I can't imagine an A-pillar that is damaged with the rest of the car being deformed as well, the A-pillar of a modern car is ridiculously strong and meant to be the outer boundary of the safety cage for the passengers. Any deformation there and you'll have a deformed bottom, roof, firewall and probably other parts as well.
It's physically possible to do it and maintain reasonable safety but you need proper equipment, skills and time.
The frame is generally not designed to be welded like that, so without reinforcement it will be significantly weaker.
He did is as a hobby project but generally done properly such operations are not cost-effective.
Nevertheless it's still a service some shops provide at the cost of safety.
My aunt used to have such a car - she only noticed because she was blowing through sets of tires - the halves were misaligned(rotated) by less than one degree in each axis, but it was enough to make proper tire alignment impossible.
Typically the reason is not that the heat affected metal will be come weaker, typically the reason is that the weld is thicker than the material right next to it creating a stress point in the structure. The hardening can be taken care of by annealing.
The best way to fix cars is to increase the length of the weld if you can, the original weld points are there for a balance between economy and strength. If you start welding in 'original new and interesting places' you need to plan how you want to achieve the required strength since economy is likely the least of your worries.
Every stretch limo is essentially a demonstration piece to show that this does not need to be a problem, and that you actually can re-inforce a body quite nicely. Keep in mind that the wheelbase of a stretch limo pretty much guarantees much higher forces on all of the welding in the body including the existing seams.
-Schengen(so a steady stream of cars imported from Germany with no additional fees).
-A Skilled workforce.
-Cost-conscious customers.
-Badly enforced regulations.
Which create an ideal environment for a cottage industry of shops which will take your storm-damaged aluminium roof sheets and turn them into an inspection, passing, moving car with a real VIN by next week.
I could create a Blade Runner'esque quote on stuff I've seen on the roads around here - especially regarding commercial vehicles.
It's less so like that than comparing to the 90s, but still.
Welds can definitely be strong enough if done properly, as evidenced by the fact that welded parts involved in accidents can often be found to have broken somewhere other than a nearby weld.
However achieving the proper level of welding is easier said than done, and in particular being confident that a particular weld is done properly requires advanced equipment for non-destructive testing (x-ray, conductivity, echo ...)
Vehicles build on frames are cut and extended/shortened all the time as a part of routine modifications for commercial use and it's far less labor intensive to "do right" than a unibody vehicle. Putting two good halfs together is no big deal and is a relatively standard operation, all the known techniques and whatnot transfers right over. (I assume a 60s Mercedes falls into this category.) Unibody vehicles are also routinely repaired in this manner in eastern Europe where it's cheaper to buy wrecked stuff from the west and fix than to buy new. In the west the limo and mobility van industry does very similar things (only they're inserting stuff in the middle rather than repairing the car)
People do cut and weld jobs all the time for their own personal vehicles and classic cars. When you're doing it for your own car or a car you don't intend to flip you can afford to spend the time to do it right.
Quick hackjobs are the issue, not the technique.
HSLA (high strength low alloy) steels are stronger (and therefore lighter) than mild steels. Many alloy steels (non-HSLA) are sensitive to heat treatment and improper welds make them weaker, so tons of people were being very vocal about HSLAs ruining cars, making repairs impossible, etc etc. Things like saying you'd need proprietary filler to match the composition, that welds would be poison, etc. In reality it doesn't really make a difference.
Adhesives are also sometimes/often used to secure panels together instead of welds. The theory was that subtle differences in shape would introduce tensile stressed that would cause adhesives to pop in a crash. Not real. Alternatively stress during modifications could introduce cracks and weaken the adhesive- also bullshit, those adhesives go through stress every time they drive. They're fine.
They aren't invalid concerns, but unless you're putting a torch to the adhesive or welding seams down the middle of alloy beams, you aren't doing anything that will cause problems.
> Things like saying you'd need proprietary filler to match the composition, that welds would be poison, etc. In reality it doesn't really make a difference.
The nice thing is that the car OEMs are high enough volume that even if they use something exotic someone will come along with special consumables or procedures or procedures or whatever that makes it trivial to work with. I hope some other OEM's follow Tesla with the stainless and we get cheap weld backing tape as a result.
