Cheers
Alex
PS
And as Paul says John (Jroberts) will supply the bits at a nice price
Going to do some changes to the 7 whilst is Sorn'd.....removing the sierra back end and trying to make it lighter. But can't decide between IRS and de-dion. I basically want something - simple, cheap, light and that handles well....I know de-dion is probably the better way to go for these things but I'm not quite convinced and reckon I might be better to spend a bit more time and money trying to make a double wishbone IRS arrangement. What do you all think?? Please give reasons to votes as well, if you can be bothered.....Thanks. Oli.
Hi,
I went with de-dion because it gives me 99% of the benefits of IRS with 99% of the simplicity of live axle. I made this choice several years ago when
de-dion kits were scarce but now you can buy a de-dion beam from several suppliers for not much money.
In my mind the choice has never been clearer!
Cheers,
Craig.
If I didn't have a live axle I would go de dion as it means less alteration to the basic chassis. The kit to make them is reasonably priced from most suppliers as well.
Planning on making it all from scratch so not too woried about buying the bits from suppliers. Also chassis is a tiger cat so different from locost.....Figured I'd almost be grafting on the rear end of an avon.....Oli.
de-dion for me,
just u2u jrobert on here
he sells them and the very good
Being that you need to trash the suspension behind the rear bulkhead I would be inclined to make a subframe to fit around the diff and IRS it,
especially as you have no mountings for a live axle so this all needs making and bracketing on the main tub.
Strange so much attention to the front suspension then they stick on the whole rear from a sierra....
Regards Mark
[Edited on 6/2/07 by mark chandler]
Dedion, same reasons as given i.e. nearly as good as IRS, easier to do, cheaper, and much easier to setup
Cheers
Alex
PS
And as Paul says John (Jroberts) will supply the bits at a nice price
De-dion
I voted IRS because ultimately it is probably the better system, and can be purer in design, plus I am going for it myself. Having said that, if I had a live axle car and wanted to change I would go de-dion as it would be much easier and probably nearly as good to most drivers.
A de Dion axle has much better wheel geometry than irs, it wins on smooth surfaces, but because it is not indpendant on surfaces with single wheel
bumps irs has the advantage.
As with a live axle in a Locost de Dion is hampered by the length of the trailling links, make these as long as possible to reduce roll steer.
De-dion. IRS may have the edge on rough ground, but only if properly designed and it's much easier to make a crap IRS than a good one. Ask Tiger.
quote:
Originally posted by jroberts
De-dion
Mike,
Name and shame, i say
De dion for my choice as well. Unless you still want it sorned this time next year while your still trying to set up the rear suspension
Seriously it'd be quicker and for the price of a manufactured de dion you might be better buying one than spending time making one. However as
Mark will tell you I'm not one for being frivolous with the wallet.
I find it amusing how often rear suspension design is debated, specifically, how it's, "Easy to make a bad IRS." In other words, if
it's hard to do, don't do it. However, I never hear this arguement used in the other place that independent suspension is used - at the
front of the car. If the same logic is used there, it means we should use a straight front axle.
No one seems to shy away from building front independent suspension, and everyone agrees about the many benefits: wheel control, low upsprung weight,
smooth ride, etc. And yet, these same people completely change face when it comes to the back of the car. Suddenly, there's nothing wrong with an
sprung-to-unsprung weight ratio of 3:1?
While we all pretend to be race car drivers, the truth is that the vast majority of our cars will never see the track. Real-world streets are very
bumpy, so ride quality, much more so that wheel control, is the overriding factor. For real-world streets, nothing beats IRS for a smooth ride.
Is it harder to do? Yes. Do you need to know what you are doing? Yes. Can it be done badly? Yes - just like at the front of the car.
[Edited on 2/6/07 by kb58]
I agree - do de-dion if you want it easy, but IRS is better. And it's really not that hard to engineer
When I completed my back end & weighed the unsprung weight with bathroom scales I asked on here if any de-dion (or live axle)users could do the
same - only got a reply from another IRS user (who's unsprung weight was the same as mine at 31kg/corner) Incidentally front & back are the
same.
Bob
Oli good move to junk all that scrap! I vote De-Dion with a Panhard rod, funny that both ideas from French in the early 20th Century! I think the easy
to make and set up wins out over the theoretical advantages of independent I think the design for rear independent suspension for locosts is not
sorted yet so each set up needs way too much tinkering.
If you really want it simple I still have a spare Capri axle . . . . .
Caber
quote:
Originally posted by kb58
I find it amusing how often rear suspension design is debated, specifically, how it's, "Easy to make a bad IRS." In other words, if it's hard to do, don't do it. However, I never hear this arguement used in the other place that independent suspension is used - at the front of the car.
