Hi All,
Sorry to drag up what must be a question that's been asked many times (I have searched the Forum but can't find the answer)

I have built a good portion of my chassis along the lines of the McS 7+4 and had originally decided to go down the IRS route using Sierra 4x4 back end with IRS.

However, I was originally under the impression that this had been done before but now I can't seem to find a decent set of plans for the IRS back-end.

I'm now wondering whether the IRS is too much hassle for what will be a pretty big challenge even without it. However, since I want to use a Rover V8 I need the extra width and therefore I don't know if there are any live axles of the appropriate width that I could use to fit the 7+4 chassis.

Basically I need some good "practical" advice on whether to pursue IRS or not. I am a graduate engineer (electronic) and have a decent mechanical knowledge having worked on Mini's since the age of twelve. However, I am aware of my limitations when it comes to suspension design and can't help but conclude that a simple live axle has to be better than a badly designed IRS system. I also want to complete my car within 12 months if at all possible.

What difference to handling characteristics will IRS give me on the road and the occasional track day?

Is there such a thing as a tried and tested (as in modelled and/or dynamically tested) IRS design for the Locost or should I look at Live Axle instead?

Also, does anyone know of a suitable live axle donor car that could handle V8 torque and is the correct width?

Finally, what width of axle do I actually need for a +4 inch chassis so I can go and look around the scrap yard for a quitable donor?

Thanks guys,
Craig.

Cortina axle would do fine, bit wider than escort and in a light chassis is man enough for the job, its personal choice, live or IRS, i have no probs with the live axle set up, just back from a run in the peak district cornering at suicidal speeds, overtaking at will and knowing exactly what the car will do when push'd hard, i prefare live, others won't, your choice.

You can't really get a live axle installation wrong. Theoretically a well set up independant back end is going to be better, but it will be marginal. A poorly set up one will be much worse.

I think you know the answer to your own question live axles work excellently and are much quicker/easier to build.

I suspect that many builders have not actually driven or ridden in a se7en. If not I can tell you that if you find a live axle installation wanting the you are some nutter!

To accomodate the extra width and power of your V8 it would be worth considering an Atlas axle from a 2.8 Capri.

Jon/David,
Thanks for your words of wisdom

Okay, lets say I wanted to go for a live axle from a Cortina or Capri. Aren't these getting a bit rare these days? Do you know (or know where I can find) the actual width of these and whether there are any complications such as 5 stub hubs etc.

Part of the reason I was shying away from the live axle was due to availability of spare parts as well as the issues of unsprung weight and ride quality etc. However, as I think you picked up on David, I do want to get my car on the road at some point hence IRS may be a bit much to take on...

Does anyone know how wide the track on a Rover SD1 is? Could it be a realistic donor for the axle? A bit too wide I would think but worth checking since it would simplify the donor situation a bit. I think from memory it uses a Watt Linkage, do you think this will be a problem compared with a panhard rod?

Okay, live axle it is for now, let's see if anyone from the IRS camp can persuade me to defect!

Cheers,
Craig.

have you completed your front susspension yet ??? thats one reason i suggested Cortina, if you still need cortina uprights then a doner cortina will provide all you need, ???? just a thought, David as a point re capri axle but the chassis n car is so light they are up to it, the hardest problem is getting the power down.......but the handling on mine is very predictable with no suprises, the ride is very smooth n comfy too,

Jon,
Yes it makes sense to get everything from one car if possible although I'm not sure if my Wife will be very happy with an old Cortina sitting beside the house while I take it to bits... I think I'm going to have to negotiate something with my local scrapyard so that I can "store" my vehicle at the yard for a few weeks while I strip it for a fixed price and then leave them the wreck. That way I can flip it upside down and use large hammers and chisels etc to effect the salvage

I would like an LSD to help control the V8 torque, is the Atlas on the Capri an LSD or just a beefier non-LSD?

