Detecting Frame Cracks
Discussion
Hi, Folks:
For those who've had cracked frame tubes, I'm curious to learn how they've been detected.
I cracked a tube in the left rear of my 280i - from jacking it up. This crack clanked and clanged loudly particularly when I'd drive up raised driveway ramps with the car at an angle to the ramp. It wasn't hard to find on inspection, after I'd decided it was a frame crack I was looking for.
A friend with an S2 Vixen, a very successful autox'er with the SCCA and other clubs, as well as turning laps occasionally at road course track events, was cracking tube fairly regularly under the competition stresses of sticky tires. He found them all through simple visual inspection, and tapping tubes, but the tubes otherwise gave no indication of having cracked.
- SJ
'67 Lotus Elan S3 dhc 45/6210
'76 TVR 2500M 3559TM
'85 TVR 280i dhc
For those who've had cracked frame tubes, I'm curious to learn how they've been detected.
I cracked a tube in the left rear of my 280i - from jacking it up. This crack clanked and clanged loudly particularly when I'd drive up raised driveway ramps with the car at an angle to the ramp. It wasn't hard to find on inspection, after I'd decided it was a frame crack I was looking for.
A friend with an S2 Vixen, a very successful autox'er with the SCCA and other clubs, as well as turning laps occasionally at road course track events, was cracking tube fairly regularly under the competition stresses of sticky tires. He found them all through simple visual inspection, and tapping tubes, but the tubes otherwise gave no indication of having cracked.
- SJ
'67 Lotus Elan S3 dhc 45/6210
'76 TVR 2500M 3559TM
'85 TVR 280i dhc
I've always found it vaguely disturbing that no non-destructive testing is used on chassis welds: not for that matter does it appear that the welders have to pass any but the most cursory welding test... this applies to all small-volume makers, not just TVR.
OK, so any ape can MIG weld, but that doesn't guarantee anything
OK, so any ape can MIG weld, but that doesn't guarantee anything
Have you seen the hourly rate for a coded welder though!
Edited to add;
I just checked, and I'm amazed how low it is at the moment! The again, most of the jobs were going by experience! Anyway, to get someone decent, I guess you're going to have to pay well. Then there's the ultrasonics! Is it really worth it?
Make your replacement chassis out of stainless, and be done with it!
Edited to add;
I just checked, and I'm amazed how low it is at the moment! The again, most of the jobs were going by experience! Anyway, to get someone decent, I guess you're going to have to pay well. Then there's the ultrasonics! Is it really worth it?
Make your replacement chassis out of stainless, and be done with it!
Edited by dilbert on Tuesday 20th June 00:48
Any ape can mig weld....... but its easy to mistakenly think that welding has taken place when it hasnt!
Most chassis welds would have been carried out on jigs in position with the vertical section of the weld being done vertically down. This is where I imagine the majority of welding defects take place, as there may be lack of fusion which goes undetected.
oh and most car manufacturing type companies dont pay welders highly so the dont get 'coded' welders working there anyway!
Most chassis welds would have been carried out on jigs in position with the vertical section of the weld being done vertically down. This is where I imagine the majority of welding defects take place, as there may be lack of fusion which goes undetected.
oh and most car manufacturing type companies dont pay welders highly so the dont get 'coded' welders working there anyway!
Edited by ferlin on Tuesday 20th June 22:41
ferlin said:
Any ape can mig weld....... but its easy to mistakenly think that welding has taken place when it hasnt!
Most chassis welds would have been carried out on jigs in position with the vertical section of the weld being done vertically down. This is where I imagine the majority of welding defects take place, as there may be lack of fusion which goes undetected.
oh and most car manufacturing type companies dont pay welders highly so the dont get 'coded' welders working there anyway!
Most chassis welds would have been carried out on jigs in position with the vertical section of the weld being done vertically down. This is where I imagine the majority of welding defects take place, as there may be lack of fusion which goes undetected.
oh and most car manufacturing type companies dont pay welders highly so the dont get 'coded' welders working there anyway!
Edited by ferlin on Tuesday 20th June 22:41
Yeah, that's what I meant!
If it was the ultimate in inspection, you'd need to xray the welds... but you couldn't do them panoramically, so virtually every weld would have to be shot from several angles! Jeez, a radiographer on 'butt-rate' would make more than the chassis cost!
I would have thought that they would really only have needed a percentage of the welds inspected (say 10%)using magnetic particle inspection for that type of job, and perhaps they were?
Chassis welding aint exactly difficult for a trained welder. But hey we are assuming that the welds were dodgy!