Lol - thanks, but no thanks Caber! You've all made me more confused than ever! My heart says IRS and make the effort etc to make it good. My brain tells me I'll end up with a much better De-dion setup that I'll be able to use during the summer! I just can't decide though! How bad is de-dion on bumpy roads - we have a lot around here and I don't really plan on going on track so want the best road setup possible! Funny how the 3 ppl who know me and would theoretically be involved in it all say de-dion! hmmm...some more thinking to do I think....Oli.
I am hoping the new book will offer the answer to the IRS design question.
It's all subjective; there'll never be consensus. If you put Schumacher in a straight-axle Seven, he'll blow away a IRS setup driven by
"normal" people. But put him in the IRS car, and it'll be faster than the straight-axle car, by "some amount."
I think that the lap-time advantage of the IRS is real, but the skills (as both driver and builder) or lack thereof, are a much bigger slice of the
pie.
[Edited on 2/6/07 by kb58]
perhaps one difference is this......
the front end design exists, the rear end design doesn't for IRS. Its easy to copy the book and make the front end.
As for name and shame, Mr JRoberts, would i do that? I mean, who would I name Mr JRoberts? Can you think of anyone? apart from NS Dev obviously
This is all more than a little amusing.
Let me ask this;
How many (modern, since 1960) racecars do you see with DeDion backends?
Now, how many racecars do you see with IRS?
What is the back end in a BMW? Why?
What is the back end in a Merc? Why?
Still, you are building a 1950's heritage car, so keep the faith with '50s technology!
Cheers,
Syd. 
In the mid 70s Ferrari built a test car with a de Dion axle, Lauda spent a lot of time playing with it, they came to the conclusion it was as least
as good as the the irs BUT the existing irs set up was a known quantity for them so the de Dion got ditched.
Fitting a de Dion into in an F1 car and getting the beam stiff enough for use with slick tyres was always going to be awkward to package but then
along came the Lotus 78 & 79 to rewrite the book of F1 aerodynamics using a de dion on a venturi car is just not possible.
Astom Martin use de Dion, while Jaguar use IRS on the same platform.
Very true, Syd. Considering how much heavier these cars are ,makes the IRS solution that much more important. No matter how much work it takes, or how much it costs, getting the unsprung weight down WILL make a big difference in ride quality. And, as said before, most cars will be driven on real world, bumpy streets, where the sprung-to-unsprung weight ratio is a big deal.
quote:
Originally posted by kb58
Very true, Syd. Considering how much heavier these cars are ,makes the IRS solution that much more important. No matter how much work it takes, or how much it costs, getting the unsprung weight down WILL make a big difference in ride quality. And, as said before, most cars will be driven on real world, bumpy streets, where the sprung-to-unsprung weight ratio is a big deal.
He does have a point about ride quality though. Would you really drive a car that was flat and smooth on a track, but shook your teeth out on the way
home? I know I wouldn't. For most on here losing some all out handling won't matter at all, but the improvement in general
drivability/comfort will be do, as most of the use will be on the road.
PS, I agree with you on the De-Dion being quicker and easier to set up though.
[Edited on 6/2/07 by DIY Si]
quote:
Originally posted by kb58
Very true, Syd. Considering how much heavier these cars are ,makes the IRS solution that much more important. No matter how much work it takes, or how much it costs, getting the unsprung weight down WILL make a big difference in ride quality. And, as said before, most cars will be driven on real world, bumpy streets, where the sprung-to-unsprung weight ratio is a big deal.
quote:
Originally posted by DIY Si
He does have a point about ride quality though. Would you really drive a car that was flat and smooth on a track, but shook your teeth out on the way home? I know I wouldn't. For most on here losing some all out handling won't matter at all, but the improvement in general drivability/comfort will be do, as most of the use will be on the road.
PS, I agree with you on the De-Dion being quicker and easier to set up though.
[Edited on 6/2/07 by DIY Si]
quote:
Originally posted by Syd Bridge
This is all more than a little amusing.
Let me ask this;
How many (modern, since 1960) racecars do you see with DeDion backends?
The most convincing arguments against IRS that I've seen are all about geometry and creating potentially lethally bad handling if you don't
really, really know what you're doing.
Syd's arguments that IRS is best for professional race teams are fair enough, but as far as I'm aware there is no generally available highly
regarded set of plans like a "mcsorley IRS".. so the problem is being capable of designing your own IRS that's a) safe and b) better
than de-dion.
I have some idea what rear toe-out conditions can do for your life expectancy.
