|Written by Administrator|
|Saturday, 20 June 2009|
UWA Motorsport has a very prestigious history in Formula SAE. Founded in 2000, the team first entered the FSAE-Australasian competition in 2001 with a very simple space-frame chassis and 4 cylinder Honda engine. In 2002 the team achieved a 2nd place finish in their second competition. In 2003, the team built their first carbon chassis driver bay with space-frame rear bay. The team which built the 2003 car was also the first team to travel to the FSAE international competition, winning the prestigious Carroll Smith Design Award for design.
The 2004 vehicle was the first full monocoque chassis, achieving 3rd place in FSAE-Australasia and a second place finish in the international competition, also winning the design award. The 2005 team was the first UWA Motorsport vehicle to win a competition, achieving first in the Australasian event held that same year. The 2006 vehicle did extremely well and came a close second in both Australasian and International events. The most recent vehicle on which this article is written on, the 2007 vehicle, won both the 2007 Australasian competition and the 2008 World Cup FSAE event that was held at Michigan International Speedway, USA.
for this project, which is broken up into individual competition years, is made
up of University and industry funding. The team relies heavily on the kind
donations and support given by the many sponsors that support us. The
university supplies the working space for the team, as well as financial
support and use of its manufacturing facilities. Additional sponsors provide
materials such as high-grade aluminium and specialist manufacturing including
CNC. The team’s platinum sponsors are Goodyear, who provides the team with
tyres and testing facilities in the
The team is structured into four main areas being power-train, vehicle dynamics, electrical and chassis. Each team has a leader responsible for that section and who supervises the work being conducted under them. Their job is to manage their budget and resources efficiently in order to successfully complete the job. Further to this, the team also has financial and managerial officers. The team manager oversees the team, and has a heavy involvement in the team’s image and marketability. The finance officer must take care of the budget and take care of the fiscal responsibility of the team. Below the management team is the technical director, whose role is to ensure the day to day functioning of the technical team, oversee the four sections and ensure the vehicle is produced on time.
The car is named the IHS-007, which stands for the Ian Hamilton Special (IHS) to commemorate Ian Hamilton, the head technician who helped us greatly in the Mechanical Engineering workshop often after hours and who has now retired. The 007 is for the year in which it was built.
The IHS-007 was engineered to suit the local autocross market as this is what the car is built for, according to the rules specified by Formula SAE. This market which has been specified to us demands not only a fast car that looks good, is easy to maintain but also incorporates current automotive technologies as found in modern high performance road cars. Such technologies which will be explained include CAN bus electronics system, electronic traction control, steering wheel mounted controls as well as potential for analysing and altering the engine tune and logging data, an option that some production cars and motorcycles offer. As such, IHS-007 is a fantastic car for an autocross driver due to the ease at which the power and performance is accessible.
To achieve the design goals of creating a useable high performance vehicle that looks good and features new technology, the team must scrutinise all parts of the vehicle before a new car is designed and subsequently constructed. A high standard of engineering is employed so that each part is as focussed and well designed as possible, whilst integrating it with the rest of the vehicle to ensure an extremely high level of performance as a whole. All these designs are developed to maximise performance within safety, reliability, regulatory and resource constraints. Every system in the vehicle is designed to either benefit the driver, the tyres or the engine and thus non-essential items are removed. This is achieved via detailed analysis methods and physical testing and tuning parameters on the dynamometer and on previous vehicles. This type of engineering ensures that parts are efficient and effective whilst reducing manufacture time and minimising production cost.
Some of the successful ideas incorporated into the IHS-007 vehicle which typify the design iteration process include a one piece, carbon fibre monocoque chassis and fully independent Kinetic™ suspension system. Key developments and designs with respect to previous cars include significant wheelbase reduction, all round pull rod suspension, dual stage fuel injection, integrated CAN bus network and a carbon-fibre/steel integrated rear bay structure (RBS) that mounts all major drive-train and suspension components while also attaching the engine to the chassis. These developments will all be explained further in the article.
