Paul Drawmer Posted December 2, 2000 Share Posted December 2, 2000 Once again, I’m asking for a web-challenged neighbour! The rear suspension: De-dion, wide track, progressive sprigs; doesn’t appear to fit quite right. The problem is the lower mounting of the spring/shock unit. To mount it onto the internally threaded lug welded onto the bottom of the de-dion tube, there has to be about 10mm (3) spacer washers to pack out the bottom of the shocker from the de-dion tube, otherwise the body of the shock absorber will foul on the tube. This can’t be right, surely? As this bolt will transmit the whole of the load from each rear corner, it seems pretty crude to have to put any packing in at all. Is it due to: a) the logs being in the wrong place, or b) the A- frame being too long, and having the effect of rotating the tube so that the lugs are too far rearwards? In addition, I notice that the diff output flange appears to be about 25mm forward of the rear wheel hubs, is that right? I suppose the answer would be to have a heavier de-dion tube with a ‘bow’ in it to clear the diff. More weight would be bad news there. Link to comment Share on other sites More sharing options...
simonwelton Posted December 2, 2000 Share Posted December 2, 2000 Paul, this had me very confused and bothered recently so I ahem "forced" it to fit, post build check confirmed I was wrong and it should be packed with washers! This is what Caterham do. Simon Link to comment Share on other sites More sharing options...
Paul Drawmer Posted December 3, 2000 Author Share Posted December 3, 2000 Thanks for the re-assurance Simon, I'm not happy with the engineering really, I'll post some pictures soon to show the others what I'm on about. Link to comment Share on other sites More sharing options...
Blatman Posted December 3, 2000 Share Posted December 3, 2000 Can I suggest that you attempt to obtain some aircraft spec bolts (identified by having AN stamped on the head). They have a much higher shear strength, to further ease the load, so to speak. Link to comment Share on other sites More sharing options...
StewartG Posted December 3, 2000 Share Posted December 3, 2000 It's a good job you don't seem to have adjustable platforms because they foul the de dion tube making it even more of a dog's dinner. Link to comment Share on other sites More sharing options...
Paul Drawmer Posted December 3, 2000 Author Share Posted December 3, 2000 Errr they ARE adjustable platforms!! I've put a quick n'dirty web page up to show you here Two big (800 X 600) pictures - may take a bit of time to load, But I've moved them into Demon's cache, so it shouldn't be tooooo long! Edited by - Paul Drawmer on 3 Dec 2000 20:32:01 Link to comment Share on other sites More sharing options...
StewartG Posted December 3, 2000 Share Posted December 3, 2000 Yes mine looks exactly the same only a lot dirtier. If you rotate the adjuster collar so that the flat is against the de dion tube it helps a bit and means you can adjust without the spanner. Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted December 3, 2000 Share Posted December 3, 2000 You're right Paul. It does look a bit 'gash'. Hope you can sort it!!!!!!! Good luckthumbsup.gif Link to comment Share on other sites More sharing options...
Petrolhead Posted December 6, 2000 Share Posted December 6, 2000 Bloody hell. Looked at the photos and this is typical of Caterham. I am not saying it is wright or wrong but the use of spacers seem to be one of their trates. So long as you use aircraft quality bolts you should not have any problems. Regarding the body fouling on the tube this is not good and should have been sorted at the design stage. PS How easy is it to change the diff? (1994 1,4 K series) Link to comment Share on other sites More sharing options...
Paul Ranson Posted December 6, 2000 Share Posted December 6, 2000 Does it fit better if you mount the damper the other way up? The photos appear to indicate that the trailing arms/Watts things aren't fitted. These will obviously change the orientation of the De dion tube, so don't make any final judgements on clearances until you have everything in place. And thirdly you could take a grinder to the unused thing welded through the De dion tube. Paul Link to comment Share on other sites More sharing options...
mark.hall Posted December 6, 2000 Share Posted December 6, 2000 I wouldn't fit "standard" shocks upside down, as they have a reservoir (not sure if it's fluid or gas) which won't work if they are inverted. Only shocks designed to mounted upside down should be mounted thus. Link to comment Share on other sites More sharing options...
StewartG Posted December 6, 2000 Share Posted December 6, 2000 People seem to mount the front shocks USD with gay abandon! Link to comment Share on other sites More sharing options...
mark.hall Posted December 6, 2000 Share Posted December 6, 2000 Yeah I know. The idea first (as far as I know) appeared on motorbikes. I believe it makes a difference to unsprung weight, but I'm sure a proper "techie" will tell us. However, unless the shocks are specifically designed to be inverted, then you will have problems. The first one that springs (sic) to mind, is the fact that if you burst a seal, the shock will dump ALL it's oil, cos the reservoir is not designed to defy gravity! Instant zero damping capability. Not cool. At least that's my understanding. I'm sure a call to Spax, Leda, or whoever, will clear this up. Link to comment Share on other sites More sharing options...