I judged myself not capable of designing a safe and effective IRS and not willing to put the effort in to become capable.
i think its quite a simple one this. If you just want to make the car lighter and get back on the road asap, its a de dion. If you enjoy fiddling in
the garage (insert joke here) then irs is probably more for you. I can guarantee that if you blindfolded someone and stuck them in someones locost,
for a drive on a large airstrip, they wouldnt be able to tell the difference at all. And i bet a few bumps wouldnt give you any clue either.
Im putting IRS on my new car, because i can and i want to.
Mike RJ - the latest Caterham chassis has moved to IRS.
Surely, just as easily as it is possible to make a bad IRS, anything not aligned correctly on a de-dion would be pretty difficult to sort out and
would wear tyres out quickly.
Whilst there may be aerodynamic issues with de-dion on an F1 car, for all the enclosed bodywork racers this wouldn't apply, but very few of them
(particularly those designed specifically as race cars) deviate away from IRS, yet they run on the smoothest tarmac surfaces available. Says enough
for me to be convinced which ultimately works best.
I agree that IRS is probably better for out and out race cars because you want as many variables as possible to tweak to gain an edge but it is
exactly the large number of variables which makes it more difficult for an amateur builder to get IRS right.
Most amateurs don't have access to sophisticated computer modelling , can't afford to have multiple sets of slightly different components
(springs, dampers, anti-roll bars etc.) made to order and don't want to spend thousands of hours on a track trying to get it all to work. Most
amateur's won't have the engineering know-how to do it either even if they did have unlimited money and time.
Blueshift's point about rear toe-out strikes a chord with me too because I nearly had a bad accident in a mini when I was 17 because I
didn't realise that the inner radius arm pivot hole was slotted on a new rear subframe which I had fitted. The resulting rear toe-out made the
car oversteer badly when I went over a bump mid corner and I very very nearly crashed.
It's much easier to make a de-dion axle up in a jig to be either perfectly parallel (or to have very slight toe-in and negative camber as mine
has) than it is to construct an inherently safe IRS setup from scratch. You could of course use rod-ends on all the joints to allow you to adjust out
any gremlins but that will bring additional challenges.
I would confidently predict that an amateur built de-dion car would out perform an otherwise equivalent amateur built IRS car on any track in the
country.
Cheers,
Craig.
quote:
Originally posted by craig1410
Who cares about handling characteristics on a "bumpy street"?
quote:
If you don't mind me saying so, you have a very blinkered opinion which isn't going to help Oli make a balanced decision.
quote:
One more thing to favour de-dion in case you need more convincing - it has reputedly much better traction off the start line than an IRS setup. This is because the camber doesn't change on squat like a standard IRS setup and the tyres stay flat to the road.
quote:
Of course you could go the whole hog and dial in anti-dive and anti-squat to your IRS setup but that is adding to the complexity and will make setup even more difficult.
to make it all better.
quote:
Originally posted by craig1410
I agree that IRS is probably better for out and out race cars because you want as many variables as possible to tweak to gain an edge but it is exactly the large number of variables which makes it more difficult for an amateur builder to get IRS right.
Most amateurs don't have access to sophisticated computer modelling , can't afford to have multiple sets of slightly different components (springs, dampers, anti-roll bars etc.) made to order and don't want to spend thousands of hours on a track trying to get it all to work. Most amateur's won't have the engineering know-how to do it either even if they did have unlimited money and time.
Blueshift's point about rear toe-out strikes a chord with me too because I nearly had a bad accident in a mini when I was 17 because I didn't realise that the inner radius arm pivot hole was slotted on a new rear subframe which I had fitted. The resulting rear toe-out made the car oversteer badly when I went over a bump mid corner and I very very nearly crashed.
It's much easier to make a de-dion axle up in a jig to be either perfectly parallel (or to have very slight toe-in and negative camber as mine has) than it is to construct an inherently safe IRS setup from scratch. You could of course use rod-ends on all the joints to allow you to adjust out any gremlins but that will bring additional challenges.
I would confidently predict that an amateur built de-dion car would out perform an otherwise equivalent amateur built IRS car on any track in the country.
Cheers,
Craig.
Hi if you really want light go with live axle as this is the lightest option by far. The so called problems of unsprung weight is only a problem if
you dont sort out the dampers to match the setup these dampers can be had for £90 ea.
cheers matt
There's a lot of talk about 'ride' quality.
This is another of my hobby horses.
The quality of ride with any rear end system should differ little.
The biggest problem is educating you lot to put the SOFTEST springs in the car all round.
Far too many locosts are oversprung, overdamped, then complaints are made about dodgy handling and hard ride quality.
The rubbery chassis will not tolerate hard springs, and ends up acting as part of the spring/suspension medium itself.
Put whatever backend in you fancy, but please, spring it properly and then set the dampers as soft as is tolerable.