I just came across a website that explains a lot about what's involved in a wider chassis and it recommends the Cortina too. No I don't yet have any of the donor bits, I just waded straight in to welding bits of steel together...Doh! As you can see from my Avatar, I am not too far down any particular road just yet. I stopped building because I need to start making decisions about engine bay, trannie tunnel and rear suspension before I can do any more chassis construction. It was fun while it lasted though

Thanks again for the advice, I think some research into Cortina's and Capri's is in order now.
Craig.

how bout the volve 740 series axles,they are everywhere and never break.

An LSD would be good for a V8 powered 7. As Jon has said, getting the power down can be a problem, even with a modest 1700 X'Flow the inside wheel spins in the wet.

For a common donor the Cortina makes good sense but I'm not sure about where youll find an LSD. Some of the Capri 2.8's had LSDs' as std but not all. I'm sure someone on here will tell us which! Capri axles are same width as Cortina and same stud pattern.

If you go independent route then the XR4x4 Sierra had a LSD as std.

Hi again,
Any idea how wide a 740 Volvo is? These don't have the gearbox at the back on the diff like the 340 series do they?

Yes David, I'm worried about not being able to powerslide properly without an LSD

I've just been reading about Atlas v English etc on another post and it seems that Atlas is the axle type as opposed to English (which seems to be better in that it's easier to get the diff out) Am I correct in thinking that either the Atlas or English axle could be fitted with an LSD diff? What I am getting at is, could I just build the car with, say, a Capri 2.0 axle and then fit the LSD diff from a 2.8i later? Same goes for the Cortina, is there a souped up version of it with an LSD?

Another option I found suggested was to use the Opel Manta axle which seems to be 1320mm track the same as the Capri. There have got to be motorsport bits for the Manta, surely!

Cheers,
Craig.

ps. I'd rather use a tried and tested combination so maybe the Cortina isn't so bad, especially if I can fit an LSD diff.

Craig,

The Atlas and English parts are not interchangeable. English LSD's are available but reckon on about £350 s/hand for a good one.

For heavy competition, certainly with an heavier car you'll shear driveshafts with an English or Cortina axle. That said Quaiffe do super strong floating shafts for English axles but the conversion costs about £700. A std Capri axle with the LSD is probably the cheapest/strongest route with the Ford gear. As Jon said in an earlier post though, strength is unlikely to need consideration in such a lightweight car.

Not sure about Mantas and Volvos, something may be available, worth the research - let the rest of us know.

Craig, there is another option....Dedion rear axle.
I got mine from Dax minus their suspension brackets (slightly different setup and would of needed too many mods to the already built frame I had waiting...) which I five linked a-la live axle. I went this route because
a) Less unsprung weight=better handling
b) The axle utilises standard Sierra components, no mods required and loads of easy to find spares compared to Cortina/Crapi/Escort live axles,
c) Also able to use Sierra LSD-to drop on one for any live axle variant is rare and usually expensive,
d) No set up probs, just get in and drive!

HTH Stu.

I have fitted a Capri axle, pdf on its way to you on how I did it

Mark,
Thanks for the PDF of the Capri fitment, I'll have a study of this later. It looks at first glance to be very detailed and useful.

Stu,
I'm intrigued at your dedion setup and I think I finally understand what a de-dion setup actually is! It's basically a live axle without the drive shafts and diff which are now "sprung" leaving only the tube itself as unsprung weight (correct?)

One thing I'm not clear on is how the ends of the tube fit to the uprights. Are the uprights Sierra items?

Also, can you tell me how much it would cost me to get the bits from Dax that I'd need?

Finally, what sort of chassis did you build, with respect to the book chassis (mods etc). Mine is currently McSorley 7+4. Would this be compatible do you think?

You may well have offered the compromise that I am looking for. This setup would solve my main problem which I see with the Live axle - That of parts availability for Cortina's and Capri's up here in Scotland (I can't remember the last time I saw one!)

Thanks again,
Craig.

Stu,
I've just been onto the Dax website looking at the de-dion stuff. Can you confirm what you actually needed from them and whether you had any trouble getting the bits you needed considering it was for a Locost...

I've got their pricelist but it doesn't have the de-dion tube on it as a separate item and there are an abundance of brackets and fixings which I don't know if I need.

This whole idea is growing on me by the minute! Anyone else out there using de-dion?

Cheers,
Craig.

