Hi guys, im a newbie here,

Ive brought a 99% complete ron champion chassis of Ebay and want to modify it for sierra running gear ie IRS and sierra front hubs etc, just wondering if anyone had done this and if they hit any major issues.

thanks in advance

Carl

how is your welding? You could buy Chris's IRS locost book and use that as the base for the conversion. Plenty of good quality pictures and plans in there, all you need really.

here's a link to his home page, plenty of tips on there

http://www.gibbs111.fsnet.co.uk/



[Edited on 20/3/08 by Mr Whippy]

why do you want to run IRS? the live axle is easier and nicer in my opinion.

oh oh now it's going to be a unsprung weight debate

Welcome Carl

Mr Whippys right just get the new roadster book and make the necessary changes from the plans in that book.

ditch

quote:

---

Originally posted by Mr Whippy
oh oh now it's going to be a unsprung weight debate

---

and look at the post i've just made comparing live axle vs de-dion on "de-dion pointless the proof" in running gear section.

I'm now curious how much IRS actually weighs - but i think if you've got the bits i'd stay with live at the moment. if you haven't and don't want too much hassle, go de-dion as the axle parts will be easier to get (heck, i may even sell you mine if my maths etc is right in the other post). If you want a challenge then go IRS.

As above.

There is a lot to be said for the handling comparitives to Live and IRS axle.

It would be best if you could get a drive out in two similar cars, but that isn't always the easiest thing to do.

I would reiterate IanK's comments though, the work involved to do it is not worth the handlings gains, and thats if you get all work done perfectly, whereas the Live axle chassis is pretty hard to get wrong!

Having said all that, you could try the Haynes Forum (which is the forum setup for the builders of ChrisG's "new" book as stated by Whippy above)

HTH
Steve

I converted mine to use IRS copying dimensions from the Tiger Avon book.
I had bought and stripped a sierra so I had all the bits.

However, the work involved in making up the wishbones and uprights, working out what bushes to use and making everything fit was horrendous, plus I haven't had it on the road yet so I don't even know if it will all work.

I wish I had just spent some time looking for a suitable live axle instead, would have been much less painful and I would be more confident that it would work!

As above, go live axle.

I would also agree with looking for a live axle because of the hassle changing it... They not that bad anyway, keeps to the KiSS principle "keep it simple stupid".

but if you like a challenge....

Cheers

Dan

[Edited on 20/3/08 by Bluemoon]

It seems to be a fairly common misconception that if you fit the most complicated suspension arrangement you can think of and an engine with 3 million or so horsepower into a 7alike you will end up with a better car........ 9.9 times out of 10 you don't - you just end up spending lots more money

Another vote for keeping it live axle

Another ridiculous thread.

Im not going to try and debate this, just look at a formula one car, they are pretty much the peak of engineering- and make your decision.

and they're constructed and designed by the peak of automotive engineering talent - not some bloke in his garage who for a living works in an accounts office and who's previous automotive training is having once changed the spark plugs and oil filter on a Ford Orion.

Ok I'm exaggerating but the point is still valid.....

CApn. Josh, This is the LOCOST forum F1 is not really relevant! I vote for a DeDion if you have the Sierra back end bits or a live axle if not. I went through al this stuff during my planning phase 2 years and a bit ago I went for the live axle option in the end. So far I have the wrong spring rates and not correctly set up front end and the thing still handles way better than anything else I have driven. It is rather tail happy but it is oh so predictable and responds immediately to corrections by accelerator or steering, this will be better when I have 160lb springs at the back instead of 275lb and 275lb springs at the front insted of 200lb!

Caber

I'm bored so I'll refine my answer

is IRS ultimately better than a live axle or a de dion set up? yes - but only if it's properly designed, accurately fabricated and properly set up.

will someone with limited automotive/fabrication experience be able to construct from scratch an IRS setup that will be significantly better than a live axle? almost certainly not....

