fondelli Posted November 3, 2012 Share Posted November 3, 2012 I guess this is what needs clarified. If the current mod does all these things- then all is good. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 3, 2012 Share Posted November 3, 2012 This can be done quite easily. Maybe Grubbster who is in mid-build could do it? Assemble rear struts without springs and bumpstops. Leave all bolts through bushes just done up so they still act as hinge pivots (ie not clamping the centre tube of the bush). Set to work with jacks and levers to push and pull the back axle throughout its envelope of travel For this specific issue it may only be necessary to analyse one particular zone, where it gets closest to the diff cage/fixings. Report findings of minimum clearances to CC or on here. Peter Link to comment Share on other sites More sharing options...
Grubbster Posted November 3, 2012 Share Posted November 3, 2012 As I mentioned earlier in the thread - with dedion held in place with radius arms and A frame, if you raise the dedion it hits the little bit of casting before reaching the 2 countersunk bolts that go through the carrier. I tried to take photos of it but they didn't come out very well. Look at the bit I've circled here, on the left side of the carrier you can see that the little cast lump with something stamped on it sticks out further than the carrier does, this is where my dedion made contact in my simple test. My test was done without shocks attached so it could be different with them on. I've gone a bit too far in the build to pull it apart again to do a more thorough test though. Edited by - Grubbster on 3 Nov 2012 09:31:42 Link to comment Share on other sites More sharing options...
mic Posted November 3, 2012 Share Posted November 3, 2012 Is that with the radius arms in the upper mounting holes? Link to comment Share on other sites More sharing options...
Grubbster Posted November 3, 2012 Share Posted November 3, 2012 No, in the lower ones. Link to comment Share on other sites More sharing options...
mic Posted November 3, 2012 Share Posted November 3, 2012 I think they need to be in the top holes with the BMW diff Link to comment Share on other sites More sharing options...
wjblundell Posted November 3, 2012 Share Posted November 3, 2012 On-line build manual says top hole for the rear radius arm and CCM fitted my BMW diff to the top hole. When I built the car in 2010 with the Ford diff that manual said the top hole. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 3, 2012 Share Posted November 3, 2012 But the upper holes are generally less preferred for handling as they induce more roll oversteer. If CC have only specified the upper hole as acceptable for the BMW diff, do they say that anywhere? To clear that casting shape on the rear of the diff may need a mod to the deDion tube. Peter Link to comment Share on other sites More sharing options...
Z3MCJez Posted November 3, 2012 Share Posted November 3, 2012 Caterham racing regs specify lower holes, but I'm not sure if that's Ford diffs only as I don't have the Academy regs. Jez Link to comment Share on other sites More sharing options...
Grubbster Posted November 3, 2012 Share Posted November 3, 2012 The latest assembly guide has this note - NOTE On some series 3 chassis a lower fixing boss is supplied to give optimum suspension geometry when used only for race and track purposes. This setting is not recommended for road usage. The regs on the Caterham forum for the Academy (dated 2011) don't mention radius arms, from the photo's I have of this years competitors cars it looks like the lower point is used. I'll see what they do at PBC, maybe they'll move them Link to comment Share on other sites More sharing options...
CharlesElliott Posted November 3, 2012 Share Posted November 3, 2012 They should be in the lower position. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 4, 2012 Share Posted November 4, 2012 Top hole recommended for road use as it gives a slightly better ride. It reduces the vertical acceleration of the axle when hitting steps or ridges by allowing the axle to move upwards in a path on a sector of arc which slopes backwards not vertically up. Irrespective of recommendations for road, track, ride quality, etc, the car will have better handling dynamics with the links in the bottom holes, especially on L to R or R to L transitions (S-bends). Peter Link to comment Share on other sites More sharing options...
CB Posted November 4, 2012 Share Posted November 4, 2012 This year's Academy race regs are here Section 5.8 - "Radius arms should be mounted with the forward point in the lower of the two mounting holes in the chassis." Link to comment Share on other sites More sharing options...
Grubbster Posted November 4, 2012 Share Posted November 4, 2012 Thanks for that link, a page full of stuff I didn't know existed! The regs posted in the Academy forum are from 2011. The positioning of the radius arms was added to the 2012 regs. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 4, 2012 Share Posted November 4, 2012 ....so they add a line into the regs to specify the bottom hole simultaneously with redesigning the car so the bottom hole is no longer useable? Peter Link to comment Share on other sites More sharing options...
