chunkielad
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 posted on 31/1/05 at 09:51 AM |
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IRS AGAIN!!!
Well then lads and lasses (are there any females on here?
Has anyone actually set up an IRS back end? I know it's going to be hard to set up (God knows I understand the problems) but I just want to see
if anyone has set up a WORKING and correct IRS on a Locost style frame (i suppose Tiger etc would work too) and what the setup and measure ments were.
Mainly just interested for knowledge but may well have a go at it.
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locoboy
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| posted on 31/1/05 at 11:11 AM |
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Chunkielad,
Photo deleted !
[Edited on 18/4/05 by locoboy]
ATB
Locoboy
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chunkielad
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| posted on 31/1/05 at 11:23 AM |
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Don't want to sound funny or anything but - does it work? Have you tried it out on the road yet? I want to try an dtake dimensions of someone
for set up, wishbones etc for a WORKING IRS that has no serious handling problems. I know this can be a very difficult this to setup.
PS I would preferable like a Sierra width version - none of that MG, Lotus, other wonderfully unusual setups!! I already have sierra diff and shafts!
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locoboy
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| posted on 31/1/05 at 11:35 AM |
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Dream on! Not on the road yet, it was bulit by Triton Racing and came with wishbones and uprights to fit sierra back end.
So there is more chance of it working than if it was designed and biult by me 
I Can post wishbone dims if you want when i get a chance?
ATB
Locoboy
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chunkielad
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| posted on 31/1/05 at 11:52 AM |
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The main data I need mate is the location (distance from side of chassis) of the support bars (Diff location and wishbone support) the layout of the
wishbones and a drawing of the hubs (which I assume are custom made).
I hope this isn't asking too much. I really want to try and make as much as possible myself (when my welding is up to scratch!) so ANY and ALL
measurements would be a fantastic help.
Ofset, castor, camber etc are needed too if you have them.
I have plans for a second car already but it's a little more unique to the locost!! I haven't even started this one yet!!!
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locoboy
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| posted on 31/1/05 at 12:17 PM |
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Will see what i can do, it may have to wait until the weekend for the chassis measurments because the chassis is under cover outside and its dark when
i get home from work!
The bones i can measure no probs.
The bones have rose joints on the outer ends so you can set toe in/out and camber to suit.
The measurement on the bones will be as accurate as i can make them but it doesnt really matter because they are adjustable for length with the rose
joints in so a mm or 2 is neither here nor there - so long as it +2mm not -2mm
ATB
Locoboy
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Mix
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| posted on 31/1/05 at 12:20 PM |
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I have the dimensions I'm using on a book width chassis but like Col, it's untested yet. If you can read either Turbocad or Autocad I
could cobble together some drawings when I get a minute.
Mine uses the IRS from an XR4x4i.
Mick
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chunkielad
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| posted on 31/1/05 at 12:21 PM |
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Sounds great fella - I keep asking for trouble on this one don't I?
I just have a feeling that this is going to cause a better vehicle in the end. Puls if I don't use it niw, I will defo use it on the new one.
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Bob C
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| posted on 31/1/05 at 12:28 PM |
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Another still building... but you can checkout photos in my photo archive and on www below. I've used mx5 uprights so my geometry is different
to everybody else, but the dimnsions are all on the website if you want to do the same.
BTW there are stacks of MK indy's on the road already with irs
Bob C
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Hellfire
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| posted on 31/1/05 at 05:12 PM |
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Ours for a start - if you need any pictures let me know! Just starting to re-assemble the rear... again! 
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chunkielad
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| posted on 31/1/05 at 05:14 PM |
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Defo pics and as many measurements as you can Hell fire - I really want to try this - what's the worst that could happen?
Oh hang on you crashed yours!!
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Vet Will
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| posted on 31/1/05 at 06:43 PM |
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Sorry to ask what is probably a really stupi question, but why are the rose joints on Bob C's set up horizontal, not vertical? I guess there is
a really simple answer to this.
Thanks Will
Will
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chunkielad
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| posted on 31/1/05 at 08:19 PM |
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If I use a pair of wishbones at the rear, am I right in thinking that there is no need for any links or anything else of this sort?
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JoelP
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| posted on 31/1/05 at 08:34 PM |
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bob has his roses that way round cos they have enough flex to take it, and they are not prone to popping out under braking like they would be the
other way round. 
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Bob C
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| posted on 31/1/05 at 09:48 PM |
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JoelP nailed it in one - I would have put them the other way round but was pursuaded by the arguments set forth in this very forum!
Cheers
Bob
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Alfalfameister
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| posted on 1/2/05 at 09:24 AM |
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I haven't actually started my chassis, but I'll be following this thread closely. I have a preference for the live axle because
that's "by the book" and should make less of a hassle. But the de dion is enticing.
Since I plan to make it a track day car, I am scared about having an IRS (or rather, an IMPROPERLY designed IRS). But since the roads of my country,
are, well, 3rd world (potholes and general lack of smoothness), the IRS looks very tempting.
I have some nice books that I am trying to pore over: Chassis Engineering by Herb Adams, Staniforth's Suspension book, some of Carrol
Smith's (Tune, and Engineer to Win), and even a Steve Smith book(let) on suspension. After a few pages though, the headaches it gives me is
overwhelming. Heheh.