Craig,

Nobody has mentioned it in this thread, but what people are doing (if you want to go the IRS route), is to buy a couple a Jim Dudley's Tiger Avon book, and graft the IRS design onto RC's chassis.

It's what I've done, and I've put a piccy in the photo archive.

You may also be interested to see the pics of my (unfinished) exhaust system. I'm quite pround of it!!

ATB

Simon

Hi Simon,
Yes, I've heard of people doing that in other threads but I've also heard a lot of criticism about the quality of the drawings in the Avon book (sounds like a cosmetic book my Wife has) which worries me. As I said in my original post, I'm not sufficiently skilled at suspension design to "join the dots" as it were, and so would prefer a potted solution that I can build upon later once I gain experience and confidence. I really like the idea of the De-Dion setup if the de-dion beam can be sourced cheaply enough (or manufactured for that matter). I especially like the fact that it uses Sierra running gear but sticks to the book chassis (more or less) since this is nice and simple (or at least it sounds simple...)

I've heard lots of talk of 2 - 5 year build times from those who seek perfection and I know that I do not have enough patience to last much more than 1 year which is why it's crucial that I keep making steady progress along tried and tested lines towards a known goal (as opposed to an own goal!)
I would in fact be using a live axle right now if it was not for the shortage of suitable donor cars up here in bonnie Scotland. Also, Sierra's can be had for peanuts whereas Cortina's and Capri's are either shot to s**t or a proudly restored collectors item.

I'm not ruling out the full IRS as you suggest but I must fully understand the pro's and con's of each choice. As I understand it now(rightly or wrongly) the full IRS is the best for comfort, the live axle is best for grip on a smooth track with the de-dion best for a typical road where it strikes a balance between grip and roadholding whilst maintaining decent comfort due in large part to low unsprung weight.

Does anyone "fundamentally" disagree with this statement, individual tastes excepted?

Thanks to all once again,
Craig.

Simon, Just had a look at your pics..is the angle of your rear shocks as acute as they appear? I would have thought that they could do with being a bit more vertical..Don't get me wrong , i am not critisising your work, have you tried removing the spring from the damper and then seeing how the shock changes plane when you compress the damper? Take a look at my photo's to see how i have differed from tigers design and to see what i am getting at...

Viper,

You're correct - shock angle is rather excessive - so's the compression.

When I ordered them, I was told of their fully open and closed lengths and took a mid point for their "resting" length. Made some steel tube "coil overs" to use in the mean time and to set top mounting position.

I'm going to go for stiffer strings to start with - the angle will reduce their effective poundage. If that doesn't work - I'll cut the little blighters out and start again.

Might do it first!! After all it'll only take a couple of hours (including dismantling car and turning chassis over).

ATB

Simon

Craig.
the rear end debate will probably go on forever, the real advantage i can see to using an irs rather than a live axle is adjustability and less unsprung weight... to me that is more beneficial..

Viper,
You're right, that's why I was reluctant in some ways to bring this thread up in the first place. However, I think my choice will be de-dion if I can get a suitable beam from Dax. I contacted their sales department but they won't talk to me and have referred me to the technical department.

If I did go down the IRS route, do you think the MK indy rear wishbones would be a good starting point?

What I mean is, I could buy the wishbones (planning to do that anyway since my welding isn't tidy enough) and then build the extra chassis members to suit the required mountings. Ideally I'd like to get some plans for the mounting locations on the MK chassis but I don't suppose those are available are they?

Has anyone reverse engineered the Mk Indy chassis IRS setup yet? I'd have more faith in it than in the Tiger Avon rear end. All I really need is rough measurements of the centerlines and spacings. I could figure out most of the rest of it from the photographs I think (albeit crudely.) Let's just hope for my sake that Dax will sell me a De-Dion beam axle...

Cheers,
Craig.

Craig,

Have you tried MK for a de-dion tube? Before they went full IRS (and for a while in tandem) they were supplying de-dion setups.

I remember them saying that the drag racers preferred them.

Neil.

Neil,
Now you mention it I think I've heard about that elsewhere too. I'll drop them an email and ask if they can supply it still.
Will let you know.
Cheers,
Craig.

dont bother e-mailing as they dont seem to have the time to reply they are really busy! you will be better off ringing them.

