Chassis welding quality

[langy]

I've seen many manufacturers chassis with welding like that, they don't have the same exacting standards as some of us.

 

[marlinspike]

I assumed it was a self-build. Bit scary to think that might be from a mainstream car maker, though as said, presumably it was up to the job. You don't usually hear of cars falling apart because of a badly welded chassis.

 

[Jan]

What I can't understand is the 'need' to see fully seam welded patches or replacement panels. In my time cars used to come from the factory with gaps in the welds to allow the chassis/body interface some 'wiggle room' to flex rather put too much strain on the joints. Is that no longer the case?

 

[dan.taylor.1]

I think it's probably because the ends of a weld can cause stress fractures which thenallow rust in where as a full seam won't?!

 

[pedrobedro]

What I can't understand is the 'need' to see fully seam welded patches or replacement panels. In my time cars used to come from the factory with gaps in the welds to allow the chassis/body interface some 'wiggle room' to flex rather put too much strain on the joints. Is that no longer the case?

Chassis are designed not to flex so body gaps stay the same and suspension does it's job properly. Flexing metal is what causes it to crack and fail. Only vehicles like 4x4 and commercials come with separate chassis and body and they have some rubber mounting to allow for any movement.

 

[Rocketman]

Chassis are designed not to flex so body gaps stay the same and suspension does it's job properly. Flexing metal is what causes it to crack and fail. Only vehicles like 4x4 and commercials come with separate chassis and body and they have some rubber mounting to allow for any movement.

Well all car bodies flex to some degree. In recent years manufacturers have been reducing it massively with each new vehicle platform, which can be seen in conjunction with modern suspension and other items giving far better handling characteristics than was previously obtained for the mass market models.

 

[Robotstar5]

Well all car bodies flex to some degree. In recent years manufacturers have been reducing it massively with each new vehicle platform, which can be seen in conjunction with modern suspension and other items giving far better handling characteristics than was previously obtained for the mass market models.

I saw a good example of body flex a few years ago, A Jeep Grand something parked with one front wheel on a grass bank at the side of a track, the drivers door wouldn't close and the passenger couldn't open his door!.
The owner vowed to go back to Land Rovers

 

[CompoSimmonite]

I saw a good example of body flex a few years ago, A Jeep Grand something parked with one front wheel on a grass bank at the side of a track, the drivers door wouldn't close and the passenger couldn't open his door!.
The owner vowed to go back to Land Rovers

With a Land Rover the gaps are so big they make doors irrelevant
Jeep's were originally designed to flex. During the 1950's both Jeep and Land Rover were going through a difficult patch and a couple of prototype vehicles with Land Rover body on Jeep chassis were produced for evaluation of a joint venture. Proved a complete failure as the Jeep relied on the rigidity of the body tub and Land Rover the chassis but the concepts used the worse aspects of both ! A Jeep body on a Land Rover chassis however would have been a winner !

 

[hotrodder]

No such thing as a perfectly rigid body and while stiffer is usually better it's only upto a point, seam weld a modern 5* NCAP rated car and then crash test it and see how much higher the forces that the dummy occupants are exposed to are...

What I can't understand is the 'need' to see fully seam welded patches or replacement panels. In my time cars used to come from the factory with gaps in the welds to allow the chassis/body interface some 'wiggle room' to flex rather put too much strain on the joints. Is that no longer the case?

The MOT doesn't require replacement panels to be seam welded, just patch repairs. Take an outer sill for example... replace the entire thing and it can be spot (or plug) welded just like the origional was. Do a localised repair to the same sill and you need to seam weld because the origional wasn't made like a patchwork quilt. In the real world complete panel replacement often involves both spot and seam welding because it's more common to either only use part of the replacement panel or there's no choice, a rear quarter for example as the complete thing extends into the door shut, upto the roof and can include the outer window frame

 