UWA motorsport has always had class leading vehicle dynamic design and is the only Formula SAE car to utilise the unique Kinetic™ Suspension System. This is proven when compared to previous car’s performance such as being noted as the quickest car in the world in 2007, as well as winning prestigious industry awards such as the Arvin-Meritor suspension award. The Kinetic™ Suspension that is utilised on the car is known as ‘H2’ and is a patented by Kinetic™ Suspension Technology. In simplified terms, the system works by interconnecting all four dampers via hydraulic lines. Each damper is connected to a valve unit and these in turn are connected to pressure reservoirs. As the vehicle rolls, hydraulic fluid is transferred across the car to increase the roll stiffness. This system has many advantages over a conventional coil-over-damper suspension system in that it allows vehicle mode separation. This in combination with additional heave springs means very low warp rates combined with relatively high pitch, heave and roll rates. This basically means that the bump and rebound settings can be tuned separately, thereby making tuning more efficient and effective. Heave springs reduce pitch and heave such as when both wheels on an axle move up or down at the same time like in a straight-line braking or acceleration situation. In a normal system, high roll rates mean that the car has a high warp rate (in that a one wheel bump will have a high impact on the rest of the vehicle), however the system this car uses allows high roll rates (which are good for lateral capability) yet low warp rates, so the car is more composed over bumps. Overall, the system reduces roll whilst being soft in bump for increased dynamic performance whilst still being controllable over undulations and road changes.
Additionally, IHS-007 has several innovations and unique features such as pull type dampers (working in the reverse manner when compared to a conventional damper –ED) and heave springs (previously mentioned), lightweight two-piece wheels, brake bias control and the composite rear bay structure. It also has easy and effective suspension adjustment with comprehensive data acquisition such as linear potentiometers on the dampers that make the suspension quite easy to tune and develop, even for the non-professional weekend autocross racer. It also contains features such as thread toe adjusters, camber shims that do not affect toe settings, four-way external damper adjusters, easily changed corner springs and a chassis that is stiff enough to make the changes effective.
The IHS-007 vehicle’s performance attributes stem from concentrating on improving the combined lateral and longitudinal acceleration at lower speeds and during corner exit. This is important in FSAE racing due to the tight nature of the tracks and the large amounts of time spent in corner entry and exit. This combined with fast yet controllable transient response delivers the ability to ‘flick and punch’ the car through a series of sharp corners at great speed. Transient behaviour is when the car is changing direction or phase, as opposed to steady state turns where the car’s direction is constant. The best way to describe transience in vehicle dynamics is when the yaw rate of the vehicle is changing (and therefore non-zero yaw acceleration), whereas a steady state vehicle has a constant yaw rate (zero yaw acceleration). The types of corners in FSAE included tight, quick slaloms, 180 degree hairpins followed by quick lane changes, as well as 120 degree tight left hand turns. The lengths of straights, the spacing of the straights and the corner radii are all set in the FSAE rules. These state that straights must be no longer than 60m with hairpins no longer than 45m at both ends. Constant turns must be 23 to 45m in diameter and hairpins must have a minimum outside diameter of 9m. Slaloms must have cones in a straight line with 7.6 to 12.2 m spacing between them. There are also miscellaneous sections of the track which may include chicanes, multiple turns and decreasing radius turns while maintaining a minimum track width of 3.5m.
In a car that weighs less than 200 kilograms yet makes over 100 hp, the rear wheels are often traction limited. To enhance rearward weight transfer which increases the normal load on the rear driven tyres (thereby increasing the available traction), a short wheelbase is designed into the vehicle whilst still ensuring that an optimal static weight distribution is maintained.
Achieving the required weight distribution along with the short wheelbase is difficult to attain, with great effort being applied to the packaging of major components in the car. This includes the selection of a shorter engine and reduced engine/firewall clearance to shorten the wheelbase further. With the relatively small size of the car, each component must be carefully positioned in the car to ensure the correct static weight distribution is maintained. The track width is determined by the designed centre of gravity and lateral capability. The lateral capability of the car is the amount of lateral acceleration the car can achieve, which is dependant on many things including the suspension geometry, roll stiffness and corner weights amongst other things.
The brakes are a custom package comprising of calipers from the rear wheel of a production motorcycle with the rotors having a floating configuration. The petal-shaped rotors are custom made from nodular cast iron for its higher yield strength and hardness. The team machines, grinds and drills the rotors whereby they are then heat treated to achieve the required hardness levels. The braking system proves extremely effective with up to 1.6g being achieved in some circumstances.
The pedal box used is an assembly that is extremely adjustable to suit the height of the driver with a fore-aft movement via a quick and easy to use adjustment system. It has a light-weight carbon fibre composite construction incorporating all components into one system including the master cylinders, brake bias bar, brake fluid reservoir, brake and accelerator pedal and mounting system for the throttle cable.