James

Sorry Craig, havent been about recently (working on car....).
Dax were more than helpful with the order, the only downfall was that when I ordered they were extremely busy so it did take a long time to arrive (but they were totally honest and did warn me). IIRC it was 120 GBP with p+p.
It uses standard Sierra bearing carriers discs, driveshafts and diff.

HTH Stu.

Oh yeah, my chassis is all my own work, using the RC book for inspiration rather than plans. It is 4" wider, and 3" shorter in the cab area (Likkle legs ). The Dax tube was ordered minus their suspension brackets, basically just the tube with the flanges to locate hub carriers, so i could fit my own.

Cheers, Stu.

Stu,
Thanks and no worries about the delay in getting back, I have plenty of things to think through just now. I'm sure we all go through this stage where we rush into the project with lots of enthusiasm and not much knowledge only to quickly realise that it's not quite so simple and some thought is required after all!!

At 120GBP, it's probably on par with getting wishbones made up by someone like MK and it will be much easier to fit to my chassis I think. If they can supply it in the next couple of weeks at about £120 then problem solved, I'll join the de-dion club!

Can you please confirm what I'm going to need:
1. De-dion beam axle from Dax without brackets
2. Diff from Sierra with driveshafts
3. Uprights from Sierra
4. Discs or drums (What do you use?)
5. Four front link rods
6. Coilover shocks with mounts
Is that it?

I'd really appreciate any pictures you can send me from as many angles as possible or parts lists etc which might help. I can't remember what pictures you had on your photo area and the photos ain't working just now on this site so I can't check. (Oi Webmaster, what's happened to the photo section?)

Oh one final thing, when you say your chassis is +4", do you mean that tube O is 46" and B1 is 44" ?

Thanks again Stu,
Craig.

Sorry mate, dont do tubes, RC book became occiasional reading a long time ago......
Chassis is standard RC width at front of chassis, widening along engine bay area to 4" wider in seating area (where the chassis rails run parallel, and where I have lost three inches in it's length).
I am running discs.
I havent got the use of a digi cam at mo (borrowed one to take the piccys in the photo area) but when I have the use of it again I will mate.

Don't do tubes?? What kind of Locofreak are you!! I thought everyone on this forum knew their tubes back to front and inside out (or at least that's how I've built my chassis...)


No probs, I get the idea and it should be the same as mine if the backend is 4" wider as you have described which is good

I'm sure I can figure things out from your existing pics but if you do get a digicam again then extra pics never go wrong.

Thanks again for your time,
Craig.

Stu,

I've just spoken to someone from Dax who told me point blank that they don't sell parts separately. I explained that I knew of at least one person who had bought the de-dion beam axle to which they seemed surprised to say the least. The guy I spoke to is going to check with his Boss and get back to me but it doesn't look good...

As for MK, they don't produce the de-dion beam any more so no joy there either. It's looking more and more like I'm going to end up with a live axle unfortunately...

Any ideas?
Cheers,
Craig.

quote:

---

As for MK, they don't produce the de-dion beam any more so no joy there either. It's looking more and more like I'm going to end up with a live axle unfortunately...

Any ideas?
Cheers,
Craig.

---

Hi James,
I know, I know...

Actually, given the situation with MK and Dax, I 'm currently trying to find a suitable Cortina or Capri live axle. If I find one then job done, I'm back in the live axle camp again.

I'm off out to my local scrappies to see what he has for me.

Cheers,
Craig.

Well Dax have come back to say that they WILL supply a de-dion axle but it will take 3-4 weeks (next production run) to get one without the brackets, or I can have one ex-stock right now. The catch is that the ex-stock one has all the additional brackets and costs £180 +VAT +p&p (Best part of £250!)

If I wait 3-4 weeks and get a basic axle then it will be £130 +VAT +p&p which is a bit better but still quite steep for a long tube with two brackets on it...

I think I will spend the next 2 or 3 weeks hunting for a Capri axle and if I still haven't got one then I might just get the basic de-dion from Dax. I just hate all this waiting about, I want to weld something!!!

