(First-time submitter, so here goes)
On your question about strength of welds -- I have a mechanical engineering
background (and degree) and also went to welding school training at my first
job. It was a while ago, but here is some of what I remember.
Weld strength depends on a number of factors. The most important is the
quality of the weld itself and the design of the joint. In most situations
applicable to auto repair, weld filler materials have strength that is at
least as strong as the base metal ("base metal" is the material(s) you are
welding together). There are some situations where weld filler metal
strength is weaker, but these can usually be ignored for common auto
repairs. Weld filler metals have specifications that define the tensile
strength and other characteristics. The filler type usually has some
relationship to the strength. For example, in "stick welding", the rod type,
such as "3030" tells you the metal type and its tensile strength. The last
"30" indicates tensile strength of 30,000 psi.
Because the weld cools relatively rapidly, you have to watch out for
embrittlement in some metals. There are other concerns too (like,
inclusions, porosity, carbides, etc.) but these need more time to cover than
this posting allows. You can find out more in most any good welding book
(textbook type, not "how-to" manual).
There are numerous weld joint types. The most common are butt, lap and seam.
Generally, the more weld metal you use, the stronger the joint will be (not
due to the metal strength, but due to the fact that there is more metal in
the loading path). Different joint types are used to achieve similar affect
without necessarily having to use more weld filler. The more weld filler
used, the more likely to get distortion, inclusions, and other welding
defects which degrade the joint strength.
Hope this helps you.
'60 TR3a TS63103OL (just starting restoration)
'59 TR3 (had it from '74 - '76, sold it, and wish I could get it back)
"Bill" and others wrote:
>I remember many years back reading an article in one of the DIY orientated
>Classic Car mags about the pros and cons of various welds. What stuck in my
>mind was the statement that a MIG weld typically has 80% of the strength of
>an arc weld. Would anyone feel qualified to comment on this?
>Bill (who's chassis' are all MIG welded)