucked 60 MPH



1 153.0484 152.1386 153.5049

1 -‐58.7105 -‐119.605 -‐61.6527 2 332.4937 340.483 338.5831

2 12.07352 -‐14.1198 9.164884

3 -‐369.013 -‐322.473 -‐361.559

3 297.5693 322.8156 284.0602 4 187.3412 148.269 175.04

4 -‐263.578 -‐170.969 -‐210.295

Below

Below 1 -‐311.731 -‐308.117 -‐301.594

1 -‐17.8256 -‐76.116 -‐13.9932

2 -‐121.832 -‐118.51 -‐110.114

2 -‐94.7529 -‐100.032 -‐91.7509 3 -‐76.7602 -‐90.4606 -‐76.9184

3 19.54037 -‐93.4306 12.98968

4 4.68219 -‐5.2912 18.36967

4 99.6392 -‐113.553 66.50008 Table 2-Stand Alone Pressure Data 60MPH

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 342.4346 340.7026 343.3855

1 -‐125.772 -‐256.083 -‐256.526 2 747.4228 765.3553 761.1207

2 28.16249 -‐29.2623 -‐15.5074

3 -‐805.548 -‐709.699 -‐793.861

3 668.9672 722.2505 437.3465 4 423.1888 333.9174 396.4886

4 -‐591.963 -‐358.516 -‐331.331

Below

Below 1 -‐648.585 -‐643.15 -‐630.52

1 -‐41.0016 -‐184.713 -‐45.0415

2 -‐273.819 -‐268.479 -‐252.404

2 -‐217.67 -‐260.59 -‐181.251 3 -‐174.218 -‐204.428 -‐179.533

3 42.38074 -‐215.652 126.0436

4 12.50772 -‐9.87393 34.47751


120 MPH (53.64 M/S)

Un-‐Tucked 120 MPH



1 608.9625 605.4438 610.1524

1 -‐234.428 -‐488.227 -‐246.729 2 1326.995 1358.95 1351.484

2 46.35767 -‐60.0976 34.61302

3 -‐1478.43 -‐1293.31 -‐1447.24

3 1187.271 1289.57 1113.408 4 754.8411 595.2561 706.1248

4 -‐1057.62 -‐554.569 -‐844.131

Below

Below 1 -‐1250.46 -‐1234.79 -‐1211.89

1 19.4747 -‐305.576 -‐56.6667

2 -‐489.491 -‐475.863 -‐447.751

2 -‐384.929 -‐381.79 -‐372.595 3 -‐309.258 -‐363.714 -‐320.201

3 74.42581 -‐376.573 49.22929

4 16.98736 -‐22.3056 59.23936


32

Velocity Data

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH



1 10.65784 10.68333 10.64882

1 14.37496 15.26229 14.40007 2 6.511498 6.30042 6.35082

2 13.32793 13.73436 13.35788

3 16.5177 15.83618 16.31069

3 7.381697 6.696409 7.741613 4 5.718078 6.281748 6.033728

4 16.12279 3.16014 13.50325

Below

Below 1 15.87233 15.69554 15.62699

1 13.15241 14.46955 13.01641

2 13.19105 13.75555 13.62073

2 5.357169 3.389833 5.232509 3 12.27168 12.57026 12.31227

3 6.361933 2.650479 5.889726

4 10.01643 10.47406 9.769445

4 8.965046 3.030023 7.373234 Table 5-Stand Alone Velocity Data 30MPH

60 MPH (26.82 M/S)

Un-‐Tucked 60 MPH



1 21.3168 21.36691 21.29803

1 28.72079 30.56911 28.76432 2 13.01891 12.59692 12.6917

2 26.64595 27.48019 26.70504

3 33.23912 31.83643 32.7845

3 14.76123 13.40301 15.48077 4 11.5436 26.31851 12.18232

4 32.30057 7.002954 27.0366

Below

Below 1 31.75054 31.38742 31.25059

1 26.12288 29.14818 25.03214

2 27.62617 27.49485 27.22549

2 10.80899 7.467982 10.59082 3 24.55389 25.12943 24.61286

3 12.86649 4.681636 11.8856

4 20.06379 20.94005 19.35834


33

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 32.00143 32.06746 31.97248

1 42.97532 45.59001 43.80615 2 19.51226 18.88021 19.02362

2 39.92176 41.13400 39.78674

3 49.5436 47.70992 49.07182

3 22.12775 20.21969 29.51206 4 17.40476 19.09372 18.35649

4 48.14184 11.23362 42.02004

Below

Below 1 48.35123 47.9194 47.7302

1 39.42859 43.83892 39.05521

2 42.73358 42.41833 42.08634

2 16.34777 10.67115 39.05521 3 37.7808 38.2743 37.64856

3 19.37497 7.633508 17.90121

4 30.10057 31.06264 29.40344


120 MPH (53.64 M/S)




1 42.63465 42.73291 42.60816

1 57.3937 61.33796 57.49034 2 26.03166 25.18841 25.37932

2 53.27446 55.01957 53.39505

3 66.80247 63.94006 65.80816

3 29.52012 26.81052 30.95773 4 54.07288 25.53974 24.5521

4 64.68585 12.07675 54.11362

Below

Below 1 63.50937 62.76708 62.52686

1 52.24837 58.44018 51.0842

2 55.24752 54.96289 54.5193

2 25.91294 9.128918 23.92022 3 49.12614 50.24149 49.43356

3 21.75701 15.00982 21.34789

4 40.18167 41.8702 39.72


34

Pressure Coeffients/Gradients

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH



1 -‐0.568 -‐0.570 -‐0.567

1 -‐1.049 -‐1.191 -‐1.056 2 -‐0.163 -‐0.144 -‐0.149

2 -‐0.887 -‐0.948 -‐0.894

3 -‐1.748 -‐1.643 -‐1.731

3 -‐0.242 -‐0.184 -‐0.272 4 -‐0.497 -‐0.583 -‐0.524

4 -‐1.509 -‐1.271 -‐1.389

Below

Below 1 -‐0.033 -‐0.033 -‐0.033

1 -‐0.955 -‐1.096 -‐0.948

2 -‐0.024 -‐0.024 -‐0.024

2 -‐1.127 -‐1.157 -‐1.119 3 -‐0.022 -‐0.023 -‐0.022

3 -‐0.868 -‐1.119 -‐0.884

4 -‐0.019 -‐0.019 -‐0.018

4 -‐0.691 -‐1.194 -‐0.766 Table 9-Stand Alone Pressure Coefficient Data 30MPH

60 MPH (26.82 M/S)

Un-‐Tucked 60 MPH



1 0.117 0.115 0.118

1 -‐0.361 -‐0.499 -‐0.368 2 0.522 0.540 0.536

2 -‐0.202 -‐0.261 -‐0.208

3 -‐1.062 -‐0.957 -‐1.045

3 0.443 0.500 0.413 4 0.194 0.106 0.166

4 -‐0.824 -‐0.615 -‐0.704

Below

Below 1 -‐0.933 -‐0.925 -‐0.910

1 -‐0.269 -‐0.401 -‐0.260

2 -‐0.504 -‐0.496 -‐0.477

2 -‐0.443 -‐0.455 -‐0.436 3 -‐0.402 -‐0.433 -‐0.403

3 -‐0.185 -‐0.440 -‐0.199

4 -‐0.218 -‐0.241 -‐0.185