I suspect that perhaps there is just too much stress in certain areas in our wedge chassis and it was a poor design. Gusset / fillet plates between tubulars would have been a better idea and wouldnt have taken much longer to insert and would almost definately have stopped the cracks from appearing anyway (even if the welds were slightly dodgy!! lol
Chassis welding aint exactly difficult for a trained welder. But hey we are assuming that the welds were dodgy!
I suspect that perhaps there is just too much stress in certain areas in our wedge chassis and it was a poor design. Gusset / fillet plates between tubulars would have been a better idea and wouldnt have taken much longer to insert and would almost definately have stopped the cracks from appearing anyway (even if the welds were slightly dodgy!! lol
Yes, most of the cracks I've seen on the 280i frame, barring other types of damage like rust or collison, have been near the welds. I've not seen, at least myself, broken welds.
I also agree about the gusset plates. They could be a good idea. I can easily imagine, though, why the factory wouldn't have done these. The example of the Lotus Elan factory race cars is an interesting one. Just a few extra pounds of steel, of the right shape and the right place took a frame that would quickly get torn up the stresses of competition use to being more than up to task of competition stresses. Really, a small amount of metal was/is very cleverly applied to entirely transform the reliability and durability of the frame. Really neat stuff, I think.
The M frames are pretty tough. They were the result of privateer and factory competition development, though I think they don't need to be as heavy as they are to acheive the same strength/stiffness result.
The 280i frame, though, and given how little the Wedge chassis changed over the life of the Wedge cars, doesn't seem to be as robust, while the car overall weighs much more than an M, as the M frame.
- SJ
'67 Lotus Elan S3 dhc 45/6210
'76 TVR 2500M 3550TM
'85 TVR 280i dhc
I also agree about the gusset plates. They could be a good idea. I can easily imagine, though, why the factory wouldn't have done these. The example of the Lotus Elan factory race cars is an interesting one. Just a few extra pounds of steel, of the right shape and the right place took a frame that would quickly get torn up the stresses of competition use to being more than up to task of competition stresses. Really, a small amount of metal was/is very cleverly applied to entirely transform the reliability and durability of the frame. Really neat stuff, I think.
The M frames are pretty tough. They were the result of privateer and factory competition development, though I think they don't need to be as heavy as they are to acheive the same strength/stiffness result.
The 280i frame, though, and given how little the Wedge chassis changed over the life of the Wedge cars, doesn't seem to be as robust, while the car overall weighs much more than an M, as the M frame.
- SJ
'67 Lotus Elan S3 dhc 45/6210
'76 TVR 2500M 3550TM
'85 TVR 280i dhc
Edited by m2500tvr on Wednesday 21st June 18:54
Usually mine gets detected by the MOT man! Being descended from an ape I MIG-weld them back upmyself, with reasonable results. I usually get cracks near the rear of the diff on the outrigger tubes, next to the welds. When they go again it's usually a bit further along, so at least my welding is up to scratch, albeit a little ugly.
adam quantrill said:
Usually mine gets detected by the MOT man! Being descended from an ape I MIG-weld them back upmyself, with reasonable results. I usually get cracks near the rear of the diff on the outrigger tubes, next to the welds. When they go again it's usually a bit further along, so at least my welding is up to scratch, albeit a little ugly.
Was it you that made the section of SE chassis that was floating about at the BBWF?
JR said:
It's all very good talking about welding but most cracks occur near, not at or in/through welds.
that's because the material next to the weld is the weakest, thin and hard, then when the chassis flexes a couple of milion times, that will be the place where it will crack first.
at least this happened to mine, discovered this as i was checking up the tusc for pistonfest
. espacially when it's welded at a very high temperature with litle adding of weld thread the weld will lie deeper then the tube itself and is prone to crack. that's in my amateur opinion 
I had a couple of cracks on mine which I duely welded up but then added a 'gusset' or corner brace to that area.
As most people know the welds themselves don't break rather the area immediatly after it does, due to the welding process changing the hardness of the metal. Consequently anything you can do to add strength to that joint and reduce flex will help the life of the weld considerably.
Also Stainless cracks worse than regular steel so it'd probably be worse if the entire chassis was made out of it.
Matt
As most people know the welds themselves don't break rather the area immediatly after it does, due to the welding process changing the hardness of the metal. Consequently anything you can do to add strength to that joint and reduce flex will help the life of the weld considerably.
Also Stainless cracks worse than regular steel so it'd probably be worse if the entire chassis was made out of it.
Matt
wedg1e said:
adam quantrill said:
Usually mine gets detected by the MOT man! Being descended from an ape I MIG-weld them back upmyself, with reasonable results. I usually get cracks near the rear of the diff on the outrigger tubes, next to the welds. When they go again it's usually a bit further along, so at least my welding is up to scratch, albeit a little ugly.
Was it you that made the section of SE chassis that was floating about at the BBWF?
No - I was the APE..
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