The thing that no one ever seems to mention either is the availability of diff ratios - if you have a CEC and want a diff ratio over 3.9:1 it is going to cost you a small fortune to get one for a sierra diff whereas you can fairly readily get 4:1s for English axles for £80ish and 4:4s for £150ish - cheaper if you know where to look

well i thought i was the only one using a live axle!!! thought everyone had gone dedion and irs now! im using a toyota rear axle which is lsd standard. was thinking about dedion but put a stop to it because i would like to get the car done sometime this year!

rob

F1 cars are also designed, to a specific set of rues detailing what they can do, they are designed to run on nearly perfect tracks, the tyre actually takes up a large amount of the suspension movement, so I think it's safe to argue there an entirley different car,

neglecting the 700hp, engine behind the driver and only one seat. (apart from all that and a few other things yeah its a fair comparison)

another bit that make me angry is if you ever have the chance to have alook at an F1 car close up (I was llucky in what my work is) you'll find it a little dissappointing. they have mismatched bolts, wishbones are date stamped and some are two years old, gaffa tape is suprisingly common. etc etc

Live axle is fine ---

De Dion and IRS are slightly better especially on rougher tarmac.

Argument between IRS ans de Dion is very finely balanced, De Dion is easier to get right.

[Edited on 23/3/08 by britishtrident]

I have said this a few times Ferrari built a Formula 1 mule back in the mid/late 1970s with a live front axle and a De Dion rear -- the axles were composite very high tech for the time.

It worked perfectly well but Ferrari took it no further because (1) It was a higher risk strategy than irs (2) Aero dynamics no way could it be made to work with a wing car/ground effects.

[Edited on 20/3/08 by britishtrident]

Most hotrods in the USA have a single front axle that is suspended by two coil overs, aka a live axle- their not exactly known for going around corners well.


As I don't believe everything I read on the internet, I seriousely doubt that ferreri built a live axle based F1 car and even if they did, why are they not using them today? A dedion or liveaxle could be shaped into a wing to help aero and handling?


Most people completely overlook the positive side of a changing camper angle with independent suspension and how it can be designed to improve grip in and out of a corner.

Almost all American cars have shocking handling independent of their suspension configuration in my experience. They are designed for straight roads and fat arses rather than being sportscars.

F1 cars are all mid engined, so go build an Ultima (or give RussBost some money for his mid engined car). It's also rather noticable that the handling is now rather less impressive than last year now the computers have been switched off. So I presume you'll be advocating traction control on your car?

After adding all the strengthening you need to run IRS and a heavy diff the overall weight of a IRS 7 is considerably more than a live axle car, considering on a good flat road/track a live axle will handle just as well as any other suspension live will give better performance. That's even before you consider the scope for getting suspension geometry wrong on IRS.

Some legendarily good 7's (based on winning races rather than forum discussions around rear suspension design) Caterham 7 and Sylva Striker Mk2 both live axles to start off (Caterham using a Marina axle for many years before moving to de-dion). Caterham have now moved to IRS more for marketing reasons than anything else (the cars aren't handling better), but presumably have spent the money and time getting it right rather than a guy with a welder a tape measure and a fag packet design.

Most predudice against fixed axles has come from a combination of shockingly badly designed 50/60/70's 1-2 tonne tin-tops and pub wisdom IMO.

The live axle is the simplest one to get right with IRS the most demanding and asking the most compromises.
It is true you can get camber gain in corners on IRS improving the grip, but you then also get camber change during acceleration/braking reducing the grip...

The chassis design should be made based on the suspension type as the forces load the chassis differently. So a live axle chassis converted to IRS as example will not reap all the benefits that it could, making the chassis unnecessarily heavy.
The torque reaction in live axles are eliminated in IRS and deDion.
There are so many different things to consider when chosing suspension, the availability of live axles being one. There are fine, very light live axles out there but they are far between...

quote:

---

Originally posted by CaptainJosh
Most hotrods in the USA have a single front axle that is suspended by two coil overs, aka a live axle- their not exactly known for going around corners well.


As I don't believe everything I read on the internet, I seriousely doubt that ferreri built a live axle based F1 car and even if they did, why are they not using them today? A dedion or liveaxle could be shaped into a wing to help aero and handling?


Most people completely overlook the positive side of a changing camper angle with independent suspension and how it can be designed to improve grip in and out of a corner.

---

These type of thread crack me up...

1. This is a car building forum populated by a group of reasonably like mined lunatics who ignore the friends, relatives, etc who ask "why do that? Its not worth the effort" and who then go on to tell us that the men in white coats with fancy equipment can make a much better job of the whole car building thing and we'd best leave it to them.
And then comes along a chap who wants to go one step further than most with the car building experience, for some reason thats entirely up to him, and he gets the exact same arguments recycled at him????

