More books Racing And Sports Car Chassis Design, By Michael Costin you read, more understanding you get, as well as more opportunities to constantly love reviewing publications. Due to this factor, reading publication ought to be begun with earlier.
Get the advantages of reviewing behavior for your lifestyle. The real life, expertise, scientific research, health, religious beliefs, enjoyment, and a lot more can be discovered in created e-books. Lots of authors supply their encounter, science, study, and also all points to show you. Life will be finished if you know more points with reading books. From discussed e-book by on-line, you could give a lot more perks for several individuals. The Chassis Designers Bible, Amen By Ian Carter There is yet to be a book written, that describes the why's and how's of designing a light-weight, high-performance sports car chassis in a more informative, yet pleasantly readable style than "Racing and Sports Car Chassis Design".
There are other, more contemporary titles on this topic, and having read many of them, I have a strong impression that their authors were much influenced by this book; perhaps having studied it in their college and university years.
Allington completed what was to be acclaimed by the industry, and motoring enthusiasts, as the Chassis Designers' Bible. Costin was also a chief chassis designer at Lotus Engineering, one-time home of many of the most creative and innovative thinkers in the history of motor-sports. He later became the Cos' of Cosworth fame. Quite a motor-sports pedigree! The theory and basic principles of chassis design, including methods for chassis stress calculation, plotting suspension geometry, and selecting materials for a winning space-frame chassis are all comprehensively covered.
It is complemented with excellent illustrations and now historical photographs, and the reader will enjoy a revealing treatise from a fascinating period in motor-sports development. Reference to the appendices explaining the essential mathematical calculations, tables of materials specifications and the glossary will assist understanding of the engineering principles, and will be invaluable to the novice chassis designer.
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Translate PDF. The most convenient chassis types, materials and production methods are gathered from literature and represented. Also by considering Formula Student regulation, it is analyzed that how a Formula Student race car chassis must be designed.
This report is mainly constructed of basic approaches and easy methods for first year teams. And also I want to use this opportunity to thank the Hacettepe University Mechanical Engineering Department for the education which I have taken and international experience. Finally I have to thank to all my team mates which we are worked together day-and-night. Definition and History Chassis Types Ladder Chassis Self-Support Chassis Space Frame Chassis Monocoque Chassis Comparison of Chassis Types Material Selection Criteria Mechanical Joint MIG Welding TIG Welding Hybrid Chassis Design Overview CAD Design Analysis Methods This competition is supported by big automotive companies and also Formula One teams and it is considered as the top level engineering competition for students.
The aim of Formula Student series is to incite and encourage young candidate engineers and improve their abilities in the areas of engineering skills, team work capabilities, time and project management and presentations skills.
On the other hand, Formula Student is a very suitable environment for automotive and racing industry to find their employees in future. So the second event of the Formula Student series started in UK in Besides, the given importance to the Formula Student competitions increased each passing day. This drawed interests of big automotive companies and more importantly Formula One teams. Many leading names in the sector began to support and became Patron, judges or volunteers of Formula Student.
All these developments provided to spread all over the world. The competition consists of several events aspiring better learning and self-improvement of students. There are two main entry categories in FS which are Class 2 and Class 1. In this class, teams compete with only their designs. Teams are judged in three static events; Design, Business Presentation as well as Cost and Sustainability.
Teams are also encouraged to produce some parts of vehicle. Class 1 is for the teams which have fully constructed a running car.
This class is more extensive and consists of static and dynamic events. Static events are same with Class 2. Additionally, there is a technical inspection and five tests which are safety, chassis, brake, noise and tilt tests. The teams which pass the technical inspection scrutineering and five tests are qualified for dynamic events.
Definition and History With the first appearance of automobiles in the end of the 18th century, it took almost a century, the development of combustion engine powered automobiles. Before long the first automobile race was organized in United States in www. Being a strong competitive environment, automobile races have taken the lead of faster development of cars. Thus automobile races are good opportunity for the manufacturers. Because they always have to be faster, stronger and safer.
