Norman Atkinson
Titanium
- Joined
- Feb 8, 2005
- Location
- TYNE AND WEAR, ENGLAND
In my E-mails tiday, I got a rather nice one from
Doug from PA.
Perhaps I was going on about standards of vehicle repair and conrasting the US with what I knew in much of Europe.
I was delighted to have such a detailed account and I fear that I appear to have refered to "duct tape" and " bailing wire". I can sort of guess but I haven't a clue about duct tape or baiiling wire and doubt if I could have used the expressions. If I have, well I sincerely apolgise. Doug does go on- and on about the standards in his County and contrasts them with other less stringent Counties.His appears to have little to criticise and I would admire the detail and care of his preparation. It does worry me about elsewere- and he supplied very worrying instances.
In Doug's very detailed expose, he does mention the use of arc welding and he rightly sounds due warnings and misgivings. I believe that this is the nub of my criticism and I certainly would go on about the use of plastic fillers. The two go together.
In modern vehicle repair, steel as we knew it was
mild steel. Provided there was enough metal left, it could be joined with arc, oxy, mig-mag or Tig. It could joined satisfactorily.
Today, steels are thinner, lighter and stronger than then. These benefits are only achieved with the addition of alloys such as small quantities of niobium. Here comes the crunch, bodies are constructed by spot welding and without going into a long dissertation, are designed to tear in a collision. The impact is lessened and occupants are no longer the shock absorbers.
Today, if detailed inspection is done, an auto body has the precise number of spot welds- and no more or less. An alteration in the seam constitutes a risk. An older vehicle which needs a repair may not have complete repair panel to replace the bad one. Even if one was available, the joining would or should be by spot welding or stitching with a Mig to approximate the manufacturers specification.A continuous seam is totally wrong whether by any of the joining methods mentioned. Here comes the question of Why. High strength low alloy steels become brittle during the joining process. they cannot be "let down" to their original temper as they came out of the factory.
The risk- and this is where I came in, is the joint made by arc or oxy will fail by cracking along the side of the weld. The only relatively safe joins are by spot welding- or by Mig-mag or Tig emulating spot welds as before.
I am sure that Doug and other readers will appreciate that the construction techniques of vehicles bodies are world wide. My knowledge is almost a decade out of date but movement will be towards more and more sophisticated techniques rather moving back to what was Ok for me- then.
I hope that this will be a change from my more usual view of things!
Norman
[ 02-12-2006, 11:13 AM: Message edited by: D. Thomas ]
Doug from PA.
Perhaps I was going on about standards of vehicle repair and conrasting the US with what I knew in much of Europe.
I was delighted to have such a detailed account and I fear that I appear to have refered to "duct tape" and " bailing wire". I can sort of guess but I haven't a clue about duct tape or baiiling wire and doubt if I could have used the expressions. If I have, well I sincerely apolgise. Doug does go on- and on about the standards in his County and contrasts them with other less stringent Counties.His appears to have little to criticise and I would admire the detail and care of his preparation. It does worry me about elsewere- and he supplied very worrying instances.
In Doug's very detailed expose, he does mention the use of arc welding and he rightly sounds due warnings and misgivings. I believe that this is the nub of my criticism and I certainly would go on about the use of plastic fillers. The two go together.
In modern vehicle repair, steel as we knew it was
mild steel. Provided there was enough metal left, it could be joined with arc, oxy, mig-mag or Tig. It could joined satisfactorily.
Today, steels are thinner, lighter and stronger than then. These benefits are only achieved with the addition of alloys such as small quantities of niobium. Here comes the crunch, bodies are constructed by spot welding and without going into a long dissertation, are designed to tear in a collision. The impact is lessened and occupants are no longer the shock absorbers.
Today, if detailed inspection is done, an auto body has the precise number of spot welds- and no more or less. An alteration in the seam constitutes a risk. An older vehicle which needs a repair may not have complete repair panel to replace the bad one. Even if one was available, the joining would or should be by spot welding or stitching with a Mig to approximate the manufacturers specification.A continuous seam is totally wrong whether by any of the joining methods mentioned. Here comes the question of Why. High strength low alloy steels become brittle during the joining process. they cannot be "let down" to their original temper as they came out of the factory.
The risk- and this is where I came in, is the joint made by arc or oxy will fail by cracking along the side of the weld. The only relatively safe joins are by spot welding- or by Mig-mag or Tig emulating spot welds as before.
I am sure that Doug and other readers will appreciate that the construction techniques of vehicles bodies are world wide. My knowledge is almost a decade out of date but movement will be towards more and more sophisticated techniques rather moving back to what was Ok for me- then.
I hope that this will be a change from my more usual view of things!
Norman
[ 02-12-2006, 11:13 AM: Message edited by: D. Thomas ]