Cheers,
Craig.

Why not use an old de dion as per alfa?
I plan to use one?
Comments
The shifty swede

Hi Shifty Swede,

Interesting, tell me more...

What sort of alfa are we talking about, there is an Alfa 33 in my local scrapyard right now. Any use? These are front wheel drive though aren't they, or are you talking about using the front end of the alfa in the back of a Locost (with steering fixed I expect

I'm certainly interested in all the options available but my patience is running out and I have to DO SOMETHING soon...

Cheers,
Craig.

ps. I've just unloaded my RV8 gearbox and the seller has loaned me a V8 block, sump, heads, manifolds, rocker covers and crank pulley from a Vitesse which I can use to accurately build my chassis around. What a nice man - Thanks John!

I guess you might have been talking about the Alfa 75 or similar. I'd forgotten about those. The handling was supposed to be excellent, due mainly to the use of the de-dion back end. The only downside of using the backend from one of these that I can see is that the rear brake calipers were apparently problematic and required lots of attention. I'm only going by what I've read on a website devoted to the Alfa 75 since I don't have any special knowledge of it myself.

I've ordered a copy of the Tiger Avon book from Amazon.co.uk which should be here tomorrow or Thursday. I'll take a look at what is involved in grafting IRS from the Avon onto the Locost as per some advice others have given.

Cheers,
Craig.

i think i have a solution.
im going de dion and have got a de dion tube off a volvo 340. if you use the sierra hub carriers with the tube ( only a small amount of fetteling) then this will give a track of around 1370mm (perfect for you).
the tube has a nice bend to clear a sierra diff and is very strong.
personally i have removed all the steel fabrication on the tube and have used machined aluminium 'ears' to cary the hubs and to take it out to sierra track width (+100mm). altough my setup will be a fair bit lighter and the width i want, i suspect i will fall into the 2 years+ catagory.
all you need to do for a very easy cost effective solution is to get the volvo tube (i paid £10) and a sierra rear suspension/drive sub assembely for which i paid £50 for a xr4x4 with lsd and discs. all that is then needed is to weld od the brackets a la rc and extent the trailing arms by the tube offset from the drive centre line (about 4" and cut off some surpless brackets iff you fell like it.
hope this helps
pete.

ps any more questions just ask

Hmm!
Sounds interesting Pete, I think I'll take a look at a 340 at the weekend, I think I saw one at my local scrapyard last weekend (may have been a 440 though).

I have lots of questions about this but I suspect I will answer many of them by looking at the 340 installation so I'll wait until then for most.

A couple of things which do interest me for now though:

1. Track width - I am hoping to use Sierra LSD and drive shafts without any changes and thus I think track should be 1470mm unless I'm missing something. That figure is from www.carfolio.com and I am assuming it is tyre centre to centre. Perhaps you didn't realise that I am building the 4" (100mm) wider chassis as in the McSorley plans.

2. The machined aluminium "ears" - Did you fabricate these and if so, do you have dimensions and/or drawings which you'd be prepared to share? Is aluminium strong enough for this task or is it a harder alloy of aluminium?

I am indeed very interested in this idea and will certainly seek a 340 at the weekend to have a look-see. I'd appreciate some more detail on the above two points if you get a moment.

Thanks for the promising suggestion,
Craig.

Just for interest the Cateringvans used a Dedion rear end with a Sierra diff. You can pic up the tubes second hand for about £70-100

Hi,
Thanks for that, where would I be likely to find a second hand cateringvan de-dion tube ? (Ebay?)
Cheers,
Craig.

Don't know if this is any help to you or not but have you seen this ad in the for sale section? If the link doesn't work, its the ad selling to LSD's.

http://forum.locostbuilders.co.uk/xmb/viewthread.php?tid=4128

Hi,
Thanks, I had actually seen this post but discounted it initially due to the distance factor. (Cambridge to Glasgow is a fair trek!)

On second thoughts though I've emailed Chaz to ask a bit more about the de-dion tube and he's going to send me a photo of it. It seems to be quite different to the one from Dax as Chaz says the driveshafts actually run inside the tubes. I can't picture it but hopefully the photo's will make everything clear. Has anyone out there seen or used the MK Engineering version of the de-dion axle? Is it any good?