Chassis is one of the most important part of vehicles. It has several functions. It is analogous to skeleton of animals. Chassis hold almost all of the components of vehicle together. At the same time, it serves a safe zone for drivers to protect them. Chassis must be strong enough to remain robust in every operational conditions for its expected life and also be as light as possible to be fast.
With the continuous advancement of technology in terms of analysis methods and production, chassis used in races has become more effective and complex.
In this part, most used chassis types will be compared and the selection criteria will be referred to the appropriate chassis.
Ladder Chassis Ladder chassis is the oldest type of chassis. It is quite primitive and has very simple design. This type of chassis has been used since s and today, very few vehicles have ladder chassis.
They mainly consist of two longitudinal frame member and this design looks like ladder. But ladder chassis are so weak in terms of torsional rigidity.
There are cross members which supports the vehicle to the lateral forces. Their production and material costs are quite low. Self-Support Chassis Self-support chassis, also known as Unibody Chassis are the most used chassis types today. It is widely used especially in passenger cars. The design of this chassis type consists of one main strong structure by integrating frame and body together. The entire body is formed from shaped metal panels. It is easier to weld these panels compared to the conventional chassis and bodies.
Self- support chassis also have the advantage of good load capability. Being fully integrated structure makes the chassis to have well load distribution. Another advantage of this design is space saving and weight reducing. Minimizing wasted material and production processes are valid reason for mass production European Aluminum Association, Space Frame Chassis Space Frame or Tubular Space Frame chassis are made from steel or aluminum tubes integrated together with triangulation.
Main advantage of this design is its three dimensional structure. This structure increases the torsional rigidity of the vehicle significantly. In the triangulated form, there are only tension and compression. The frame members are not exposed to bending or twisting loads Oshinibosi, August 30, Figure 3 - Triangulation in Structures By taking advantage of reducing weight, the performance capabilities of the vehicle are increased.
On the other hand, being a very stiff structure in all directions minimize the body deflection under operating stress. This aspect this helps the suspension geometry to keep the road as much as possible Adams, Monocoque Chassis Monocoque chassis are consists of one primary structure that is the body and frame of the vehicle.
It also gives the vehicle the outer shape of it. These type of chassis are made of composite materials. It has great rigidity to weight ratio. Additional chassis members, apart from those necessary for the primary structure, may be required to disperse point loads into the chassis, and as a basic design feature-since the power unit mountings carry a large proportion of the sprung weight-it is 2 THE PURPOSE OF THE CHASSIS desirable to have good load paths direct from engine mountings to suspension pick-ups to dissipate energy.
On a front-engined car, with engine and gearbox mounted in unit, the location of the rear mounting often presents difficulty-particularly when it is desirable to use a proprietary gearbox mounting. In this case extra chassis members or some form of sheet metal structure may become essential. Mountings for smaller items are almost invariably disregarded in the initial stages of design, but it is a great advantage if all components can be borne in mind all the time.
For instance, it would help to bear in mind two or three alternative positions for the battery, a dead weight of around 40 Ib which can materially affect weight distribution and can be regarded as a useful balance weight.
In a car with two or more seats placed side by side it is structurally preferable to use a front-mounted engine, as the chassis normally provides better supports for this layout. In the case of a single-seater, however, the use of a front-mounted engine driving the rear wheels leads to numerous problems, most of them based on the transmission line. In itself, however, a single-seater chassis presents far fewer problems than a two-seater.
The simplest and most efficient layout is to place the engine in unit with the transmission and this, as a result of experiments with front-wheel-drive racing cars, leads to a rear-engined layout. Front-wheel-drive can function extremely well, and has many practical advantages for passenger cars, but thus far it has not been shown to provide cornering power in line with that of the more advanced rear-wheel-driven sports and racing cars.
In the case of a front-engined, rear-wheel-driven single-seater, the transmission line must pass either beneath or alongside the driver's seat. With the current trend for the centre of gravity to be at the lowest possible point this makes an offset transmission line virtually essential. Numerous complications result, however, such as asymmetrical engine mountings, angles in the transmission line and further complications to obviate power losses and complex offsets in the final drive unit.