Cheers,
Syd.
quote:
Originally posted by Syd Bridge
There's a lot of talk about 'ride' quality.
This is another of my hobby horses.
The quality of ride with any rear end system should differ little.
Hi wise words from syd.
cheers matt
quote:
Originally posted by craig1410
One more thing to favour de-dion in case you need more convincing - it has reputedly much better traction off the start line than an IRS setup. This is because the camber doesn't change on squat like a standard IRS setup and the tyres stay flat to the road.
quote:
Originally posted by kb58
Why is it then that many race cars that use straight axle tubes, bend them to add camber? It's because when the car corners, the tires roll, causing positive camber - a bad thing.
The reason Caterham went over to the De-dion axle was because of supply issues over live axles, the De-dion was a logical choice to keep the handling
pretty much the same as the live axle.
F1 cars are a bad example of IRS, as they're set so stiff the only travel in the set up is in the side walls of the tyres!
Alot of competion cars have to race in classes where the rules state that location points cannot vary from the production vehicles, so they have to
follow what the road car has, which in general is very biased to comfort!
Production cars are also designed to offer maximum interior space, so the suspension is often designed to fit into what space is left, not really an
ideal situation.
IRS has an advantage in the fact that it can be designed to be highly adjustable. Which is great if you're one of life's tinkerers, but in
something as light as a 7, you are hard pushed to beat a De-dion set up.
As MikeRj has said, they are all just a compromise.
[Edited on 7/2/07 by jroberts]
oli
You're not going to ask if you should change to a BEC next are you?
FWIW
I'm not sure that the Cat has sufficient room to fit the trailing arms in place, also as the car was designed(in the widest terms) to take a
Sierra back end you may need to think carefully about the track width, you could also look, as you have already said, at grafting on an Avon back end
or using Rorty's drawings.
[Edited on 7/2/07 by Schrodinger]
quote:
Originally posted by Syd Bridge
There's a lot of talk about 'ride' quality.
This is another of my hobby horses.
The quality of ride with any rear end system should differ little.
The biggest problem is educating you lot to put the SOFTEST springs in the car all round.
Far too many locosts are oversprung, overdamped, then complaints are made about dodgy handling and hard ride quality.
The rubbery chassis will not tolerate hard springs, and ends up acting as part of the spring/suspension medium itself.
Put whatever backend in you fancy, but please, spring it properly and then set the dampers as soft as is tolerable.
Cheers,
Syd.
Theres designs for both de dion and irs on my website. What the geometry is like I dont know, but they might offer a starting point for designs.
Just know there are advantages and disadvantages to each solution. De dion is the quickest to retro fit to a locost as you dont need to do any chassis
mods. IRS is much more involved. Theres enough literature and knowledge out there to let you build a very good IRS set up, all depends how much time
and effort you are willing to put into the design.
Most people will never drive a locost to its true limit, and so the small differences between a good live axle/de dion/irs set up are irrelevant
IMO.
David
quote:
Originally posted by Syd Bridge
...
The biggest problem is educating you lot to put the SOFTEST springs in the car all round.
...
Put whatever backend in you fancy, but please, spring it properly and then set the dampers as soft as is tolerable.
Cheers,
Syd.
) was an advocate of soft springs allied to firm damping. Lotus models
have been accused of many things, but I can't remember poor handling being in the list.
quote:
Originally posted by Fozzie
quote:
Originally posted by Syd Bridge
There's a lot of talk about 'ride' quality.
This is another of my hobby horses.
The quality of ride with any rear end system should differ little.
The biggest problem is educating you lot to put the SOFTEST springs in the car all round.
Far too many locosts are oversprung, overdamped, then complaints are made about dodgy handling and hard ride quality.
The rubbery chassis will not tolerate hard springs, and ends up acting as part of the spring/suspension medium itself.
Put whatever backend in you fancy, but please, spring it properly and then set the dampers as soft as is tolerable.
Cheers,
Syd.
Oh so very, very true!........ I have had many conversations on that exact point....
Some listen, most do not.....
Sadly,you can lead a horse to water Syd, but you can't make it drink....
IMHO a very important part of the build, where not enough thought is given ...
Fozzie
quote:
Originally posted by MikeRJ
Some static negative camber is added to live axles/de-dions to help the tyre stay flat during cornering, it's not there to help with traction when the suspension squats.
I've deleted a few posts. This was getting way off topic and heading towards juvenile.
And Flakmonkey, my knowledge is all I have to sell, I don't give it away. You will learn this one day. As for losing it with my passing, my sons
are well educated, and in my methods as well.
If someone wants to pay for my knowledge, then they get that benefit.
Syd.
