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The Atom prototype chassis was tested to determine the value of its global torsional stiffness. This value was calculated to be 1330Nm/deg. This value was to be improved upon by the following method:
The creation of a Finite Element baseline validation model using MSC Patran/Nastran software compared favourably with the physical test results with a torsional stiffness value of 1352Nm/deg for a mass of 47 Kg and an efficiency of 88g/Nm/deg.
The discussed modifications had been suggested to Atom upon initial appraisal of the chassis were incorporated into this baseline model and resulted in increases in both torsional stiffness and efficiency.
Further, the design improvement study performed resulted in a maximum torsional stiffness of 6448Nm/deg, an increase of 377% over the baseline model. A maximum increase in efficiency of 286% to 23g/Nm/deg for a mass of 148.3Kg accompanied this increase in torsional stiffness.
Following optimisation of the model to gain minimum mass for a stiffness of 6000Nm/deg a torsional stiffness of 6030Nm/deg was realised for a mass of 127Kg, giving an increase in efficiency of 322% over the baseline model to 20.99g/Nm/deg.
First, I would like to thank my parents for their support and encouragement throughout my university career.
I would like to sincerely thank my supervisor Mr. Mike Dickison for his continual support and enthusiasm for this thesis. Thanks to Brunthinthorpe Car Ltd for providing a very interesting design project and great support throughout.
Finally, a special thanks to all my friends at Coventry who have made this such a great year.
1.1 Bruntingthorpe Sports Cars Ltd
Bruntingthorpe Sports Cars Ltd has been involved in the Lightweight car industry for a number of years. They have produced work for many other companies.
1.2 Aims of Project
The purpose of the design project:
To perform a torsion test on the prototype chassis to determine its torsional stiffness;
To create a finite element model of the chassis;
To incorporate a design improvement study and note the effects on the global torsional stiffness of the chassis;
To attempt an optimisation for maximum efficiency.
The following limitations are given for this project:
The body shape is fixed and therefore the overall external shape of the chassis must not be altered;
Overview of Chassis Types
Definition of a Chassis
The chassis is the framework to which everything is attached in a vehicle. In a modern vehicle, it is expected to fulfil the following functions:
Provide mounting points for the suspensions, the steering mechanism, the engine and gearbox, the final drive, the fuel tank and the seating for the occupants;
Provide rigidity for accurate handling;
Protect the occupants against external impact.
While fulfilling these functions, the chassis should be light enough to reduce inertia and offer satisfactory performance. It should also be tough enough to resist fatigue loads that are produced due to the interaction between the driver, the engine and power transmission and the road.
The history of the ladder frame chassis dates back to the times of the horse drawn carriage. It was used for the construction of 'body on chassis' vehicles, which meant a separately constructed body was mounted on a rolling chassis. The chassis consisted of two parallel beams mounted down each side of the car where the front and rear axles were leaf sprung beam axles. The beams were mainly channel sections with lateral cross members, hence the name. The main factor influencing the design was resistance to bending but there was no consideration of torsional stiffness.
A ladder frame acts as a grillage structure with the beams resisting the shear forces and bending loads. To increase the torsional stiffness of the ladder chassis cruciform bracing was added in the 1930's. The torque in the chassis is reacted by placing the cruciform members in bending, although the connections between the beams and the cruciform must be rigid. Ladder frames were used in car construction until the 1950's but in racing only until the mid 1930's . A typical ladder frame is shown below.
Fig. 1 [Ref. 2]
The ladder frame chassis became obsolete in the mid 1930's with the advent of all-round independent suspension, pioneered by Mercedes Benz and Auto Union. The suspension was unable to operate effectively due to the lack of torsional stiffness. The ladder frame was modified to overcome these failings by making the side rails deeper and boxing them. A closed section has approximately one thousand times the torsional stiffness of an open section. Mercedes initially chose rectangular section, later switching to oval section, which has high torsional stiffness and high bending stiffness due to increased section depth, while Auto Union used tubular section. The original Mercedes design was further improved by mounting the cross members through the side rails and welding on both sides. The efficiency of twin tube chassis' is usually low due to the weight of the large tubes. They were still in use into the 1950's, the 1958 Lister-Jaguar being an example of this type .
Fig. 2 [Ref. 2]
As designers sought to improve the bending stiffness of a chassis, the twin tube chassis evolved into the four tube chassis. The original twin tube design was modified by adding two more longitudinal tubes that ran from the front of the car, around the cockpit opening and on to the rear of the car. The top and bottom side rails are connected by vertical or diagonal members, essentially creating a very deep side rail and thus improving the bending characteristics. The two sides are joined by a series of bulkheads, normally located at the front, footwells, dash area, seatback, and rear of the chassis.
