Strengthening the body: purpose, existing options. What, where and how is done to strengthen the body? For whom body reinforcement is especially important

12.06.2019

Salon

Introduction

The rigidity of the body is its property to elastically resist external static and dynamic loads that occur during the operation of the car. The higher the hardness, the better handling and maneuverability of the machine, especially on high speeds. With an increase in rigidity, the comfort of the car increases - due to the reduction of vibrations, the absence of squeaks from panels and upholstery, etc. That's why the body modern cars tend to be tougher.

When designing a car, several types of body stiffness are calculated - for torsion and bending (longitudinal and transverse). The ability of a body to resist the working loads acting on it is characterized in bending by the value of maximum deflection, and in torsion - by the angle of twist along the length of the base. However, the maximum deflection and angle of twist over the length of the base obtained as a result of calculation or testing on the bench cannot be used for comparison. this body with the bodies of other vehicles having a different base and a different nominal load.

Therefore, the concepts of specific torsional and flexural stiffness are introduced. The specific torsional stiffness of the body characterizes the resistance of the body to twisting and is the ratio of the torque to the angle of twist of the body along the length of the vehicle base, multiplied by the size of the base. For cars specific torsional rigidity of the body is 130…300 N*m 2 /?. The specific bending stiffness of the body characterizes the bending of the body in the vertical plane and is the ratio of the load to the deflection of the body, multiplied by the size of the vehicle base to the third power. For passenger cars, the specific flexural rigidity of the body is in the range of 850 ... 2200 N * m 3 /?.

Rigidity largely depends on the type of body (sedan, hatchback, etc.), design ("geometry" and the method of attaching wings, bumpers), car dimensions, number of doors, window openings, and even the position of the rear seat backs. The method of fastening the windshield and rear windows: their gluing increases the overall rigidity of the body by 20-40%. Improve this characteristic and additional power elements- for example, spacers-amplifiers between the rear or front suspension strut cups.

Most modern passenger cars have one-piece steel load-bearing bodies frameless design, which reduces their weight. The rigidity of such bodies is ensured by the presence in them special elements- spars, longitudinal and transverse beams. To increase the rigidity of bodies made of thin sheet steel, welded box-shaped parts are widely used, as well as power struts and racks, which are given a certain shape and section. The greatest rigidity in sedan-type bodies, the smallest - in hatchbacks and elongated station wagons. Additional strengthening of the body is usually subjected to sports cars: additional amplifiers-struts are installed on them, and in the cabin - a power safety cage made of thin-walled steel pipes.

After 4-6 years of vehicle operation, the rigidity of the body decreases markedly due to corrosion of metal elements - both power and cladding. Especially quickly rust affects thin-sheet parts connected spot welding. Violation of the rigidity of the load-bearing elements of the body reduces its overall strength and can make further operation of the car dangerous.

How some elements of the car affect the rigidity can be seen on the example of the VAZ-2111. When the rear seat backs are fixed, compared to their unfolded state, the rigidity of the body is 29.4% higher (the initial value is 6501 Nm/deg). When installing an additional strut-reinforcement of the rear beam (closed U-shaped arc), the rigidity increases by another 43.9%.

Body stiffness can be assessed by comparing this characteristic of new and old cars. To do this, jacking up the body new car at rear wheel at point B to a certain height H, we measure the distance h from an arbitrarily chosen point A of the body (y front wheel) to the ground. We repeat the same procedure with the old car. If, when its body is raised at point B to a height H, the value h turns out to be less than that of a new car, then the body is "twisted", i.e. he lost his toughness.

The rigidity of the body can also be estimated by another method - by the magnitude of the linear deviations of the control points of the body from the initial position. The car is jacked up until one of the wheels is hung out and the changes in the door gaps are monitored. With sufficient rigidity of the body, they should not change, and the doors should not jam.

During bench tests, the rigidity of the body is measured by the magnitude of the force that causes its permissible deformation. If a torsional force of 1 ton is applied to a car with a body rigidity of 6501 Nm/deg, the deformation will not exceed 1.8 degrees. The values of deformations in the conditions of auto production are measured by a special technique using strain gauges.

1. Ways to ensure the rigidity of the bodies

Strut front.

This is an element of the power structure of the front suspension mounts.

Front struts are the most common type of body reinforcement, its advantages are obvious - ease of installation, low price, visual appeal and a fairly strong increase in the rigidity of the front of the car. Their purpose is to reduce the deformation and movement of the body cups when turning the car. The installation result depends on the vehicle. If its design is generally balanced, then the result, most likely, will not be visible. But for others this device strongly recommended. For example, for the VAZ "tenth" family. Not only the racks "walk" there, but the entire bulkhead shield is deformed! By the way, there is also a special amplifier for it, but more on that later. On the market now you can observe an abundance of front struts, but only the material and method of attachment are fundamentally different.

The usual spacer works exclusively in compression, but you can make it work in torsion, for this the cup is additionally reinforced with one more element - scarves (special thick steel plates). As a result, the spacer begins to work also in torsion. Kerchiefs can also strengthen places wheel arches, suspension struts and stiffeners of the entire body, for the most part, for this you will have to disassemble almost the floor of the car, at least the entire interior for sure, so this technique is used mainly on racing cars.