With a 2020 car? I wouldn't trust it unless the person performing the work was a pretty good engineer. As engineering is more optimized, you can't just do stuff like this without being very careful:
1) Welds do leave a heat-affected zone around the weld which is weaker. If you're overengineered (1956) and everything is thicker than necessary, this doesn't matter. If you're near-optimal (2020), and using the exact amount of material needed to avoid failure under expected driving conditions, you might weaken things enough to see failures.
2) If reinforced, you'll affect the overall systems design. Engineered objects flex. Making one part more rigid than expected will put additional strain on other parts.
Counterintuitive as it might sound, optimal engineering makes designs safer. You analyze failure modes, put in appropriate safety margins, and do things right. Engineering classes drill that over-engineering is bad engineering. The flip side, though, is that if you can't tweak optimized designs like you can over-engineered ones without being careful and thoughtful about it.
Same thing with bikes. You can fix up a $100 Huffy with any old welder. A $2000 steel frame with thin-wall double-butted tubes? You want a really skilled welder and close inspection to make sure it's not compromised.
The repairs you are proclaiming to be impossible are perfectly possible to do with good results. These repairs are often performed often, just not in the high cost of labor parts of the world where HN lives (the low cost areas buy our wrecked cars to fix and sell to the point where sourcing parts for major repairs is often easier there than in the vehicle's country of origin). There's autobody industry specific tools and literature that help professionals in the industry perform the repairs properly. It's perfectly possible to take a car apart and reassemble (with good parts) the way an OEM would have if you're willing to invest in the tooling (mostly for welding in hard to reach areas). Car passenger cabins aren't supposed to flex (but in practice they do so within acceptable limits) and OEMs provide service literature telling you what you can and can't modify, much repair info can be gleaned by reading between the lines of such service literature. The welding issues you are describing are simply not an issue for skilled welders. Your opinion of engineering education is hard to reconcile with the observed performance of new engineers in any/every field.
The conclusion of what you're replying to: "You can fix up a $100 Huffy with any old welder. A $2000 steel frame with thin-wall double-butted tubes? You want a really skilled welder and close inspection to make sure it's not compromised."
Yes, it's possible, and yes, I know folks whom I'd trust to do it. The guy in my local auto shop? Definitely not. Random car shop in the developing world? I've seen the results. They'll drive, but they're far from save by Western standards.
What you wrote: "if you're willing to invest in the tooling" "The welding issues you are describing are simply not an issue for skilled welders"
I mean, seriously. You responded to a something entirely different from what I wrote, repeated roughly what I actually DID write, and mixed a few errors in (if car cabins weren't made to flex, they'd be using a very different type of steel; virtually everything made to be tough is made to flex).
Please find a place in my post where I "proclaiming [repairs] to be impossible"
Have you tried doing that to anything other than a 1960s convertible?
My 90s junk handles that just fine (and they're not particularly rigid cars). Matter of fact I did it yesterday afternoon to change rear pads.
Generally speaking you need to get a floppy vehicle really bound up (think 80s Jeep Cherokee or minivan off road) in order to have issues with doors and even then it's usually rear hatch only. OEMs specially try to avoid having bodies that flex enough to be noticeable to consumers, let alone to the point of doors not opening. Heck, I'd be surprised if you can even design a car to pass modern roof strength requirements without also making it stiff enough to have the doors open and close regardless of how bound up it is. (Pickup tailgates are another thing since the bed is open top and bolted to a frame designed to flex somewhat and even then being able to open the tailgate with two tires off the ground is not unheard of)
1) How much force it takes to flex it -- the spring constant
2) How far it will flex before it breaks
Multiply the two together (or specifically, 1/2 kd^2 where d is how far it will bend before it breaks, k is the spring constant, and 1/2 kd is the average force you're applying), and you get how much energy it takes to break it.
*Everything* flexes. Rigid things just flex less for the same force.
Things which break when flexed just a little bit are called brittle.
It's similar in microelectronics. I can do a ton of stuff with an arduino because it uses really basic old, tough eletronics. I can put too much current into a pin, ok the pin dies but the AVR is still fine. A modern ESP32? A little bit of current or voltage above the rating and the whole thing is toast.
