DaveMorris Posted May 18, 2008 Share Posted May 18, 2008 Looking at Maury's column the start of the crack appears to be the same - square cut corner to the machined slot. On my column the crack just worked out from there. On Maurys it appears to have spad up teh column a little bit. On that basis Caterham ARE already aware of this potential mode of failure. It would not hurt to send these pictures to them aswell. IIRC the design of the top section of the column WAS to have radiusses on the machined corners - but some batches came through without the corners being radiussed. Hence my posting last year Dave. Link to comment Share on other sites More sharing options...
MAURY712 Posted May 18, 2008 Author Share Posted May 18, 2008 continuing my investigation,I have removed the lower steering column to check it; it s very strait ...no trouble about it. the clamp was too tightened. The lower column was in the upper column ,but less than 15 mm from the machined corner I know (because i were a triumph spitfire owner for 17 Years long) it s the same assembly ,exept the clamp in full metal,and the length which is in the upper section(in memory more than 50 mm). I am agree with those who argue that the machining of these part can promote the appearance of cracks.radiusses were be wellcome.. my job is to draw industrial machine,and i have learn to not doing such machining... on the over hand,a 1973 triumph spitfire ,my previous 1993 super 7 1700ss,all the seven in the world.... maybe there is something goes wrong in my seven . and it would be a great thing to know what is the problem *rolleyes*I have ,Wife ,3 children,a house,a cat ,a boss,a bed ,....to be continued.. I have email Daren from CC to have a quotation for the parts and to tell him the problem. I have seen on the CC online here what is it ? My seven (1996 HPC)dont have such shim under the steering rack. Is it for align the steering rack with the column? 1996 road legal 7HPC Link to comment Share on other sites More sharing options...
rj Posted May 18, 2008 Share Posted May 18, 2008 The shim is for adjusting the steering rack to reduce bump steer. Link to comment Share on other sites More sharing options...
Grim Reaper Posted May 19, 2008 Share Posted May 19, 2008 Interesting that I found this here though it would seem to relate to the Universal Joint not the sliding joint and only affects 16 cars from March to April 2007. I will be checking mine regularly from now on... edited dates... Edited by - Grim Reaper on 19 May 2008 07:53:53 Link to comment Share on other sites More sharing options...
elie boone Posted May 19, 2008 Share Posted May 19, 2008 Can't it be that if the slot in the upper collum isn't machined deep enough it will cause it to crack and lead to failure. Since the clamp is only touching the upper collum and only the grub screw holds the lower collum in place. Link to comment Share on other sites More sharing options...
Graham Perry Posted May 19, 2008 Share Posted May 19, 2008 So if my steering column has a square corner and no crack would it be safe to file it away so that the square corner was removed ? Link to comment Share on other sites More sharing options...
Bob Simon Posted May 19, 2008 Share Posted May 19, 2008 So if my steering column has a square corner and no crack would it be safe to file it away so that the square corner was removed ? Only if you could be sure a micro crack has not already propagated itself through the column. If the crack has already started, radiusing will do no good unless it completely removes the crack. -Bob 94 HPC VX Evo III Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted May 19, 2008 Leadership Team Share Posted May 19, 2008 There would appear to be more than just the radiusing of the slot at issue. Maury is also stating: The lower column was in the upper column ,but less than 15 mm from the machined corner This is likely to be a contributing factor. The join will flex as the column is used - there would appear to be only 15mm between the 2 stress points, causing not only the propagation of the crack from the square corner, but also a complete failure of the tube as shown in the photographs. I'll bet there's never an issue with cracks propagating from the lower square corner! Not only must the corner ALWAYS be radiused, but there must also be enough overlap of column inner and outer to spread the bending stresses over a wider area - nearer 50mm may be more appropriate but maybe not possible with the current upper/lower columns. I think I'll check mine! For anyone unfamiliar with the propagation of cracks from corners, the issue was first discovered in steel ship building, and quite a few ships went down before the engineers realised the doorways & hatches needed rounded corners!!! Stu. Joint Area Representative MAD Sevens (Merseyside And District) www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
strij Posted May 19, 2008 Share Posted May 19, 2008 It would be interesting to know which type of rack was fitted to the cars with failures. I have the 22% quickrack and have often thought the load on the column seemed excessive at low speed and mid corner. I suspect a quickrack and dodgy column is a bad combination. Superlight #11 now R400R powered Link to comment Share on other sites More sharing options...