In addition to this, to additional element front struts can be attributed to the so-called "rods". A rod is a special movable mount connecting the engine and a strut, in addition to this, there are rods connecting the engine with other "strong" elements. This element works mainly during engine braking and sharp starts, the effect is a decrease in the movement of the power unit under extreme loads, a decrease in the car's withdrawal during a sharp start, a decrease in the movement of the gearshift lever handle, and, of course, an increase in the overall rigidity of the body. The disadvantages of using rods include an increase in the noise level in the car

bottom brace

The lower strut reduces the movement of the front suspension arm bracket, reduces the stress generated in the arm bracket and the spar-to-floor connector. Taking part of the load on itself, the lower strut takes the body parts out of the zone high voltage. As a result, improved handling, stability, increased body life. Installation is quite laborious.

rear brace

Reduces the movement of the rear mount cups, increases the overall torsional rigidity of the body. Result: improved handling, stability. The main thing to consider: the rear strut gives effect only if it is fixed to the power elements of the body, and not to intermediate elements (seat mounting brackets, for example). The rear strut is also quite easy to install and dismantle, but there is also negative points: firstly, this is extra space in the cargo compartment, and secondly, there are pitfalls, the rear strut can increase understeer, especially if rear end the machine is reinforced with some other elements. If the car is stock suspension it is better to refuse to strengthen the rear or to strengthen it with only one stiffening element.

In addition to struts, there are many more ways to strengthen the body - increasing welds, reinforced subframes, stabilizers roll stability and crossbars, various reinforcing elements in places of weak rigidity, designed for specific model and, of course, frames.

Enlargement of welds and welded elements.

Enlargement of welds. The fact is that the body on the conveyor is welded by spot welding, i.e. gaps remain between welding points. Naturally, the denser these points are, the more rigid the structure. However, their increase is hindered by technological problems in production and the complexity of their implementation without special tools. But this problem is easily fixed by a skilled welder with decent equipment. The main thing is not to run into an unskilled welder and not violate the physics of the body. It is also common to weld new additional iron elements into weak areas of the body.

Stabilizers and cross bars

These units are also present in stock and have many properties that affect handling and comfort, so usually factory cars have intermediate ones, so to speak, not too soft, not too hard. There are two options for their improvement - reinforcement and replacement. Side effects - increased noise, sensitivity to irregularities and all the same positive properties: handling and rigidity. It is strongly not recommended to install stabilizers, crossbars in tandem with the rear strut, especially on the stock suspension.

Subframes

Subframes are in many ways similar to stabilizers and crossbars, the difference is only in globality, for some versions of the subframe, serious improvements will be required to the entire front of the car - overcooking and cutting, glasses and even shock absorbers are being redone, and such work does not look very friendly. But the effect! You can completely change the geometry of the suspension, improve stabilization by increasing the castor, increase the track and, as a result, stability and controllability. Rigidity, of course, will also increase.

safety cage

car body rigidity frame

frame, in racing car, performs not only its direct functions to protect the pilot, but also superbly strengthens the body. It is mandatory for use in any racing car, the difference is only in its complexity (although the obligation appeared not so long ago in 1994, before that the installation of the frame was a purely personal matter). The frame is a combination of rigidly interconnected steel (steel with temporary resistance on rupture not less than 45 kg/sq. mm) of cold-drawn seamless pipes, for example 30HGSA. By type, frameworks can be roughly divided into two categories: homologated and non-homologated. You can install the first ones in your car and you can be admitted to official competitions. However, it is very complex and causes certain difficulties, which we will discuss below. The second type is "civilian" frames, simpler and naturally cheaper.

According to the type of installation, two types can also be distinguished - welded and collapsible. The former are welded directly into the power structure of the body, i.e. it will be impossible to extract it from there without a "grinder". In the second case, only loops are welded into the body, and the pipes themselves are bolted to them. In this case, the rigidity is slightly lower, but it is possible to remove the frame. I note that almost all the cars of the USSR circuit racing championships of the 70-80s had a removable frame. Pipes (or arcs) in the frame can be divided into main and safety. There are "mixed" options, for example, where the main frame is welded in, and the arc near the seats is removed. You can make the frame yourself (naturally not homologated and possibly extremely dangerous, not safe), or you can purchase a ready-made kit. The main side effect of a frame is weight. The average frame weighs about 40 kg, which is quite a lot. Plus, the deterioration of visibility and landing-disembarkation, as well as only non-elastic ones can be used as belts multi-point harnesses. So in everyday use this thing will cause certain difficulties, well, but for the most main problem is the difficulty of obtaining a technical inspection, if you have a frame installed, you will have to go through more than one instance. The carcasses have a fairly complex structure and various gadgets, such as pipe wraps, which protect the rider from injuries that the carcass can cause during an accident. In civil tuning, frames are more often used for beauty, for example, in Germany they cost almost every second tuning car. If you are racing, the issue of the frame is solved by itself, but before installing it in civil car, you need to think a hundred times, in addition to worsening visibility and physical inconvenience, a safety cage can play the role of a danger cage. If in racing a frame can save you from a terrible accident while preserving living space, then in life it can kill. Frames allow you to avoid some traumatic factors in favor of others. living space is preserved, but the installation of the frame excludes airbags, and inelastic multi-point belts expose the pilot in case of accidents to significant overloads that may well kill (for example, a break internal organs), but the frame reinforces the body as much as no other element, the same WRC race cars there is nothing more than a frame on which the body panels are planted and these facts make you think.