The rims are made by UWA and are of two-piece construction with the inner rim being cast and then machined to reduce unnecessary weight. The outer rim, which is the cylinder section of the rim, is spun and then attached to the inner cast rim. Finite Element Modelling is used to test the deflection and stress concentrations on the inner rim before production, ensuring that too much material isn’t removed which may compromise the strength and stiffness of the part. Stiffness of the rim is extremely important in motor racing and if the rim is not stiff enough, the tyre may deflect during cornering. This would reduce the effect of suspension geometry and induces unwanted dynamic camber. Reduction in the weight of the rim produces enormous advantages with regards to unsprung mass and therefore the general handling of the car. These wheels support Goodyear’s 13 inch tyres that are specially made for the FSAE competition. The Goodyear’s are most commonly used due to their all-round ability and the ease at which peak performance can be obtained. There is, however, a tyre test consortium which independently supplies teams which pay for the CALSPAN program test data on the tyres. These tyres and the data makes an enormous difference on how the suspension package is designed
A race team’s normal power-train goals of peak power and torque are replaced in FSAE by improved drivability and handling through predictable and linear power delivery. The 2007 car is able to accelerate from stand-still to 100km/h in approximately 3.5 seconds, proving its blistering speed not only in corners but also in a straight line. The rules also state that there must be a 20mm restrictor/orifice on the air intake in an attempt to limit the amount of power that the engines can produce. The UWA Motorsport power-train team uses tuning techniques such as runner length harmonics and plenum volume adjustment to overcome the choking that may occur due to the orifice. The objectives of power-train’s design for the IHS-007 were to provide improved drivability, thermal and fuel efficiency and overall power without compromising reliability. This allows an amateur driver to drive fast with confidence through the rev range on tight and twisty tracks while limiting the need to worry about such things as snap oversteer. These goals also allow maximum points to be gained for lap times and fuel economy. Further to this, the high-level tuning of the engine also puts focus on the amount of fuel used. Tuning for fuel efficiency is a high priority since a portion of the points available for competition incorporates the amount of fuel used during the endurance event with the more fuel efficient cars earning better scores.
A Honda CBR600RR motorcycle engine forms the basis of the power-train package for the IHS-007. UWA Motorsport has always used Honda engines for their power, reliability, cheap parts and ease of maintenance and disassembly. These motorcycle engines have a high specific power output and a very good power-to-weight ratio. The 600RR was chosen over the previous 600F4i in 2007 as it was slightly lighter with smaller dimensions, allowing better integration with the rest of the vehicle.
The hydraulic gear shifting and clutch system is located directly behind the steering wheel meaning that driver ergonomics are not compromised. Utilising hydraulics linkages between the paddles and the engine means rapid shifting is possible and removes the problems of stretching and slack that may be experienced with a cable system. The paddles have sensors and switches which act as inputs to the engine management system telling when to cut the ignition for shifting. This is explained in greater detail later.
Several modifications are made to the engine to increase its efficiency and performance. Compression ratio is increased to improve thermal efficiency, fuel economy and performance. The MoTec M800 is used on the current model with the 2002 and 2001 cars using an M4. The engine control unit (ECU) allows fuel delivery and spark timing tables to be tuned and calibrated. This can be tuned and uploaded for different tracks, situations and events. The unit also includes compensations for engine temperature, manifold air pressure, fuel temperature and battery voltage to ensure robust performance under various conditions.
Being traction limited, the car runs a traction control system that works on either ignition or fuel cut. The ignition cut has better response so is used in autocross events, however fuel cut is used in endurance as there are added benefits of fuel economy that outweigh the small increase in response.
As has been noted, FSAE tracks are very tight and winding. Taking such a track configuration into consideration, the engine must be tuned primarily for the mid-rpm range, as this is the most frequently used area of the rev band. Peak torque is designed to occur in this area to maximise the availability of the engine’s power whilst ensuring drivability from 6000 rpm all the way to the 15000 rpm redline.
The intake and exhaust are custom made with the geometry being designed using computer simulation and physical testing on the university’s engine dynamometer. The dynamometer has adjustable intake and exhaust lengths which allow for tuning of the corresponding peaks in the torque band. Full sweeps of inlet and exhaust phasing was carried out to improve torque in the most common engine speed range.
The fuel injection system on IHS-007 has been designed to improve fuel delivery accuracy as well as improve charge cooling and air/fuel mixing. The system incorporates a total of six injectors utilising a dual stage injection system. Four injectors are located at the intake ports, with a further two located in the diffuser, immediately downstream of the restrictor. This configuration provides good response from the lower injectors by placing the fuel at the intake valves, whilst the diffuser injectors increases fuel mixing and charge cooling effect by allowing the fuel to stay in the air for as long as possible. This results in higher torque with less fuel consumption and without sacrificing throttle response. In fact, tuning the engine in this way yields an increase of approximately 10Nm of torque with similar power figures at the crank as the stock engines. The dyno chart shows the torque and power curves of the tuned engine.
