11 Dec 2008

Phil pointed out a couple things about tube chassis construction that I was aware of but hadn’t really thought through. He stressed trying not to have a bunch of tubes coming together into one node. Technically it’s the right way to do it but causes a number of fabrication problems. The cuts on each tube can end up being very hard to fabricate, including being impossible to install without cutting off one fishmouthed end. Many tubes in one spot results in such a large mass of metal that a lot of heat must be pumped in to weld all the tubes which leads to heat warpage. Also, it can be near impossible to reach in between all the tubes and weld every inch of every joint. It’s easy to skip the hard-to-reach ones, which start corroding from the inside out since it’s open to oxygen and moisture (never mind rain water wicking inside.) Seems like good advice so I’ll see what I can do, space the tubes slightly to allow getting the torch in between and to simplify the tubing cuts. In many cases it doesn’t take much to greatly simplify the end-cut, sometimes just moving the end of the tube 1/4″ is enough to change a 3D cut to a single-plane cut.

Ordered some Christmas presents for myself. Google Sketchup works pretty well for creating the chassis but Google knows what they’re doing. Their free version only exports JPEG drawings which is very limiting. No .EPS format for the book, no .DXF for sending to metal fabricators, or .PDFs, or .TIFFs. Fine, they win; Sketchup Pro was purchased which has all the export formats.

Back when building Kimini, there were times it was nearly impossible to use the TIG welder foot pedal when welding in awkward positions. A finger-operated current controller fixes that. Since moving a finger to change current will likely move the torch head slightly it’s not a perfect solution, but better than the antics of struggling with the foot pedal.

Replaced the leather cover for the TIG torch hoses; it was worn through and contrary to my cheapskate nature it was replaced rather than waiting for a hose to spring a leak. Also ordered bandsaw blades for the weenie-but-faithful Harbor Freight bandsaw; we’ll see if it lasts another build. They have a larger $600 saw but as long as this one keeps running there’s no reason to consider it, plus it would consume sacred floor space.