omega0684
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| posted on 14/1/06 at 09:07 PM |
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de-dion vs IRS
what is the difference between a de-dion and an IRS chassis? im plan to run a cossie rear diff and drive shafts, with a suspension set up from dax
with a de-dion chassis, have i picked the right one?
Alex
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JoelP
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| posted on 14/1/06 at 09:22 PM |
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not this one again!
Its been flogged to death and back many times, use the search engine! 
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graememk
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| posted on 14/1/06 at 10:52 PM |
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if i knew i'd tell you
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Avoneer
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| posted on 14/1/06 at 10:57 PM |
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In a nutshell - YES.
IRS is best, but bugger to set up properly.
De-Dion is best compromise between live axle and IRS.
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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kb58
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| posted on 15/1/06 at 03:17 AM |
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That's what I said, "not again."
Okay, weigh all your unsprung components and calculate what the numbers add up to in both a de-dion and IRS configuration. That's the
difference in ride quality.
De-dion is considered simpler to build. IRS can compensate for a leaning chassis in a turn while a de-dion cannot. Does it matter? It depends.
The easy way out of this issue is to get a ride in two identical cars, one with each suspension type...
I have my own *opinion* about this, as does everyone else here, but it's all *opinion* Either car will be fine (your definition will vary) in
day-to-day driving. It's all opinion and also dependant upon what you're building and how it will be used.
[Edited on 1/15/06 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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scotty g
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| posted on 15/1/06 at 08:11 AM |
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I'm using de-dion and it works fine, basically makes your IRS behave more like a live axle and keeps the build nice and simple.
Unless you're planning on some serious motor racing you really won't notice much difference anyway.
Cheers.
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Minicooper
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| posted on 15/1/06 at 11:36 AM |
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quote:
Originally posted by kb58
"IRS can compensate for a leaning chassis in a turn while a de-dion cannot. Does it matter? It depends."
De Dion doesn't need to compensate for a leaning chassis. It doesn't suffer from roll induced camber change? It would be sensible to keep
body roll to reasonable limits though
I'm using it, for the ease of setup, fabrication is fairly straight forward, great traction and in my application mid engined it leaves loads of
space for the just about any engine you care to fit
Cheers
David
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MikeRJ
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| posted on 15/1/06 at 02:21 PM |
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quote:
Originally posted by kb58
IRS can compensate for a leaning chassis in a turn while a de-dion cannot.
As minicooper has said, one of the greatest strengths of the De-dion (and live axle) is that body roll gives no camber change whatsoever, the same
cannot be said of IRS in general.
The advantage of IRS is that suspension movement of one wheel does not affect the camber of the other wheel on that axle.
Both IRS and de-dion can give usefull reductions in unsprung weight over a live axle, with IRS usualy having the edge over de-dion but the absolute
difference is quite small.
In terms of a Locost, a de-dion requires minimal modifcations to the "book" chassis, wheras an IRS design is substantialy different, and
there is also no "standard" design. Most people seem to use one of the kit manufacturers parts (e.g. MK, MNR, Luego etc.), or even the
Tiger Avon IRS, ( whose design has attracted rather a lot of criticism in the past).
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britishtrident
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| posted on 15/1/06 at 06:52 PM |
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de Dion is the suspension Harods would sell, IRS is more M&S.
Or to put it another way under Ford ownership Jag and Astom Martin share the same chassis, Jag uses IRS the Aston uses a de Dion -- the Aston sells
at 3 times the price.
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dnmalc
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| posted on 15/1/06 at 09:14 PM |
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Yes but remember the top gear comments the jag that follows the Aston by a couple of years is always the better car
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andyps
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| posted on 16/1/06 at 10:23 AM |
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I think with the Aston it is more tradition than it being better.
A better comparison is how many top race cars use DeDion? Also, Caterham have recently moved from DeDion to IRS for their top car - must be a reason
for that.
Andy
An expert is someone who knows more and more about less and less
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smart51
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| posted on 16/1/06 at 10:37 AM |
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quote:
Originally posted by britishtrident
Jag uses IRS the Aston uses a de Dion -- the Aston sells at 3 times the price.
You say that as if the price is solely dictated by the suspension and that the ali body or interior trim or brand image have nothing to do with it
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cymtriks
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| posted on 17/1/06 at 10:27 PM |
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Deon and Aston
quote:
Originally posted by britishtrident
de Dion is the suspension Harods would sell, IRS is more M&S.