The basic alternatives here are either an offset differential unit with unequal length drive shafts or extremely complicated gearing. It is also possible to offset the driver in which case, taken to extremes, the driver may have less feeling of control than when placed symmetrically but unless the transmission is also offset this leads to the production of a car having two-seater proportions.
The position of the gearbox also has an important influence in this respect. If in unit with the engine it is liable to increase the amount of offset required. Thus it is best in this case to have both clutch and gearbox at the rear, with the propeller shaft running at engine speed. This also leads to a reduction of the rotating mass between engine and gearbox and may help weight distribution, allowing the engine to be mounted further back than would otherwise be possible.
These problems have been largely responsible for the swing to rear-engined racing cars in recent years. For 3 1 Single-seater offsets. One of the simplest ways of lowering the driving position-and centre of gravity-on a front-engined car is to lower the transmission line, bringing the drive back up to hub height by means of transfer gears just ahead of the differential unit 2 Complex offsets.
On the Formula One Lotus the centre of gravity was lowered by means of an angled engine and offset transmission and seat. Owing largely to the complications involved this car was not particularly successful 3 The Formula Junior Lola used offset engine, seat and final drive unit in the interests of a low centre of gravity and minimum frontal area.
The transmission layout necessitated the use ofunequal length drive shafts and -as these also constituted suspension linkages-asymmetrical radius arms THB PURPOSB OF THB CHASSIS anyone still contemplating building a front-engined, rear-drive singleseater, however, the simplest method is to avoid complication by using a central propeller shaft passing under the seat and driving the rear wheels through vertical transfer gears.
It might also be possible to use an offset engine layout with horizontal transfer gears. To sum up, whatever type of chassis is used, it should, ideally, be a perfect structure designed to link up the mounting points for all the components that go to make up the car. Chassis History The development of chassis having adequate torsional stiffness is a fairly recent one. The early sports car chassis was constructed on massive lines, and its design owed more to bridge-building than to light engineering.
Even today the chassis of many production sports cars are stiff only in bending. The history of the development of the more advanced types of chassis is an interesting one. Prior to the Second World War almost all sports car chassis were of the girder type, generally with live axles at both front and rear.
In Auto Union initiated a change to twin tube chassis on racing cars, with a layout of this type composed of round-section tube. In the same year Mercedes-Benz used box-section members in a similar layout but, in , they too went over to tubes-in this case of oval section.
At the same time they also "progressed" from independent rear suspension to a de Dion layout, of the type first used in the late nineteenth century. The twin tube chassis, with de Dion rear suspension, remained in vogue for racing cars in the years following the war, and indeed the de Dion axle was not superseded until the end of the s.
The need for increased chassis stiffness was recognised by the addition of tubular superstructure to the basic twin tube layout, but this contributed more to ease of body mounting than to torsional capacity. Early attempts at chassis of the space frame type also appeared at this time, but lacked the triangulation necessary to form complete structures. One came from a small concern with very limited resources and a largely part-time staff, the other from a major manufacturer with an impressive record in both racing and passenger car construction.
Unitary construction has also become fashionable for single-seaters since the introduction, in , ofthe Lotus In its centre section, the modem rear-engined racing car is admirably suited to monocoque construction. The general requirements of the area ahead of the driver's feet can also be met by this type of structure, but it is not well suited for use in the engine bay, the chief problems being lack of torsional stiffness, interference with the exhaust layout and accessibilitythe latter being far more important than some designers seem to think.
As regards torsional stiffness, a great deal can be gained in this sphere by making the engine a structural member. However, this practice is not to be recommended unless the crankcase has been designed for this purpose-in addition to its major function of providing positive location for the crankshaft and cylinder head s.
Furthermore, a complex series of mountings at both front and rear is required to deal with both torsional and bending loads, whereas only two front and one rear mountings are normally necessary when the engine is not used structurally.
The practice of using the power unit as a structural member was taken to its logical extremes on the first monocoque Ferrari, the engine aided by a fabricated bulkhead bolted to it in the vicinity of the rear suspension being the only structural component behind the seat back bulkhead, where the chassis proper stopped short.