4 -‐0.004 -‐0.485 -‐0.079 Table 10-Stand Alone Pressure Coefficient Data 60MPH

35

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 0.242 0.240 0.243

1 -‐0.228 -‐0.359 -‐0.359 2 0.649 0.667 0.663

2 -‐0.073 -‐0.131 -‐0.117

3 -‐0.911 -‐0.815 -‐0.899

3 0.570 0.624 0.338 4 0.323 0.234 0.296

4 -‐0.696 -‐0.462 -‐0.435

Below

Below 1 -‐0.753 -‐0.748 -‐0.735

1 -‐0.143 -‐0.287 -‐0.147

2 -‐0.377 -‐0.371 -‐0.355

2 -‐0.320 -‐0.364 -‐0.284 3 -‐0.277 -‐0.307 -‐0.282

3 -‐0.059 -‐0.318 0.025

4 -‐0.089 -‐0.112 -‐0.067

4 0.123 -‐0.384 -‐0.007 Table 11-Stand Alone Pressure Coefficient Data 90MPH

120 MPH (53.64 M/S)




1 0.287 0.285 0.288

1 -‐0.190 -‐0.333 -‐0.197 2 0.693 0.711 0.706

2 -‐0.031 -‐0.091 -‐0.038

3 -‐0.893 -‐0.788 -‐0.875

3 0.614 0.671 0.572 4 0.369 0.279 0.342

4 -‐0.655 -‐0.371 -‐0.534

Below

Below 1 -‐0.764 -‐0.755 -‐0.742

1 -‐0.046 -‐0.230 -‐0.089

2 -‐0.334 -‐0.326 -‐0.310

2 -‐0.275 -‐0.273 -‐0.268 3 -‐0.232 -‐0.263 -‐0.238

3 -‐0.015 -‐0.270 -‐0.029

4 -‐0.048 -‐0.070 -‐0.024

4 0.169 -‐0.320 0.093 Table 12-Stand Alone Pressure Coefficient Data 120MPH

Pressure Gradients Basic Helmet (Un-‐Tucked)

Figure 30-Pressure Gradient Basic Helmet Un-Tucked

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

30 MPH (Above)

30 MPH (Below)

60 MPH (Above)

60 MPH (Below)

90 MPH (Above)

90 MPH (Below)

120 MPH (Above)

120 MPH (Above)

36

Pressure Gradients Basic Helmet (Tucked)

Figure 31-Pressure Gradient Basic Helmet Tucked

Pressure Gradients Wing 1 (Un-‐Tucked)

Figure 32-Pressure Gradient Solid Wing Un-Tucked

Pressure Gradients Wing 1 (Tucked)

Figure 33-Pressure Gradient Solid Wing Tucked

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 1 2 3 4 5

30 MPH (Above)

30 MPH (Below)

60 MPH (Above)

60 MPH (Below)

90 MPH (Above)

90 MPH (Below)

120 MPH (Above)

120 MPH (Below)

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 1 2 3 4 5

30 MPH (Above)

30 MPH (Below)

60 MPH (Above)

60 MPH (Below)

90 MPH (Above)

90 MPH (Below)

120 MPH (Above)

120 MPH (Below)

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 1 2 3 4 5

30 MPH (Above)

30 MPH (Above)

60 MPH (Above)

60 MPH (Below)

90 MPH (Above)

90 MPH (Below)

120 MPH (Above)

120 MPH (Below)

37

Pressure Gradients Wing 2 (Un-‐Tucked)

Figure 34-Pressure Gradient Slot Gap Wing Un-Tucked

Pressure Gradients Wing 2 (Tucked)

Figure 35-Pressure Gradient Slot Gap Wing Tucked

Stand-‐Alone Helmet Testing Discussion

Un-‐Tucked The first noticeable thing we can see from these test is the areas of low pressure created on the front of the helmet around the visor area, these pressures increase furthermore as the air speed velocity is increased. The pressures collected from points one to three above the helmet are similar because there have been no design alterations to the front of the helmet it is not until we reach point four from above and the below points of helmet we begin to see variants. On the basic helmet we can see a small bubble of low pressure on top of the helmet this is where the air speeds up and feeds to the back of the helmet. The two other designs aim to utilize this faster moving air to keep the flow attached and reduce drag behind the helmet. The best way to see this drag

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 1 2 3 4 5

30 MPH (Above)

30 MPH (Below)

60 MPH (Above)

60 MPH Below

90 MPH (Above)

90 MPH (Below)

120 MPH (Above)

120 MPH (Below)

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 1 2 3 4 5

30 MPH (Above)

30 MPH (Below)

60 MPH (Above)

60 MPH (Below)

90 MPH (Above)

120 MPH (Above)

120 MPH (Below)

38

bubble at the back of the helmet is to look at the velocity diagram; the drag shows up as blue which is vacuum created by the low speed creating turbulence. Out of the three tests the worst drag is seen on Wing 1, this is because the other the basic helmet and the slot gap helmet have one main bubble of low pressure at the rear whereas Wing 1 has the main bubble like the other two but also a secondary part of drag located under the lip of the rear wing. However the air flowing off of the top of the wing is faster than the other two designs at the same point (above 4) which is then matched with a lower pressure reading to further confirm the presence of faster air flowing off the top of the wing. The basic helmet has less drag trailing the helmet over a longer distance meaning air settles faster behind the helmet and the air is less turbulent trailing the helmet this turbulence decreases at higher speeds as seen in the logbook on page 57. On Wing 1 and the slot gap wing the trailing air stays unsettled for longer and the turbulent air is wider; this shows that attachments can induce more turbulent airflow behind the helmet than a helmet with attachments.