So, chunkie, thanks for starting this thread. By the time I get to my build, I hope all the other guys have contributed a lot to this thread.
BTW, since MK already has IRS, can't someone just post the dimensions for all of us? Or would MK get upset about this?
Cheers!
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chunkielad
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| posted on 1/2/05 at 10:41 AM |
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MK are VERY helpful mate but I don't think they'd approve of their design being half hinched!!!!
Glad to be of service though!! If my stupidity and ignorance can help, I'll stay that way for a while!!!
I'm sure someone on here with a working car will bob out and get the tape measure out in the next few days though!!!
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Alfalfameister
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| posted on 1/2/05 at 12:19 PM |
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quote:
MK are VERY helpful mate but I don't think they'd approve of their design being half hinched!!!!
Well, it's not like they're giving us the blueprints, or that we're doing it for mass production -- else, Caterham would be suing
all of us, eh? So maybe someone can take pictures of it and put some tape measure(s)/ruler(s) beside it, and we can work it out ourselves. Don't
see anything wrong with that.
quote:
Glad to be of service though!! If my stupidity and ignorance can help, I'll stay that way for a while!!!
Godz, that was funny!
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pbura
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| posted on 1/2/05 at 12:38 PM |
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One of the ways I've been burning off frustrated Locost-building energy has been studying suspension design. Resources have been pretty much
those cited by Alfameister plus everything I could find online. I've assisted a few builders by helping to set up computer models and working
through some modifications, but generally there were some compromises because chassis were already built.
Some conclusions I've reached in my research and tinkering thus far:
--Were it not for the ability to deal with bumps, a solid rear axle would be preferable because: (A) most obviously, squat in acceleration will cause
some camber change with IRS; (B) in independent FRONT suspension, KPI and caster work together to keep the wheels upright in turns, which
doesn't happen at the rear, and (C) forces generated in cornering travel along paths from tire contact patches to the instant centers of the
wishbones, making the inside wheel want to lift. This last point is true for any wishbone suspension, even the book front suspension, and the effect
is usually minimized by keeping the roll center under about 80mm.
--With a maximum height for rear roll center being ideally no more than about 75-80mm, the front RC must now be lower, say about 30-35mm, to maintain
a typical sort of roll axis. This necessitates a re-do of the book front suspension layout, which has an RC of about 75-80mm.
--Now that the roll axis has been lowered, the car is going to need more roll resistance than a book car, unless more body lean is acceptable.
Stiffer springs are pretty much out, so you are now looking at anti-roll bars front and rear. The use of anti-roll bars is somewhat detrimental as
they transfer some additional load from the inside tire to the outside.
--As far as specific goals for camber change, can't really say because intended use of the car rules the decision. Generally, people go with
more camber change in bump (and less in roll) for the front because it's doing the work of steering, and vice versa for the back, for the job of
accelerating. Because of the aforementioned steering effects, I've found that getting a pleasing setup for the front is fairly easy, but the
back is much less satisfying because of the compromises involved. My personal goals for camber change are .5-.6 degrees per inch of bump for the rear
and .75-.85 for the front (similar to book).
Despite the case against IRS for hard-core track performance, I still want to build it because the car will mainly see service on bumpy roads. Also,
I want to use cheap motorcycle shocks front and rear, and cannot think of a way except with IRS. There are some pics in my archive of a chassis
I'd like to emulate. Please ignore the ones with a plus (+) sign in the names as I can't delete them.
Pete
Pete
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phelpsa
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| posted on 1/2/05 at 02:21 PM |
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I'm making an IRS setup based on the Stuart Taylor designs.
It uses shortened driveshafts but I can get some dimensions if you want.
Adam
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chunkielad
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| posted on 3/2/05 at 12:53 PM |
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I take it that from the distinct lack of response including measurements, I'm not going to be let in on the trade secrets!!!
Someone must have a set of measurements for their IRS on Sierra width. Anyone? I only need the wishbones, hubs and where to put the members (metal
ones not the people on here!)
Cheers in advance.
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locoboy
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| posted on 3/2/05 at 03:45 PM |
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patience young man!
Wait till the weekend and i can give you the chassis dimensions - if it aint pissing down!
And i can give you the lower and upper bone dims tonight.
ATB
Locoboy
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chunkielad
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| posted on 3/2/05 at 04:35 PM |
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Not good enough col!! Get out there in the rain and earn your wage!!!
Sorry - I keep wanting to do bit then stop myself as I don't have all the info - then get stressed because I've done nothing!!!
Maybe I need to finnish my attic quicker and I can get welding some more - a bit of welding practise would get me a lot further than these
dimensions
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Mix
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| posted on 4/2/05 at 09:25 AM |
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Heres a few of the figures I'm working with to be going on with:
Sierra width from outer face of hub carriers 1391mm
Lower wishbone length 462mm
Distance between lower wishbone mounts 418mm
Distance between upper wishbone mounts 679mm
Upper wishbone length 308mm
Upright height 255mm
SAL 2540mm
Camber change C .5 degree per 25mm bump or droop
Vertical separation beween upper and lower bone inboard monts 224.5mm
All of the above refer to the rear suspension.
Mick
[Edited on 4/2/05 by Mix]
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James
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| posted on 4/2/05 at 09:51 AM |
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Chunkie,
What about buying a GTS or MK DeDion system? That way you'll get something that you know works.
HTH,
James
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