Mike Bees Posted December 7, 2000 Share Posted December 7, 2000 The standard Bilsteins work just as well either way up (as do most shocks in fact). Mike Link to comment Share on other sites More sharing options...
simonwelton Posted December 7, 2000 Share Posted December 7, 2000 Caterham quite happily recommend fitting at least the front shocks upsidedown, it makes changing the springs easier on race cars, the rear ones though would be very difficult to adjust if they were fitted upsidedown Link to comment Share on other sites More sharing options...
Andy Checkley Posted December 7, 2000 Share Posted December 7, 2000 I had the same issue when building my car. If you look at the base of the damper you will see a flat on the shoulder that is fouling your dedion tube. You can turn this shoulder through 90 degrees to stop the damper shoulder fouling. (So that the flat face is facing the dedion tube). I understand from Gary May (Ex factory build technician), that this is the way the factory get around the problem. My car has been fine without any fouling problems or funny clonks. If anyone out there has a recent factory built car, perhaps they can confirm this. Regards, Andy Link to comment Share on other sites More sharing options...
Paul Drawmer Posted December 7, 2000 Author Share Posted December 7, 2000 Thanks for all the replies.. We understand that a wee bit extra clearance can be obtained by turning the flat of the udjuster so that it is alongside the tube. Still think some spacers will be needed - still think the spacers will compromise the shear strength of the bolt. Due to the forces being given a lever (the length of the spacer(s)). Oh, the suspension is all fitted in the photos - I just used a piece of paper to reflect light back on the subject! Link to comment Share on other sites More sharing options...
Graham Perry Posted December 7, 2000 Share Posted December 7, 2000 Looking at the Photos, have Caterham changed the design of the Tube ? On my 1990 car the bolt go's thru the middle of the tube and isn't fitted into lug hanging off the bottom of the Di-Dion. As it sits an inch higher fouling isn't an issue. I notice that Caterhams haven't changed the alignment of this lower mounting. On some of the race cars people have changed the bottom mount so that the bottom bush is aligned across the car rather than down its length ie turned it through 90 degrees.There was some debate as to whether the factory would eventually adopt this mod. Apparently in hard use thay have been known to damage the bushes in the standard position. Mine have distorted certainly, but are not damaged. Link to comment Share on other sites More sharing options...
Paul Ranson Posted December 7, 2000 Share Posted December 7, 2000 > I wouldn't fit "standard" shocks upside down, as they have > a reservoir (not sure if it's fluid or gas) which won't work > if they are inverted. Only shocks designed to mounted upside > down should be mounted thus. It depends on the make and type. Most Ledas should be operated upright, Bilsteins as supplied by Caterham are fine inverted. > the rear ones though would be very difficult to adjust if they > were fitted upsidedown You aren't constrained to use the long installed length springs supplied. With the right sort of spring you can get the adjuster to a rather more convenient place than touching the De dion tube, and you have the added advantage of quick spring changes..... (Essential for track day coolness?) Paul Link to comment Share on other sites More sharing options...
Paul Drawmer Posted December 7, 2000 Author Share Posted December 7, 2000 You are correct, the design has changed. The part of the tube which the shocker is hitting is the old through mount for the previous fixing. I think that the new, lower mount is for the adjustable platforms. I'm not sure, about that....ignorance showing, not my car, posting for a friend etc. Still not happy with the design though! Link to comment Share on other sites More sharing options...
Mike Bees Posted December 8, 2000 Share Posted December 8, 2000 Yep, as Paul says it's changed - around 1996 I think as my '94 car had the bolt-through-the-DD-tube arrangement whilst the '97 one had the threaded-bush-welded-to-the-bottom-of-the-DD-tube arrangement. I discovered this when I couldn't find any bolts in the 1997 kit long enough to go through the DD tube - serves me right for assuming that I knew how it went together and not reading the manual. If you've got the later arrangement then check the welds on the DD tube every now and then - they've been known to peel off. Mike Link to comment Share on other sites More sharing options...
Graham Perry Posted December 8, 2000 Share Posted December 8, 2000 To me the new arrangement looks like a step backwards. The loadings on the whole lug must be really quite large. Link to comment Share on other sites More sharing options...
Mike Bees Posted December 8, 2000 Share Posted December 8, 2000 I agree Graham, it looks like a horrible afterthought. I do wonder why it was changed. Mike Link to comment Share on other sites More sharing options...
Matt Prior Posted December 8, 2000 Share Posted December 8, 2000 At least Tamiya are spot on with their models. The rear dampers on my Tamiya Cosworth model foul around the De-Dion tube too! As for mounting dampers upside down, I can't see how that reduces unsprung weight. I'd have thought that the oil-filled casing part weighs more than the shaft part, so mounting the shaft on the lower ('unsprung', wheel) end of the suspension seems to make a lot more sense to me. That way, the heavier (oil-filled case) bit is attached to the bodywork, where it's 'sprung'. On bikes, I can see how the oil-filled part can be made lighter than the inner fork legs, because it has a larger outside-diameter, promoting stiffness and negating the need for seperate, heavy brackets for the inner-fork/hub joint down by the wheel. Anyone who can confirm? Link to comment Share on other sites More sharing options...
Matt Prior Posted December 8, 2000 Share Posted December 8, 2000 Blimey, that would have been so much easier to describe with a picture! Link to comment Share on other sites More sharing options...
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