Looking at the tables which display the lift, drag and side values the key figures are the lift and drag ones. From these tables it is possible to see that Wing 1 produces negative lift which is downforce this is a positive thing followed by the slot gap wing which produced more downforce from the basic helmet; this means that the two attachments have improved downforce. The drag results are different to this however and show that the slot gap produces the least drag and Wing1 produces more drag than the basic helmet.

Tucked For the helmet tucked, the helmet file is tilted forward 85 degrees to simulate the diver tucking there head down to gain speed. This is where the performance modifications of the helmet can have benefits or be worse than the helmet in the upright position. We can see similar to the un-tucked test there is a bubble of high pressure where the air flow first impacts the helmet, in this case though the forward area of the top of the head. In the tucked position we can see by the velocity diagrams that Wing 1 produces large amounts of drag as the wing acts as an air brake when the helmet is dipped forward. On the basic helmet there is an area of low pressure flowing off the back of the helmet which means increased air speed velocity off the back of the helmet. The concept for the slot gap helmet is to provide downforce when the helmet is up right and then when the helmet is tucked down allows the air to flow through the slot gap and reduce drag. From the table of lift and drag we can see that the slot gap produces the least drag out of all three helmets and the second most downforce; Wing 1 produces the most downforce. However Wing 1’s downforce is due to the large amount of drag which is created. The effects of the wings can be seen on the table

39

below at point 4 above the helmet just behind where the attachments go at 90 MPH (40.23 M/S).


4 48.14184 11.23362 42.02004 Table 13-Comparison between Helmets Tucked at 90MPH

The table shows that the air speed behind Wing 1 is 28.9 M/S less than the air hitting the front of the helmet indicating turbulent air and drag behind the wing when tucked. However the other two designs speed up the initial airflow which is an indication of less drag and the helmet cutting through the air smoothly; the basic helmet speeds the air up 6.2 M/S faster than the slot gap wing. The next stage of testing is to see if the body of the driver and the kart affects the helmets performance diffently to the stand-alone testing and to see if the combination of a drive, kart and helmet influences the airflow to simulate a real world scenario.

Kart Testing

Kart Test (Empty Kart) This is a simple test to see how the airflow affects the kart and how the air is directed up the Nassau panel and where it goes from there and the aero performance of the kart empty can be looked at. The kart will be tested at 30 MPH and 90 MPH to test it a low speed and at high speed.

Figure 36-Data Collection Points Empty Kart

Kart Testing Data (Empty Kart)

Kart Alone Kart Lift Drag Side

40

30 -‐9.618587 41.33762 0.2904717 90 -‐88.41568 373.4778 1.642106

Table 14-Empty Kart Drag & Lift Data

Pressure Data

Figure 37-Empty Kart Pressure Contours

Figure 38-Empty Kart Surface Pressure Contours

Kart Alone

Pressure Readings 30 90 1 38.78788 348.2028 2 -‐6.567357 -‐63.16888 3 -‐16.53627 -‐153.0811 4 -‐8.155544 -‐72.66078 1 -‐33.31752 -‐332.006 2 -‐2.267359 -‐15.6761 3 -‐2.803776 -‐24.21543 4 -‐6.041564 -‐53.64288

Table 15-Empty Kart Pressure Data

41

Velocity Data

Figure 39-Empty Kart Velocity Contours & Vectors

Figure 40-Empty Kart Velocity Surface Vectors

42

Figure 41-Empty Kart Velocity Vectors

Kart Alone

Velocity Readings 30 90 1 10.65682 31.85718 2 14.3712 43.12883 3 10.46941 30.92887 4 7.623174 23.6691 1 15.36624 46.85453 2 12.52951 37.54054 3 11.94772 37.97117 4 9.320667 28.98281

Table 16-Empty Kart Velocity Data

43

Empty Kart Pressure Coefficients & Gradient Graph

Pressure Coefficient Over The Top 30 90

1 -‐0.565379993 0.557530283 2 -‐0.975423557 -‐0.371480625 3 -‐1.065549613 -‐0.57453163 4 -‐0.989781896 -‐0.392916419

Underneath 30 90 1 -‐0.016635942 -‐0.978602187 2 -‐0.012799496 -‐0.264226497 3 -‐0.012865774 -‐0.283511079 4 -‐0.013265824 -‐0.349967822

Table 17-Empty Kart Pressure Coefficient Data

Figure 42-Empty Kart Pressure Gradients

Empty Kart Testing Discussion The first thing to look at is the data collected from the results file which display the drag and lift of the kart, the most noticeable figure is the negative lift which indicates that downforce is produced over the whole body of the kart. The drag figure will be more useful when comparing data to when there is a body in the kart as it will show the difference having a body in the kart affects the overall aerodynamic performance of the kart. From the pressure diagram it is possible to see that that there is high pressure at the front of the kart as it hits the front bumper and hits the joint between the Nassau panel and the bumper, however below the bumper there is low pressure indicating a high velocity, the data below shows the velocity figures which go from ‘one’ which is at the rear of the kart to ‘four’ which is underneath the front bumper.

-‐1.2 -‐1

-‐0.8 -‐0.6 -‐0.4 -‐0.2 0

0.2 0.4 0.6 0.8

0 1 2 3 4 5

Kart 30MPH Above

Kart 30MPH Below

Kart 90MPH Above

Kart 90MPH Below

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Kart Alone

Velocity Readings 30 90 1 9.320667 28.98281 2 11.94772 37.97117 3 12.52951 37.54054 4 15.36624 46.85453

Table 18-Air Speeding Up From the Front to the Back of the Kart Underneath It

As we can see that the air slows down as it goes from the back to the front of the kart, this is due to a turbulent boundary created between the kart and the road which causes the air to swirl around and slow down. We can also see that the airflow under the bumper is faster than the airflow entering the domain meaning air is accelerated as it passes under the front of the kart. Another characteristic which is seen is the areas of low velocity air in the cockpit area underneath he Nassau panel which is because the air obviously hits the front of the nassau panel and doesn’t go though it creating low velocity behind it and low pressure which is also seen behind the seat. The other major area of low velocity is the drag created by the kart; it is possible to see the drag as it leaves the top of the kart in a large arc flowing off of the back of the kart downstream. From the pressure distribution graphs we can see that over the top of the kart there is unfavorable pressure distribution as the air passes over the top of the Nassau panel and over the seat, this is because there is no longer a surface for the air to cling onto and speed up along. However the last reading for the op is placed where the air has just come out from underneath the kart and means the pressure distribution curve goes up at the bottom showing a sign of favorable distribution due to the faster air coming from underneath the kart meeting the slow air behind the seat.