A significant increase in bending stiffness was realised but there is little increase in the torsional stiffness due to the lack of triangulation causing lozenge of the bays.
Fig. 3 Lotus 21 [Ref. 4]
The backbone chassis has a long history in automobile design with its origins credited to Hans Ledwinka, an engineer with Czech automaker Tatra. Ferdinand Porsche worked with Ledwinka in the 1920's and arguably learned much of his craft from him. When a chassis derives its torsional stiffness from one large central tube running the length of the car, the resistance to twist depends almost entirely on the cross-sectional area of that tube. Clearly, that cross section can be much larger than the typical drive shaft tunnel. Depending on the vehicle configuration it is possible to arrange for an approximately rectangular tube of substantial dimensions. This arrangement fits in well with conventional side-by-side seating, with the large central spine forming a centre console. Such an arrangement was utilised by Colin Chapman on the Lotus Elan .
Fig. 4 1962 Lotus Elan backbone chassis [Ref.4]
Although the spaceframe demonstrated a logical development of the four-tube chassis, the space frame differs in several key areas and offers enormous advantages over its predecessors. A spaceframe is one in which many straight tubes are arranged so that the loads experienced all act in either tension or compression. This is a major advantage, since none of the tubes are subject to a bending load. Since space frames are inherently stiff in torsion, very little material is needed so they can be lightweight.
The growing realisation of the need for increased chassis torsional stiffness in the years following World War II led to the space frame, or a variation of it, becoming universal among European road race cars following its appearance on both the Lotus Mk IV and the Mercedes 300 SL in 1952. While these cars were not strictly the first to use space frames, they were widely successful, and the attention they received popularised the idea.
Fig. 5 1952 Lotus Mk.IV spaceframe
The next logical step for chassis development was the stressed skin design. This is more difficult to construct than a spaceframe with the accurate folding, forming, drilling and riveting of sheet steel or modern composite materials. The lessons learnt in the aircraft industry do not usually apply directly in automotive practice. The loads on aircraft are widely distributed - the lift that holds a plane up, for example, is spread over the entire area of its wings. On a race/sports car, the loads are much more concentrated, being focused on the suspension mounting points.
Even when a method is developed to accept forces and spread them over a load bearing skin, it becomes extremely inconvenient to make any modifications and may even require a major redesign. Analysis of the stresses in stressed skin construction is more difficult.
The continuous surface considerably complicates access for repair or replacement of the cars mechanical components. This may also explain why stressed skin construction was virtually unheard of in race cars before the modern mid-engine configuration. The majority of mid-engine race cars end their stressed skin construction at the back of the cockpit, with either a space frame or the engine itself forming the remainder of the structure. For all these drawbacks, stressed skin construction can potentially outperform any other form of race car construction in terms of torsional stiffness.
A chassis is subjected to three load cases: bending, torsion and dynamic loads.
The bending (vertical symmetrical) load case occurs when both wheels on one axle of the vehicle encounter a symmetrical bump simultaneously. The suspension on this axle is displaced, and the compression of the springs causes an upward force on the suspension mounting points. This applies a bending moment to the chassis about a lateral axis.
Fig. 6 Bending Load case [Ref. 2]
The torsion (vertical asymmetric) load case occurs when one wheel on an axle strikes a bump. This loads the chassis in torsion as well as bending. It has been found both in theory and in practice that torsion is a more severe load case than bending.
Fig. 7 Torsion Load case [Ref. 2]
The dynamic load case comprises longitudinal and lateral loads during acceleration, braking and cornering. These loads are usually ignored when analysing structural performance.
A torsionally stiff chassis offers a number of advantages:
According to vehicle dynamics principles for predictable and safe handling the geometry of the suspension and steering must remain as designed. For instance the camber, castor and toe angles could change with torsional twist or the steering geometry could change causing "bump steer."
Once again according to vehicle dynamics principles a suspension should be stiff and well damped to obtain good handling. To this end the front suspension, chassis and the rear suspension can be seen as three springs in series as shown in Fig. 8. If the chassis is not sufficiently stiff in torsion then any advantages gained by stiff suspension will be lost. Furthermore, a chassis without adequate stiffness can make the suspension and handling unpredictable, as it acts as an undamped spring.