However, the Ferrari has vestigial "wheelbarrow arms" beneath the engine, which presumably take some of the bending loads and help to locate the rear bulkhead. With a wide engine, the only satisfactory alternative to the use of rigid mountings may well be the use of a tubular structure for the engine bay. There are difficulties in taking out the point loads involved into a sheet metal centre section, but it is possible to do this with careful design and it should also be possible to layout a space frame for the engine bay which will provide adequate torsional stiffness without adverse effect on exhaust layout or accessibility-both of which are liable to suffer when..
It may be necessary to make some members detachable, to facilitate installation and removal of the engine, but it is possible to do this without any loss of torsional capacity. A tubular frame may also provide better load paths from the rear bulkhead to the centre section than either the engine or the combination of engine and wheelbarrow arms.
A useful alternative to the monocoque for a two-seater is the backbone chassis, as used on the Lotus Elan front-engined and the Lotus 30 rearengined. Although this type of chassis requires separate bodywork it has a great deal in common-from a structural point of view-with the Lotus style monocoque, the central part being compressed into a single..
Both types of construction owe a great deal to aircraft practice; this is hardly surprising, as a great deal of time and money has been spent on research in this sphere-far more than in the car world. Outwardly it may appear strange that the most advanced sports car chassis of today are the work of specialist firms rather than major manufacturers. It is all a question of economics. The tubular space frame, although involving little in the way of tooling costs, is relatively expensive to manufacture, requiring a great deal of skilled welding.
The only comparable alternative, unitary construction, involves very considerable tooling costs and is less satisfactory for open cars than saloons owing to lack of bracing in the cockpit area. But it has the great advantage over all other designs that separate bodywork is not required. By comparison, the conventional chassis is much simpler to make and involves far fewer snags in the fitting and servicing of mechanical components.
For ultimate chassis performance, however, there is no substitute for torsional stiffness, and this can only be provided by the more advanced type of layout. Snspension History As has been mentioned above, the development of chassis having adequate torsional stiffness is a fairly recent one.
Sports cars of an earlier era made up for this deficiency by using extremely stiff suspension; many, in fact, gave the impression that there were no suspension springs in their make-up. Today the ride is mOre acceptable, but the cornering speed of the mass-produced sports car has not improved as much as might have been expected-particularly in view of the tremendous advances in tyre design.
On many production carS one of the only ways of improving roadholding is the fitting of stiffer springs or anti-roll bars-both of which have much the same effect. This applies particularly at the front, where the types of independent suspension most commonly used are subject to considerable camber change on roll.
Increased roll stiffness-whether via the springs or the anti-roll bar-increases the adhesion of the front tyres and thus improves the car's roadholding by bringing the cornering power of the front wheels almost up to that of the back ones, which are kept almost upright on their live axle. Such perfection is only achieved on very smooth surfaces, however. With stiffer springs at the front the tyres frequently lose contact with the road on rough surfaces, while each rear wheel reacts to every movement of the other one.
Stiffened or flattened rear springs may also show some advantages in terms of circuit speeds, but a car fully modified in this way usually suffers the penalty of a very harsh ride. On the whole, the production sports car of today offers a reasonable compromise between roadholding and ride. With a more up-to-date approach, however, both of these conflicting features can be vastly improved at one and the same time.
The basic requirements are a stiff chassis, advanced independent suspension and soft springs. Thus, disregarding the torsionally inefficient girder type, the simplest form of chassis is the twin tube or ladder frame, with two large diameter side members and either lateral or diagonal bracing, or a mixture of both, in either similar or smaller diameter tubes; the latter provide both increased torsional rigidity and mountings for main and subsidiary components.
The most common material for this type of frame is 3 or 31 inch 16 gauge mild steel tube, and the normal method of construction is by electric or gas welding. Care is necessary when joining tubes of differing diameters to avoid local failure, and this is normally overcome by the use of gusset plates as illustrated in fig. The twin tube type of chassis, although relatively heavy and lacking torsional stiffness, is easy to make and very durable, due to the use of heavy gauge material.
Furthermore, it is not prone to accidental damage and provides good accessibility of mechanical components. By the use of sub-frames it is fairly easy to arrange mountings for all components. In designing a chassis of this type it is necessary first of all to locate suspension, engine, gearbox, differential and seat mountings.