Kart Testing With Helmets Tucked & Un-‐Tucked This testing stage is key; as it brings all the previous tests together and will begin to provide conclusions to how well the helmets will perform in a real situation on track. For these test the kart model will be used that was developed for the previous kart test. A body is then created in the seat to simulate a human torso which the helmet will be place on in the un-tucked and tucked positions in each design. This will create more accurate results to be drawn up than the stand-alone testing as the airflow hitting the helmet will be more turbulent as it would of hit the kart first and the then the helmet rather than clean air hitting a floating helmet. Also when the kart is ducked the air

45

won’t just flow off of the back of the helmet it will have to travel over the drivers upper back and neck are when he or she is tucked down.

Basic Helmet

Figure 43-Data Collection Points For the Basic Helmet

Pressure Un-‐Tucked

Figure 44-Basic Helmet Kart Pressure Contours (Un-Tucked)

46

Velocity Un-‐Tucked

Figure 45-Basic Helmet Kart Velocity Contours & Vectors (Un-Tucked)

Pressure Tucked

Figure 46-Basic Helmet Kart Pressure Contours (Tucked)

47

Velocity Tucked

Figure 47-Basic Helmet Kart Velocity Contours & Vectors (Tucked)

48

Wing 1

Figure 48-Solid Wing Kart Data Collection Points


Figure 49-Solid Wing Kart Pressure Contours (Un-Tucked)

49


Figure 50-Solid Wing Kart Velocity Contours & Vectors (Un-Tucked)

Pressure Tucked

Figure 51-Solid Wing Kart Pressure Contours (Tucked)

50

Velocity Tucked

Figure 52-Solid Wing Kart Velocity Contours & Vectors (Tucked)

Wing 2

51

Figure 53-Slot Gap Kart Data Collection Points


Figure 54-Slot Gap Wing Kart Pressure Contours (Un-Tucked)


52

Figure 55-Slot Gap Wing Velocity Contours & Vectors (Un-Tucked)

Pressure Tucked

Figure 56-Slot Gap Wing Kart Pressure Contours (Tucked)

Velocity Tucked

Figure 57-Figure 55-Slot Gap Wing Velocity Contours & Vectors (Tucked)

53

Kart Testing With Helmets Tucked & Un-‐Tucked Data

Pressure Data

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH



1 44.94845 45.415 43.9408

1 52.53806 52.92212 52.66164 2 11.54064 11.641 12.13852

2 2.476758 4.487577 3.410377

3 -‐131.795 -‐131.229 -‐138.876

3 -‐79.9988 -‐78.7836 -‐62.9126 4 -‐14.9434 -‐14.099 -‐8.58606

4 -‐82.0071 -‐75.3156 -‐58.2785

Below

Below 1 -‐16.9198 -‐17.4545 -‐16.9083

1 -‐16.1665 -‐15.8865 -‐16.2018

2 12.35464 12.07357 12.66775

2 10.09426 10.01808 9.945779 3 -‐26.6735 -‐27.0645 -‐25.7582

3 -‐26.3342 -‐26.6994 -‐23.1379

4 -‐13.3763 -‐16.854 -‐13.484

4 -‐9.39013 -‐9.48138 -‐6.16806 Table 19-Kart Testing Pressure Data 30MPH

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 404.9234 411.8706 415.3558

1 470.0943 473.7788 479.7788 2 107.5462 111.6924 114.9298

2 -‐29.826 16.38859 16.38859

3 -‐1185.19 -‐1176.09 -‐1252.64

3 -‐738.192 -‐756.946 -‐756.946 4 -‐126.749 -‐99.4304 -‐88.7229

4 -‐768.429 -‐753.176 -‐752.176

Below

Below 1 -‐151.983 -‐155.604 -‐151.713

1 -‐144.705 -‐137.453 -‐111.534

2 117.2364 113.9666 116.2588

2 58.41482 86.25976 -‐171.353 3 -‐241.271 -‐256.975 -‐241.746

3 -‐193.955 -‐171.353 -‐171.353

4 -‐258.244 -‐135.275 -‐113.149

4 -‐40.2772 -‐11.5336 -‐137.453 Table 20-Kart Testing Pressure Data 90MPH

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Velocity Data

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH



1 10.57113 10.53375 10.5338

1 9.713701 9.705 9.711 2 13.27556 13.26201 13.26162

2 12.5832 12.385 12.406

3 19.05367 18.84422 19.19345

3 17.5921 4.105 17.069 4 10.43936 7.456525 9.462009

4 16.49189 5.045 15.627

Below

Below 1 14.299 14.33461 14.333

1 14.63283 14.63284 14.640

2 11.623 11.66839 11.66391

2 12.38075 12.42614 12.399 3 14.060 14.09422 14.03901

3 10.68307 11.12195 10.879

4 2.491 2.58941 2.336923

4 7.586056 5.724106 3.470 Table 21-Kart Testing Velocity Data 30MPH

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 31.71289 31.60294 31.6024

1 29.12945 29.12371 29.124 2 39.76075 39.70518 39.71259

2 39.03011 37.88669 37.887

3 57.37412 56.73925 57.8712

3 53.18908 12.68798 12.688 4 31.54142 23.53764 29.03965

4 50.47623 16.74256 16.743

Below

Below 1 43.34888 43.47429 43.47231

1 44.14779 44.1972 44.197

2 35.87291 35.94753 35.98981

2 38.06961 40.04897 40.049 3 42.39253 43.04589 43.42492

3 38.58538 34.75166 34.752

4 13.26552 8.553784 10.29025

4 13.42572 13.81367 13.814 Table 22-Kart Testing Velocity Data 90MPH

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Pressure Coefficients/Gradients