Fig. 8 Chassis and suspension as springs
Movement of the chassis can also cause squeaks and rattles, which are unacceptable in modern vehicles.
Simple Structural Surfaces:
The simple structural surfaces method SSS originated from the work of Pawlowski and is described in the notes by Brown and the book by Brown, Robertson and Serpento. These references should be consulted for a thorough understanding of this approach.
The SSS method provides a simple way of determining load paths through a structure. Each surface is assumed only to have in-plane stiffness and no out-of-plane stiffness. Each surface is acted on by forces, e.g. the engine mounts. For equilibrium, adjacent surfaces must provide reactions. This process is continued throughout the structure and determines the load on each SSS. It can then be realised if an SSS has insufficient supports or reactions and therefore determines the continuity of load paths and the structures overall integrity.
Fig. 9 [Ref. 2] Fig. 10 [Ref. 2]
As can be seen in the SSS example in Fig. 9 the box structure is loaded in torsion by the moment Ms, which causes the shear forces Q1 and Q3. All the surfaces are in complementary shear, and the structure is stiff in torsion. If one shear surface is removed, none of the complementary shear forces can exist.
The torsion load is then transferred to the floor of the box via the edge forces Q, so the floor panel is loaded out of plane rather than in complementary shear
The Lightweight cars competitors and their structures
Atom Car -
Atom car is a brilliant example of the lightweight sports car philosophy. You strip out all the heavy crap that sits in the big fat sports cars, put in a small, light but powerful engine, and you have something you can have tremendous fun in. The Atom, like its fellow lightweights the Caterhams and the Elises, delivers high thrills for low costs. This is a brilliant weekend car, a trackday car, that you can go very fast in very easily. And I like doing that (on the track obviously) which is why this takes my third and final garage space.
Ariel Atom 500 V8 built to celebrate 10th birthday
To mark the occasion, Ariel employees assembled an example of their upcoming Ariel Atom 500 V8 high performance car in a personal record of five hours, fifteen minutes. The Ariel Atom 500 V8 is a highly-anticipated ultra light-weight sports car that has been in the making for around two years. The car, although it's not your conventional 'car' perse, is more of a superbike with four wheels. Ariel has confirmed the car will use a 500 horsepower - that's 373kW - V8 in the car that will weigh around 500kg. With a superbike like power-to-weight, the Ariel Atom 500 V8 is sure to be the scariest car ever to hit the market. The engine will be a 32-valve Hartley 3.0 -litre V8 which was derived from merging two Suzuki Hayabusa 1300cc superbike four-cylinder engines together. The engine is said to spin to 16,500rpm, like a superbike. And with a gearbox that allows flat-shifting, like a superbike, Ariel says the car will easily achieve 0-160km/h in under six seconds and go on to a top speed of 270km/hâ€¦ like a superbike. In a recent Autocar report, Atom designer Simon Saunders summed up the Atom 500 V8 build in a few words, The GT-R is the daily driven car that performs excellent everywhere. The Zonda F is the supercar for the long exploration trips through Europe. The Atom is the little insane car for scaring the crap out of yourself
Lotus is increasingly building on its 60 year history of creating more with less with all its recent efforts on electric and hybrid drive cars. Besides the power train work, Lotus has plenty of experience with lightweight structures. The latest evolution of that is the architecture of the new Evora sports car that debuted at the London Motor Show this summer. Lotus has now won an award for the aluminium chassis of the Evora at the Aluminium 2008 trade fair at Messe Essen in Germany. The Lotus architecture is comprised mainly of aluminium extrusions combined with some casting. The components are in part riveted together but are primarily joined by adhesive bonding. Lotus developed much of the technology while creating the Elise and has created structures with greater strength and lower weight. With the combination of aluminium structures and the expertise that Lotus also has in advanced composites, car makers can tap into a lot of technology to help reduce weight and improve fuel efficiency.