Having decided these, it is fairly easy to find the optimum position for the chassis tubes. With a twin tube car this is not very critical, as torsional stiffness does not alter greatly with varying tube positions. The load capacity of such a chassis in bending is poor, as the frame has to cater for quite high loads and round tube is not suitable for heavy loading in this manner.
The torsional capacity also is very low, because the torsional stiffness of the chassis depends solely on the section of the tube used. Cruciform bracing helps by taking out torsional loads in bending.
Bearing in mind the loads involved, oval section tube would possibly prove better than round for secondary installations where only bending loads are encountered. Oval tube is not satisfactory for main members, however, because of its lack of torsional rigidity. For any given weight of tubing, the torsional stiffness of a cross section of twin tube frame could be improved by using a single tube of slightly greater diameter.
A twin tube chassis must always be relatively heavy, owing to the extra weight made necessary by the low efficiency of the frame. Complication in construction is kept to a minimum because of the small number of individual members involved, their greater wall thickness and the use of arc welding-all of which cut down the cost of construction.
In addition, in this type of chassis the minimum of distortion due to welding is encountered during fabrication. With a twin tube chassis it is important to build up a front suspension frame which gives adequate support to the suspension units and at the same time transmits suspension loads into the main chassis structure.
In this instance square or rectangular section tube may well be better than round tube from the design point of view. Much the same can be said for rear suspension if coil springs are used, but with independent rear suspension a load-carrying frame is required in the centre of the chassis, and this must be capable of feeding transmission loads into the main structure. One heavy cross-frame, usually located at the scuttle on a front-engined car, should provide support for such relatively heavy items as the battery, steering column, body, door hinges, flame-proof bulkhead and brake, clutch and accelerator pedals.
For simplicity, cheapness and general ease of building, a twin tube type structure is quite satisfactory for a low- or medium-powered road sports car, and in this particular application could possibly be more satisfactory than a high performance chassis structure.
However, because of the current rate of chassis development, the twin tube frame is not advised for any serious competitive motoring of National or International class. Multi-tnbular Chassis See fig. In practice, however, the term can perhaps be best applied to those chassis which utilise four main side rails but cannot be classified in the true space frame category.
Multi-tubular frames are basically of very low efficiency, but have proved to be a successful compromise between the twin tube chassis and the space frame in terms of both stiffness and production cost.
With a multitubular layout, relatively large section tubes are necessary to attain stiffness from welded joints and from the torsional rigidity of individual members. The load capacity of a multi-tube frame in bending is generally quite adequate, provided there is sufficient diagonal bracing throughout the length of the chassis to prevent lozenging.
Torsional capacity depends largely on the number of members and the diameter and section of tubing employed, but is very much inferior to that of a space frame. An effective 10 5 A multi-tubular sports car chassis-the Cooper Monaco. This consists of four tubes, of relatively large diameter, linked by a series of unbraced bulkheads I the top right-hand member also acts as a water pipe. Accessibility is hardly likely to be as good as on a twin tube car, but this depends largely on the design.
Durability depends mainly on weight, but even a heavily-constructed chassis of this type is more liable to structural failure than a well-designed lightweight space frame because of the bending loads taken by the welded joints.
Chassis of this type can also be very difficult to repair after even quite slight impacts, owing to the fact that loads are transmitted throughout the frame rather than restricted to a small area, as is often the case with a space frame. Construction costs are similar to those for a space frame, but unless the chassis is made to wide manufacturing tolerances and the brackets are fitted afterwards, irrespective of their position, it is sometimes extremely difficult to make the chassis and the components fit together.
Experience generally shows that it is very difficult to keep a chassis of this type dimensionally accurate during manufacture. In the multi-tube category can be included many chassis which are normally described as being of the space frame type but which are, in fact, merely four-rail chassis with diagonal bracing where convenient.
Conversely, as very few true space frames have ever been made, it is necessary to consider in this category many chassis which come near to the ideal but with some compromise in important areas.