30 MPH (13.41 M/S)

Un-‐Tucked 30 MPH



1 -‐0.510 -‐0.505 -‐0.519

1 -‐0.441 -‐0.438 -‐0.440 2 -‐0.812 -‐0.811 -‐0.806

2 -‐0.894 -‐0.875 -‐0.885

3 -‐2.108 -‐2.102 -‐2.172

3 -‐1.639 -‐1.628 -‐1.485 4 -‐1.051 -‐1.044 -‐0.994

4 -‐1.657 -‐1.597 -‐1.443

Below

Below 1 -‐0.015 -‐0.015 -‐0.014

1 -‐1.062 -‐1.060 -‐1.063

2 -‐0.011 -‐0.011 -‐0.016

2 -‐0.825 -‐0.825 -‐0.826 3 -‐0.016 -‐0.016 -‐0.011

3 -‐1.154 -‐1.157 -‐1.125

4 -‐0.014 -‐0.015 -‐0.015

4 -‐1.001 -‐1.002 -‐0.972 Table 23-Kart Testing Pressure Coefficient Data 30MPH

90 MPH (40.23 M/S)

Un-‐Tucked 90 MPH



1 0.686 0.701 0.709

1 0.833 0.841 0.855 2 0.014 0.023 0.031

2 -‐0.296 -‐0.192 -‐0.192

3 -‐2.905 -‐2.885 -‐3.058

3 -‐1.896 -‐1.938 -‐1.938 4 -‐0.515 -‐0.453 -‐0.429

4 -‐1.964 -‐1.930 -‐1.927

Below

Below 1 -‐0.572 -‐0.580 -‐1.063

1 -‐0.556 -‐0.539 -‐0.539

2 0.036 0.029 -‐0.826

2 -‐0.097 -‐0.034 -‐0.034 3 -‐0.774 -‐0.809 -‐1.125

3 -‐0.667 -‐0.616 -‐0.616

4 -‐0.812 -‐0.534 -‐0.972

4 -‐0.320 -‐0.255 -‐0.481 Table 24-Kart Testing Pressure Coefficient Data 90MPH

Un-‐Tucked 30 MPH (13.41 M/S)

-‐2.500

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000 -‐0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Basic Above

Basic Below

Wing 1 Above

Wing 1 Below

Wing 2 Above

Wing 2 Below

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Figure 58-Kart Testing Pressure Gradient 30MPH (Un-Tucked)

Tucked 30 MPH (40.23 M/S)

Figure 59-Kart Testing Pressure Gradient 30MPH (Tucked)

Un-‐Tucked 90 MPH (13.41 M/S)

Figure 60-Kart Testing Pressure Gradient 90MPH (Un-Tucked)

Tucked 90 MPH (40.23 M/S)

Figure 61-Kart Testing Pressure Gradient 90MPH (Tucked)

-‐1.800

-‐1.600

-‐1.400

-‐1.200

-‐1.000

-‐0.800

-‐0.600

-‐0.400

-‐0.200

0.000 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Basic Above

Basic Below

Wing 1 Above

Wing 1 Below

Wing 2 Above

Wing 2 Below

-‐3.500

-‐3.000

-‐2.500

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Basic Above

Basic Below

Wing 1 Above

Wing 1 Below

Wing 2 Above

Wing 2 Below

-‐2.500

-‐2.000

-‐1.500

-‐1.000

-‐0.500

0.000

0.500

1.000

1.500

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Basic Above

Basic Below

Wing 1 ABove

Wing 1 Below

Wing 2 Above

Wing 2 Below

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Helmet in Kart Testing Discussion

Un-‐Tucked First of all we can see a few similar characteristics of the airflow around the helmet as seen in the stand-alone testing which is the area of high pressure on the front of the helmet and the low pressure over the top of the helmet which indicates accelerated air over the top of the helmet. We can see aswell that there is high pressure build up on the drivers chest and torso which is as the air hits it. Unlike the empty kart test there is not an arc of drag leaving the kart instead it is less uniform but the height of drag is reduced as the air stays attached over the top of the helmet and then separates as it leaves the back of the helmet rather than carry on the trajectory angle of the Nassau panel. When looking at the two wing designs wing 1 has an area behind it where there is incredibly low speed, this is where the drag is behind the wing. Whereas wing 2 has the slot gap enabling some air to pass through the slot gap to eliminate this area of low speed to an extent and attempt reduce drag. Which can be compared in the tables below: -

Helmet Un-‐Tucked Basic Lift Drag

30 9.486603 48.35467 90 86.01637 436.2997

Helmet Un-‐Tucked

Wing 1 Lift Drag

30 6.486714 49.09951 90 40.53199 439.7275

Helmet Un-‐Tucked

Wing 2 Lift Drag

30 7.380229 48.90914

90 65.82913 442.7034 Table 25-Comparison between Un-Tucked Kart Test Data

These tables show that Wing 1 has the least lift which means it has the most downforce of all the designs however also produced the most drag at low speeds. Wing 2 produces more downforce than the basic helmet but less than Wing 1 Also at high speeds the design creates the most drag this may be due to the turbulent air struggling to pass through the slot gap and stay

58

attached. These results therefore suggest that Wing 1 would be more beneficial for downforce and the basic helmet for less drag this is because the spherical shape of the helmet with not attachments does not have devices on it to reduce the amount of time the airflow remains attached to the helmet. When looking at the pressure gradients for the un-tucked test at 30 MPH Wing 2 above shows a more unfavorable pressure distribution than the other two designs. If the above line was inverted and showed favorable distribution it should mar out the shape around the top side of the kart and the below lines would show the below shape of the kart. Then at 90 MPH the Wing 2 above line dips further down than at 30 MPH test. However at the higher speed the below line becomes much more wavy due to the turbulent boundary layer below the kart becoming more turbulent as the speed increases. It is possible to see that the air pressure distribution is favorable for the first part under the kart and then towards the back becomes unfavorable and finally favorable as it comes out from underneath the car into the drag path. Wing 2 has lower pressure coefficients than the other two below the kart. Also Wing 1 has a more favorable pressure distribution on point 4 running underneath the car, this would suggest that the air pressures created by the helmet are more favorable for the air coming from underneath the kart meeting the air coming off of the back of the helmet.

