Z20let Corsa
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| posted on 24/2/09 at 09:33 PM |
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what rear suspension setup???
i was going to do a fully independant rear suspension setup on my locost but my brother seems to think that the de dion setup will get the power down
better and make it handle better because the wheels will be flat on the ground at all times. what are peoples opinions??? Im using a sierra LSD off a
xr4 with disks. thanks.
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nick205
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| posted on 24/2/09 at 09:59 PM |
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Which way's the wind blowing...?
In an ideal world with flat, smooth road surfaces (or a track) then a well designed De Dion set-up has the potential to offer better handling.
In real world UK road driving a well designed IRS set-up should give a better ride and road holding.
From what I've seen/read it appears that it might be easier to design a good De Dion set-up than IRS - that's my take on it.
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mookaloid
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| posted on 24/2/09 at 10:24 PM |
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From discussions/observations at hill climbs, I reckon that a live axle (or a de dion) will put the power down better off the line, however as the car
experiences body roll through corners (and subsequent geometry changes), the independant set up potentially offers more options if there is enough
adjustability and the design is good to start with.
As with most things, whichever way you go it will be a compromise
"That thing you're thinking - it wont be that."
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Cobra289
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| posted on 24/2/09 at 11:47 PM |
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If the DeDion setup was better suspension the F1 boys will use it.
They have the best flat tracks of the world too.
Watch out for the TRUST LINE on a DeDion. The car will always go in that direction!. [Shake it! baby]
But for a normal use, it is a solution.
Regards,
Cobra289
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James
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| posted on 25/2/09 at 12:48 AM |
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Suspension questions are no fun any more since Rorty/Syd left!!! 
Whichever you use, Z20let Corsa, it'll be great. I've never heard anyone say: I've built a De Dion/IRS/Live Axle Locost and it
handles crap!
Cheers,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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Ivan
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| posted on 25/2/09 at 06:00 AM |
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quote:
Originally posted by Cobra289
Watch out for the TRUST LINE on a DeDion. The car will always go in that direction!. [Shake it! baby]
Cobra289
What is the "TRUST LINE" - have never seen this term before.
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Cobra289
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| posted on 25/2/09 at 08:28 AM |
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quote:
Originally posted by Ivan
quote:
Originally posted by Cobra289
Watch out for the TRUST LINE on a DeDion. The car will always go in that direction!. [Shake it! baby]
Cobra289
What is the "TRUST LINE" - have never seen this term before.
TRUST-LINE is a line that is perpendicular to the imaginary rear axle shaft and departs exactly from the center of the axle.
It is very often overlooked item during alignment and in some suspensions very difficult to set and others impossible.
If the trust line has an angle, your car will drive like a "dog runs"
It doesn't matter what you try to correct with the front wheels, the problem will be the same, and once it will put you 1 meter side wise.
Regards,
Cobra289
[Edited on 25/2/09 by Cobra289]
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MikeCapon
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| posted on 25/2/09 at 09:18 AM |
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I think you guys are talking about the THRUST line. The imamaginary line along which the rear wheels "push" (or thrust) the car
forwards.
Not difficult to imagine the result if this line is well off centre.
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Cobra289
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| posted on 25/2/09 at 10:24 AM |
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quote:
Originally posted by MikeCapon
I think you guys are talking about the THRUST line. The imamaginary line along which the rear wheels "push" (or thrust) the car
forwards.
Not difficult to imagine the result if this line is well off centre.
Sorry for my bad English.!
Regards,
Cobra289
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Chippy
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| posted on 25/2/09 at 10:48 AM |
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I dont think that for normal road, and the occasional track day, that you can beat IRS. De dion is fine if the road is flat, but for normal, (read
bumpy), english roads a well set up IRS can't be beaten. Just my oppinion. Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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Phil.J
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| posted on 25/2/09 at 11:18 AM |
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IRS everytime given the choice. Much lighter and infinitely more tunable.
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MikeR
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| posted on 25/2/09 at 12:44 PM |
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MUCH lighter????
Interesting statement.
How do you figure that?
For de-dion you've got the bar running left to right which increases your unsprung weight - but you haven't got all the associated boxing
of the back of the car to hold the trailing arms.
I won't argue it may be lighter - and i won't argue it may be heavier. But MUCH lighter seems a contentious statement to me.
If someone can weight an original MK IRS and Live axle chassis then add on the IRS or my (previous) de-dion weights we'll have some interesting
facts.
(note i'm not suggesting comparing a standard MK chassis as its different to the book - perhaps the good comparison would be a Aries / Stuart
Taylor race vs road chassis)
Also infinitely more tunable also equals infinitely harder to set up and much more likely to muck up.
[Edited on 25/2/09 by MikeR]
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SPYDER
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| posted on 25/2/09 at 09:26 PM |
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quote:
Originally posted by MikeR
For de-dion you've got the bar running left to right which increases your unsprung weight - but you haven't got all the associated boxing
of the back of the car to hold the trailing arms....
You still need trailing arms to locate the De Dion tube?? And a Panhard rod or similar for sideways location. And there still needs to be something
central in which to mount the diff.Or am I missing something?