Or to put it another way under Ford ownership Jag and Astom Martin share the same chassis, Jag uses IRS the Aston uses a de Dion -- the Aston sells
at 3 times the price.
Not so.
Deon was used on the Aston V8 cars, including the supercharged Vantage version with 550bhp (minimum - upgrades were offered up to 650 bhp). These cars
were developed when Victor Gauntlett was still in charge but were completed under Ford ownership.
The first Ford/Jaguar/Aston car was the DB7 with a chassis that was originaly destined for the 80s "F type" Jaguar. It relies heavily on
Jaguar bits and design but it was never a Jaguar chassis because Jaguar never made the F type. It's suspension is double wishbone all round. I
don't know if the rear suspension uses the drive shaft as a suspension arm as on older Jaguars.
The F type was resurected as a completely different mid engined concept car then as a front engined concept car and was then forgotten about. Shame,
the concept cars looked lovely.
The V12 Vanquish is an aluminium chassis unique to Aston. The engine is derived from the Mondeo V6, just withe twice as much of everything. Double
wishbone suspension here.
Aston didn't use the DB8 name. I don't know why.
The V12 DB9 is another new chassis, designed to be very flexible in design terms to accomodate lots of variations in the future. Wishbones again.
The V8 Vantage is based on a shortened DB9 chassis (the first variant!) and is powered by a derivative of the Jaguar V8. Wisbones again
Deon hasn't featured very much in cars over the last couple of decades.
There was the Alfa 75 and the Alfa Zagato.
There was the Strathcarron, developed by Reynard racing, Triumph bike powered, ali honeycombe chassis, carbon bodywork. They only made 11 or was it
12? Marlin now make a similar looking car in the 5EXi but it's nothing to do with the Strathcarron project. Apparently the project was sold. Who
to? I want one!
There was the Aston V8 Virage/Vantage as above.
And of course there's the Caterham. However they are ditching it in favour of double wishbones, along with push rod front suspension and inboard
springs and dampers at the front. See the the new Caterham CSR.
That's 4 cars in the last 20 years!
OK, I forgot the Caterham 21, one of the most beautiful sportscars ever, but strangely not in production (What happened to it? Is Caterham just
letting the moulds fill with rain water in their back yard - tragic!)
And there's the La Bala.
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Mark Allanson
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| posted on 17/1/06 at 10:44 PM |
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Don't forget the P6 Rover..
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Triton
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| posted on 17/1/06 at 11:15 PM |
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Then there is the gulval linkage designed to aid the TOE out syndrome
My Daughter has taken over production of the damn fine Triton race seats and her contact email is emmatrs@live.co.uk.
www.tritonraceseats.com
www.hairyhedgehog.com
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Triton
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| posted on 17/1/06 at 11:20 PM |
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Cat amongst pigeons then....Live axle for simplicity
My Daughter has taken over production of the damn fine Triton race seats and her contact email is emmatrs@live.co.uk.
www.tritonraceseats.com
www.hairyhedgehog.com
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andyps
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| posted on 17/1/06 at 11:35 PM |
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quote:
Originally posted by snoopy
lets get back to whats better? irs or de dion
in the early days of video there was betamax and vhs
betamax was way better than vhs but vhs
took the market so it seems that the best is not neccessarley the most popular system?
[Edited on 17/1/06 by snoopy]
But that was down to cost and availability of pre-recorded material on the two formats. Sony lost out because their competitors in the film industry
did not want to support their format so went with the other - VHS.
I am pretty sure if it was better De-Dion would be used on a lot more cars (making it fashionable), but most have independant, multi-link systems
these days - after all, it isn't how it does it that counts, it is how it performs. The equivalent to De-Dion for fwd cars would be a dead axle,
and I can't think of any that use that (although I am sure someone might correct me).
Andy
An expert is someone who knows more and more about less and less
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stevebubs
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| posted on 18/1/06 at 01:07 AM |
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timing of the Caterham 21 clashed horribly with the Elise....no real competition at the time....
Strathcarron...keep an eye on pistonheads and ebay - they DO pop up every now and again...
There is still a website, though... http://www.strathcarron-sports-cars.com/
Still prefer the Pell Genesis (now the Aeon Blaze...)