The power unit is rigidly connected to the body.

Even in motorsport, such a method of increasing body rigidity is widely used as the inclusion of units in its power structure, for example, an engine, gearbox and main gear. This means that they are all rigidly connected to the body, which also greatly increases the rigidity. For example, similar solutions are found in almost all "formulas". In general, the ancestor of this idea was the legendary Colin Chapman, the founder of the Lotus company, who first brought the idea to life on the Lotus-25 Formula 1.

Folk ways.

There are also folk ways, for example: the openings of the sills and spars are filled mounting foam. The method is cheap and angry. In the pros, a slight increase in rigidity, in the minuses - the lack of ventilation and, as a result, increased corrosivity. Also, when replacing these parts by welding, there is a risk of fire.

Conclusion

The rigidity of the body is significantly affected by how it is installed power unit. Therefore, the difference in results is higher for cars with a classic layout - there the torsional rigidity is increased by the front suspension beam. But in front wheel drive cars with a transverse engine and McPherson-type front suspension, a noticeable increase can be given ... by the back of the rear seat! For example, in the "eights" and "nines" the rear seat increases the rigidity of the body by about 1000 Nm / deg due to the fact that the back is solid and rigid, and on the long-suffering tenth family the back is separate and this 1000 Nm evaporates. Therefore, VAZ recommends that owners drive as rarely as possible with a folded back seat-- the body at the same time is weakened and resists torsional load worse. In fact, two enemies can be distinguished in tuning - weight reduction and body rigidity, and these are mutually exclusive things, fighting for weight reduction, you can reduce rigidity, and what more important question not unambiguous.

Indicators of the Lada Kalina model

ATTENTION! Found a completely simple way to reduce fuel consumption! Don't believe? An auto mechanic with 15 years of experience also did not believe until he tried it. And now he saves 35,000 rubles a year on gasoline!

The car skeleton of Kalina was designed taking into account the most important canons of industrial safety. Approximately twelve percent body elements on this domestic car are made of high-strength steel. More than half of the iron is covered with zinc. For comparison, for example, on the popular "top ten" only 33 percent of iron was galvanized.

As for the liquid / c, then Kalina's figure is as much as twenty percent higher than that of the same “ten”. The PB of the Lada Kalina sedan, even without the use of pillows, has 3 out of 5 stars according to the Euro crash test system.

Despite a large number of critics of Kalina, designers and engineers of the domestic automobile plant regularly make improvements. In particular, if we take a closer look at Kalina of the second generation, we will see important points.

For example, what a successful exterior is worth - more solid, aggressive and, of course, attractive. All this was achieved with simple tricks: slightly raised the hood, added more chrome lining and improved appearance optics.

Now, as for the management itself. On the former Kalina, it was worth turning the steering wheel to the right and left, as the car began to roll over, although it retained the straightness of movement. It is not known whether anyone dared to experiment with the steering wheel on bad roads, because it threatened almost a "changeling".

The new Kalina will definitely not give such a reason, since in addition to increasing the value of ZhK / c, a clear steering adjustment was carried out. As a result, it became easier to get around road bumps, bumps and pits.

Interesting. acute steering helped to make the following settings. The “short” rack technology mastered on foreign cars was used, and instead of four turns of the steering wheel, only three were left. And another change concerned more rigid fasteners.

One more fact is noteworthy. Previously, the fixation of the steering was carried out by means of rubber bushings. The technology is proven, but clearly outdated. And at AvtoVAZ they decided to try, however, only on the left rail support a more rigid method of fastening. This immediately paid off, the stiffness of the steering system increased by as much as 25 percent!

AvtoVAZ engineers did a good job adding also a new compression buffer rear suspension. The item has advanced features, reducing rolls by several times. Together with the increased rates of liquid / c, this gives a powerful effect, and more and more Kalina began to resemble Grant with her confident “taxiing” and smooth operation pendants.

Lada Priora

Next domestic model, produced at the Volga Automobile Plant, is the Lada Priora. Today it is produced in 4 body variations. Priora Coupe is also present in the line of models - it has not won, however, any other popularity among Russians.

An important parameter of the body of the Priora, again, is the value of zhK / c. It is noteworthy that for Priora this figure is 12,000 Nm / deg in the sedan version. For other variations, except for the coupe, it is one row lower.

Despite this, there are general indicators for all 3 models, implying body dimensions. So, the same for all body types (except for the coupe) wheelbase, ground clearance and width. As for the length, we recall that the sedan indicators are 4350 mm, the hatchback ones are 4210 mm, and the universal ones are 4340 mm. The body height is also different: sedan - 1420 mm, hatchback - 1435 mm, and station wagon - 1508 mm.