Geoff
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Chippy
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| posted on 25/2/09 at 11:40 PM |
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I would say that the de-dion is definately heavier than the IRS system. You have almost the same set up as for IRS, (in the way of tubing), plus that
bloody great steel tube that holds the wheels on. Just my opinion. Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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MikeR
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| posted on 25/2/09 at 11:48 PM |
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You need to put a box around the diff. This should be braced to take the forces of the IRS suspension - its got to mount somewhere. This isn't
present on de-dion.
You need 10 tubes to make up the rear suspension on IRS, only 4 on de-dion + panhard. I'd guess that the total of the 10 tubes would be a
smidgen greater than the 4 + panhard on de-dion.
So its down to does the de-dion tube weigh more or less than the bracketing for the IRS suspension mounts. Hence my comment about it not being MUCH
lighter - just perhaps a little BUT far easier to set up the geometry.
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Cobra289
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| posted on 25/2/09 at 11:54 PM |
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Hi guy's,
It doesn't matter witch one is heavier, this just a advertising item.
The important thing is that you get a good handling and that you choose the axle that suit your needs.
Suppose that it is 5 Kg heavier what happens when the driver is 20 Kg lighter than you????
So this kind of discussion about the weight is not relevant.
Take as an example the McPherson suspension, every one that goes into the design get into troubles and a lot of problems to verify all the theories
and methods of suspension design, but well this type [McPherson] is a well proved suspension that no ones can clarify why?
Regards,
Cobra289
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SPYDER
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| posted on 26/2/09 at 12:26 PM |
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quote:
Originally posted by Cobra289
So this kind of discussion about the weight is not relevant...
If Colin Chapman were alive today he'd be turning in his grave!!
The consideration of weight, in particularly unsprung, is surely of primary consideration.
I was always led to believe that a live axle setup was the lightest, although I have never seen any figures. It does, however, also have the greatest
unsprung weight.
I dare say the difference in lap times between the various setups may be minimal, but the difference in ride quality on the road may be more
noticeable.
A lightweight De Dion setup, with ally cross tube and arms or a billet CNC cross member may be the best compromise.
Not exactly "locost" though.
"Locost" option has to be live axle.
But as Mike R said "Also infinitely more tunable also equals infinitely harder to set up and much more likely to muck up."
Unless you are thinking about weight ALL the time it would be easy to compromise a little bit here, a little bit there, then suddenly it adds up to 30
kilos.
Conversely, saving the EXTRA litle bit here and there will add up too.
Geoff.
[Edited on 26/2/09 by SPYDER]
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Cobra289
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| posted on 27/2/09 at 09:23 AM |
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quote:
Originally posted by SPYDER
quote:
Originally posted by Cobra289
So this kind of discussion about the weight is not relevant...
If Colin Chapman were alive today he'd be turning in his grave!!
The consideration of weight, in particularly unsprung, is surely of primary consideration.
I was always led to believe that a live axle setup was the lightest, although I have never seen any figures. It does, however, also have the greatest
unsprung weight.
I dare say the difference in lap times between the various setups may be minimal, but the difference in ride quality on the road may be more
noticeable.
A lightweight De Dion setup, with ally cross tube and arms or a billet CNC cross member may be the best compromise.
Not exactly "locost" though.
"Locost" option has to be live axle.
But as Mike R said "Also infinitely more tunable also equals infinitely harder to set up and much more likely to muck up."
Unless you are thinking about weight ALL the time it would be easy to compromise a little bit here, a little bit there, then suddenly it adds up to 30
kilos.
Conversely, saving the EXTRA litle bit here and there will add up too.
Geoff.
[Edited on 26/2/09 by SPYDER]
Hi Geoff,
My comments where placed in the context of the person that did start the thread.
As you can see he plan or is all ready building a Locost V8.
The unsprung weight is very important and there are more components that need to be check to reduce that weight.
- Steel wheels are lighter than normal aluminum ones.
- There are lighter [small] tires on the market.
- Calipers
etc.
But with a V8 you have some restrictions in this area.
Anyway I prefer the Independent Rear Suspension but I can accept a "Well fabricated DeDion"
The big problem that I find of a DeDion is the good fabrication and design.
Regards,
Cobra289
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RK
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| posted on 27/2/09 at 06:44 PM |
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Let's say you're car is 40 kgs heavier due to engine, suspension or you're carrying a lot of doughnuts. That represents about 10 BHP
more that you'll need to push it around. Big bloody deal. Don't eat so many chips that week if that is the concern.
[Edited on 27/2/09 by RK]
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SPYDER
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| posted on 27/2/09 at 11:45 PM |
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quote:
Originally posted by RK
Let's say you're car is 40 kgs heavier due to engine, suspension or you're carrying a lot of doughnuts. That represents about 10 BHP
more that you'll need to push it around. Big bloody deal. Don't eat so many chips that week if that is the concern.
[Edited on 27/2/09 by RK]
Thankyou for your helpfull post. An additional boost in horsepower might help with getting back the loss in acceleration but what about braking and
cornering with the extra 40 kilos on board?
Should we fit wider tyres and bigger brakes, maybe?
The whole essence of the "seven" type sportscar revolves around its nimbleness and responsiveness, both directly affected by weight. The
fairly recent move towards Bike engines within some areas of the community typifies this.
If you were in the market for a locost chassis and there were two available, identical other than one being 40 kilos more than the other, which would
any sane person choose?
Don't be fanatical about weight but do keep it under consideration at all times.
As for doughnuts, try Tescos car park on a Friday night.
All IMHO.
Pass the chips...
Geoff.
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