De Dion tube

de Dion suspension characteristics: Camber change on one sided bumps, none on rebound. de Dion tube is shown in blue. The differential (yellow) is connected directly to the chassis (orange).

De Dion rear axle

A de Dion tube is an automobile suspension technology. It is a sophisticated form of non-independent suspension and is a considerable improvement over the swing axle, Hotchkiss drive, or live axle.^[1] Because it plays no part in transmitting power to the drive wheels, it is sometimes called a "dead axle".^[2]

De Dion suspension uses universal joints at both the wheel hubs and differential, and uses a solid tubular beam to hold the opposite wheels in parallel. Unlike an anti-roll bar, a de Dion tube is not directly connected to the chassis nor is it intended to flex. In suspension geometry it is a beam axle suspension.

History

The de Dion tube was named after Comte Jules-Albert de Dion, founder of French automobile manufacturer De Dion-Bouton. The tube, however, was invented around 1894 by co-founder Charles Trépardoux for use on the company's steam tricycles.^[3]

Advantages and disadvantages

Advantages:^[4]

1. Reduced unsprung weight compared to the Hotchkiss drive (live axle), since the differential and half-shafts are connected to the chassis.
2. Unlike most fully independent suspension there are no camber changes on axle loading and unloading (or rebound). Fixing the camber of both wheels at 0° assists in obtaining good traction from wide tires and also tends to reduce wheel hop under high power operations compared to an independent suspension.
3. The choice of shock absorbers and springs is made easier.^[2]
4. The two wheels may be individually aligned, allowing for independent camber (vertical) and track (horizontal) alignment.

Disadvantages:

1. A pair of CV or universal joints is required for each wheel, adding complexity, cost, and weight.^[2]
2. If coil springs are used, then a lateral location link (usually either a Panhard rod or Watt's linkage) is required, plus additional torque links on each side (five link suspension) or a combination of lower trailing links and an upper transverse wishbone. None of these additional links are required if leaf springs are used, but ride can be compromised due to the leaves having to do double duty as both locating links and springs. The torque links are not required if the setup uses inboard brakes, like in the Pegaso 1502, Rover P6, all Iso cars^[5] and Alfa Romeo type 116 (and derivatives), as the wheels do not transmit torque to the suspension.
3. Sympathetic camber changes on opposite wheels are seen on single-wheel suspension compression, just as in a Hotchkiss drive or live axle. This is not important for operation on improved surfaces but is more critical for rough road or off road use.

Use in production cars

de Dion tube used in a 1998 Ford Ranger EV

Older cars

Alfa Romeo is probably the most famous adopter of this technology, using it on the Alfa Romeo Alfetta, GT, GTV, GTV6, Giulietta, Alfa 6, 90, 75/Milano, SZ/RZ. Other production vehicles using this suspension include the Lancia Aurelia (fourth series onwards) and Flaminia, first and second generation Prince Gloria, the original Mazda Cosmo, Volvo 300-series, Rover P6 and Dodge Caravan & Grand Caravan (all wheel drive version from 1991–2004), DAF 46, DAF 66, all Iso cars (Iso Rivolta IR 300, Iso Grifo, Iso Fidia, Iso Lele) and early Bizzarrini 5300 GT Stradas, some of the largest Opels, such as the Opel Diplomat "B" of 1969, all Aston Martins from 1967 to 1989, Ferrari 375 and 250TR, first generation Maserati Quattroporte, Bugatti Type 251, Mercedes-Benz W125 and W154 as well as Auto Union Type D.

Recent cars

The Smart Fortwo and Smart Roadster micro-compact cars produced by Daimler AG, Mitsubishi i kei car produced by Mitsubishi Motors and the Caterham 7 (a development of the Lotus Seven after Lotus sold the design rights to Caterham Cars), are the only cars currently in production that utilize this arrangement, as well as the products of some kit car companies. A recent vehicle to use this suspension coupled with leaf springs was the Ford Ranger EV. Note the black Z shaped Watt's linkage mounted to the top of the silver De Dion tube in the photo above. The American built MV-1 van by VPG also uses this suspension in the rear with leaf springs and is just starting production in spring 2010.^[6] 4WD variants of the Honda Fit use a De Dion style suspension^[7] in lieu of a torsion bar.

Other Notable Uses

Most models of the Kawasaki MULE line of utility vehicles feature a leaf sprung DeDion rear suspension with a distinctively curved tube axle that clears the rear subframe to provide 50mm of wheel travel.^[8] Benefits include simplicity, durability, compactness and a relatively low liftover height for the cargo bed.

Walter Snow Fighter plow trucks produced by the Walter Truck Company of Long Island, New York throughout the mid 20th century used DeDion axles with portal gear hubs for both the front and the rear suspension, allowing the use of large differentials for durability without increasing unsprung weight or reducing ground clearance. Forged steel axles were used instead of tubes.

References

Sources

• G.N. Georgano (1990). Cars: Early and Vintage, 1886-1930. London: Grange-Universal.  (reprints AB Nordbok 1985 edition).
• Setright, L. J. K. "De Dion axle: The First Step to Independence", in Ward, Ian, executive editor. World of Automobiles, Volume 5, pp. 515–516. London: Orbis, 1974.