Tucked When the drivers head is tucked we are able to see that the drivers head goes close to the steering wheel and the driver attempt to match the curvature of the helmets lobe to the Nassau panel in a tangent. There is low pressure an d high velocity passing over rear lobe area of the helmet but this area is larger due to there being a much smaller area of high pressure at the front of the helmet. The tables below show the lift and drag figures for the three designs to compare against each other and against their un-tucked results: -

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Helmet Tucked Basic Lift Drag

30 6.911769 48.85403 90 61.68914 439.9783

Helmet Tucked

Wing 1 Lift Drag

30 5.964473 51.5906 90 53.63248 465.8448

Helmet Tucked Wing 2 Lift Drag

30 6.426059 49.53237

90 59.7743 448.5274 Table 26-Comparison between Tucked Kart Test Data

Looking at Wing 1 there is more downforce produced at low speeds than the other two designs and more downforce than that of the previous test under the same conditions. But then as the car approaches high speeds the upright solid wing essentially acts as a helmet air brake creating more drag than any previous tests from all designs, rendering the use of a solid wing ineffective at ducking at high speed areas of the track. Then looking at the other two designs we can see that both produce more downforce than the un-tucked position, however Wing 2 and the basic design both create slightly more drag behind the kart. Therefor Wing 2 and the basic design are better than Wing 1 when tucked as they produces a large amount less drag than Wing 1 at high speed due to wing 1 acting as an airbrake. The pressure distribution graphs show that Wing 2 has a more favorable pressure distribution at low speed as the gradient is less and the curve picks up quicker than the other two, which means the pressures coming off of the back of the helmet are more favorable. However when looking at 90 MPH the distribution lines are all on top of each other meaning the distributions are very similar however Wing 2 still maintains the most favorable pressure distribution. Below the kart the pressure gradients are the same as the un-tucked tests because the helmet has no influence on the pressure distribution underneath the kart but except for maybe the last point

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as it is where the airflow from the helmet meets the airflow from underneath the kart.

Nassau Panel Testing To see if modification s to parts around the cockpit work the Nassau panel has been designed in three different shapes to see if they can be modified to work with the helmet to increase streamlining when tucked down low. The first is the one used in all the previous testing which is based on the M4 design (_). The second design is a lipped Nassau panel designed to direct air over the helmet when the driver is tucked down low. Finally there is a design which is more like a big foot Nassau panel (_) which covers the front end of the kart up.

M4 Based Design For images please refer back to Fig……. as this is the M4 design and uses the same testing process used for the other Nassau panel tests.

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Lipped Nassau Panel (Un-‐Tucked)

Velocity

Figure 62-Lipped Nassau Panel Velocity Contours & Vectors (Un-Tucked)

62

Figure 63-Lipped Nassau Panel Velocity Streamlines (Un-Tucked)

Pressure

Figure 64-Lipped Nassau Panel Pressure Contours (Un-Tucked)

63

Lipped Nassau Panel (Tucked)

Velocity

Figure 65-Lipped Nassau Panel Velocity Contours & Vectors (Tucked)

64

Figure 66-Lipped Nassau Panel Velocity Streamlines (Tucked)

Pressure

Figure 67-Lipped Nassau Panel Pressure Contours (Tucked)

65

Large Lipped Plate Nassau Panel (Un-‐Tucked)

Pressure

Figure 68-Plate Nassau Panel Pressure Contours (Un-Tucked)

Velocity

Figure 69-Plate Nassau Panel Velocity Contours & Vectors (Un-Tucked)

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Figure 70-Plate Nassau Panel Velocity Streamlines (Un-Tucked)

Large Lipped Plate Nassau Panel (Tucked)

Pressure

Figure 71-Plate Nassau Panel Pressure Contours (Tucked)

67

Velocity

Figure 72-Plate Nassau Panel Velocity Contours & Vectors (Tucked)

Figure 73-Plate Nassau Panel Velocity Streamlines 1 (Tucked)

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Figure 74-Plate Nassau Panel Velocity Streamlines 2 (Tucked)

Nassau Panel Variations Discussion When looking at the karts when they are in the un-tucked position it is possible to see some differences between the results. Firstly we can see that the plate design creates a larger area of high pressure at the front of the kart this is due to the airflow hitting a larger body. There is also higher pressure created on the lipped Nassau panel where the airflow reaches the point of incline to try and force air upwards. There is also a noticeable difference in the drag patterns behind the karts; it appears that the plate design has reduced the drag behind the driver’s helmet, as there is much less blue or green behind his head, However there is a higher concentration of drag created by the plate design at the front of the kart which appears to significantly greater than before. The other two designs produce similar amounts of drag in a similar pattern. The results from the helmets ducking show that the lipped design and the standard M4 design have similar outcomes however there is a difference in the drag produced. From Fig…… and Fig…… we can see that the lipped Nassau panel eliminates a bubble of low speed air which trails the kart and that the airflow is speeding up as it leaves the top of the Nassau panel. The plate design has some interesting results aswell, it is possible to see in Fig……. that there is a areas of fast air above the drivers head, this is possibly a sign of the plate speeding air up and sending into the air over the drivers head. Fig…… shows the airflow passing over the top of the drivers head and not dropping down under the front of the helmet compared to Fig…. which shows that the air drops down into the drivers lap with the lipped design, However creates a lot of drag which is also see in the untucked position, there may be the option to design a plate that wraps around the front of the kart a bit more like the big foot design used already but with a lip at the top of it to send air over the helmet.

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Conclusion

Testing Conclusions This report has compared several helmet designs used in karting and how they performed aerodynamically in two positions ducked down and sat up to demonstrate what kart drivers do on high speed straights. The helmets were tested on their own and in a kart to see the affects the front of the kart has on the airflow hitting the helmet and how they react on their own. What is firstly noticeable is that there is a large area of high pressure and low velocity at the point the airflow first hits the helmet. There is also higher pressure and low velocity at the rear of the helmet which is the drag, the smaller this is the less drag there is. The three designs aimed to demonstrate the three main design manufacturers use the first is a basic helmet which has no aero attachments or features. The second helmet has a solid wing which aims to induce downforce, and finally a slotted wing which is a relatively new concept in helmet design. When the helmets are sat up there are a few noticeable differences in pressures and velocity patterns, First of all there are areas of higher pressure located behind the basic helmet and the slot gap. Whereas behind the solid wing there is slightly lower pressure than those two as there is no are of dark red just dark orange(). However when we start looking at the velocity overlays there is an area of low speed air behind the wing which is a sign of drag at the behind the aero wing. On the basic helmet and the slot gap wing they have relatively similar areas of drag (), the reason the slot gap helmet is like this is because the slot in the wing allows air to flow through it. When looking at the helmets ducked down there are several differences in the airflow; as the air is flowing over the helmet and then onto the drivers upper back. First of all the solid wing has a large amount of drag behind it, this is due to the solid wing acting as an airbrake similar to that found on the wings of planes to slow them down on the runway. The slot gap

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wing aims to eliminate this by allowing the air to flow through when ducked, in a similar way a DRS flap opens on a Formula One to let more air flow through to speed the car up by reducing drag.

