Yeah, it is a variant. Normally the DeDion tube is located laterally by a Watts linkage between the sides of the frame and the centerpoint of the tube. The linkage allows the whole tube to move up-and-down, but not side-to-side. The Caterham Seven also had a torsion bar along with the DeDion with adjustable pickup points to alter the suspension hardness (or softness).
And the smart is the only DeDion that I have seen that does not pass behind a chassis-mounted differential.
The semi-independent DeDion suspension had been the choice of front-engine, RWD racecar builders from the ’40 onward, both formula cars and sports/GTs. It only went out of common use with the advent of rear engine cars with transaxles located behind the engine (no room for the DeDion tube, but plenty of room for long-“A arm†fully-independant). Porsche never used it; they used a swing axle instead.
The design has three distinct advantages: it will accommodate a tremendous amount of torque and stress for its mass; it reduces a lot of un-sprung weight at the wheels; it keeps the rear wheels vertical regardless of body lean or suspension travel (no negative camber needed). The smart DeDion looks relatively massive, but its tube does have to pass around forward both the transaxle and engine, not just behind a differential.
I assume that DeDion was chosen for the smart because there wasn’t sufficient room for the lateral “A-arms†used in a fully independent suspension.
1976 Rover Mini
2003 Chevrolet Corvette Z06
2007 Mercedes-Benz E320 Bluetec (SOLD)
2009 smart Passion (Gone)
2011 smart Passion
Today
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