Engine cooling was a high priority for IHS-007
as testing in hot weather for extended periods is often required in the hot
summer temperatures of
A dry-sump lubrication system was made to allow the engine to be lowered whilst still providing adequate lubrication to the engine. The stock motorcycle engine has a large wet sump that protrudes out of the bottom of the engine, hindering one of the team’s goals of lowering the centre of gravity as much as possible. The modified lubrication system includes a semi-stressed sump plate, which also incorporates the engine mounts, a pump mounted inside the engine and a cyclone separator which separates oil from air and also stores surplus oil. The flow of oil within the engine is improved using baffles in the sump which help the oil to be picked up and subsequently pumped around the engine during hard cornering. The system has proved to provide a continuous oil supply, even under hard lateral acceleration.
Engine power is transmitted to the wheels via a chain-driven viscous limited slip differential that is tensioned via simple eccentrics and integrated into a custom composite laminate Rear Bay Structure (RBS). The viscous housing, mounting and sprocket are all custom-made to hold a viscous inner coupling from a Subaru WRX. Prior to 2005, the team used a Torsen differential; however this had many undesirable features including corner-entry understeer and mid corner oversteer. The viscous coupling is seen as smooth and progressive due to its speed sensing nature (rather than the torque sensing of the Torsen achieved via series of gear sets) and therefore improves driver confidence. The RBS also mounts the engine, rear rockers, dampers, upper and lower wishbones and incorporates the chain guard and lift bar. The RBS is an example of the design philosophy that is adopted by the team, whereby each part does a maximum number of jobs whilst minimising its weight.
The IHS-007 chassis employs composite materials in the form of several types of carbon fibre sandwiching a honeycomb core with the fibre orientation designed for maximum stiffness and force dispersal. This forms the basis for the monocoque chassis that exhibits high rigidity and minimal weight, whilst maintaining uncompromised driver safety. Many FSAE vehicles feature a welded steel-tube space-frame chassis with only a small number of teams utilising the strength and light weight properties of carbon fibre. Yet each team using a monocoque chassis must prove that it is structurally equivalent to a steel space-frame. UWA Motorsport has proven this a number of times using a force-controlled pendulum test where a heavy weight is dropped from a prescribed height and swings down until it hits the test specimen. This is a controlled way of testing how much force the side-impact structure can withstand. From these conclusive tests we ascertained that the carbon monocoque exhibits higher strength whilst also being substantially lighter. The chassis is specially designed and constructed such that the various suspension and engine loads are transmitted correctly and safely. Construction incorporates a technique in carbon fibre orientation which ensures that chassis loading is distributed throughout. Inserts and brackets are engineered and tested according to load, and detailed analysis of physical chassis testing has led to a stronger, more rigid chassis. The torsional rigidity of the chassis has been measured and exhibits very high levels given its light weight.
The chassis was also designed for enhanced aesthetic appeal with a considerable amount of design and thought put into its layout and looks. Bare carbon side-pods and air scoop are highlighted against the yellow painted chassis which presents itself as a very aesthetically pleasing combination. The side-pods play an important role in housing and hiding the radiator and exhaust whilst the air scoop houses the air filter and engine intake.
The chassis consists of a 3 bay design with the first being the sloped leg bay, which is where the driver’s legs are. This is also where the front suspension bolts onto the car along with the Kinetic™ suspension components. The sloped leg bay offers increased protection to front suspension components and also assists in the lowering of the Centre of Mass height of the car by lowering the height of the driver’s feet and impact attenuator. The second is the driver bay where the driver mainly sits. This area must protect the driver in the event of a mishap and must also transmit loads through between the rear of the car and the leg bay. The third and final bay is the open rear cowling which assists in cooling the engine and allows for easy access to engine bay components from above. The engine is bolted to this and thus it must exhibit high rigidity. The rear bay allows easy removal of engine and the differential, with mounting to the chassis occurring at the firewall, and rear bulkhead through the RBS. Component integration improves maintenance, by allowing fewer operations during repairs and modifications. The chain and sprocket are also covered by the rear cowling, reducing the exposure of moving components, thereby improving aesthetics and safety.
The electrics on the UWA Motorsport cars are designed to be reliable, efficient and user friendly. The use of high quality light weight components means an improvement in the overall weight of the car, with a large number of components making up the electrical system. The onboard diagnostics have also been improved to cover more dynamic variables which help the race engineer locate problems and subsequently repair them.