The image above shows the drag behind the three helmets and it’s

easy to see that there is a large amount of drag behind the solid wing. Also there is an area of high velocity as the air passes through the slotted gap of the wing which is not as big as the air passing over the smooth surface of the basic helmet. By looking at the data collected it is possible to see the velocity of the air just behind the aero feature which is point three above the helmet below is a table displaying the data from point three in the stand-alone tests at a full range of speeds.

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Un-‐Tucked (MPH)

Tucked (MPH) Basic Solid Slot Basic Solid Slot 30 MPH 36.98 35.45 36.53 36.1 7.07 30.24 60 MPH 74.44 71.29 73.43 72.35 15.68 60.54 90 MPH 110.97 106.85 109.92 107.83 25.15 94.12 120 MPH 149.63 143.23 147.39 144.88 27.03 121.2

Table 27-Airflow Speeds over Helmets

We can see from this table that the solid wing and the slot gap designs both slow down the airflow slightly this may be sue to them creating turbulence on the flow and detaching the flow of air. However when we look at the tucked position the airflow behind the attachments we can see a significant reduction in speed behind the solid wing. Therefore I believe that the best solution for a kart driver is to have a helmet which has no attachments because it creates a smoother flow of air around the helmet because the air flow can stay attached for longer and therefore less drag. However a well-designed slot gap wing could potentially be beneficial if a project focuses on this type of design. When looking at the Nassau panel variations three designs were tested to see if modifying the panel would have a direct effect on the aero performance of the kart un-tucked and tucked. From testing it is concluded that the M4 design benefits the driver more when they are un-tucked as it produced less drag and less high pressure at the front of the kart. However when looking at when the kart driver is tucked I believe that the lipped Nassau panel is better as it reduces the drag behind the kart when comparing fig…. and fig….. Aswell as the lipped design the plate design shows potential for a re-design and altering as Fig…. shows that air speeds up as it leaves the plate and then sends it over the drivers head which is then seen in Fig…..

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Project Limitations & What Would Be Done Differently Next Time? Firstly if the project was to be done again I would have had models made up of the helmets on their own to test in a real wind tunnel. However this also expensive and it would be more realistic to make a basic wind tunnel. This would provide primary research and data as real helmet models and real wind is being used which would also provide more real world data than that created by a CFD product as real wind is being used and the issues creating the right mesh and setting all of the parameters up would not be such an issue as the air is there and requires a way to force air into the tunnel and to exhaust it out and also a way to control the air speed accurately. It would also be possible to use smoke in the tunnel or to use a form of aero paint to visualize how the air flows around the helmet. Also if there was a longer period of time it would also be possible to test chin spoilers and other various attachments to create the best package for the helmet. The other possibility is to investigate the helmet vents to optimize the airflow getting to the drivers head in order to cool them and help them to focus on the race.

Appendices

Works Cited Barnard, R. H. (2009). Road Vehicle Aerodynamic Design: An Introduction.

Third Edition. Hertford: MechAero Publishing. Katz, J. (2006). Race Car Aerodynamics: Designing For Speed. Cambridge:

BentleyPublishers.com. Katz, J. (2006). Race Car Aerodynamics: Designing For Speed.

BentleyPublishers.com. Cambridge. McBeat, S. (2006). Competition Car Aerodynamics: A Practical Handbook.

Yeovil: Haynes Publishings. Tsai, D. G. (2003). Composite Materials Design and Applications. Washington

D.C: CRC Press. www.kartdavid.co.uk. (n.d.). Freeleine Body. www.kartstore.co.uk. (n.d.). BigFoot Nassau Panel. www.spellframe.co.uk. (n.d.). New Age 2 Body Panels.

Figures Figure 1 http://www.shoei-helmets.com/Safety_ActiveSafety.aspx ................. 6 Figure 2 http://www.schuberthnorthamerica.com/categories/motorcycle/s2/ .. 7 Figure 3 (Katz 2006 Fig 2-20) .......................................................................... 8

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Figure 4 - Self Taken Photo Arai SK-5 ............................................................ 9 Figure 5 - Self Taken Photo Vemar Helmet ................................................... 10 Figure 6 - http://racinghelmetsgarage.blogspot.co.uk/2012/04/schuberth-sf1-falonso-2012-by-jens.html ............................................................................. 10 Figure 7-Self Taken Photo Untucked Kart ..................................................... 11 Figure 8-Self Taken Photo Tucked Kart ........................................................ 11 Figure 9 - M4 Design (www.spellframe.co.uk) ............................................... 12 Figure 10 - New Age 2 (www.spellframe.co.uk) ............................................ 13 Figure 11 - Freeline (www.kartdavid.co.uk) ................................................... 13 Figure 12 - Bigfoot Nassau Panel (www.kartdavid.co.uk) ............................. 13 Figure 13 (Tsai, 2003) ................................................................................... 15 Figure 14 - Basic Helmet Design ................................................................... 17 Figure 15 - Solid Wing Helmet Design ........................................................... 18 Figure 16 - Slot Gap Wing Design ................................................................. 19 Figure 17 - Basic Helmet Velocity Stand-Alone Contours & Streamlines (Un-Tucked) .......................................................................................................... 22 Figure 18 - Basic Helmet Pressure Stand-Alone Contours (Un-Tucked) ...... 23 Figure 19 - Solid Wing Velocity Stand-Alone Contours & Streamlines (Un-Tucked) .......................................................................................................... 23 Figure 20 - Basic Helmet Pressure Stand-Alone Contours (Un-Tucked) ...... 24 Figure 21-Slot Gap Wing Velocity Stand-Alone Contours & Streamlines (Un-Tucked) .......................................................................................................... 24 Figure 22-Airflow through the Slot Gap Design ............................................. 25 Figure 23-Slot Gap Wing Pressure Stand-Alone Contours (Un-Tucked) ...... 25 Figure 24-Basic Helmet Velocity Stand-Alone Contours & Stramlines (Tucked) ....................................................................................................................... 26 Figure 25-Basic Helmet Pressure Stand-Alone Contours (Tucked) .............. 26 Figure 26-Solid Wing Velocity Stand-Alone Contours & Streamlines (Tucked) ....................................................................................................................... 27 Figure 27-Solid Wing Pressure Stand-Alone Contours (Tucked) .................. 27 Figure 28-Slot Gap Wing Helmet Velocity Stand-Alone Contours & Streamlines (Tucked) ..................................................................................... 28 Figure 29-Slot Gap Wing Pressure Stand-Alone Test Contours (Tucked) .... 28 Figure 30-Pressure Gradient Basic Helmet Un-Tucked ................................ 35 Figure 31-Pressure Gradient Basic Helmet Tucked ...................................... 36 Figure 32-Pressure Gradient Solid Wing Un-Tucked .................................... 36 Figure 33-Pressure Gradient Solid Wing Tucked .......................................... 36 Figure 34-Pressure Gradient Slot Gap Wing Un-Tucked .............................. 37 Figure 35-Pressure Gradient Slot Gap Wing Tucked .................................... 37 Figure 36-Data Collection Points Empty Kart ................................................ 39 Figure 37-Empty Kart Pressure Contours ...................................................... 40 Figure 38-Empty Kart Surface Pressure Contours ........................................ 40 Figure 39-Empty Kart Velocity Contours & Vectors ....................................... 41

