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Has anyone heard of one of these components? I got one.
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yes they were fitted on the old rovers 2000/2200/3500.s need a fair bit of looking after but were pretty good axles.inboard discs as I remember.ie on diff?
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If I've attached the name to the right thing, it's a bit similar to a live rear axle in that a solid tube/section carries the wheels which are therefore linked together and kept parallel to each other and perpendicular to the road, but unlike the live axle the drive is separate so the differential is attached to the car. This removes some torque effects as the axle does not try to twist and must reduce reduce unsprung weight. I couldn't name a car in production that uses it - what have you?
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You won't find an arrangement like de dion on any volume production car because it's comparatively heavy and old-fashioned. You can get kits to convert older live axle cars to the semi-independent de dion (described admirably above) and I've half an idea that it has been offered on the Caterham 7 at some stage.
On flat, smooth surfaces live axles aren't as bad as you might think (remember that Rover raced the SD1 with some success in the 80s), but having one rear wheel connected directly to the other is bound to weaken ride and handling on poor surfaces - i.e., 99% of all modern roads!
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Quite a nice bit of info here, with a reasonable drawing of the P6 Rover axle down towards the bottom of the page.
www.roversd1.nl/sd1web/liveaxle.html
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I'm sure 3500S can tell us all about the De Deon rear suspension. Like mech1, the only 'modern' car I can recall it being fitted to the Rover 2000 and derivatives ... and the discs *were* inboard and were awful to work on.
Morris Ox says that the De Dion was comparatively heavy, and I'm sure he's right. However, because the bulk of the assembly was direct-mounted on the body of the car, the all-important unsprung weight was reduced.
I have read that this arrangement was first used on the De Dion Bouton steam carriage. That must be getting on for 100 years ago. I think Rover did well to incorporate it on the 2000 series but, like several other things on that car, the benefits were fairly insignificant relative to the cost of incorporation.
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Fif,
Just took a look at the site you pointed us to. Fascinating and very informative! But haven't they got 'sprung' and 'unsprung' weight about-face in the main text? Or am I reading it wrong? ... Or I am getting even more senile than usual(don't answer that!!)
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Or I am getting even more senile than usual (don't answer that!!)
I won't answer because that would involve pots calling kettles black!
But haven't they got 'sprung' and 'unsprung' weight about-face in the main text?
Well spotted that man! I'd missed that.
It seems that they have it the right way some of the time, and then there is a paragraph where it is indeed about-face.
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Alfa GTV6 also used a De Dion set-up. Loads of interesting/useful stuff at this link for the GTV6 enthusiast - scroll halfway down for De Dion piccie.
www.oldebottles.com/italiancarspage2.htm
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I think it was also used on the Aston Martin V8 up to the 1980s, with such a heavy car the weight of that component didn't matter so much.
Gareth
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Thanks for the interesting info in the de dion tube.Very informative.I should have the P6 3500s on the road soon after nearly 10 years of toil and sweat.Cant make up my mind whether to slot the injected v8 in out of a sd1.Should solve the fuel vapourisation trouble,and go better too.
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The De Dion tube arrangement was also used very successfully on the DAF 66 in 1972 and continued in the Volvo 66 followed by the Volvo 340, right up to the end of manufacture in 1992. It made an ideal companion to the brilliant, much maligned and misunderstood, DAF Variomatic CVT transmission and enabled surprisingly competent and comfortable handling.
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Yep, the Rover P6 was fitted with a De Dion rear axle. It's not a live axle and not independent but kind of a happy medium. Lotus in their 61 experimented with it (as well as Jaguar, Maserati and Alfa) and as such it has developed a reputation as a racing suspension setup.
It's main advantage is low unsprung weight.
A De-dion is essentially an elongated D shape with the De-Dion tube in the middle of the curve.
The advantage is excellent ride. All the weight is bolted to the body, the diff mainly. It has very little sprung weight meaning that softer springs can be used. This also explains why on the Rover P6 that the rear disks are inboard either side of the diff, again, unsprung. The drive splines have to be removed to replace the disks. Expensive.
Unique to Rover's De-Dion their is a sliding joint on the tube to reduce tracking problems in cornering like a live axle, also in terms of camber the wheels are always level to the road.
Think if it as a compromise between a live axle and independent suspension.
It delivers excellent ride, refusing to pitch up over potholes like a live axle and deposit you sideways, allows the use of softer springs and yet delivers a lot of power to the rear wheels consistently as the wheels track perfectly.
The only weakness is a lot of road energy is absorbed through the trailing arms, in old cars prone to rust and corrosion, these must be tested regulary, one of these breaks at speed, you could easily lose a wheel.
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The only weakness is a lot of road energy is absorbed through the trailing arms,
Plus cost and weight of course!
Gareth
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In the late 1950s, early 60s, independent rear suspension was very expensive and not technically mature enough so this was the mid-priced alternative that offered a well established compromise.
It's a weighty solution but with 3.5L of V8 horses, not a problem. Even the 115Bhp 2L twin carbs could move almost 2800lbs of metal 0-60 in 12 seconds.
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