Can of worms or what! Firstly - this is a ROAD car not a track day weapon or racer. I'm really not that interested in how it performs on track. If I was I'd have a striker with a bike engine and IRS rear setup (but I don't). Secondly - your all right I probably wont ever get near the limits of the car but its always nice to know its there! Thirdly - I'm not planning on designing an IRS setup from scratch. There are (as flakmonkey) says various designs already available. The original IRS plan was to graft an Avon rear end in place. Far from making the choice clearer you are all confusing me more than ever. What I really want to know is - given the extra expense and hassle of IRS over de-dion (for a road car) is it worth it??? Opinions gladly received but please don't go on about F1 cars again! I wish I could afford one but it aint gonna happen so lets stick to 7's please.....Thanks in advance. Oli.
Sorry if we have confused you....
Okay, simple answer:
The extra expense and hassle of IRS is NOT worth it compared to an off the shelf de-dion axle.
Good luck,
Craig.
"go with live axle as this is the lightest option by far. The so called problems of unsprung weight is only a problem if you dont sort out the
dampers to match"
Fraid I don't buy this. The way I see it you have a choice of spring rates. The one you choose determines the bounce frequency of the car then
the dampers are set to damp these oscillations. The bounce frequency is sometimes quoted in cpm (cycles per minute). Unsprung mass doesn't come
into that at all. The problem with unsprung weight is that it has to be accelerated downwards to stay in contact with the road, after a bump, when the
surface is rough, and the force available to do the accelerating is the corner weight (sprung) of the car. Stiff dampers make this WORSE as the job of
a damper is to resist movement, ie force proportional to velocity.
Another point I'd love to discover is what unsprung weight is achieved with different solutions. Easy to measure - release the spring, jack up
the chassis & put bathroom scales under the wheel. My mx5 based IRS, including disc brakes wheel tyre & driveshafts is 31kg/corner (same front
as back). Can anyone tell us what they get with say a GTS dedion or an escort axle? It would be nice to know for sure what (if any) unsprung weight
penalty different designs exact.
I have 125lb/inch springs on the back. It's actually a bit too soft (grounds sometimes with a passenger) so I'll probably settle at 150.
This still gives quite a high bounce frequency (calculated at 108cpm from memory)
Bob
All I can say is the GTS de dion is very light indeed. Definately lighter than an bare escort axle. So this would lead me to the guestimate that the
de dion has considerably lower unsprung weight than the live axle by the time the diff etc is added to the live axle...
IRS gives you the lowest unsprung weight, but in total mass terms it is heavier than the de dion. I believe the de dion is the lightest overall
solution (depending on the diff weights) with some penalty on unsprung weight.
David
Hi very sad that yet again people can not have a discusion whith different opinions whithout turning it into a personel slanging match .
At the end of the day for a locost that is not exactly going to get pushed hard it really dosent matter what system is used as there is already one
appalling irs setup in use with many people saying how well it handels on the road.
However if it is for track use there is no one diffinitive best but a case of choosing what gives the best advantage over all for all circuits
used.
cheers matt
For me it has to be the de dion, I have used it in the past and it works very well, easy to setup, a touch of toe in, a little negative camber,
adjusted by shims under the bolted hubs, I use 24" long links and a watts linkage across the back.
A few years back I was interested in the caterham which was de dion at the time and maybe some of them still are I don't know, I went out for a
spin and it was great, at that time they were just introducing the IRS version, I asked why they had changed the rear suspension design he told me it
was more to do with fashion than any short comings of the de dion
Cheers
David
Hi David,
yes I'm sure it is very light, particularly compared with a truck axle - I was hoping someone could quantify with a physical measurement.
Matt, I hope I didnt cause you grief - I quoted your text 'cos it suggested that unsprung weight didn't matter & you could fix it by
damper changes - I was saying I think that's wrong. I'd never "slag anyone off"
cheers
Bob
BobC,
I wasn't answering any questions just saying that I like the de dion and a conversation that I had with a caterham chap.
My de dion tube bare is 6kgs, I haven't bothered weighing other stuff
David
quote:
Originally posted by craig1410
Sorry if we have confused you....
Okay, simple answer:
The extra expense and hassle of IRS is NOT worth it compared to an off the shelf de-dion axle.
Good luck,
Craig.
quote:
Originally posted by oliwbSo if I'm going to that effort would it not make sense to go the full hog and use one of the existing IRS designs to base mine on??