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gazza285
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| posted on 18/1/06 at 06:06 AM |
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quote:
Originally posted by andyps
The equivalent to De-Dion for fwd cars would be a dead axle, and I can't think of any that use that (although I am sure someone might correct
me).
Go on then. Alfasud, Alfa sprint, Alfa 33 and probably some other Alfas. Other than that, no idea
DO NOT PUT ON KNOB OR BOLLOCKS!
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smart51
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| posted on 18/1/06 at 08:19 AM |
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Rather than listing cars with each suspension type, why not describe the effectf of each type of suspension to get an idea of their good / bad
chatacteristics?
De Dion suspension keeps the wheels parallel with each other, or slightly less than parallel depending on the design or welding of the de dion tube.
This keeps the wheels perpendicular to the road, normally, which gives good grip. If one of the wheels goes over a bump, or through a pothole,
however, the whole axle tilts making the wheels not parallel to the road.
A wheel at an angle to the road tends to turn in a circle about the point where the axis of the wheel intersects the plane of the road. So, if you
rear right wheel goes over a lump in the road, the rear of the car tries to pull to the left. If this occurs on a right hand bend then you get
oversteer.
With an IRS car, the rear left wheel is hardly affected by the rear right wheel's bump so less steering affect.
IRS rears can have a degree of camber angle designed into them. This camber angle can be designed to change with bump and roll. This allows the
amount and character of oversteer to be designed in. Negative camber reduces understeer because the outside wheel leans into the corner. The design
is such that as the car rolls into the corner, the wheel becomes more vertical at first, increasing grip. As the car rolls further, the camber angle
becomes positive and oversteer increases, letting go gently.
De dion axles are not affected by roll and the camber angle is fixed when the dedion tube is welded.
Oversteer can be combated by reducing roll or building understeer into the front axle geometry.
So De dion is not affected by roll but is affected by bump, not that you have those on a track.
IRS is not affected by bump but is by roll, of which you get very little in a seven.
De dion is easy to set up as there is nothing to set up.
IRS has designed in control of camber (and toe) over the whole suspension range and so may offer better overall suspension control, but you have to
set up that geometry
perhaps its a matter of horses for courses
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andyps
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| posted on 18/1/06 at 10:28 AM |
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quote:
Originally posted by gazza285
quote:
Originally posted by andyps
The equivalent to De-Dion for fwd cars would be a dead axle, and I can't think of any that use that (although I am sure someone might correct
me).
Go on then. Alfasud, Alfa sprint, Alfa 33 and probably some other Alfas. Other than that, no idea
They were the last ones I could remember too - hardly current though - the Alfasud was an early 70's introduction, and the 33 an update of it.
Andy
An expert is someone who knows more and more about less and less
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britishtrident
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| posted on 18/1/06 at 12:40 PM |
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quote:
Originally posted by andyps
quote:
Originally posted by gazza285
quote:
Originally posted by andyps
The equivalent to De-Dion for fwd cars would be a dead axle, and I can't think of any that use that (although I am sure someone might correct
me).
Go on then. Alfasud, Alfa sprint, Alfa 33 and probably some other Alfas. Other than that, no idea
They were the last ones I could remember too - hardly current though - the Alfasud was an early 70's introduction, and the 33 an update of it.
Ford used a very cheap nasty version on the MK1/MK2 Fiesta but it was really designed soley for minimum cost.
Honda and Rover used a much better version in the early 80s -- it worked really well beter than the late 80 early 90s multilink irs Honda/Rover ,
however it uses a lot of boot space and a fwd car really only needs rear suspension to keep it fom rubbing on the road, the Torsion beam gave better
boot space was just so cheap/simple and worked so well it killed the beam axle dead.
The real reason de Dion isn't used more is that it takes up a lot of space at the rear.
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MikeRJ
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| posted on 18/1/06 at 03:14 PM |
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quote:
Originally posted by smart51
A wheel at an angle to the road tends to turn in a circle about the point where the axis of the wheel intersects the plane of the road. So, if you
rear right wheel goes over a lump in the road, the rear of the car tries to pull to the left. If this occurs on a right hand bend then you get
oversteer.
Surely this effect is negligible with radial tyres?
Even so, you could say the same about IRS, a bump on one side would cause the camber to be different from one side to the other (unless you have equal
length & equal angled wishbones).
Also, if a car wants to pull to the left on a right hand bend, wouldn't that be understeer rather than oversteer?
[Edited on 18/1/06 by MikeRJ]
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