Initially, the roof, hood and trunk were considered the weak areas of Priora bodies. It is for this reason that experts insist on the mandatory treatment by the owner of the car of all internal surfaces of problem areas with anticorrosive.

Priora body protection against corrosion is given for 6 years. In practice, this period is determined by: zinc coating of thresholds, bottoms and arches, as well as the use of low-alloy steel.

Indeed, practical experience has proven that the body of the Priora is incredibly resistant to corrosion. If problems begin, then bumpers fall into the risk group first of all, then bubbles form on the paintwork in winter time years, the paint peels off.

12,000 Nm / deg on the Priory sedan is not a big value. Even the VAZ-21106, not to mention foreign cars, this figure is higher. Thus, it would be good for Priora owners who prefer active driving to strengthen the car frame. In particular, reinforcement should include the installation of strut braces and the modernization of the STC on the axle at the rear.

Lada Granta

Grant's liftback is a 3-volume body, meaning good combination luggage cover with rear window. It is noteworthy that in the era of the USSR, liftbacks as such did not exist. There was such a model - IZH-2125 Kombi, but it only embodied some liftback ideas. In fact, such a word was not legalized in the CAS, although there were such concepts as fastback, phaeton and even bregam.

Thus, the Lada Granta Liftback restores historical justice, because in addition to the new name, the car was produced just at the IAP, now referred to as the OAS.

Note. Izhevsk Automobile Plant today it represents more a branch of the Togliatti enterprise, which does not engage in its own developments.

Liftback is not just a word. So, given type the body looks good in terms of LCD performance. This figure has become twice as high as that of hatchbacks, although less than that of sedans due to design features.

In particular, the difference in design features between the liftback and the sedan lies primarily in the "rear cross member". The liftback does not have this part at all, it is not provided for, and for sedans it passes behind the back of the rear sofa.

Note. In principle, the crossbar could be put on the liftback, but in this case all the convenience associated with loading into the trunk would disappear. The car would have lost half its practicality, which is unacceptable under any circumstances, even for the sake of the performance of the LCD.

Trying to somehow compensate for the loss in the housing complex, the engineers went to the following. They added amplifiers in some places, thus increasing the figure significantly, and only slightly falling short of the sedan's result.

In addition, due to the introduction of amplifiers, the liftback became 15 kg heavier, and this, in turn, had a negative effect on the torsion indicator.