Lotus provides an automotive structure with a unique approach. They combined adhesive bonding techniques with mechanical joining, resulting in innovative and creative solutions. Lotus used their expertise in lightweight materials to complete this structure, achieving a low weight and a high structural stiffness and therefore ensuring a major impact on environmental and sustainable performance. The Lotus Evora demonstrates an accumulation of our core competencies in aluminum and composite body engineering, jointing techniques and vehicle systems integration. Lotus pioneered the technology of bonded aluminum extrusions for use in road vehicles and has successfully developed high performance cars for other car companies around the world. One great advantage of our low volume vehicle architecture technology is that it can be used by one car manufacturer looking to develop a range of niche products, or by a group of car manufacturers looking to share investment, but still retain a high degree of end product separation. The Evora's chassis is an evolution of the Lotus vehicle architecture from the Lotus aluminum crossover concept vehicle previously showcased at the Geneva Motor show, and allows for the development of a range of vehicles up to a gross vehicle weight of 1,900 kg. This architecture has been designed to be more applicable to mid-volume applications by utilizing low capital investment manufacturing processes. The Evora structure progresses the Lotus 'bonded and riveted' technology used in the Elise family of vehicles with unique extrusions and folded panels, whilst providing contemporary ease of ingress/egress, build modularity and improved, lower cost repairs. The Lotus Evora employs a composite roof as a stressed structural member to give an exceptional vehicle stiffness of 26,000 Nm per degree, thanks in part to the seatbelt anchorage frame's secondary function as a roll over structure, and partly because the high-tech composite body panels are stressed items. However, despite this high stiffness, the complete chassis and modules weigh just 200 kg (prototype weight), helping to keep the weight of the whole car to just 1350 kg (prototype weight). To deliver this high performance structure, bonded and riveted high grade aluminum extrusions and simple, elegant folded sheet elements are used in the lower structure, which complements the stressed composite roof upper structure. Attached to the high strength central tub are sacrificial energy absorbing sub frames of extruded aluminum at the front and lightweight welded steel at the rear. These sub frame modules also offer advantages in terms of convenience and low cost of repair, and during manufacturing can be brought to the production line fully assembled, ready to be attached to the fully assembled tub.
Luso Motors is a Portuguese car design and development house which has brought us a lightweight sports car - LM 23. This design inspired from the Lotus 23b. The Luso Motors 23 is powered by a 150-horsepower 1.0-litre Honda CBR1000 engine, is mated to a six-speed sequential transmission. According to LusoMotors founder Ernesto Freitas says customers can choose a number of different engines, including a Subaru turbo boxer. This sport car features a steel tube frame chassis, double skin aluminium alloy sheets, riveted and glued with inner foam reinforcements, the outer skin is made out of fibreglass and carbon fibre components. It weighs just 881 pounds, a lightweight sports car, and 150 hp! The car will start at â‚¬15,000(about $23,600).
Close your eyes and build the ultimate two-seat sports car. Start with a lightweight, tube-frame chassis and then add race-bred suspension and oversized brakes. Wrap the vehicle in an aero-inspired carbon fiber body shell, but keep the generous cockpit open for wind-in-your-hair enjoyment. Lastly, wedge a huge, torque-laden, tire-shredding engine into the middle of the chassis, and tune the exhaust note so it scares the gophers out of your neighbor's front lawn. Now, open your eyes and take a look at the Deronda G400.
We recently had an afternoon with this exceptional hand-built brute in the mountains above Malibu. With a mid-mounted V8 sourced from a Chevrolet Corvette and the curb weight of a Smart fortwo, the Deronda seems powerful enough to move the economy. What's the story behind the car? Who makes it, and how? Most importantly, can the Deronda be tamed? Read our full adventure after the jump.
The Deronda was originally developed in the United Kingdom by Andy Round, a successful aeronautical engineer. Round wanted to purchase a lightweight high-performance road car, but was frustrated and dissatisfied with what he found after looking at offerings from Caterham, Ultima and Westfield. In a bold move, Round decided to build his own sports car using the most advanced components and materials he could get his hands on. Driving dynamics and safety were key priorities, while styling was to be influenced by Formula 1 and Le Mans Series race cars. The first prototype, manufactured by Fabrication Techniques, was called the Deronda F400. Powered by a turbocharged Audi 1.8-liter four-cylinder rated at 210 hp, Round's new open-cockpit sports car made its debut at the 2004 Auto sport International Racing Car Show in the UK.
At this point, Auto sport Development, a North American manufacturer and importer of unique street and race cars, was sufficiently impressed with the engineering and design of the Deronda that it wanted to build it. Discussions ensued, and the company licensed the rights to build and sell the car on this continent. Before production started, the team of engineers at Auto sport made a few changes in order to appeal to American drivers. The small 1.8-liter Audi engine was dropped, and a Corvette-sourced 6.0-liter V-8 took its place. To accommodate the much larger power plant, the team stretched the wheelbase by five inches (increasing overall length by eight inches). The brakes were upgraded, and the suspension was modified to accept the new running gear. The finished product was called the Deronda G400. Available directly from Sirius Motorsports, it is sold turn-key and according to the company, it is 50-state street legal (when licensed as a component car).