An integrated CAN bus network installed on IHS-007 allows a ‘plug and play’ type functionality and design variables can easily be changed through the software designed by the electronics team. CAN stands for Controller Area Network while bus means Databus which is a Binary Unit System. The system works by using only four wires – input, output, power and ground, which run between controllers. The controllers manage a specific functional area such as the engine and communicate with each other and a central unit to fulfil their required function. This improves the electrical system by reducing the amount of wiring, relays and connections needed, thereby reducing weight. The CAN bus system removes the need to hard-wire all components, which requires a large amount of wiring and complexity. This allows users to easily add in new components to the car as they become available with minimum hassle. Such systems make developing the electrics/electronics and the rest of the car much easier, allowing more focussed attention on other areas.
A programmable intelligent steering wheel includes a shift warning light and LED’s indicating the revs of the engine progressing as they approach the limiter. This allows the driver to know what the engine is doing and thus allows gear changing at the optimum time. The wheel can be rapidly removed via an integrated electrical connector within the wheel’s quick-release, which alleviates the reliability issues associated with a separate cable connection. This is important in highly-stressful situations where speed of removal is vital and simplicity is sacred. Further to this, the wheel must be quickly and easily removable to ensure the driver can exit the car as quickly as possible in the unlikely event of an accident or fire.
A 16 volt electrical system is used on the car as this allows us to utilise high energy density Lithium-Polymer batteries which are lighter while also allowing the starter motor to rev higher than stock, increasing the ease of hot restarts during an endurance driver change. This delivers a substantial weight reduction of approximately 75% over traditional lead acid batteries. A custom regulator and power-boards allow increased reliability by providing safe and efficient charging from the engine’s stock alternator and eliminates the need for relays. A number of systems on the car such as the gear actuation system cause considerable drain on the battery and electrical system of the car.
DRIVER INTERFACE AND SAFETY
The UWAM car is noted within FSAE and its judges as one of the most comfortable vehicles to drive, which surprises many due to the small overall size of the car and the cockpit. The driver interface including the steering wheel and read-outs can be adjusted to meet the driver’s preference and size. Ergonomic studies with a driver bay mock-up assessed the comfort levels of various seating positions aimed at minimizing driver Centre of Mass height and ensured the vehicle can easily accommodate a 95% percentile male and 5% percentile female driver. This simply means that 95% of the population could easily drive this car without ergonomic issues. For this reason we have always been praised for dismissing the myth that high performance race cars are uncomfortable and only suit a small percentage of the population.
Further comfort measures taken are a fore-aft adjustable pedal box (mentioned previously) and seat inserts that are made from expandable foam and then covered in cloth. These are to mould the seat to individual drivers providing them with maximum comfort. Further to this, ample elbow room is incorporated into the monocoque chassis to ensure freedom of movement thereby helping to reduce driver fatigue. A custom carbon fibre steering wheel with optimum geometry for maximum steering effectiveness was developed which ensures there is a mix of good ergonomics and control. The steering wheel contains controls such as push to talk (PTT), which allows the driver to speak to the team while on the track. There are also controls such as a clutch override on the 06 car, ensuring the driver had a choice of control without having to exit the vehicle. Also located on the steering wheel is the gear position indicator and shift lights as mentioned previously.
The hydraulic gear shift and clutch system which is actuated by paddles behind the steering wheel, allows rapid shifting without the driver having to remove their hands from the optimum driving position. The hydraulic gearshift replaced the electric shifting system to improve reliability and reduce weight and complexity of the car. The unit works by having a master cylinder on the steering column which is actuated via an attachment to the paddles. Hydraulic hoses run along the car to the clutch slave which, when pulled, engages the clutch, and also to the gearshift mechanism such that when pushed it shifts up and when pulled it shifts down. This means that pulling on the paddle to the right of the steering wheel will shift up, with help from an ignition cut for full throttle up-shifts, and the left side will shift down and engage the clutch at the same time.
The IHS-007 incorporates successful design, innovation and clever engineering, producing a highly desirable FSAE vehicle. This car, along with the other UWA Motorsport race-cars, is a product of an incredibly high level of commitment, motivation, passion, knowledge and skill. The success of the vehicles and the group is testament to the UWA Motorsport program in providing students with the chance to be part of a real race team, having to understand thing such as management, marketing, corporate relations, team work, budgeting and the engineering design process and problem solving. Being part of the team prepares students for work life like nothing else can, placing students in an environment similar to what is experienced by a professional after completing university. This is what makes graduates who have contributed to UWA Motorsport and other such programs so much more employable than students who have simply completed the minimum degree requirements.