It's just like people putting turbochargers on their 90s Hondas. Naysayers could claim it's a fool's errand because if Honda, with all their engineering resources, didn't feel they could add turbocharging to their engines in the 90s and have it be cost effective and reliable enough, surely someone in their garage can't do it? But what they overlook is that if 5% of one of Honda's mass market cars blew an engine that would be a disaster, whereas a 5% chance an individual blows his own engine, which he may be able to replace for $500 to $1500: that may be a risk an individual is willing to take that a carmaker cannot.
I used to be around the rally racing scene, and it's utterly routine there to weld tons of re-enforcements into the unibody. Most people with the money will straight up laminate the suspension mounts with plate. The safety cage makes the car incredibly rigid, as does replacing all bushings. The cars work just fine. The people doing this have relatively ordinary welding skills. Modern cars are not some sort of high tech magic that can't be modified or repaired with ordinary metalworking skills... it's just usually not cost effective to do so.
But you are on the money with the cost effectiveness bit, that's exactly why it is perfectly possible to do these modifications with confidence: you are not operating under a budget that gets counted out to the last 1/10th of a cent, so you can do it right, even if it costs a few bucks more. Something a car company operating at scale would never do. Once the cost constraint disappears there isn't a whole lot you can't do.
1) reinforcing the whole car for a rally (which brings the car up to 1965 overengineered standards, and well beyond); and
2) simply welding two halves of a car together.
If you were to weld two halves of a car together, and weld a ton of reinforcements into the unibody, it would very obviously work fine.
I would say it greatly depends on your welding skills. The same welded materials can be very solid of very weak depending on how they were welded. I would not dare to do that, personally.
Though any sort of big modification like this probably changes the characteristics of how it crushes in a crash, flexes under load, etc.
I've welded up cars that were so rusted through that you had to re-inforce the body before you could start working on them in order for them to stay true (tubeframe inside the main body to fixate the remains). It's all doable, mostly a matter of time and skill.
Felt very unsafe but we got there
I'm pretty sure 99.999% of HN would say the same thing about a normal Lada.
"In Comments
Don't be snarky. [...] Please don't sneer, including at the rest of the community.
When disagreeing, please reply to the argument instead of calling names.
Eschew flamebait. Avoid unrelated controversies and generic tangents.
Please don't use Hacker News for political or ideological battle."
The joke could instead be that Ladas are safe enough, the stretch Lada was probably safe enough, and the thing to laugh at is the 99.999% of HN who can't judge the safety of cars, or naively aren't used to a world outside their Silicon Valley spafe-space luxury. i.e. it's a sneering putdown at HN users and nothing to do with Ladas per-se. Given the context of the last two comments I read by throwaway account starting with sneering at HN and Reddit users, and the need to specify "99.999% of HN users would say X", I lean towards this interpretation.
That doesn't mean you can't find it a hilarious witty comment, sneering at some "inferior" group is a popular thing people laugh at. (Weirdly?[1]) You might find it a funny joke, and it might be sneering and against the guidelines, both at the same time. "I loled" isn't sufficient to say it's on-topic, you should be arguing that it wasn't sneering. Better again, arguing that it was within the spirit of the guidelines more than the letter of them; just jokes alone are not against the guidelines explicitly but are frequently frowned on.
Sneerclub and status grabbing are my own personal soupnazi topics of the moment; once you see comments where the main purpose is to sneer at how dumb some large disparate group is, or the flip-side to claim status as a superior, you see them everywhere. e.g. these two just seen in tabs I have open:
- https://news.ycombinator.com/item?id=26821673
- https://news.ycombinator.com/item?id=26822285
both where the point is to call someone dumb/inferior.
(And e.g. much of my internet commenting history, tbh)
[1] (is it more social signalling than humour?)
https://www.justacargeek.com/2013/11/1984-volvo-240-pick-up-...
And obviously because Volvo is swedish, that is the most common model to modify.
One of the required modifications is to remove the rear seat so that it is no longer built for personell transport. It should also not be possible to drive faster than 30km/h.
You can see the images here, but there is no corresponding page in english. https://sv.wikipedia.org/wiki/A-traktor