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irs or de deon
dougal - 13/8/02 at 11:43 PM

which is better
from what i understand
de deon keeps the tyres perpendicular to the ground which in simple theory is what you want.
irs with wishbones will give a lower unsprung mass an introduce a desirable camber change under roll.
which is the best solution to a track and road car.
f1 use unequal length wishbones so i suppose that must be the best grip solution.
any comments
also what if any advantages if any would inboard shocks give

interestedparty - 14/8/02 at 08:36 AM

F1 not a good comparison because the rear mounted gearbox would obstruct a de dion tube.
In general, de dion is thought best for grip and racing, irs best for road

John

cymtriks - 14/8/02 at 08:43 PM

IRS is more suited to heavier cars than the lowcost. The camber changes with IRS will be too large as the differences that changing weights, such as having a passenger or loading luggage, have on a light weight car would be excessive. These weight changes will also affect heavier cars but the changes will be smaller and this tips the balance in favour of IRS for heavier cars. It is worth pointing out that Caterham and Strathcarron both use Deon. The designers of the Strathcarron (525Kg)stated that the weight at which IRS became the best choice lay between their design and the Elise (735Kg). Deon would seem to be best for the lowcost.

philgregson - 15/8/02 at 08:02 AM

My first choice when deciding to build was for a de dion but I could not find any drawings (or even a sneaky photo) to conform how I thought it should be done (I assume it could be based around the 'standard' locost trailing links with a sierra diff and manufactured uprights). In the end I decided to follow the live axle route for now and look into it again at a later date.

Has anyone out there done a de dion? and, if so, how?

interestedparty - 15/8/02 at 10:19 AM

quote:
IRS is more suited to heavier cars than the lowcost. The camber changes with IRS will be too large as the differences that changing weights, such as having a passenger or loading luggage, have on a light weight car would be excessive.


That will depend on the suspension stiffness. If for instance the car is fitted with 200lb springs at the rear, then that means that an extra 200lbs will be needed to compress the spring a further inch. With two springs, one each side of course,mounted near enough vertically, then an extra 400lb of load will be needed to make the car ride an inch lower. The camber change will depend on the ride height. Moral of the story- if you are running stiff springs and irs then don't worry too much about camber changes due to load fluctuations unless your passengers/luggage are unusually heavy

John

cymtriks - 17/8/02 at 10:12 PM

true; but harder springs can reduce grip. A very hard suspension will not be as good at coping with all those road surface irregularities and can have less grip than a softer suspension over a given surface. There is an optimum spring rate for a given unsprung weight and a given performance. For sportscars this would seem to be somewhere in the region of 90cpm (cycles per minute natural suspension frequency) to 110cpm. The Elise and the Mc Laren F1 fall in this range for the rear suspensions. There seems little point in using a drastically harder spring to cover up a suspension failing to do its job with a more appropriate spring rate especially if this results in reduced all round capability. The book states that springs should be about 200 lbs which is very hard. The range for cpm quoted above would indicate 75lbs to 115lbs for the rear springs. Has anyone tried springs softer than the book values?

interestedparty - 18/8/02 at 07:39 AM

quote:
A very hard suspension will not be as good at coping with all those road surface irregularities and can have less grip than a softer suspension over a given surface.


I agree, and if there were no other considerations then softer springs would be better. Unfortunately the basic locost design does not allow for anything other than pretty limited suspension movement.

John

dougal - 18/8/02 at 10:27 PM

what i am after is the best i can cet from my limited resorces and not having to compromise one area as a result of another areas failings. so de dion it is. im going to be basing my design around the avon book plans but now i am using a de dion rear i will have to use champions trailing arm linkage which ill draw up on pro/E.
on another matter does anyone see much advantage in a watts linkage instead of the panhard link?
pete

Simon - 25/8/02 at 09:22 PM

Dougal,

"what i am after is the best i can cet from my limited resorces ......"

Aren't we all.

Did a bit of research on De Dion (pics only) and found that P6 Rover had DD. Had inboard discs too.

Just a thought.

ATB

Simon

cymtriks - 2/9/02 at 10:44 PM

I would suggest a Satchell link ( two lower links from the axle ends angled inwards to mounts on the back of the transmission tunnel and two upper links forwards to the chassis sides as the upper links in the book) This linkage is simpler than a five link, is used in NASCAR and so can handle power and is also used on the Strathcarron and the Rover mentioned earlier. I honestly can't think why anyone would want to bother with five links unless they owned shares in a rod end company.

Noodle - 4/9/02 at 06:04 AM

quote:
I would suggest a Satchell link... used on the Strathcarron and the Rover


Check out http://www.locostbuilders.co.uk/photos/cgi-bin/showpic.pl?p6_de_dion.jpg

billy - 14/10/02 at 08:03 PM

i have a lo-cost with de deon set up,if anyone needs some pics i can post them here,its not quite finished but its rolling

billy - 14/10/02 at 08:04 PM

would help if i spelt it right,lol

philgregson - 21/10/02 at 12:08 PM

I have been pondering the De Dion option myself now for some time as I think it is probably the best compromise for this type of car.
I would love to see how you did it - If you could post some photos it would be great.
Cheers, Phil

Hallsy - 21/10/02 at 02:00 PM

I'd like to see some pictures of the DeDion set up as well if you don't mind.

Dunc - 21/10/02 at 02:47 PM

Don't bother with any of the proposed rear suspension design. Just have the hubs bolted straight onto the chassis, then fit 70 profile tyres and that should soften then the ride, of course they'll be no damping and you'll bounce along like a JCB. Hehehe.