Right, I thought I remembered a previous post on rear suspension weights and an agonisingly slow search turned this up:
http://www.locostbuilders.co.uk/viewthread.php?tid=17111
Might be worth repeating the info to make it easier to find next time! These are the numbers that Stressy measured for himself:
--------------------------------------------------------
live axle
axle casing inc brackets, standard diff, trailing and lateral links, coilovers, prop, brakes.
unsprung 56kg / sprung 7kg / total 63kg
dedion
std diff, trailing links, coilovers,lateral linkage, disc brakes and calipers,driveshafts and joints (narrow), propshaft, dedion tube an alloy ears
unsprung 37kg / sprung 37kg / total total 74kg
IRS
std diff, driveshafts, hubs/uprights(alloy), wisbones (std bushes), brakes, coilovers, propshaft, additional chassis work
unsprung 37kg / spung 46kg / total 83kg
--------------------------------------------------------
This confirms that the overall lightest solution is the good old live axle (english I suspect), followed by the de-dion and IRS coming in last. The
sprung weights are the more important issue though, and the IRS and De-Dion tie for first place, both significantly better than the Live axle.
Of course this is only representative of the designs that stressy looked at, but most IRS and De-Dion solutions for the locost are very simmilar.
most locosts with IRS have a very poor inefficient lay out. You could save loads of weight if you actually designed it into the chassis rather than welding a big box on as an afterthought.
The point that is missed about double wishbone IRS is that the camber axle are only correct when the car is in steady state straight ahead conditions,
if you set up to give enough negative camber for cornering the camber angles under braking and acceleration are all wrong.
This camber problem is worse on an IRS than IFS, because at the front the castor angle can be engineered to give some negative camber gain when
cornering.
De Dion dosen't have this problem BUT (nb a big but) single wheel bumps upset things badly the camber on both rear wheels gets disturbed.
Live axles also share this problem of course but on live axle the unsprung mass to sprung mass ratio becomes silly on a very light car, not so big a
problem if you are building a Range Rover. High unsprung mass really becomes a problem on two wheel bumps, I remember from my MG TF days that a two
wheel bump mid corner could make the rear end of the car jump a couple of feet accross the road.
De Dion was the rear suspension of choice in sports car racing and GP up to the cars went mid engined, it was used by Connaught, Aston Martin, Lotus,
Maserati, Ferrari Bristol. When cars went rear engined the gearbox section of the transaxle was located behind the final drive. In fact most of the
rear engined racing car of this era were used the Colotti gearbox which was base on the Citroën DS unit which had an enormous rear over hang making a
de Dion a non starter.
In the 1970s when Ferrari built a 312 mule with a de Dion rear end the had to design a transverse gearbox to make it possible. The transverse box was
adopted the de Dion wasn't.
Another reason that de Dion went out of main stream thinking was one of the few mass production examples of the de Dion and the one most commonly used
to illustrate it in books was that used in the Rover 2000 of the early 1960s. The Rover layout was not a typical de Dion layout, to save the cost of
using plunge accepting cv joints fixed length drive shafts were used with telescopic de dion tube. This comprimise although it didn't affect the
road holding made the handling feel just a bit odd until the driver got used to it.
[Edited on 8/2/07 by britishtrident]
quote:
Originally posted by oliwb
quote:
Originally posted by craig1410
Sorry if we have confused you....
Okay, simple answer:
The extra expense and hassle of IRS is NOT worth it compared to an off the shelf de-dion axle.
Good luck,
Craig.
But I'm not going to be using an off the shelf de-dion setup. The whole thing is going to be bespoke. So if I'm going to that effort would it not make sense to go the full hog and use one of the existing IRS designs to base mine on??
Matt - (I don't really understand anything about damper, spring rates etc etc so can't comment on your suggestions) but could you clarify which IRS design is and isn't good? (Feel free to u2u or e-mail if you don't want it "out there"! I'd be very grateful though if you could give some proffessional advice and help me steer clear of an inherently bad design.
Whats the best length of trailing arms to have on a de-dion? I'm going to measure my existing bodywork and see if it will accomodate a de-dion easily. Thanks Oli.
Seeing the bull-fight from the barriers,
It is all a matter of weighted compromise...
What do you want?
- (I think cost is Nr 1) Cost.
- Ease of Build
- Ease of set up.
- Comfort.
Assign percentage to each desirable characteristic
Then assign grade to each setup on every characteristic.
Multiply both values and add up.
Best setup for you will be the one with the highest total.
IMHO
PS: I have a choice of 2 donors, Live axle and IRS, Planning on a Live axle as first build and IF funds, will and self confidence still alive, IRS for
the second.
I had originaly intended to use a solid axle for simplicity but with further investigation will do an IRS. http://locost7.info/files/suspension/RortyLocostIRSAssembly.pdf
Does anyone know how the IRS from the Sierra from England compares with that of an 80's Toyota Celica GTS (not the frame maker)? I want IRS cause
our roads are all very bumpy, unlike most of yours. Also, you can't get any solid axles here in this part of Canada, unless they come from a Ford
Ranger or Mazda B2000 pickup truck.