Do any of you guys know of any couriers which are good at transporting this sort of stuff cheaply. Ideally on a C.O.D. basis.

Cheers,
Craig.

the wider setup as i am using is infact easyer as i forgot to concider that the drive shafts would have to be shortened.
to run a sierra rear track the beam has to be 1400mm (i cheaked again today at work on a sierra we had in) end to end and the volvo tube is 1300. the simplest solution i came up with is to butcher the sierra trailing arms and weld the hub mounting section onto the volvo tube which will give almost exactly the right track.
i do not feel that the tube width has to be perfect as the cv juints give quite alot of movement in this direction.
the bolt on ears idea came from caterham which uses an almost identical setup so the alloy design should be up to the job.
i am very lucky in the fact that my boss has just bought a milling machine so there is no problem.
i have no formal designs drawn up yet but when i do i will have no issues with giving you a copy ( i use pro/e but can be persuaded to use autocad 2000)
in general after stripping the tube bare two end plates have to be acuratly welded on ( these have to be set to the desired toe and camber). then the alloy plates will be about 200x120x40mm and will simply need four holes to suit the end plate, four holes to suit the sierra rear hub and a large boring of 82 mm ( for drums not sure if same for disc version). if you have a colunb drill and can find some 40mm thick stock then you can make them at home. a machine shop could knock them up in an hour or so if you cut the profile so would not be expensive.
of course it may prove more time/cost effective for you to find a cater/dax tube but i want to make everything on my car.
hope my waffelings have helped a bit.

pete

Dougal,
Thanks for the details, I think I get the idea now.
I'm currently talking to another forum user about an MK engineering de-dion tube which he has available. That may be easier for me in the absence is machining equipment. I will, however, have a look at the Volvo tube at the weekend.
Thanks,
Craig.

ps
this caterham build diary gives a good look at the setup but they dont use the sierra disc hubs so ignor the caliper mounts built into the ears
http://www.apgreenaway.freeserve.co.uk/RearSuspension.html

Looks nice doesn't it?
Cheers,
Craig.

Have you looked at the drawings in the Tiger Avon book for Irs?
I know what you mean about wading off into the chassis. I have just decided to re do mine as my trans won't fit a book width chassis. I'm using a oldsmobile Quad 4 engine and a T5 trans from a camaro. We have to find all kinds of stuff here in the states. Good luck. My web site is Texaslocost.homestead.com

quote:

---

My web site is Texaslocost.homestead.com

---

James,
I thought initially that you were talking about my website and I was worried for your sanity for a moment! My engine in the photo's on my website is just a block and sump with the heads set on top! I'm using it for a sizing guide.

I then realised that you were talking about TexasLocost and I agree with you, it is a nice site and engine. Nice one EleWayne!

Cheers,
Craig.

Hi guys, Thanks, That Quad 4 is a GM copy of an Offenhauser design used in the indy cars of the late fiftys and early sixtys. the offies had 250 cubic in. and mine has 135 Cubic in. A little less power but it still gets over 200hp. The heads and cam carriers are alum and can be polished too.I'm using one of Jim McSorleys chassis designs as a basis for my new one which will be a 2+2+1 1/2 and I'm using his desigh with
a front like the Tiger Avon, only not tilted up. The T5 camaro trans just won't fit the standard chassis. My son is 6'3" and i'm making it a little longer for him. Be a shame if he couldn't drive it.

Hi All,
Since it was me who started this thread I just wanted to thank you all for your advice and comments and to let you know that I've resolved my dilemma!!

Chazpowerslide has just posted (today) a complete MK Engineering de-dion suspension setup with Sierra hubs, driveshafts, ears etc and since he's such a nice chap he even threw in a free differential unit from a Granada. He can obviously tell that I need all the help I can get...

Anyway, thanks everyone and especially thanks to Chaz who I might add, went to great lengths to organise postage for 81Kg's of locost bits from Cambridge to Kilmarnock. He also gave me some sound advice over the phone which will help no end.

Cheers,
Craig.