carlknight1982
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| posted on 20/3/08 at 11:35 AM |
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Chassis modification
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
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Mr Whippy
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| posted on 20/3/08 at 11:40 AM |
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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]
Fame is when your old car is plastered all over the internet
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nib1980
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| posted on 20/3/08 at 11:42 AM |
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why do you want to run IRS? the live axle is easier and nicer in my opinion.
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Mr Whippy
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| posted on 20/3/08 at 11:45 AM |
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oh oh now it's going to be a unsprung weight debate 
Fame is when your old car is plastered all over the internet
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ditchlewis
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| posted on 20/3/08 at 11:51 AM |
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Welcome Carl
Mr Whippys right just get the new roadster book and make the necessary changes from the plans in that book.
ditch
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iank
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| posted on 20/3/08 at 11:52 AM |
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quote:
Originally posted by Mr Whippy
oh oh now it's going to be a unsprung weight debate
Is this going to be for a BEC or a CEC, and what sized wheels 
p.s. Adding IRS to a chassis designed for a live axle is a lot of pain for little to no improvement in handling. In some cases performance is
actually made worse.
Not that that actually ever seems to make any difference to the large number of people who ask if/how it can be done.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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MikeR
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| posted on 20/3/08 at 12:00 PM |
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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.
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worX
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| posted on 20/3/08 at 12:01 PM |
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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
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sammy
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| posted on 20/3/08 at 12:20 PM |
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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.
Build diaries...
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Bluemoon
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| posted on 20/3/08 at 12:42 PM |
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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]
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D Beddows
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| posted on 20/3/08 at 01:37 PM |
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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
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CaptainJosh
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| posted on 20/3/08 at 02:16 PM |
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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.
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D Beddows
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| posted on 20/3/08 at 02:28 PM |
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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.....
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caber
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| posted on 20/3/08 at 02:36 PM |
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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
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D Beddows
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| posted on 20/3/08 at 02:53 PM |
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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 
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COREdevelopments
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| posted on 20/3/08 at 03:35 PM |
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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
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nib1980
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| posted on 20/3/08 at 04:43 PM |
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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
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britishtrident
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| posted on 20/3/08 at 04:43 PM |
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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]
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britishtrident
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| posted on 20/3/08 at 04:48 PM |
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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]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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CaptainJosh
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| posted on 20/3/08 at 10:08 PM |
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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.
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iank
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| posted on 20/3/08 at 11:01 PM |
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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.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Lippoman
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| posted on 21/3/08 at 05:43 AM |
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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...
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britishtrident
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| posted on 23/3/08 at 11:35 AM |
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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.
(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
(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.
(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.
(4) The bigest problem with any fully independent suspension is camber change .
Independent suspension can never give the correct amount of camber for all situations. In cornering unless a very short virtual swing axle length
is used a independent suspension will give excess positive camber. In contrast a beam type axle will always give near ideal camber in a corner and
under braking/acceleration.
(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.
[Edited on 23/3/08 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Doug68
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| posted on 23/3/08 at 02:16 PM |
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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.
Doug. 1TG
Sports Car Builders WA
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907
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| posted on 23/3/08 at 04:34 PM |
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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
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