Seems to me that DeDion is easier for you though. This can all get too complicated, and is beginning to put me off the whole project. As soon as you
go non-standard, you introduce a whole bunch of variables that confuse mere mortals like me, who haven't changed oil in a car for over 20 years.
There I said it.
I'm with Mansfield, have a look at Haynes new book, PPC have driven the car and give it a glowing report, if that means anything.
Wimmera
quote:
Originally posted by RK
Does anyone know how the IRS from the Sierra from England compares with that of an 80's Toyota Celica GTS
Well OLI have you made your mind up??
Seems to have become very confusing and argumentative all of a sudden.
Perhaps what this forum needs is a technical area, where all the well informed and hi tech members can post their findings, and high spec drawings,
for us all to wonder at, and perhaps benefit from.
I for one am amazed at the very different (and personally definative) views that have appeared on this thread and find them interesting. However some
of them IMHO are too in depth (for me and probably many others) and must be making it more difficult for you to make your mind up.
I see it simply as the following
1 ease and speed of getting you on the road.
2 innovatative design with little or no pointers to a proven system that'll fit your car. Or a proven system that there are plans/pointers for
available (for free)
3 It's your car and if you want IRS then go for it regardless of the time/money required to get it right. It'll make for much kudos at any
meeting when you're asked who designed/built it.
Good luck see you on Saturday.
[Edited on 8/2/07 by omega 24 v6]
The answer becomes absolutely clear then.
which ever one a person likes best is the best one.
And unless you've got a race to win that is, then lap times tell the complete story.
You might as well argue whats a better colour blue or red (obviously red is but that won't stop some silly bugger arguing the point)?
quote:
Originally posted by oliwb
But I'm not going to be using an off the shelf de-dion setup. The whole thing is going to be bespoke. So if I'm going to that effort would it not make sense to go the full hog and use one of the existing IRS designs to base mine on??
Matt - (I don't really understand anything about damper, spring rates etc etc so can't comment on your suggestions) but could you clarify which IRS design is and isn't good? (Feel free to u2u or e-mail if you don't want it "out there"! I'd be very grateful though if you could give some proffessional advice and help me steer clear of an inherently bad design.
Whats the best length of trailing arms to have on a de-dion? I'm going to measure my existing bodywork and see if it will accomodate a de-dion easily. Thanks Oli.
quote:
Originally posted by andyps
I am sure there are people who have contributed to this thread who will design you a bespoke de-dion set up - after all, there have been expectations that others will do so for an IRS version so maybe someone will put their own time where their mouths are....
quote:
Originally posted by MikeRJ
quote:
Originally posted by andyps
I am sure there are people who have contributed to this thread who will design you a bespoke de-dion set up - after all, there have been expectations that others will do so for an IRS version so maybe someone will put their own time where their mouths are....
What can you make bespoke with a De-Dion though? The whole point is that it's simple to make as there are no tricky kinematics to sort out (apart from trailing arms, but you are pretty much stuck with the book ones on a book chassis). Even if you want to fabricate one from some exotic material, it will be fundamentaly the same as one you can buy wrt geometry.
With a double wishbone IRS you have lots of design decisions to make regarding the length and angles of wishbones, dimensions of uprights, significant chassis mods etc.
Rorty's IRS AND dedion designs and drawings are freely available for download from "flakmonkey"'s website. Alternatively my IRS
design using mx5 uprights can be downloaded FOC from my website (used by 1 or 2 others as well as myself). This is not a comprehensive set of drawings
like rorty's but there are some drawings, dimensions, photos and solid models - enough to do the job.
You can also buy the Avon book or the GTS plans; though the Avon geometry may be considered less than ideal plenty of folk find it just fine (which
sort of underlines the point that maybe us mere mortals will never appreciate the fractional differences between IRS and dedion.....)
cheers
Bob
quote:
Originally posted by andyps
I think the original request relates to a car which doesn't have a book chassis so may need to be bespoke in terms of width and mounting points - that is what i was trying to say.
quote:
Seems to me that this thread has become a bit of a slanging match
quote:
Originally posted by MikeRJ
Sorry if my post sounded argumentative, it was not intended.
This is all he asked for. Live axle or de dion gives him this. Double wishbone is not simple and. I think we've lost the original thread a bit and got carried away.
And there we have it.
Quite.....decided the other night that de-dion was probably gonna be the best option. What I loose in ride on bumpy roads I make up for in not having to arse about setting it all up for months if not years! Cheers for the input though. Oli.
WHoo Hoo we win
Sorry if that sounds childish.