Car body stiffness table

car model	Rigidity, Nm/deg
Alfa Romeo 147 3d	18800
Alfa Romeo 147 5d	16250
Alfa Romeo 156	18800
Alfa Romeo 159	31400
Alfa Romeo 166	24400
Alfa Romeo	17650
Aston Martin DB9 Convertible	15500
Aston Martin DB9 Coupe	27000
Aston Martin Vanquish	28500
Audi A2	11900
Audi A8 D2	25000
Audi A8 D3	36000
Audi A8 D4	45000
Audi R8	40000
Audi TT Coupe mk1	19000
Audi TT Roadster mk1	10000
Audi TT Roadster mk2	22000
Bentley Azure	18000
Bentley Continental Supersports	24000
Bentley Flying Spur mk2	36500
BMW 7 series E65	31200
BMW 7 series F01	37500
BMW E34	17200
BMW E36 Touring	10900
BMW E39	24000
BMW E46 Convertible	10500
BMW E46 Coupe	12500
BMW E46 Sedan	13000
BMW E46 Wagon	14000
BMW E60	24000
BMW E90	22500
BMW F10	37500
BMW F30	25000
BMW X5 E53	23100
BMW X5 E70	28000
BMW Z3 mk1	5600
BMW Z4 Coupé mk1	32000
BMW Z4 Roadster mk1	14500
BMW Z8	40000
Bugatti EB110	19000
Bugatti Veyron	50000
Chevrolet Corvette C5	9100
Chrysler Crossfire	20140
Citroen Picasso mk1	17000
Daewoo Lanos 3d 1997	10500
Daewoo Nubira 1997	14500
Dodge Durango mk1	6800
Dodge Viper Coupe mk2	7600
Ferrari 360 Spider	8500
Ferrari 575M Maranello	14700
Ferrari F50	34600
Fiat Brava	9100
Fiat Bravo	10600
Fiat Punto 3d	19700
Fiat Tempra	6700
Ford Fiesta 3d 1995	6500
Ford Focus 3d mk1	19600
Ford Focus 5d mk1	17900
Ford GT	27100
Ford GT40 MkI	17000
Ford Maverick 5d 1995	4400
Ford Mustang 2003	16000
Ford Mustang 2005	21000
Ford Mustang Convertible (2003)	4800
Ford Mustang Convertible (2005)	9500
Jaguar XK mk2	16000
Jaguar X-Type Estate	16300
Jaguar X-Type Sedan	22000
Koenigsegg Agera	58000
Koenigsegg Agera R	65000
Koenigsegg CC-8	28100
Lamborghini Aventador	35000
Lamborghini Gallardo	23000
Lamborghini Murciélago	20000
Lancia Kappa Coupe	27350
land Rover Freelander 2	28000
Lexus LFA	39130
Lotus Elan	7900
Lotus Elise S2/Exige (2004)	10500
Lotus Esprit SE Turbo	5850
Maserati Quattroporte 2008	18000
Mazda CX-5	27000
Mazda CX-7	23700
Mazda Rx-7FD	15000
Mazda Rx-8	30000
McLaren F1	13500
Mercedes SL R230	16400
Mercedes SL R231	19400
Mercedes SLS Roadster	18000
Mercedes E-Class W212	29920
Mercedes S-Class W221	27500
Mercedes S-Class W222	40500
Mini (2003)	24500
Nissan Micra 1995	4000
Nissan Prairie 4x4 5d 1995	7500
Nissan Sunny 3d 1995	8200
Opel Astra 3d 1998	10500
Opel Astra 4d 1998	11900
Opel Astra 5d 1998	11700
Opel Combo 1999	18500
Opel Corsa 3d 1995	6500
Opel Corsa 3d 1999	8000
Opel Omega 1999	13000
Opel Vectra 4d 1999	8800
Pagani Zonda C12 S	26300
Pagani Zonda F	27000
Pagani Zonda Roadster	18000
Peugeot 206CC	8000
Peugeot 407	22700
Porsche 911 Carrera S 991	30400
Porsche 911 Turbo 993	13500
Porsche 911 Turbo 996	27000
Porsche 911 Turbo 996 Convertible	11600
Porsche 911 Turbo 997	34000
Porsche 959	12900
Porsche Carrera GT	26000
Porsche Cayman 981	42000
Porsche Panamera	25000
Range Rover mk3	32500
Renault Sport Spider	10000
Renault Twingo 1995	14200
Rolls-Royce Phantom	40500
Saab 9-3 Cabriolet mk2	11500
Saab 9-3 Sedan mk2	22000
Saab 9-3 Sportcombi mk2	21000
Seat Leon 2005	23800
Toyota Corolla 3d 1995	10500
Toyota Prius 2001	22700
Toyota Starlet 5d 1995	7600
Volkswagen Fox 2007	17900
Volvo S60 mk1	20000
Volvo S80 mk1	18600
VW Golf V GTI	25000
VW Passat B6	32400
VW Phaeton	37000
VAZ-1111E Oka	7000
VAZ-21043	6300
VAZ-2105	7300
VAZ-2106	6500
VAZ-2107	7200
VAZ-21083	8200
VAZ-21093	6800
VAZ-21099	5500
VAZ-2110	8000
VAZ-21102	8400
VAZ-21106	12200
VAZ-21106 (racing)	51800
VAZ-21108 Premier	10500
VAZ-21109 Consul	14300
VAZ-2111	7400
VAZ-2112	8100
VAZ-2115	5500
VAZ-2120 Hope	10000
VAZ-21213 Niva	8900
VAZ-2123 Chevy-Niva	12000
VAZ-2131 Niva	7400
GAZ-M20 Pobeda	4600
MZMA-400 Moskvich	2500

Of course, the torsional rigidity of the body is one of the key indicators modern car. Let's hope that over time our engineers will come up with more efficient schemes and refine the design so that domestic cars occupied the top lines in the ranking of the best autocars in the world for this indicator.

Not only a person can walk, breathe and swim, but also a car body. Only in the case of hardware, there can be no talk of a healthy lifestyle - all these phenomena are detrimental, and automakers are trying to avoid them. It does not always work out, and tuning comes to the rescue.

Despite the overall integrity, the car body is a complex structure, welded together from dozens, and sometimes hundreds of elements. Add to this the loads acting on it from the suspension and units, causing internal stresses in the metal. Factors external environment also do not benefit the body and negatively affect its durability. Summarizing, we get that the "skeleton" of the car is not at all as fundamental as it might seem at first glance.

Why do manufacturers with their astronomical budgets do not provide sufficient body rigidity at the stage of designing and manufacturing a car, leaving a field for us, “tuningists”? First, they lay it down, but for ordinary, civilian driving. Secondly, during operation, it is lost, as well as obsolete “horses” running away from under the hood. Finally, design engineers cannot increase stiffness indefinitely, as they are constrained by dozens of other factors. For example, the use of high-strength steels increases the mass of the car and increases the cost of production, and individual elements, such as front spars, to please passive safety must absorb the impact energy in the event of a collision. Therefore, they must be made of soft alloys. In addition, there are layout restrictions that force elements to be curved, which in turn reduces their rigidity.

So, the cornerstone value, for the sake of increasing which everything is started, is the torsional rigidity of the body along the longitudinal axis of the car body. It is measured in Nm / degree and shows how much force must be applied to the body in order to bend it one degree. By modern standards, the normal indicator for cars with a monocoque body is 20,000 Nm / deg and above, while at the beginning of the century the figures were half as low. The maximum value of rigidity is possessed by the so-called "single-volume vehicles", whose power structure conditionally resembles a cube. Worse with this case in three-volume machines, especially with big amount doors, since the latter are not part of the power structure of the body. The most a big problem, therefore, open bodies: roadsters, convertibles and the like. That is why convertibles are often heavier than similar coupes - to compensate for the rigidity of the body due to the "went roof", their design is further enhanced.

