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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo Frame modification.
Post Subject: Tube Frame : Some Thoughts on ConstructionPosted by jessie.dazzle on: 12/26/2006
You are correct, the idea is to "hard tie" the tubes together (otherwise you don't get the rigidity... think of a paintbrush where the paint has dried in the bristles... this is what you want). You would need small welds between each tube... a 1 inch weld every foot would be plenty (on both sides)... avoid running long welds which would cause the whole thing to over heat and probably twist. First choice here is to use a TIG torch... Next would be MIG... both keep the heat down, but TIG ususally ends up prettier.
In the drawings, all tubes are of 2 inch square section (not rectangular... those cost more)... cutting them at an angle makes them look like they have a rectangular section.
For the horizontal upper member, you could of course use three tubes (instead of two) this would definitely give you enough beam strength.
.065 wall thickness is enough if done right. The important thing to remember in this case is to attach the members in such a way that you load the joints in shear (clamping the vertical member between the two base parts for example) and distribute the load over a large area.
If you want to get fancy, one elegant means of attaching the upper member would be to not attach it at all, but to put a notch in its under side and set it on a pivot ; give it a short tial which would hang out past the rear, then string a cable from the tail, down vertically to an attachment point low down on your vertical member. Use an in line cable tensioner to adjust the angle of the horizantal support.
Back to work...
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