Backbone chassis

Backbone tube chassisis a type of automobile constructionchassisthat is similar to thebody-on-framedesign. Instead of a two-dimensionalladder-type structure,it consists of a strong tubular backbone (usually rectangular incross section) that connects the front and rearsuspensionattachment areas. A body is then placed on this structure. It was first used in the EnglishRover 8hpof 1904 and then the FrenchSimpliciaautomobile in 1909.

1923Tatra 11chassis

Cut through the rear axles of backbone chassis ofTatra 26

The backbone chassis was extensively developed byHans Ledwinkawho used it in greater numbers on theTatra 11and subsequent vehicles. Ledwinka later used backbone frames with central tube and axles with swinging driveshafts onTatratrucks, becoming known asTatra-concept.

Design

The truck backbone chassis is a design feature of CzechTatra heavy trucks(cross-country, military etc.).Hans Ledwinkaused this style of chassis for theTatra 11car in 1923.He then developed the design on trucks with 6x4 modelTatra 26,which had excellent off-road abilities.

The chassis of aŠkoda Popular(1934)

Lotus Elanchassis with rearChapman strutsuspension

De Tomaso P70racer backbone chassis andrunning gear.The same parts were later used in productionDe Tomaso Mangusta.

This type of chassis has been used in numeroussports cars.It does not provide protection againstside collisions,and thus has to be combined with a body that would compensate for this shortcoming.

Examples of cars using a backbone chassis areSimplicia(1910),De Tomaso Mangusta,DMC DeLorean,Lloyd 600,Lotus Elan,Lotus EspritandEuropa,Škoda Popular,Škoda Rapid,Škoda Superb,Tatra 77, Tatra 87,Tatra 97,Toyota 2000GTandTVR S1.Trucks with a backbone chassis include theTatra 111,Tatra 148andTatra 815.Some cars also use a backbone as a part of the chassis to strengthen it. Examples include theVolkswagen Beetle,where the transmission tunnel forms a backbone.

Hybrid backbone-ladder chassis

TheLocostmay appear to be using a backbone in addition to the outerspace frame.But examination shows that, in standard form, it is adding negligible stiffness and only serves as a convenient support structure for the sheet metal panels forming thetransmission tunnel.TheTriumph HeraldandTriumph Vitesseused a twin flanged box sectionbackbone carrying the main torsionaland bending loads, with light channel section side rails to stiffen the body, while theTriumph SpitfireandTriumph GT6sports cars used only the twin-box section backbone, with separate side members in the body, and rear suspension fore and aft loads were also taken by the floor, not the backbone chassis directly.

Advantages

• A standard-conception truck's superstructure has to withstand the torsion twist, and subsequent wear reduces vehicle's lifespan.
• The half-axles have better contact with the ground when operated off-road. This has little importance on roads.
• The vulnerable parts of the drive shaft are covered by a thick tube. The whole system is extremely reliable. However, if a problem occurs, repairs are more complicated.
• The modular system enables configurations of 2-, 3-, 4-, 5-, 6-, or 8-axle vehicles with various wheel bases.
• The lack of structure in the sills/rocker area allows deeper doors and a lower floor, useful in low slung sportscars.

Disadvantages

• Manufacturing the backbone chassis is more complicated and more costly. However, the more axles with all-wheel drive are needed, the more cost benefit turns in favor of backbone chassis.
• The backbone chassis is heavier for a given torsional stiffness than a uni-body.
• The chassis gives no protection against side impacts.

See also

• Tatra concept
• Frame (vehicle)
• Body-on-frame
• Chassis
• Coachwork
• Monocoque
• Spaceframe
• Subframe
• Superleggera
• Swing axle

External links

• Comparison of standard ladder chassis and backbone chassis with half axles on off-road testing track with emphasis on the twist of superstructure (video):
  • Ladder chassis(Renault fire engine)
  • Backbone chassis(Tatra T815 fire engine)