Measuring the torsional stiffness of a body is a multi-stage and curious process. First of all, prototypes are tested in a virtual environment using programs that are not preinstalled on your Windows and MacOS. But the most interesting is the "live" test. In this case, the body is fixed on the frame of the measuring complex by the attachment points of the rear suspension. At this time, powerful hydraulic cylinders act on the attachment points of the front suspension, which create a “torsion” force in the vertical plane, but in different directions.

As we mentioned, during operation, the rigidity of the body inevitably decreases, and good consequences it won't work anyway. A car with a “tired” body reacts more slowly to steering turns, its reactions are lax and ambiguous. In addition, "breathing" metal is more susceptible to deformation and stretching, as well as corrosion. When lifting on a jack, hanging diagonally or driving one of the wheels onto the curb, the doors may simply not open due to the resulting skew ... or not close. In short, the lack of rigidity must be combated. In what ways? Below is a list of them with the advantages and disadvantages of each.

Spacers

This variant of strengthening the body, perhaps, is more than the others "by ear". hundreds tuning companies today we are ready to offer spacers for almost any car. Such details are installed in regular places without significant modifications, and often they are supplied with a car leaving assembly line still at the factory. But we are talking about tuning, so we will not consider “stock” options. Additional spacers are designed to tie together the most loaded, and therefore “walking” body elements, such as suspension strut cups, attachment points for levers and assemblies.

Parts designed to strengthen these nodes are made in accordance with the configuration of each car model separately - there are no universal parts here. The most popular product is the front strut brace, since it is the front of the car that experiences maximum loads from the power unit, taxiing and overcoming bumps pavement. The price of the issue is low and usually ranges from two to ten thousand rubles, while the “arrival” in handling from such a spacer is immediately noticeable, especially on a battered car. A complete set of spacers can "pull" a hundred thousand. However, remember that a “tired” body is primarily recommended for repair or replacement, and not for mounting amplifiers.

Pros:

ease of installation and dismantling;
low cost;
some improvement in handling;
a wide range of products for most vehicles.

Minuses:

take up some space under the hood and in the cabin;
slight increase in vehicle weight;
for bodies with "tired" metal, they serve as a temporary solution.

Integrated amplification

It is possible to increase the rigidity of the body without installing additional elements - by strengthening the existing ones. In this case, “finishing” is done by the manufacturer. For example, regular spot welding, used in factories to simplify production, is reinforced with additional seams. A duplicating layer of metal is applied to the attachment points of levers and assemblies, which is scalded around the perimeter and in dots over the area. The places of bending of the regular metal are reinforced with jumpers and "kerchiefs", thus protecting themselves from vibrations.

Unlike spacers, this reinforcement method is used when body repair or preparing cars for sports disciplines. It is also suitable if the car is old or there is no desire to resort to the first option. The cost of such reinforcement is determined not by details, as in the first case, but by the amount of work, since its implementation requires partial disassembly of the car, and high-quality welding requires qualifications from the master.

Pros:

does not hide the place under the hood and in the cabin;
increases durability individual elements and the body as a whole;

Minuses:

high labor intensity;
based on the first point, high cost if not performed independently;
violation of the deformation zones provided by the manufacturer;

safety cage

The most radical way to increase body rigidity is a roll cage. Why not "stiffness frame"? The main purpose it serves is to preserve the living space in the car during collisions and coups. The interior of the car and the attachment points of the suspension are connected in this case by a "cage" of cold-rolled steel pipes. Such a frame also “breathes”, like the body, but this is necessary to absorb the energy of impacts and reduce the overload experienced by the pilot.

Scope - exclusively automobile competitions. Depending on the discipline, the requirements for safety cages also differ. So, in the world rally or “adult” ring series, the welded “cage” is so developed that without proper skill it will not be possible to get into the salon at all, while in the “club” disciplines the frame can consist of only a few pipes connected by bolts.

Installation of a safety cage implies local or complete strengthening of the body, described above, therefore, it is the most time-consuming and expensive operation, which, however, is not important when it comes to the pilot's life. This is the most time-consuming process, requiring high qualifications and specialized equipment (such as a pipe bender). It is not uncommon for a car to be modified to temporarily cut off the roof in order to weld the upper junctions of the frame. The installed product is accompanied by a certificate of conformity to a specific technical regulations- the so-called homologation. Of course, this design significantly increases the torsional rigidity of the body - as a rule, by 3-5 times.

Pros:

preservation of living space during collisions;
a significant improvement in handling and body integrity.

Minuses:

high installation cost;
the complexity of the work;
increase in vehicle weight;
unsuitability of the car for civilian use.

What is the result?

If the body of your car "weakened" during operation, it needs repair with the replacement of elements that have accumulated stress. This can be combined with the strengthening of individual elements in case the loads acting on them exceed those calculated by the manufacturer. In the case when there is a lack of information content and responsiveness in management, and the reason for this is the body, it is most logical to strengthen it with the help of spacers produced for an existing car. If the path of the car is competition, then you should take care not only about the rigidity of the body, but also about additional security, therefore, the frame is the only correct solution. Let the body of your car be tough!

