A few members fabricated (and promised to!!!) custom tube K members utilizing stock control arms and strut rods but never had the means to produce more than their initial one offs.
That wasn't me! 😆
Part of me has thought about making a tubular Kmember. Now that I actually know how to weld and will have the space to do such a job, it might actually happen.
I've always wanted to start on one too!
Just don't go making it out of galvanized fence pipes or thin walled seam welded exhaust pipe tubing and I think you be fine
For a roll-cage, of course not. However, for a Tubular K-member I don't see anything wrong with using standard ERW seamed tubing
of high quality, with the appropriate OD and wall thickness, and properly triangulated/engineered.
One really great book I highly recommend to purchase is Advanced Automotive Welding, by Jerry Uttrach, 2012 (or the latest version called "Weld Like a Pro", 2015). I bought mine on Google Books for about $20. That is where I caught a glimpse of the Maserati Birdcage. A full tubular-frame car with 200, mostly ½ " diameter, thin-wall chromoly tubes. The whole frame weighed only 66 lbs! It said the trick to it's success was to keep the loads/forces on the tubes such that the tubes were only experiencing tension, not compression, nor any side-loads that would cause buckling. Pretty amazing; enough that Carol Shelby raced it and won with it!
Anyways, time to bust out the tubing bender! I just wish I had bought more dies years ago. Steel has tripled in price! UGH!! lol Heck I might try making my own bending dies, lol.