Each Deronda begins as a pile of two-inch diameter (.095 wall) 4130 chromium molybdenum tubes. Stronger and more durable than standard 1020 steel, "chrome moly" is steel that has been alloyed with small amounts of chromium and molybdenum to increase its strength. The tubing is precisely cut and placed on a large jig where it is TIG-welded by hand. Safety is principal, so the frame is engineered with double side-impact protection tubing, and double rollover hoops (four in total). Crash structures are built into the front and rear for additional occupant protection. Once complete, the intricate frame weighs 650 pounds bare.
A custom suspension, comprised of unequal-length control arms with horizontal mounted shocks, is bolted to the rigid platform. Massive cross-drilled Baer rotors are installed with dual-piston caliper Corvette C5 brakes up front (CNC-milled with the Deronda logo) and single-piston C5 calipers on the rear. Aluminum alloy front wheels measure 18Ã-9-inches (wearing 235/30R18 rubber), while the rears measure 18Ã-10-inches (with 285/35R18 tires).
Placed mid-engine in the chassis is a new 6.0-liter LS2 engine (as used in the Corvette C6), mated to a durable Porsche G50 five-speed transaxle, with power delivered to the rear wheels. With stock headers, and environmentally-friendly catalytic converters, the engine is rated at 400 hp and 400 lb-ft of torque. A 14-gallon foam-filled ATL fuel cell keeps the power plant fed, and increases safety (a tank-fed fire-suppression system is optional). The exhaust is fitted with a muffler, but it still lets plenty of the engine's anger out the back end.
The skin of each Deronda is comprised of a mixture of fiberglass and carbon fiber body panels. The head rest, dashboard, rear wing, and fenders are all carbon fiber. Twin minimally-padded fiberglass seats with six-point harnesses are installed, and the windshield is DOT-legal single-piece of laminated glass with a windshield wiper. The entire build process, from tubing to a finished vehicle, takes about eight weeks. The final curb weight is a mere 1,890 pounds.
Simple, yet functional, is the best way to describe the cabin. The dashboard presents only the most critical information. While the vehicle obviously lacks doors and a roof, heat arrives from air spilled around the front-mounted radiator. Small vents, not unlike ports found on light private aircraft, are able to bleed fresh air into the foot wells. Modeled with dimensions similar to the Porsche 996, the cockpit is accommodating even for someone who is 6'2â€³ tall or taller. The seats and pedals are both adjustable for a custom fit to accommodate nearly everyone.
After a perplexing process of flipping switches and pushing buttons, the brawny V8 spins to life and settles to a smooth idle. Stock Corvette headers dump hot gasses into the cats before they are expelled out twin howitzer-looking mufflers. The sound that penetrates the air is a deep irate rumble that will send chills up your spine.
With the clutch fully depressed, we slip the milled aluminum shifter into first gear and slowly release the clutch. Without drama, we pull away. Lacking power steering, the small, flat-bottomed Sparco steering wheel is very heavy at low speeds. The driveway to the main road is steep, but the needle nose of the Deronda offers surprisingly generous ground clearance. As the traffic breaks, we pull into traffic pointing the car down California's famed Mulholland Drive towards the Santa Monica Mountains. Warned about the power under our right foot, we treat the gas pedal as if it were a made from blown glass - we don't need to spin this vehicle just outside the gate. With the road clear, we goose the accelerator. It is immediately apparent that this could be the quickest car we've ever driven.
The engine spools to the called-for throttle input as if the transmission is in neutral, yet the car is firmly in gear. A light touch on the gas pedal is met by the white needles on the primary gauges rapidly sprinting clockwise around their dials. Behind you, the roar of the LS2 seems to scorch the pavement like the DeLorean in Back to the Future. Gearing doesn't seem to have much effect on the acceleration, either. Whether the transmission is engaged in second or fifth gear, 400 lb.-ft. of torque propels the lightweight G400 as if it were being launched from a 12-gauge shotgun.
On public roads, with the wheels wrapped in street tires, the Deronda is seriously challenged for grip (the car is equipped with an adjustable electronic traction control that can be completely defeated). The wide Toyo Proxes T1R rubber on the rears immediately spins under full throttle - initiating the electronic reigns, so we simply avoid the last 40% of the accelerator's travel. Even driven at only 6/10ths, the car offers more power than nearly everything else on the road. The company doesn't have cited official 0-60 mph times, but under the right conditions we're sure it's comfortably in the low three-second range. Deronda says the G400 runs out of gears at an ample 183 mph - well above the top ends of most minimalist competitors.