Of these, the cockpit of a sports car is usually the most critical area and the torsional stiffness of almost all space frames could be improved by as much as per cent by running a diagonal across the top of this bay. In general, uniform stiffness is essential for a proper structure, and if one part is too stiff the concentration of loads and deflection at one point may lead to fatigne failure.
Although in some respects the multi-tubular frame is an advance on the twin tube chassis, it is not to be encouraged, as it is neither simple nor efficient. The Cooper racing car may be cited as the exception which proves the rule.
Space frames See fig. Unitary construction may be superior in some instances but there are many factors against it, as will be shown later. As regards the space frame, it is difficult to imagine a chassis of this type having adequate torsional rigidity without automatically having ample rigidity in bending.
However, the criterion of chassis design-and in fact the primary function of a high-performance chassis-is torsional rigidity. In a sports car chassis it is almost impossible to arrive at a true, complete structure because of the necessity to compromise.
The best example of a space frame chassis from the point of view of torsional rigidity would be a square-section rectangular box, with ends, sides, top and bottom trianl! This would be the lightest, stiffest, simplest and cheapest 12 THI! Thus a chassis has to be split into bays, preferably two, but normally compromise creeps in, making three or four bays simpler from the point of view of localising the effects of the compromise.
However, a major advantage of the space frame is that, as the very best use is being made of the material, the minimum of material is required. In over-all car design, accessibility is almost as important a factor as chassis rigidity, because it is essential to be able to service the car and to get all components into or out of it with the minimum of delay.
If a chassis member-usually a diagonalinterferes with this, it can be made removable. In some cases the engine can be used as a chassis member but this is to be discouraged because of difficulty with engine vibration and the need for rigid mountings. Among other problems in this department are complication of the exhaust system, owing to the need to avoid chassis members, and the difficulty of accommodating carburettors. In addition, the fitting of the rear axle is made more difficult by a multiplicity of tubes, especially if independent or de Diontype suspension is used, when the drive unit is mounted centrally and maintenance work must be carried out at arm's length from above, behind or at one side.
A well-made space frame chassis should be very durable. The only danger of failure due to long service is likely to come from within the tubes because of internal rusting and corrosion.
This can be avoided by suitably treating and sealing the insides of tubes, although pop-rivet holes sometimes confuse the issue in this case.
Impact resistance should be good in the case of minor bumps, as damage should be limited to the bay receiving the blow. Major impacts are absorbed progressively, each bay taking part of the strain until it can no longer accommodate the rapidly rising load.
Thus in the case of a high-speed collision, although the car may be extensively damaged, the fact that it slows down progressively often minimises injuries to the driver. From the production point of view the space frame is probably the most expensive tubular chassis to make, because of the number of tubes used and the amount of welding involved. But it is undoubtedly the most efficient. Unitary Construction See figs. This category includes what are basically sheet metal platform chassis supplemented by superstructure which also provides stiffness.
In large quantity production this is probably the best method of construction. For limited production, however-less than a total of cars-the very 14 7 A cutaway drawing showing the general layout of components in the Lotus Elite Series Two.
Smaller scale production should be economically possible using resin-bonded glass-fibre, but this type of construction is in a very early stage of development.
In the course of design, each panel or bay of a unitary construction chassis must be stabilised to carry out the function of transferring loads. The simplest way to achieve this would be to use a large, round section tube with the ends blanked off. Such complications as holes for the doors, boot and bonnet cause this type of chassis to depart even further from the ultimate, while practical considerations generally make it necessary for the bodywork to be tapered off at each end.
Any operation on a tube, such as tapering it or cutting holes in it, must have adverse effects on it structurally. With flexing, holes crossing load paths change their shape. Since there must be holes, despite the reduction in efficiency which they cause, the design must incorporate additional frames and bulkheads to stabilise the surrounding areas. The use of this type of chassis would seem to offer many advantages, to judge from the developments carried out in recent years in aircraft manufacture.
Such a structure can be made very stiff and extremely light-an essential feature in aircraft design-and in a car of this type 30 gauge material would probably be quite adequate. It is perhaps not commonly known that the engines of the De Havilland Comet are hung in stabilised 26 gauge stainless steel. The load capacity of a unitary construction chassis in bending should be extremely good, because bending loads are resolved into pure tension and compression in the undertray and roof, to which type of loads these areas are ideally suited.