MAURY712 Posted May 19, 2008 Author Share Posted May 19, 2008 My 7 has a 8% Caterham steering rack. Darren from CC tells me""This is very unusual unless the wheels had some form of impact!"" Maybe in My 7 s live ,a previous owner had driven It on a pavement... the injury seems to be old... continuing my investigation 1996 road legal 7HPC Link to comment Share on other sites More sharing options...
RichardUSA Posted May 20, 2008 Share Posted May 20, 2008 Please keep us informed of any new info. Does it appear to be a particular vintage of car that has had this happen to or ? I hadn't realized that the column was hollow until I saw your snaps. Me thinks the quest for 'adding lightness' can at times be taken a bit too far - especially on the significant bits.......Steering column, Dedion tube fittings, differential to chassis framing, wheel lug length,? I'll gladly take a couple extra mechanical pounds (if that is what's required) and have a lighter lunch. 🙆🏻 BASIC TECH INFO: 2004/6,500 mile Cat w/Zetec SVT, widetrack, DeDion, 5 spd/3.62, 15-CR500's Link to comment Share on other sites More sharing options...
CageyH Posted May 20, 2008 Share Posted May 20, 2008 If the steering column was noy hollow, where do you think the steering wheel would go in the event of a frontal accident? Link to comment Share on other sites More sharing options...
RichardUSA Posted May 21, 2008 Share Posted May 21, 2008 You mean the accident as a result of the steering column shearing? I would guess CC put the sleeved joint in the assembly to keep the shaft out of your chest (regardless of whether the shaft is solid or hollow). Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted May 22, 2008 Leadership Team Share Posted May 22, 2008 Richard, the upper column is hollow tube, the lower is solid bar. In the event of a frontal impact the lower column can slide inside the upper column therefore reducing the total length of the steering assembly, reducing the possibility of driver chest injuries caused by the steering wheel/column. The design allows that, at a point of frontal impact the assembly clamp (that holds the two components together) will lock hard against the bulkhead steering tube, preventing any further movement of the upper column towards the driver. The lower column will continue to move by forcing past the clamp and into the upper column. This is Caterham's version of the "collapsable column" as needed by legislation. I think you actually had similar setups on cars in the USA a long time before Europe caught up! Stu. Joint Area Representative MAD Sevens (Merseyside And District) www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
Graham Perry Posted May 22, 2008 Share Posted May 22, 2008 Correct me if I am wrong but I think that Westfield have a slightly better set up using two univeral joints, one towards the top of the column and another at the bottom. It also gives the steering shaft better clearance of the engine on their set up Link to comment Share on other sites More sharing options...
Julian Thompson Posted May 22, 2008 Share Posted May 22, 2008 You are absolutely correct Graham - the westy setup is superb... ...was going to say that before but didn't want to agitate Mr Ali 😬 Ahem... Link to comment Share on other sites More sharing options...
Bob Simon Posted May 22, 2008 Share Posted May 22, 2008 The Caterham upper column is only drilled hollow a few inches past the notch. The rest is a solid bit of bar stock. I would venture the amount of collapse before it bottoms out is only enough to put the end of the shaft flush with the dash tubes. -Bob 94 HPC VX Evo III Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted May 22, 2008 Leadership Team Share Posted May 22, 2008 I would venture the amount of collapse before it bottoms out is only enough to put the end of the shaft flush with the dash tubes .... and to pass whatever bit of legislation needs passing! Stu. Joint Area Representative MAD Sevens (Merseyside And District) www.superse7ens.co.uk..........the rebuild 😬 Link to comment Share on other sites More sharing options...