The rigidity of the body is its ability to elastically resist external static and dynamic loads that occur during the operation of the car. The higher the rigidity, the better the handling and maneuverability of the machine, especially at high speeds. With an increase in rigidity, the comfort of the car increases - due to the reduction of vibrations, the absence of squeaks from panels and upholstery, etc. That's why the bodies of modern cars tend to be made more rigid.

Rigidity largely depends on the type of body (sedan, hatchback, etc.), design (“geometry” and the method of attaching wings, bumpers), car size, number of doors, window openings, and even the position of the rear seat backs. The method of fastening the windshield and rear windows matters: their gluing increases the overall rigidity of the body by 20-40%. This characteristic is also improved by additional power elements - for example, reinforcement struts between the rear or front suspension strut cups.

When designing a car, several types of body stiffness are calculated - for torsion and bending (longitudinal and transverse). Torsional stiffness is the body's resistance to twisting along its longitudinal axis.

Most modern passenger cars have one-piece steel frameless load-bearing bodies, which reduces their weight. The rigidity of such bodies is ensured by the presence of special elements in them - spars, longitudinal and transverse beams. To increase the rigidity of bodies made of thin sheet steel, welded box-shaped parts are widely used, as well as power struts and racks, which are given a certain shape and section. The greatest rigidity in sedan-type bodies, the smallest - in hatchbacks and elongated station wagons. Sports cars are usually subjected to additional strengthening of the body: additional amplifiers-struts are installed on them, and in the cabin - a power safety cage made of thin-walled steel pipes.

After 4-6 years of vehicle operation, the rigidity of the body decreases markedly due to corrosion of metal elements - both power and cladding. Especially quickly rust affects thin-sheet parts connected by spot welding. Violation of the rigidity of the load-bearing elements of the body reduces its overall strength and can make further operation of the car dangerous.

Body stiffness can be assessed by comparing this characteristic of new and old cars. To do this, jacking up the body of a new car at the rear wheel at point B to a certain height H (see photo), we measure the distance h from an arbitrarily chosen point A of the body (at the front wheel) to the ground. We repeat the same procedure with the old car. If, when its body is raised at point B to a height H, the value h turns out to be less than that of a new car, then the body is “twisted”, i.e. he lost his toughness.

Introduction

The rigidity of the body is its property to elastically resist external static and dynamic loads that occur during the operation of the car. The higher the rigidity, the better the handling and maneuverability of the machine, especially at high speeds. With an increase in rigidity, the comfort of the car increases - due to the reduction of vibrations, the absence of squeaks from panels and upholstery, etc. That's why the bodies of modern cars tend to be made more rigid.

When designing a car, several types of body stiffness are calculated - for torsion and bending (longitudinal and transverse). The ability of the body to resist the working loads acting on it is characterized during bending by the value of the maximum deflection, and during torsion - by the angle of twist along the length of the base. However, the maximum deflection and angle of twist along the length of the base obtained as a result of calculation or testing on the stand cannot be used to compare this body with the bodies of other vehicles with a different base and a different nominal load.

Therefore, the concepts of specific torsional and flexural stiffness are introduced. The specific torsional stiffness of the body characterizes the resistance of the body to twisting and is the ratio of the torque to the angle of twist of the body along the length of the vehicle base, multiplied by the size of the base. For passenger cars, the specific torsional stiffness of the body is 130 ... 300 N * m 2/˚. The specific bending stiffness of the body characterizes the bending of the body in the vertical plane and is the ratio of the load to the deflection of the body, multiplied by the size of the vehicle base to the third power. For passenger cars, the specific flexural rigidity of the body is in the range of 850 ... 2200 N * m 3/˚.

Rigidity largely depends on the type of body (sedan, hatchback, etc.), design ("geometry" and the method of attaching wings, bumpers), car dimensions, number of doors, window openings, and even the position of the rear seat backs. The method of fastening the windshield and rear windows matters: their gluing increases the overall rigidity of the body by 20-40%. This characteristic is also improved by additional power elements - for example, reinforcement struts between the rear or front suspension strut cups.

After 4-6 years of vehicle operation, the rigidity of the body decreases markedly due to corrosion of metal elements - both power and cladding. Especially quickly rust affects thin-sheet parts connected by spot welding. Violation of the rigidity of the load-bearing elements of the body reduces its overall strength and can make further operation of the car dangerous.

Body stiffness can be assessed by comparing this characteristic of new and old cars. To do this, jacking up the body of a new car at the rear wheel at point B to a certain height H, we measure the distance h from an arbitrarily chosen point A of the body (at the front wheel) to the ground. We repeat the same procedure with the old car. If, when its body is raised at point B to a height H, the value h turns out to be less than that of a new car, then the body is "twisted", i.e. he lost his toughness.

1. Ways to ensure the rigidity of the bodies

Strut front.

This is an element of the power structure of the front suspension mounts.