2. People will tell you somethings too hard or shouldn't be done if they can't do it or don't understand it themselves.

3. People seek validation of decisions that they've made by trying to force others to the same conclusions that they've made on a subject.

4. Everyone works in a shed, its just a question of how big the shed is.

I think that if you scratch build a car it will not be perfect. No one is an expert in all the aspects
of car building so compromises will always have to be made.

I've had a go at making an IRS set up and have few regrets. Yes, I could have done it better
with the benefit of hindsight, but I'm not looking for perfection.
I don't expect it to corner like an Elllise, but then I don't expect it to corner like a 2CV either.

To me the important thing is, "I had a go."

I also think it's wrong to take a certain road just because its easier or quicker. If you have an
inclination towards a certain goal, then go for it, be it IRS, or any other part of your pride and joy.

My build has been a most enjoyable learning curve, and long may it remain so.


Nothing ventured, nothing gained.


Cheers
Paul G

Relax guys,

I think it's just the parts which you have/collect make your dicisions.

If you can make an IFS you can make an IRS. Making an rear-upright is the hardest part.

If I had a Capri live-axle maybe I would have a live axle now.

As I have a sierra diff, now I have IRS.
IMO you need some(one) computer-calculation to make a suspension.

After reading and calculating a lot you will come to the conclusion: It is one BIG COMPROMISE

In the end it's important to set the car on the right track. If a live-axle is mounted straight it will felt in cornering.
If not the right springs are mounted you will notice, etc etc.

So build what you like and try to build it as accurate as possible.

Almost any setup can be made to work and give good results within limits, even a swing axle.

Originally posted by britishtrident
(1) Ferrari did build a 312 F1 mule with a beam front axle and de dion rear -- for full details and pictures see the Nicky Lauda biography. The Art and Science of Grand Prix Driving 1977 ISBN-10: 087938049

Now tell us why it never entered a race?

(2) One of the reason they are not using it is to get the required stiffness size of the composite beam is huge, the structure of the beam is a combination of carbon fibre spaceframe and monocoque. Although very light a structure of this size just won't work with modern aerodynamics.

Total b*llocks!! A composite beam can be made smaller and stiffer than steel. This is my bread and butter. But the misinformation continues......

(3) A lot of highly successful racing cars such as B class Mallocks have been built either live axles or De Dion rears. The main reason De Dion isn't widely used in passengers cars is space restrictions.

And what configuration do the current winning cars use?


(4) The bigest problem with any fully independent suspension is camber change .

Ahhh, but it can be the biggest advantage as well!!

Independent suspension can never give the correct amount of camber for all situations.
And the BS continues....

In cornering unless a very short virtual swing axle length is used a independent suspension will give excess positive camber.
Only when incorrectly designed.

In contrast a beam type axle will always give near ideal camber in a corner and under braking/acceleration.

Ahh, No. A beam will give the opposite camber change to what is normally thought of as desirable, as the car rolls in a corner.

(5) Live axles on us hotrods are based on the same tradditional A frame axle location used on the Model T and Model A Fords it was chosen by Henry Ford mainly for its ability on rough farm tracks.

Ummm, wrong again. Most use trailing or leading radius rods or arms for longitudinal placement. And use Panhard rods or a Watts type linkage for lateral support. Some still use the old transverse leaf spring for lateral support as well.

Whereas, some Se7en type clones still use the old A frame support in the back end, and still break them regularly, or tear the mount off the diff.

This whole suspension thing still comes up far too often.

If you're going to drive it on the road, put in what is easiest for you to make, and set it up properly.

If you want track performance, irs is THE only way to go. But don't take my word for it. Go down the pit lane at LeMans, and count all the Dedions and live axles, then make up your mind. And if dedion was all that fantastic, then they would be used in the closed sports cars, where the aero problems are covered by bodywork.

Have a nice day.

Cheers,
Syd.

907.....My sentiments exactly


Captain Josh.......I don't believe a word of it!!!

Ah Well! Mick

thanks for all the replies guys, i never thought it would provoke such a response,
my main reasons for using the IRS set up is that i already have it

it is after all a budget car

thanks again guys ive got a copy of both books now so should be easy peasy

as for my mechanical skills im a qualified HGV engineer by trade working on massive generators for a living, infact i run the workshop, my welding is pretty good well ive never had any problems yet

cheers guys