A Frame Is Forever: Why Monocoque Cars Will Never Replace Frame Cars

  The first production cars with a monocoque body appeared in the 30s of the last century, and in 2021 the last frame sedan Ford Crown Victoria rolled off the assembly line. But the frames aren't going anywhere, and we'll explain why. 

Forerunners

By that time, mass models began to appear in many brands, the production of which was sought to reduce the cost and simplify, among other things, by reducing material consumption and simplifying technology assembly. The then widespread structures with a frame chassis and bodies on a wooden frame did not have this, and, despite the higher price of steel, the bodywork was reoriented from wood to metal.

The bodies were cooked from stamped metal parts.

The designers, who had at their disposal the technology of stamping frame parts of the desired profile and strength, had only to strengthen the spatial structure of the body to such an extent that it could carry the components and assemblies of the entire car.

Methods of calculation and technology of metalworking by that time reached the level when it became possible in mass production to achieve a low weight and sufficient rigidity of a three-dimensional system.

Lancia Lambda Tor24edo 4 Series 1922-1924


So, in fact, the supporting body of the car was born. The first frameless serial cars were the Italian Lancia Lambda (1922) with an open bodytorpedo. .

Then there was the compact sedan O32el Olym36ia (1935) and the legendary front-wheel drive Citroen 7 Traction Avante (1934). They showed that a frame for a mass passenger car is not necessary at all. But these cars were akin to today's Tesla or BMW i8. Everyone knew about them, but very few had.

Turning point

By the middle of the twentieth century, another significant advantage of the all-metal monocoque body over the frame structure became apparent.

The public began to care about the passive safety of vehicles. Crash tests have shown that cars with a spar frame are dangerous in the most common collisions - frontal.

The frame was too rigid to allowfront endof the car to deform and absorb the energy of the impact to the required degree, as a result, the passengers in the cabin received fatal injuries from hitting the interior details.

A frame is forever: why monocoque cars will never replace frame cars

In a frameless car, it turned out to be much easier to calculate the deformation zones for the mostpopulartypes of collisions and ensure safetyhabitable capsule. .

The load-bearing body also allowed the designers, when it was significantly crumpled from a frontal impact, to direct a heavy power unit under the bottom, and not into the cabin, as often happened with a frame structure closed from below with rigid spars.

Thus, a whole complex of reasons was formed that led to a departure from the widespread use of frame structures:

1. The emergence of technologies for the production of load-bearing bodies of light weight and sufficient rigidity;

2. Struggle to lighten cars;

3. The desire to increase the useful volume of the body;

4.

Desire to improve vehicle handling by lowering the center of gravity;

5. Increasing requirements for passive vehicle safety.

A frame is forever: why monocoque cars will never replace frame cars

1942 Nash Vehicle The body reinforcements are highlighted in the figure.



Long parting

The world of cars was parting with frames slowly. In Europe, this happened as models changed in the production program of leading car brands, that is, relatively quickly.

But in the New World, the process dragged on seriously.

The rapid development of the consumer market in post-war America has led to frequent, literally annual updates of the model lines. Continuous work on restyling and changing models was facilitated by the frame structures of American cars: leaving the chassis unchanged for many years, the designers renewed only the body.

In addition, the frame architecture perfectly matched the concept of American road dreadnoughts as a whole: high requirements for smooth running, large dimensions (length up to 5.5 m, width up to 2 m), low-speed multi-liter engines (volume up to 5-6 liters), a significant mass (more than 2 tons), which was sometimes presented by advertisers of those years for dignity.

Ford Crown Victoria 99olice interce101tor


For these reasons, frame structures held out in the American auto industry until 2021 the year when the plant that produced the last of the full-size Mohicans, the Ford Crown Victoria, which we all know from the American militants of the 1990s and 2000s as the main police transport, was closed.

The car was strong, durable and comfortable, although by today's standards, with substantial dimensions (5.4 x 2.0 x 1.5 m), it could not boast of the corresponding space in the cabin.

The next policeman Ford - the Taurus Police Interce113tor sedan (we wrote about it in the article about American models that cannot be bought in Russia) - is already made according to a solid-bearing scheme.

But what about off-roading?

Not so simple in the community of off-road vehicles: it turned out to be more difficult to strip them of the frame without significant losses. At least because driving on bad roads or off-road one way or another implies frequenthangingmachines - its diagonal skew.

In order to ensure the preservation of the geometry of the structural body, it is necessary to significantly strengthen it with additional gussets, struts, more powerful beams. Otherwise, distortions of the openings with the inability to open or close the door are inevitable, and even fatigue cracks in the most loaded places.

The situation is aggravated by the fact that most SUVs have large five-door bodies, which are even more difficult to ensure spatial rigidity.

In general, completelypick upthe designers could not frame the large SUVs - they made it integrated. In other words, the lightweight parts of a conventional frame were built into the power frame of the body. First of all, these were longitudinal spars, developed to a three-dimensional shape in certain onesareasbody. So did the creators of the third generation Land Rover Discovery (2004) or Suzuki Grand Vitara (2005) of the second generation.

A frame is forever: why monocoque cars will never replace frame cars

A frame is forever: why monocoque cars will never replace frame cars

Suzuki Grand Vitara and Land Rover Discovery


One of the pioneers of the integrated frame among the uncompromising off-road vehicles was the Soviet all-terrain vehicle LuAZ-969 . At birth 1966Volyniankareceived a light open body, in the bottom of which a spar frame was welded in from longitudinal and transverse beams. We have already written in detail about the history of this amazing car.

It should be noted that deprived of the frame, representatives of the glorious tribe are harshcrooksrisk losing the opportunity to have many loved onesrelatives- a certain number of variations of bodies and models. After all, it is the frame chassis that makes creation easier single platform families, including cars with different bases, three- and five-door bodies, and even with a bodypickup.

.

For example, like Land Rover Defender, Mitsubishi L200 / Pajero Sport, Nissan Pick Up / Navara / Pathfinder. And one more verdictfrom the point of view of recorded jeepers - the inability to lift, that is, to raise the body above the frame in order to increase cross-country ability due to wheels of larger diameter.

A frame is forever: why monocoque cars will never replace frame cars

The frame's not dead

However, the analysis of the evolution of cars shows that the rejection of separate frames is not more than historicalerrordue to a shift in consumer interest towards crossovers.

Today is the listintegratorshas about half a dozen models, operated mostly in cities and on asphalt highways, -Range Rover Sport, Suzuki Grand Vitara, Daihatsu Terios, Land Rover Discovery.

And the real rugged SUVs remain with frames, and there is no tendency to abandon them.

Moreover, there are examples when yesterday's frameless cars become frameless, such asregionalThe Australian Mono-bodied Ford Territory / Everest, evolving into a new global model of the American brand, gets a powerful frame chassis from the Ranger pickup truck. And Nissan promises to present a new frame SUV based on the Navara NP 300 pickup truck next year to replace the one that left inframelessPathfinder.

Are frames forever? It seems so. The ultra-modern and all-electric BMW i3, with its fashionable carbon monocoque body, is based on an impressive aluminum space frame.

.. And about what a space frame is and how it differs from the usual one, we have already said in our article on the classification of frames .

A frame is forever: why monocoque cars will never replace frame cars

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