Such a chassis should also be very good from the torsional point of view, but in practice everything depends on general and detail design around the apertures. This is particularly true in the case of an open car, which lacks the diagonal bracing provided in a closed car by the roof. Even here, however, with careful design adequate torsional stiffness should be available.
Weight should be lower than for any equivalent chassis because, with good design, a far greater proportion of the weight of the material can be made to carry loads than is the case with a separate chassis and body. In general, a unitary construction design should be stiffer than an equivalent tubular space frame and body for the same weight, or lighter for similar stiffness.
Accessibility depends on the design, and this in tum depends on the degree of compromise reached between chassis stiffness and practicability. Durability depends on operating conditions but should be good, all other things being equal, while accident damage should be localised-given good design-making the cost of repairs fairly low. As has been mentioned in Chapter II, the type of production envisaged has a considerable influence on the type of chassis which can be used for any given car-and therefore on the materials which can be utilised.
Unitary construction in pressed metal would be ideal for many limited production cars, but the cost of tooling renders it impractical. Unitary construction in glass-fibre or wood is more feasible in such cases, but both materials are relatively so new in this application that the use of separate chassis and bodies remains the simplest solution in the majority of instances. Despite the recent trend towards monocoques, there still seems to be a considerable future for tubular steel chassis.
For such purposes a wide variety of alloy steel tubing is available, ranging from high quality chrome molybdenum and nickel chrome steel to the ordinary mild steel used by the majority of specialist sports and racing car constructors. Each of the different types has its own special properties and uses. Twenty-five ton mild steel is quite suitable for welded tubular structures of the space frame type, but some manufacturers use a material which approximates to aircraft T45 specification, a manganese steel alloy which is particularly suitable for welding.
Chrome molybdenum steel is generally used for twin tube chassis, but in this case manganese steel would possibly be even better, because it retains its physical properties during gas welding much better than do other steels. If the higher quality ton steels-chrome molybdenum and nickel chrome-are used, electric welding becomes almost essential.
At this point it might be appropriate to digress a little to consider the respective merits of welding and brazing. Both are widely used, and recent developments in nickel bronze welding and manganese bronze welding techniques-together with improvements in the composition of the basic material-have resulted in joints becoming superior in performance to the original welded joint. In this context it is important that bronze welding is not confused with brazing.
Welding Welding is a method of joining two steel tubes together by heating them to melting point locally with an oxyacetylene flame, forming a weld fillet or puddle, and keeping this constant by adding filler rod as necessary.
In general a similar method is followed for nickel bronze or manganese bronze welding, but these alloys have a much narrower heat range and greater care must be taken with them, as insufficient heat will cut down penetration and therefore the strength of the joint, whereas overheating is equally bad due to intergranular penetration of the filler rod into the surface of the steel. This not only makes a weak joint, but at the same time considerably weakens the affected steel component.
It is difficult to detect a weakness caused in this way and thus the strength of the chassis depends largely on the skill of the operator. Brazing Brazing consists of building up general heat, of a lower order than that required for welding, and applying filler rod in a stroking manner. As soon as the latter runs into the joints the area can be considered per cent treated. Very similar to brazing is silver soldering, which does much the same job at lower temperatures.
In this case extreme cleanliness and adequate coverage of flux is absolutely essential. Whichever method of making joints is employed, the strength and life of the chassis are largely dependent on the cleanliness of the parts to be joined and the general preparation which is carried out before each stage of the work is commenced. In conjunction with a space frame type chassis it is often desirable to use the undertray and other body members as load carrying panels.
For such purposes clad materials-generally high-performance copper-based alloys, with high purity cladding either side for protection-are usually the most suitable. These are normally secured to the basic chassis structure by pop rivets. For this purpose, and also for general body shape panels, it is also possible to use various alumiuium alloys.
These fall into two different classes: copper alloys, which may be heat-treated but not welded, and manganese alloys, which may be welded but are not normally heat-treated.
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