Leadership Team Shortshift Posted June 20, 2020 Leadership Team Share Posted June 20, 2020 Some of us recently hijacked a 'Marketplace' thread and ended up talking about the possibility of fitting independent rear suspension to a S3 chassis. I have just come across which is rather interesting!James Link to comment Share on other sites More sharing options...
Area Representative gileshudson Posted June 20, 2020 Area Representative Share Posted June 20, 2020 James, Owain Davies from Caterham Cars built one too and it was apparently featured in the October 2008 issue of LowFlying. Some pics below and more details on it in a PDF on the link below. Giles https://www.dropbox.com/s/wvbt0z7shjo1gyn/IRS%20R500%20details.pdf IRS R500 details.pdf Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 Link to comment Share on other sites More sharing options...
Leadership Team Shortshift Posted June 20, 2020 Author Leadership Team Share Posted June 20, 2020 Thanks Giles - good find from the Lowflying archives. That's the car (I think) that is now owned by Chris (R300Chris) and has been discussed - at some length - in the MarketPlace thread I mentioned, which is here if anyone is interested (read towards the end).James Link to comment Share on other sites More sharing options...
Leadership Team Shortshift Posted June 20, 2020 Author Leadership Team Share Posted June 20, 2020 I think that sourcing the hub carriers (which seems to involve either:- bespoke fabrication; or bespoke CNC machining from a solid billet; or using the CSR part) is perhaps the biggest practical obstacle. Would be nice to think of this as a commercially viable update on a S3 platform.I wonder what the reaction was at CC to Owain Davies' efforts? I can't believe they wouldn't have been aware and assessed it.James Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 Probably the same reaction as Gary's inboard front suspension for the S3 recieved - 'we don't want to cannibalise sales of the CSR' There's a slight irony in this now that the CSR was sadly dropped from mainstream sales..... Link to comment Share on other sites More sharing options...
Leadership Team Shortshift Posted June 20, 2020 Author Leadership Team Share Posted June 20, 2020 That could well have been a valid commercial justification at the time, but with CSR effectively no longer available in the UK, an IRS S3 derivative might open up a significant new stream of opportunity. I can imagine demand from existing owners for whom such an obvious, attractive and substantial technical improvement would be a solid justification for upgrading to a new car, as well as appealing as a premium option to buyers who would be purchasing for the first time.Probably best not to try to do David Ridley's job for him! James Link to comment Share on other sites More sharing options...
DJ. Posted June 20, 2020 Share Posted June 20, 2020 There are plenty of Seven designs with IRS out there. I think designing the set up to suit some existing hub carriers from Westfield for example would speed up development.Having previously built and owned an independent Westfield SeiW, I have to say, I much prefer the way my DeDion Caterham S3 drives. There are theoretical advantages to IRS, but I would prefer a well developed live axle or DeDion chassis to a poorly designed IRS every time.Duncan Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 DJ,I had the same thought regarding the rear hubs as a friend has a WestieProblem I found with my Westie and my firiend also agrees, is that form the factory they are very over sprung, dropping the spring rates all round made a huge difference.https://parts.westfield-sportscars.co.uk/suspension-braking/rear-suspension?product_id=146 Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 I would lke a nice light Dedion tube for mine though, like the Ti version that was made, or maybe a redesign using thinwall Reynolds tubes or similar.... with provion for a spherical centre mount for the A frame too..... Link to comment Share on other sites More sharing options...
DJ. Posted June 20, 2020 Share Posted June 20, 2020 A much lighter DeDion with better location would be more than halfway to IRS with a lot less bother. I fitted a powerflex bush to my DeDion and it reduced the rear wheel steer quite a lot. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 My A frame I Powerflexed too, I'd just like some more angular rotation in the A frame to Dedion tube mount as the current set up puts torsional stress thro the A frame as the Dedion rotates during single wheel impact or cornering load.Also made the control arms adjustable, with double rose joints so you can adjust the Dedion to be perpendicular to the centre line. Link to comment Share on other sites More sharing options...
DJ. Posted June 20, 2020 Share Posted June 20, 2020 That sounds an interesting modification Link to comment Share on other sites More sharing options...
Area Representative bluenose Posted June 20, 2020 Area Representative Share Posted June 20, 2020 I spoke to someone at Caterham at the Autosport show shortly after Owain built his IRS R500 and he said that it was a good experiment but was assessed as providing little benefit over the dedion set up and I think he said it was heavier? Regarding dedion tubes, my original one circa year 2000 was a great lighter than my replacement. When I spoke to Bruce at Arch Motors he said the gauge of tube had been increased from 12 to 10 which I assume was due to failures? A titanium one would be nice. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted June 20, 2020 Share Posted June 20, 2020 I think with careful redesign and choice of material, suitable supports etc you could save a good few kilos of unsprung mass.The change in gauge was belt and braces, the failures were on the lower mount - very well documented on here, but the addition of buttresses in this area dealt with it,you could even look at hydrorming the main tube into more benefical profiles allied with butting too...... Link to comment Share on other sites More sharing options...
DJ. Posted June 20, 2020 Share Posted June 20, 2020 The early Lotus De Dion tubes were curved and included the wheel bearing mounts without using ears. I believe they also used inboard rear brakes which would reduce unsprung mass considerably. They also had a larger diameter, but I presume a thinner gauge steel.I found a photo of an Eleven, but I've seen similar fitted to a Seven chassis.http://www.britishracecar.com/GlennStephens-Lotus-Eleven/GlennStephens-Lotus-Eleven-DE.jpg Link to comment Share on other sites More sharing options...
ECR Posted June 21, 2020 Share Posted June 21, 2020 At the time, the received wisdom was that a dedion arrangement provided less opportunities for owners to badly adjust their suspension and thus create a reputation for poorly handling Caterhams Link to comment Share on other sites More sharing options...
elie boone Posted June 21, 2020 Share Posted June 21, 2020 I think that if you convert the current DD set up to the same as a 5 link Live axle set up it would improve on all dynamic's, for sure it would offer more squat and be a lot lighter and most important there is no chassis modification needed. Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted June 21, 2020 Area Representative Share Posted June 21, 2020 At the time, the received wisdom was that a de Dion arrangement provided less opportunities for owners to badly adjust their suspension and thus create a reputation for poorly handling CaterhamsThat is a very respectable position for Caterham Cars.And this is what was written on the subject for us after the de Dion was introduced: https://www.lotus7.club/guides/technical-information/de-dion-or-irs Link to comment Share on other sites More sharing options...
Leadership Team Shortshift Posted June 21, 2020 Author Leadership Team Share Posted June 21, 2020 Perhaps 'convenient' rather than 'respectable'?I'm not aware of the CSR suffering from any such poor reputation, despite the freedom for owners to freely adjust till the cows come home... But thanks for pointing to the old (1998 +/-) Lowflying article. It makes interesting reading but the bottom line is that time (and capability) moves on. Nothing new under the sun!James Link to comment Share on other sites More sharing options...
Doctor Posted June 21, 2020 Share Posted June 21, 2020 the only drawback of CSR IRS arrangement is the lack of rear anti roll bar. Irrelevant on the road, excessive lean on the track. Link to comment Share on other sites More sharing options...
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