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Figure 40-Empty Kart Velocity Surface Vectors ............................................ 41 Figure 41-Empty Kart Velocity Vectors .......................................................... 42 Figure 42-Empty Kart Pressure Gradients ..................................................... 43 Figure 43-Data Collection Points For the Basic Helmet ................................ 45 Figure 44-Basic Helmet Kart Pressure Contours (Un-Tucked) ...................... 45 Figure 45-Basic Helmet Kart Velocity Contours & Vectors (Un-Tucked) ....... 46 Figure 46-Basic Helmet Kart Pressure Contours (Tucked) ........................... 46 Figure 47-Basic Helmet Kart Velocity Contours & Vectors (Tucked) ............. 47 Figure 48-Solid Wing Kart Data Collection Points ......................................... 48 Figure 49-Solid Wing Kart Pressure Contours (Un-Tucked) .......................... 48 Figure 50-Solid Wing Kart Velocity Contours & Vectors (Un-Tucked) ........... 49 Figure 51-Solid Wing Kart Pressure Contours (Tucked) ............................... 49 Figure 52-Solid Wing Kart Velocity Contours & Vectors (Tucked) ................. 50 Figure 53-Slot Gap Kart Data Collection Points ............................................ 51 Figure 54-Slot Gap Wing Kart Pressure Contours (Un-Tucked) .................... 51 Figure 55-Slot Gap Wing Velocity Contours & Vectors (Un-Tucked) ............ 52 Figure 56-Slot Gap Wing Kart Pressure Contours (Tucked) ......................... 52 Figure 57-Figure 55-Slot Gap Wing Velocity Contours & Vectors (Tucked) .. 52 Figure 58-Kart Testing Pressure Gradient 30MPH (Un-Tucked) ................... 56 Figure 59-Kart Testing Pressure Gradient 30MPH (Tucked) ......................... 56 Figure 60-Kart Testing Pressure Gradient 90MPH (Un-Tucked) ................... 56 Figure 61-Kart Testing Pressure Gradient 90MPH (Tucked) ......................... 56 Figure 62-Lipped Nassau Panel Velocity Contours & Vectors (Un-Tucked) . 61 Figure 63-Lipped Nassau Panel Velocity Streamlines (Un-Tucked) .............. 62 Figure 64-Lipped Nassau Panel Pressure Contours (Un-Tucked) ................ 62 Figure 65-Lipped Nassau Panel Velocity Contours & Vectors (Tucked) ....... 63 Figure 66-Lipped Nassau Panel Velocity Streamlines (Tucked) ................... 64 Figure 67-Lipped Nassau Panel Pressure Contours (Tucked) ...................... 64 Figure 68-Plate Nassau Panel Pressure Contours (Un-Tucked) ................... 65 Figure 69-Plate Nassau Panel Velocity Contours & Vectors (Un-Tucked) .... 65 Figure 70-Plate Nassau Panel Velocity Streamlines (Un-Tucked) ................ 66 Figure 71-Plate Nassau Panel Pressure Contours (Tucked) ......................... 66 Figure 72-Plate Nassau Panel Velocity Contours & Vectors (Tucked) .......... 67 Figure 73-Plate Nassau Panel Velocity Streamlines 1 (Tucked) ................... 67 Figure 74-Plate Nassau Panel Velocity Streamlines 2 (Tucked) ................... 68 Figure 75-Drag Behind Tucked Helmets ....................................................... 69

Tables Table 1-Stand Alone Pressure Data 30MPH ................................................. 30 Table 2-Stand Alone Pressure Data 60MPH ................................................. 30 Table 3-Stand Alone Pressure Data 90MPH ................................................. 30

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Table 4-Stand Alone Pressure Data 120MPH ............................................... 30 Table 5-Stand Alone Velocity Data 30MPH ................................................... 32 Table 6-Stand Alone Velocity Data 60MPH ................................................... 32 Table 7-Stand Alone Velocity Data 90MPH ................................................... 33 Table 8-Stand Alone Velocity Data 120MPH ................................................. 33 Table 9-Stand Alone Pressure Coefficient Data 30MPH ............................... 34 Table 10-Stand Alone Pressure Coefficient Data 60MPH ............................. 34 Table 11-Stand Alone Pressure Coefficient Data 90MPH ............................. 35 Table 12-Stand Alone Pressure Coefficient Data 120MPH ........................... 35 Table 13-Comparison between Helmets Tucked at 90MPH .......................... 39 Table 14-Empty Kart Drag & Lift Data ........................................................... 40 Table 15-Empty Kart Pressure Data .............................................................. 40 Table 16-Empty Kart Velocity Data ................................................................ 42 Table 17-Empty Kart Pressure Coefficient Data ............................................ 43 Table 18-Air Speeding Up From the Front to the Back of the Kart Underneath It ..................................................................................................................... 44 Table 19-Kart Testing Pressure Data 30MPH ............................................... 53 Table 20-Kart Testing Pressure Data 90MPH ............................................... 53 Table 21-Kart Testing Velocity Data 30MPH ................................................. 54 Table 22-Kart Testing Velocity Data 90MPH ................................................. 54 Table 23-Kart Testing Pressure Coefficient Data 30MPH ............................. 55 Table 24-Kart Testing Pressure Coefficient Data 90MPH ............................. 55 Table 25-Comparison between Un-Tucked Kart Test Data ........................... 57 Table 26-Comparison between Tucked Kart Test Data ................................. 59 Table 27-Airflow Speeds over Helmets ......................................................... 71

Aerodynamic & Safety Development of Open Cockpit Helmet Design

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