[norlander]

maybe its a vehicule from scrapheap challenge. But as somebody has already said it seems to be holding together, but then if its on a very expensive car, maybe it does not get much use so the welding might not be put to the test.
MIG often produces untidy or ugly looking welds but they seem to hold up (talking from limited experience on that though).MIG is also the process most likely to be used by someone who is not a welder first and foremost and possibly not really interested in welding other than using the process to stick metal parts together without drilling and using nuts n bolts?-would that be a fair comment??.
So what I'm trying to say is most of us on here like to neat n tidy welds because we take pride in welding, others are not bothered what the welds look like as long as the bits stick.
One reason I delayed buying a MIG set was because I was never happy with look of the welds I produced with the Clarke MIG I had some years back.Now I have a semi pro (I think-GYS Smartmig) inverter set with proper gas bottle and am much happier with the MIG welds I turn out.
Could be that the settings were not spot on or the earth was not good when that welding was done?? seems to me that you can plough on with MIG whereas with other processes you have to stop and correct the settings.
Anyway, most of the blokes on here would have had to grind that off and do it again.

 

[Jan]

As I implied, but may not have specified, the inner sills on my motor home are part of the bodywork which is truly separate from the truck based chassis. Due to a lot of 'stringers' it's virtually impossible to replace each whole inner sill as a single unit without removing the untouched outer sill. During a recent total internal refit the sills were crudely patched with what appear to be random squares of metal welded in place. Some are merely stitched on top of others to give almost complete coverage where the tin worm has eaten away some of the original metal. Although messy to look at they seem to be more than adequate for strength, but they have been marked down as an MOT fail due to their proximity to 'mounting points'.

 

[octo0072000]

maybe its a vehicule from scrapheap challenge. But as somebody has already said it seems to be holding together, but then if its on a very expensive car, maybe it does not get much use so the welding might not be put to the test.
MIG often produces untidy or ugly looking welds but they seem to hold up (talking from limited experience on that though).MIG is also the process most likely to be used by someone who is not a welder first and foremost and possibly not really interested in welding other than using the process to stick metal parts together without drilling and using nuts n bolts?-would that be a fair comment??.
So what I'm trying to say is most of us on here like to neat n tidy welds because we take pride in welding, others are not bothered what the welds look like as long as the bits stick.
One reason I delayed buying a MIG set was because I was never happy with look of the welds I produced with the Clarke MIG I had some years back.Now I have a semi pro (I think-GYS Smartmig) inverter set with proper gas bottle and am much happier with the MIG welds I turn out.
Could be that the settings were not spot on or the earth was not good when that welding was done?? seems to me that you can plough on with MIG whereas with other processes you have to stop and correct the settings.
Anyway, most of the blokes on here would have had to grind that off and do it again.

if you read the link i put up next to the picture of the chassis the original chassis is stick welded not mig
chassis
Tubular steel. Arc (stick) welded as original. Similar to the production C Type
frame apart from perforated swaged holes in the chassis floor cruciform. Minor
bracket and flange differences. Extra bolted flange fixings for the body
mounting along the bulkheads and floor to obtain extra structural stiffness
from the body. Chassis painted black.

link to jag blog

http://blog.dtypedevs.com/2010/06/specification-and-schedule.html

 

[dan.taylor.1]

Jan, if its within 300mm? of a mounting or structural element its a fail irrespective of how separate it is.

 

[norlander]

if you read the link i put up next to the picture of the chassis the original chassis is stick welded not mig
chassis
Tubular steel. Arc (stick) welded as original. Similar to the production C Type
frame apart from perforated swaged holes in the chassis floor cruciform. Minor
bracket and flange differences. Extra bolted flange fixings for the body
mounting along the bulkheads and floor to obtain extra structural stiffness
from the body. Chassis painted black.

link to jag blog

http://blog.dtypedevs.com/2010/06/specification-and-schedule.html

ta for that-I missed the connection in the OPs second post and did not twig first time round it was Jag chassis and as it was in the MIG section I was commenting on MIG in general really-not so much on the example of the welds in the in the image.
As they are stick welds then no comment as this is the MIG section. I actually did not click on the link as you guessed correctly as it was about shopping trolleys (very classy shoppin trollies though for sure).
Wouldn't turn it down if you offered me one though.

 

[Jan]

Jan, if its within 300mm? of a mounting or structural element its a fail irrespective of how separate it is.

That's what the failure sheet shows as the reason, but not being certain where the mounting points are I can't say if the tester is correct. Having spent a couple of hours with several power tools and failing to remove even the smallest of the patches I can see why no-one wants the job of replacing them!