DaveMorris Posted May 22, 2008 Share Posted May 22, 2008 FWIW, my failed column was vintage 1997, fitted to an Academy x-flow. Following its academy year the car was used 90% for road use. Engine was changed to 1700cc and dry sumped. IMO two contributory factors for the failure MAY BE a/. the track work and probable riding of the curbs which took place, and b/. dry sumping of the x-flow engine (using 5-port pump) which requires rolling of the rack to change the angle of the steering column to miss the oil pump. The above are, of course, in addition to the square corners on the machined out slot. Dave. Link to comment Share on other sites More sharing options...
MAURY712 Posted May 23, 2008 Author Share Posted May 23, 2008 well,the end of the investigation!! after i have remove all the parts ,i went to check if they were well assembled each other. And this evening i am sure i have found out why the upper steering column fail. 1:the steering rack was assembled on the chassis with an input shaft too lower. 2:the steering lock tube was assembled on the chassis too hight in the engine bay. on result ,I think my 7 has a steering column like the balistic of a bullet,or a cane fishing This really stress the upper column and aded to the square machined design it fail.... I haven t seen it because of the C20XE inj instalation,and i was in confidence with. No forget that the column was held up by two bush and the lower part only by the universal joint and the rack itself as said by Graham Perry ,two universal joint would be wellcome.... In a Caterham 7 the solution consist to obtain a column as straight as possible . I have now to set up the steering lock tube s hight(it s possible to set it because there is some play in the screw holes) and the steering rack angle(it s possible to rotate it to obtain the correct input shaft angle) then ,if you modify the steering rack position with spacer(for bump steering)dont forget to adjust the steering lock tube and the steering rack angle . if you dont do that ,probably whenever you turn the steering wheel it will stress the upper steering column as a piece of iron wire . and by the time it will break 😔 It wasn t the upper column fault even if it has a particular design... About the upper steering column,Darren Phillips has tell to me they are using a different metal compound nowadays.. thank you for all your answer 1996 road legal 7HPC Link to comment Share on other sites More sharing options...
ECR Posted May 23, 2008 Share Posted May 23, 2008 Glad it's sorted Alex .... Link to comment Share on other sites More sharing options...
stevefoster Posted May 23, 2008 Share Posted May 23, 2008 Great news. That would explain why this is thankfully so rare an occurrence. Don't forget to add lightness :-) My 2002/2003 racing pics here General pics (mostly of 7's and cars). here Link to comment Share on other sites More sharing options...
Graham Perry Posted May 24, 2008 Share Posted May 24, 2008 Due to Dave Morris comments on the possible risks of rotating the rack for steel crossflow applications and my car having done 15 years of sprinting I thoroughly checked my joint today as the engine is out of the car. ☹️ Using a very large set of grips I applied as much leverage to that part of the upper shaft as I could to see if I could force open any cracks and there were non visible. It was well worth checking though, so thanks MAURY712 for highlighting this and warning blatchatters Link to comment Share on other sites More sharing options...
Mickrick Posted May 24, 2008 Share Posted May 24, 2008 You can check for cracks with a special aerosol spray, two actually, one is a white powder the second a clear liquid with minute particles of iron. You then magintise around the area your checking for cracks. A crack will show by the iron particles forming around the fault. I doubt you will see any cracks without this test, with the naked eye. A good engineering or welding company should be able to do this for you. It's called "Non destructive testing" Academics are seldom any use at engineering. One must have a mistrust of theorists. (Keith Duckworth) Link to comment Share on other sites More sharing options...
CageyH Posted May 24, 2008 Share Posted May 24, 2008 Or NDT. You can also use UV NDT which is a similar process, but with use of a UV lamp can see any cracks. Alternatively, fit a QR steering wheel and you get a new upper column Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
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