Redline is a tick under 6,000 rpm, but you simply don't need to go there. The car pulls all the time, regardless of the engine speed or gear. Lug it around town in fourth at 1,200 rpm and it will deliver enough torque to annihilate the random Subaru WRX that begs to race. For all of its power, the engine is surprisingly tractable and easy to control. Drive it gently, and you flow with the traffic without concern. Step on the gas and the Deronda growls before it rips your head off. Rarely do you find a car with a bite that so exactly matches its bark.
Blinding acceleration aside, the overall impression is that the Deronda drives much more like a race car than a street car. Without power assisted steering or brakes, the primary controls feel much heavier that those on any high performance road vehicle. Both hands, and both feet, are constantly interacting with the wheel, clutch, brake, and accelerator. "Involving" would be a supreme understatement.
derondafd 02 opt Deronda G400 A race bred exotic sports car!
After time spent following the roads curving through the mountains, we became much more comfortable in the Deronda. Excellent front visibility allows the driver to precisely place the wheels exactly where intended. While the steering was a chore at low speeds, the effort eased as our velocity increased. The lack of assist soon becomes an asset as the steering feels quick, accurate and very direct.
Our insatiable appetite for the accelerator pedal kept us off the brakes, but eventually traffic forced us to call them to duty. As our speeds were relatively low (50-70 mph in the canyons), we couldn't get a lot of heat into the pad compound. The initial application of the pedal seemed futile as the drilled rotors continued to slide between the pads. Only when our foot really got on it - hard - did the Corvette-sourced stoppers feel strong. This car is fitted with generous rotors and track-ready pads, but it was clear we were underutilizing them. It also needed softer street pads (while there is a cockpit-adjustable brake-bias knob, we didn't touch it).
Open to the world, the cabin was surprisingly comfortable at speed. The driver and passenger sit low in the chassis, and the large, canopy-like windscreen does an excellent job deflecting the slip stream around the cockpit. It was cool outside, but we could feel some warm air spilling into the foot wells. Rearward visibility was poor, even through the tunnel-vision exterior mirrors, and all you can see is the jet-black carbon fiber wing (visibility really didn't matter, as nobody passed us). However, even though the Deronda is smaller than most of the other traffic on the road, we never had an overbearing feeling of being undersized. Quite the opposite, actually, as the incredible power delivery and nimble handling made us feel as confident in traffic as a squirrel running from a small child.
We never tired of darting through the canyons in the needle-nose Deronda. In fact, we felt like a fighter pilot. Our forward view was through a large glass canopy, we were strapped down with thick shoulder harnesses, and the engine's loud roar filled the void left by our wake. Like a jet, the G400 is agile, powerful, and built for speed.
Without a doubt, a prepared Deronda would dominate most conventional sports cars on a race track - a thought that has already crossed the minds of the team at Autosport Development. With a safe, strong, and proven chassis already developed, a closed -cockpit monocoque body for the platform wouldn't be too much of a stretch. We wouldn't be surprised to see something rolling out of the factory in the near future wearing competition attire.
derondafd 13 opt Deronda G400 A race bred exotic sports car!
If you have to question the styling, the choice of power plant, or whether the seats have enough padding, the Deronda G400 is not for you. With a base price of $64,000 (most customers spend about $95,000 by the time they get done customizing), it may be out of reach. If it is in your budget, take note, Sirius Motorsports is on track to hand-build only about a dozen units per year and the Deronda will be a rare site even at an exotic car show. Needless to say, those who are fortunate enough to park one of these very unique vehicles in their garage are assured a giddy smile and an eye-blurring rush with every press of the accelerator.
