Spacecraft . square pyramid jig

Posted on by dkoa
4 pcs 1in angle bar chamfer cut and welded to form square inverted pyramid with sturdy base, metal off-cuts.
4 pcs 1in angle bar chamfer cut and welded to form square inverted pyramid with sturdy base, metal off-cuts.
square pyramids made with 4 pcs. iron rod with single weld bead at tip should be self-supporting.
square pyramids made with 4 pcs. iron rod with single weld bead at tip should be self-supporting.
pre-cut all iron rods to identical length using metal cutter, saw or angle grinder.
pre-cut all iron rods to identical length using metal cutter, saw or angle grinder.
16 pyramids required to fabricate one semi-octet truss.
16 pyramids required to fabricate one semi-octet truss.

Spacecraft . 2d truss jig

Posted on by dkoa

Mild steel angle bar is liable to twist or bend before the truss is triangulated; to ensure that each octet truss you make is straight (±1 mm) use a straight and square metal jig with wood board forming welding bed (will burn over time, flip over before replacing). Use clamps to secure 2d truss frame to jig, and push metal against wood plate of jig with a nonconductive pipe or wood stick.

Welding: Tack weld first throughout to assemble octet truss, then complete full weld once all metal elements are held in contact. Usually a small amount of grinding required to clear sharp edges. Apply hardener coat to seal and spray 3-6 coats of automotive paint. Paint damage possible (e.g. scratches) during transport and assembly; paint touch-up work may be done after assembly.

use clamps to secure 2d truss frame to jig, and a nonconductive stick (preferably wood) to push metal against wood plate of jig.

2d truss jig spacer2d truss jig side viewweld flat bar ladder into 2d truss frame5 weld sides to 2d truss frameuse clamps to secure 2d truss frame to jig, and a nonconductive stick (preferably wood) to push metal against wood plate of jig.5 weld safety first6 weld pyramid chain into 2d ladder truss7 weld invert pyramid to angle bar at vertices8 semi-octet trusses should stack interlock9 7 1.5in semi-octet trusses welded, load to paint

finished octet trusses sprayed and loaded in truck bed
finished octet trusses sprayed and loaded in truck bed

Semi-octet truss first prototype

Posted on by dkoa
1 safety first
welding is dangerous; always work in a well-ventilated space, wear eye protection, and be careful!
welding the first semi-octet truss prototype at the Kokrobitey Institute makerspace
welding the first semi-octet truss prototype at the Kokrobitey Institute makerspace
octet truss KI first prototype
Emmanuel load-testing first octet truss prototype at Kokrobitey Institute makerspace, during #ampqamp14.

This was the first time we welded a complete full-length octet truss. Rudimentary structural tests after fabrication demonstrated good performance/strength but unacceptable dimensional tolerance (i.e. it was strong, but not precise).

Special thanks to Chamil, master maker at the Kokrobitey Institute makerspace, who suggested to develop a 2d truss jig (to hold 1in angle bar frame straight and square while welding) and square pyramid jig (to enable standardized production welding of square pyramids, as a component for full octet truss).

Chamil

More on spacecraft M&D from ampqamp14 here.