Front struts are the most common type of body reinforcement, its advantages are obvious - ease of installation, low price, visual appeal and a fairly strong increase in the rigidity of the front of the car. Their purpose is to reduce the deformation and movement of the body cups when turning the car. The installation result depends on the vehicle. If its design is generally balanced, then the result, most likely, will not be visible. And for others, this device is strongly recommended. For example, for the VAZ "tenth" family. Not only the racks "walk" there, but the entire bulkhead shield is deformed! By the way, there is also a special amplifier for it, but more on that later. On the market now you can observe an abundance of front struts, but only the material and method of attachment are fundamentally different.

The usual spacer works exclusively in compression, but you can make it work in torsion, for this the cup is additionally reinforced with one more element - scarves (special thick steel plates). As a result, the spacer begins to work also in torsion. With kerchiefs, you can also strengthen the places of the wheel arches, suspension struts and stiffeners of the entire body, for the most part, for this you will have to disassemble almost the floor of the car, at least the entire interior for sure, so this technique is used mainly on racing cars.

In addition, the so-called "rods" can be attributed to an additional element of the front struts. A rod is a special movable mount connecting the engine and a strut, in addition to this, there are rods connecting the engine with other "strong" elements. This element works mainly during engine braking and sudden starts, the effect is a decrease in the movement of the power unit under extreme loads, a decrease in the car's withdrawal during a sharp start, a decrease in the movement of the gearshift lever handle, and, of course, an increase in overall body rigidity. The disadvantages of using rods include an increase in the noise level in the car

bottom brace

The lower strut reduces the movement of the front suspension arm bracket, reduces the stress generated in the arm bracket and the spar-to-floor connector. Taking part of the load on itself, the lower strut takes the body parts out of the zone of high stresses. As a result, improved handling, stability, increased body life. Installation is quite laborious.

rear brace

Reduces the movement of the rear mount cups, increases the overall torsional rigidity of the body. Result: improved handling, stability. The main thing to consider: the rear strut gives effect only if it is fixed to the power elements of the body, and not to intermediate elements (seat mounting brackets, for example). The rear strut is also quite easy to install and dismantle, but there are also negative points: firstly, it is extra space in the cargo compartment, and secondly, there are pitfalls, the rear strut can increase understeer, especially if the rear of the car is reinforced with some other elements. If the car has stock suspension, it is better to refuse to strengthen the buttocks or strengthen it with only one stiffening element.

In addition to struts, there are many more ways to strengthen the body - increased welds, reinforced subframes, anti-roll bars and cross members, various reinforcing elements in places of weak rigidity, designed for a specific model and, of course, frames.

Enlargement of welds and welded elements.

Stabilizers and cross bars

These units are also present in stock and have many properties that affect handling and comfort, so usually factory cars have intermediate ones, so to speak, not too soft, not too hard. There are two options for their improvement - reinforcement and replacement. Side effects - increased noise, sensitivity to bumps and all the same positive properties: handling and stiffness. It is strongly not recommended to install stabilizers, crossbars in tandem with the rear strut, especially on the stock suspension.

Subframes

safety cage

car body rigidity frame

The frame, in a racing car, performs not only its direct function of protecting the pilot, but also superbly reinforces the body. It is mandatory for use in any racing car, the difference is only in its complexity (although the obligation appeared not so long ago in 1994, before that the installation of the frame was a purely personal matter). The frame is a combination of rigidly interconnected steel (steel with temporary resistance on rupture not less than 45 kg/sq. mm) of cold-drawn seamless pipes, for example 30HGSA. By type, frameworks can be roughly divided into two categories: homologated and non-homologated. You can install the first ones in your car and you can be admitted to official competitions. However, it is very complex and causes certain difficulties, which we will discuss below. The second type is "civilian" frames, simpler and naturally cheaper.

The power unit is rigidly connected to the body.

Even in motorsport, such a method of increasing body rigidity is widely used as the inclusion of units in its power structure, for example, an engine, gearbox and final drive. This means that they are all rigidly connected to the body, which also greatly increases the rigidity. For example, similar solutions are found in almost all "formulas". In general, the ancestor of this idea was the legendary Colin Chapman, the founder of the Lotus company, who first brought the idea to life on the Lotus-25 Formula 1.

Folk ways.

There are also folk methods, for example: the openings of the thresholds and spars are filled with mounting foam. The method is cheap and angry. In the pros, a slight increase in rigidity, in the minuses - the lack of ventilation and, as a result, increased corrosivity. Also, when replacing these parts by welding, there is a risk of fire.

Conclusion

The rigidity of the body is significantly affected by the way the power unit is installed. Therefore, the difference in results is higher for cars with a classic layout - there the torsional rigidity is increased by the front suspension beam. But in front-wheel drive vehicles with a transverse engine and McPherson-type front suspension, a noticeable increase can be given ... by the back of the rear seat! For example, in the "eights" and "nines" the rear seat increases the rigidity of the body by about 1000 Nm / deg due to the fact that the back is solid and rigid, and on the long-suffering tenth family the back is separate and this 1000 Nm evaporates. Therefore, VAZ recommends that owners drive with the rear seat folded as little as possible - the body is weakened and less resistant to torsional load. In fact, two enemies can be distinguished in tuning - weight reduction and body rigidity, and these are mutually exclusive things, fighting for weight reduction, you can reduce rigidity, and what is more important is not an unambiguous question.