KTM X BOW:
KTM X-BOW owners wishing to take the extraordinary performance of their 'Ready to Race' sports car to the next level can now benefit from a significant power upgrade. Developed by engine tuning experts ABT Sports line, the upgrade will raise the already-potent X-BOW's peak power to an impressive 300bhp (from 240bhp in standard tune) and boost torque to a formidable 400Nm (from 310Nm), lifting the vehicle's power-to-weight ratio to 380 bhp per tonne. Crucially, the ABT upgrade delivers these increases while retaining the flexibility of the engine, which provides highly accessible peak power and torque over a relatively wide rev band. Combined with the vehicle's light weight and Dallara-developed chassis, the increased power will launch X-BOW from rest to 62 mph in just 3.5 seconds - compared to 3.9 seconds in a 240bhp car. The upgrade - which is the only tuning solution recommended by KTM - will be sold as an aftermarket package and can be retrofitted to all X-BOW models. It costs £5,300 fully fitted (incl. VAT) and comes with a two year warranty - testament to the extensive development testing undertaken to meet KTM's exacting requirements. "X-BOW's race car-inspired chassis and sophisticated aerodynamic package have always given owners the ability to go head-to-head with some of the world's most exotic machinery," comments Jeff Lau, KTM's X-BOW Manager for the UK. "This power upgrade will ensure that X-BOW owners seeking an even more extreme experience can do so in total confidence, building upon the quality assurance of the expert engineering and exquisite finish for which X-BOW is recognized." Existing owners interested in equipping their X-BOW with the factory-recommended power upgrade should contact their nearest service partner, where the part can be fitted by ABT's specialist engineers. Based in Kempten, Germany, ABT Sports line is renowned for carrying out tuning work on Volkswagen Group power trains.
The car is a street-homologated sports car with racing technology, carbon fiber monocoque. The basic version's light weight and the 177 kW (240 hp) engine, the performance values of the KTM X-Bow outstrip those of super-sport cars with more than twice the power: with a deadweight of approx. 790 kilos, the KTM X-Bow accelerates to 100 kph in just 3.9 seconds. By foregoing electronic assistants and today's standard comfort features, the X-Bow offers an unfiltered adventure - aided by its stand alone wheels in the style of monoposto racing cars, transparent technology and the car's reduced concept, i.e. no roof, doors or windscreen. The sports car has only a 70-millimeter, transparent wind deflector. When your 240 HP light weight sports car is not enough, take it to ABT Sports line and they will make it even more powerful! This is the case with the KTM X-BOW that is powered by an Audi sourced 2.0 Liter TSI four cylinder engine. The tuner is offering an upgrade package that will increase the car's out put all the way up to 300 HP. With all this power, the X-BOW can sprint from 0 to 60 MPH in just 3.5 seconds - compared to 3.9 seconds in the 240 HP versions, all for only £5,300.
Cater ham Cars Ltd was founded in Cater ham, England over 40 years ago and currently produces what can be considered as the 'Original' Seven using the Lotus 7 design [Ref. 8]. The chassis is a multi-tube triangulated space frame design with riveted and bonded aluminium panels. The development of the Cater ham has often been at the leading edge of the class. The running gear is all of a modern design with current generation engines and drive trains fitted. The Cater ham is no longer available in kit form but only as turnkey cars. The Cater ham Seven is shown in Figs. 13 & 14 opposite.
Fig. 13 Cater ham Seven [caterham.co.uk]
Fig. 14 [Ref. 4]
Cater ham's new Superlight R300
The Caterham R300.
The Cater ham R300.
November 9, 2008 British lightweight sports car manufacturer Cater ham has released details of a new addition to its 'Superlight' family. The new Superlight R300 is an update the previous R300, which was originally launched in 2002 and fitted with a Rover engine. The new model offers chassis developments and increased engine performance that see the R300 go from 0-to-60mph in 4.5 seconds courtesy of a new 2.0-litre Ford Duratec engine, tuned by Cater ham Power train (CPT) to deliver 175bhp. The latest 515kg interpretation of Colin Chapman's 'lightweight minimalist' philosophy balances power and chassis to deliver an impressive 339bhp-per-tonne.
Translated through Cater ham's proven 6-speed gearbox, the 2.0-litre power plant's 175bhp and 139 lbs-ft of torque is able to spin the R300's bespoke Avon CR500-shod Superlight aluminium wheels to a top speed of 140mph. Amongst a wide range of optional extras, hardened enthusiasts will also be able to add Stack data logging instrumentation, a dry sump oil system and, for track-day regulars, a limited slip differential. The new R300 also borrows a few styling cues and technical evolutions first seen on its 'big brother', the Superlight R500, such as the addition of a similar flush button dash design and keyless ignition system fitted as standard.
Not content with updating its range Cater ham have also announced the addition of another new Seven - the Road sport 175 - which joins the 600cc Ford Sigma driven 125 and 150 in Cater ham's Road sport range. Although it is fitted with the Series 3 chassis and utilizes the same 175bhp, 2.0-litre Cater ham Power train (CPT) Duratec engine fitted to the R300, the new Road sport is aimed at drivers largely focused on B-Road blasts and touring. Instead of more track-focused features, such as lashings of carbon fibre and track-biased suspension and brakes, the Road sport 175 comes fitted with weather equipment and a heater as standard. Other differences include a 5-speed gearbox with longer ratios and 14-inch alloy wheels.
