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Combining vehicles like this is one of those things that isn't bad but gets the Reddit experts screeching because their only experience is that their mom's sist

Combining vehicles like this is one of those things that isn't bad but gets the Reddit experts screeching because their only experience is that their mom's sister's boyfriend's uncle's roommate got swindled by someone doing a crap job on a Civic that they thought they were getting a good deal on. 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.

deleted 6y ago
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hwillis 6y ago
There is/was lots of speculative armchairing as well, when HSLAs started coming into the picture. Structural adhesives also get pointed to as a reason not to do big repairs like this. In practice it isn't really borne out. 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.
- throwaway0a5e 6y ago
  I think with the benefit of hindsight structural adhesives make things easier. Way easier to apply glue and clamp (or whatever the instructions are) than to weld somewhere you can't see without a mirror or building a custom spot welder tip that replicates what the robot used in the factory. I also like that you can not ruin the paint around an area where you apply adhesive whereas welding usually cooks off the adjacent paint. This is very beneficial in environments with corrosion. Holy crap are the consumables expensive compared to welding though. > 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.

deleted 6y ago

[deleted]

hwillis 6y ago

There is/was lots of speculative armchairing as well, when HSLAs started coming into the picture. Structural adhesives also get pointed to as a reason not to do big repairs like this. In practice it isn't really borne out. 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.

throwaway0a5e 6y ago
I think with the benefit of hindsight structural adhesives make things easier. Way easier to apply glue and clamp (or whatever the instructions are) than to weld somewhere you can't see without a mirror or building a custom spot welder tip that replicates what the robot used in the factory. I also like that you can not ruin the paint around an area where you apply adhesive whereas welding usually cooks off the adjacent paint. This is very beneficial in environments with corrosion. Holy crap are the consumables expensive compared to welding though. > 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.