CB Posted November 4, 2012 Share Posted November 4, 2012 not sure why you say it isn't usable. Despite the diff issues (that affected some rather more than others), ~50 Academy cars ran with it like that all year. Link to comment Share on other sites More sharing options...
6speedmanual Posted November 4, 2012 Share Posted November 4, 2012 Quoting CB: not sure why you say it isn't usable. Because as Grubbster says he gets a foul condition with the lower holes. However on rereading his post, he says the shocks were not fitted. They limit the vertical travel of the unit so maybe his installation check took the axle beyond its normal range. Would still be interesting to know the outcome of this examination of the operating envelope of the rear suspension. Peter Link to comment Share on other sites More sharing options...
diggerman Posted November 4, 2012 Share Posted November 4, 2012 Following all the comment on the diff problems I have spent the morning in the garage with the car on axle stands to have a good look at the situation. couldn't drive as it was hissing all morning. The car is a 2010 150SV Roadsport and has now done 12000 miles. 6000 of those have been with the BMW diff which was one of the first retrofitted by Caterham Mids. I checked all the mounting bolts. They were all tight having never been checked since installation. The brake pipe on top of the dedion is undamaged. There is a small mark in the powder coating that lines up with the sharp edged protrusion on the cast backplate of the diff. I have taken a flat file to that sharp edge and chamfered it back about 5mm horizontally and 8mm vertically. This should give the dedion considerably more travel before it can make contact. My car does not have adjustable ride height and with the standard shocks I can see no way that the dedion could ever get anyway near the top carrier bolts. (Which on my car are not recessed) so my recommendation to anyone with a standard car is to file off that sharp corner to prevent contact. I am curious as to why some cases of bolts coming loose/falling out have occurred unless the cars in question are set up with a low ride height that causes the bolt heads to hit the dedion hard enough to loosen them? My experience with quite a few miles of wonderful quiet motoring is that the bolts do not come loose! Any further thoughts? Peter Link to comment Share on other sites More sharing options...
redlight Posted November 4, 2012 Share Posted November 4, 2012 Interesting comments about which mounting to use. If it was this easy, just moving the mounting, wouldn't CC have told us all to do this to cure the problem? Link to comment Share on other sites More sharing options...
ParsleyTheLion Posted November 4, 2012 Share Posted November 4, 2012 Hi Peter, I think the bolts that have been falling out for people are the ones at the front of the diff on either side, not the bolts at the back that strike the De Dion. Perhaps two completely unrelated issues? The "fix" for the loosening front bolts is the fitment of Nord-Lock washers. CC seem to have fitted some to my car, (I presume at the first service in the summer this year), because there are 2 different colour paint pen marks on these 2 bolts (the green that is on every bolt on the car, and yellow presumably added when the washers were retro fitted and torqued to spec). Edited by - ParsleyTheLion on 4 Nov 2012 18:27:58 Link to comment Share on other sites More sharing options...
diggerman Posted November 4, 2012 Share Posted November 4, 2012 Thanks P the L, I clearly misread that bit. The side bolts on my car had not come loose but I have no idea whether Cat Mids had used Nord-lock or not. Might have a look when I get a chance. Peter Link to comment Share on other sites More sharing options...
redlight Posted November 5, 2012 Share Posted November 5, 2012 Yes I also think that the fix for the front bolts is the Nord lok washers, I fitted the diff myself as a retro fit and it came with these washers. All bolts, front and rear, are tight with no sign of coming undone. Link to comment Share on other sites More sharing options...
wjblundell Posted November 8, 2012 Share Posted November 8, 2012 It bothers me somewhat that this thread is drifting down the page when a solution has not been forthcoming. I posted a thread earlier to report my diff and carrier were OK, all bolts tight, but at the start of my pre winter checks I have just removed the boot floor and directly under the top nearside bolthead there is a slight indentation in the brake line. So whilst I can't prove it was the bolthead it is a worry. I am going to let CCM know what I've found and will report back. Link to comment Share on other sites More sharing options...
Alan Reeves Posted November 8, 2012 Share Posted November 8, 2012 I am home next week. I truly cannot understand CC in this situation. I will be pursuing. As soon as i am back. Where is the new CEO....? Alan Link to comment Share on other sites More sharing options...
fondelli Posted November 8, 2012 Share Posted November 8, 2012 Are your bolts the old or new type? Link to comment Share on other sites More sharing options...
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