The Superlight R300 will start at UKP 24,995 (US$39500) in component form and UKP 27,995 (US$44400) factory built with delivery starting in spring 2009, while prices for the Road sport 175 start at UKP 21,995 (US$35000) in component form and UKP 24,995 (US$39500 at time of publication) for factory built.
Both the R300 and Road sport 175 are available in a SV 'wide chassis' version, costing an additional UKP 1,750 (USD$2800).
The Westfield self-build kit is based upon a tubular triangulated chassis with bonded and riveted aluminium panel. The chassis is designed to accept different engine options. The chassis design provides two options for the final drive and rear suspension. The solid rear axle choice uses the Ford Escort Mk.2 rear axle located with trailing arms and pan hard rod. The fully independent rear suspension version uses the Ford Sierra differential unit with Westfield manufactured drives shafts. All Westfield kits use the latest wide body chassis and body design.
Fig. 15 Westfield [westfieldcars.co.uk]
The basic way of assessing a chassis design is to establish its torsion stiffness. The torsion stiffness is stated as the torque required to twist the chassis by a given amount. One of the most common styles of space frame is the Lotus or Cater ham Seven type. Most kit cars based around Seven type chassis are in the region of 1000 to 2000 ftlbs per degree of twist. Most small mid engine car space frame designs of similar complexity also fall in this range.
A lot of builders believe that extra bracing in the form of diagonals or welded in panels will just add weight and simply omit it. This can seriously reduce the stiffness of a space frame chassis to the point where even a very basic ladder frame would easily beat it. A properly braced frame can be made out of smaller or thinner walled tubes for the same stiffness thus more than compensating for the extra tubes. My modifications for the Low-cost actually reduce the overall number of tubes and the total weight.
My initial analysis showed that a lot of space frame chassis were less effective, weight for weight, than properly designed X braced ladder frames. The reason for this is that most space frames are far from optimum and that a simple X braced ladder frame is better than most people think. This may surprise you as a lot of hype surrounds space frames and ladder frames seem to have a poor image. This situation is not really justified and it is worth noting that the main structural members of the Lotus Elise chassis are two large beams that are connected by other beams and panels to make a structure that could be regarded as a very sophisticated ladder chassis or as a hybrid ladder frame and monocoque chassis.
Overall a properly designed simple space frame has a small advantage, probably about five percent or less, in weight and stiffness for the complete car over an equally well designed simple X braced ladder frame. A more complex space frame with fully triangulated front and rear suspension regions, engine bay and sill structures may give more advantage but will be harder and more expensive to make. This difference gives an advantage in race cars especially when the budget and analysis skills to produce a good design are available. However for most road cars and some race cars a ladder frame would be perfectly adequate.
Space frames have an additional advantage in both weight and complexity where the chassis panelling forms a significant portion of the bodywork as on many Seven type cars. This maximises the advantages of a space frame by removing the need for the extra weight and complication of additional bodywork and the extra structures needed to support it.
Advantages of the ladder frame that are often overlooked are that the available space and ease of access to mechanical parts is often better and engine exhaust systems are less likely to be restricted by the need to route them around chassis tubes. Additional structures are often required with ladder frames to support bodywork but these can often be designed to brace the basic chassis structure.
The poor image of ladder frames may be due to early chassis design practice which was to use C section chassis rails instead of fully boxed in rectangular section chassis rails. Using C section chassis rails will cause a big reduction in stiffness compared to a chassis made of rectangular section.
To summarise the ladder frame versus space frame issue a space frame equipped car has a small but significant advantage over a ladder frame equipped car assuming the chassis are equally well designed and made. It is not true that all space frames are good nor is it true that all ladder frames are much worse, weight for weight, than all space frames. There is a very big difference between good and bad space frames. This allows well designed ladder frames to equal or better many space frames.
The most common mistakes for space frames are absence of sufficient triangulation or panelling around the front suspension region and the engine bay. Poor triangulation or panelling of the rear suspension region and engine bay is common on mid engine cars. Poor triangulation or panelling of the transmission tunnel is common on front engine cars. It is important to note that for a panel to be structural it should be a welded in steel panel. Panels should be stitch welded or, preferably, continuous welded by stitching twice, the second time to fill in the gaps left the first time.