Looks like we need a way of locking off this thread, as the man's made his mind up on the original question.
It could carry on like this for ages and I ain't got time to pick up all of the toys thrown out of prams cause it looks like I'm
going back to work at the end of next week (and locost building/material procuring).
I voted for IRS
It is as simple as at the front.
If you modify the AVON drawings and read a bit and don't fit a trailing arm at the front, you will not get any toe-in or out.
Only make it nice parrallel, no bump-steer, postive camber or what ever will occur.
So.. everybody can choose what he likes. I don't agree that a De Dion is easier to fabricate.
If a tiger Cat or a robin hood can drive with the original Sierra axle how bad can your own IRS, De Dion or Live axle be?
[Edited on 9/2/07 by t.j.]
I like IRS although it has to be done right. It is far more sensitive to alignment changes while driving than the front. Not sure if it was
mentioned, but if you do IRS you can do a very tidy backbone chassis to give you all the torsional stiffness you need. Having said that, mine is
going to be live axle because of simplicity of a 4link, and because I need all the traction I can get.
No idea on De dion, though. The only time I see it is on old, outdated race cars at the historic events . Seems to me they all seem to be sprung
very stiff in the rear to avoid jacking, but so were the IRS cars of their day.
Cheers.
IRS plans here: http://gtslocost.locostsites.co.uk/documents/pdf_files/RortyLocostIRSAssembly.pdf
De Dion Plans here: http://gtslocost.locostsites.co.uk/documents/pdf_files/RortyDeDionAxleAssembly.pdf
Dont ask me about the geometry, I had nowt to do with the design - but I understand rorty has a pretty good idea of what he was doing. Just hosting it
as a service to people who want it.
Cheers,
David
SEE WHAT I MEAN.
Decision has been made and pools are still being pissed in.
Pools being p*ssed in???
I think you'll find that Calvin nix has urinated big time in his own pool.
I owe him a big 'Thank You', for what he wrote, on two points.
1. He actually points to the fact that I give assistance off forum. I help many who ask, I just don't ask for any public recognition. In fact, I
insist that my help is not published. In trying to embarrass and denigrate me, he has shown that I actually DO 'walk the walk and talk the
talk.' Just privately, that's all.
2. In quoting from a private u2u to another list member, oli, both have shown their lack of respect for private communications. It puts into
perspective just how bright these two are, and the personal respect they have for the rest of the list members.
Mark Calvinx, Oli, why don't you publish the u2u in its entirety, just so everyone will know the full truth of what I said, and not just what you
wish to imply. The offer of help was not conditional on the thread being deleted. I was suggesting that the antics of a particular member were ruining
what could have been a sensible and fruitful discussion.
I've still got the original in my outbox, if you've deleted it.
The upshot of this is that I will be much more guarded in who I offer (free) help to in future.
If a member can't send a u2u with the knowledge and trust that it's contents will not be disseminated on the list openly, then what is the
use of the u2u section?? Chris may as well remove it, and put an open chat section in its place. There's one in there already, so hey, why
not?
It's truly, truly very sad that these sorts of people downgrade a very enjoyable forum.
Cheers,
Syd.
Still Smiling, despite the saddo's who would try and upset a man's life.
[Edited on 9/2/07 by Syd Bridge]
Having been away for a year or so, it's at once heartening and saddening to see that some things around here don't change - the "world vs Syd" slanging match is alive and well. Hooray.
quote:
Originally posted by t.j.
I voted for IRS
It is as simple as at the front.
If you modify the AVON drawings and read a bit and don't fit a trailing arm at the front, you will not get any toe-in or out.
Only make it nice parrallel, no bump-steer, postive camber or what ever will occur.
So.. everybody can choose what he likes. I don't agree that a De Dion is easier to fabricate.
If a tiger Cat or a robin hood can drive with the original Sierra axle how bad can your own IRS, De Dion or Live axle be?
[Edited on 9/2/07 by t.j.]
quote:
Originally posted by ch1ll1
de-dion for me,
just u2u jrobert on here
he sells them and the very good
IRS, as pretty much EVERYONE admits, it can be done to give you a better setup, just requires some tinkering, and isn't that what this is all about? Us having fun building it ourself in order to maximize the results?
quote:
--------------------------------------------------------------------------------
Originally posted by ch1ll1
de-dion for me,
just u2u jrobert on here
he sells them and the very good
--------------------------------------------------------------------------------
surely after all this free advertising youre giving him about De-Dion kits you surely deserve a discount ?
Matt
, I've made Paul my director of sales, however as i make so little it should be a registered charity
Anyway if i pay Paul, I'll have to pay Alex (ecosse) and MikeR