Trapezoidal L-truss: clip together construction module

This trapezoidal truss design has the interesting property that if you join the segments end to corresponding end, you get a curved arch, but if you join opposite ends, you get a straight section.  This lets you build a variety of curved and straight structures from identical components, which could simplify remote construction projects--such as here in Alaska, or on the moon or Mars!

The modules just push-connect together, with a flexure hook grabbing the next truss segment.  Open the hook with your thumbnail to detach again.  They can be assembled and reassembled repeatedly in many possible configurations.  A large structure will be mostly upright trusses, with just one layer of flat trusses to close the open end, and optionally some flat trusses on the bottom. 

This is a 1/10 scale model that we used to understand how multiple modules can combine into larger structures.  Other than in twisting, these seem to get substantially stronger with multiple modules combined, which is a good sign for building larger structures.  Large arches need good base support, or else the arch ends push out and the arch breaks in the middle.  With a good foundation, like in a sandbox, they can be surprisingly strong, see the picture with 12kg (26 pounds) of zinc ingots stacked on top of a 3-segment long 1-section wide arch.

This prints well in PLA without support, taking about 5 grams of plastic per module for the flat version, and 10 grams per module for the upright version.  Start by printing two flat copies to make sure they fit together well, then print several uprights to make larger structures!  During printing the upright version requires some short bridges on top, and includes small removable support plates under the vertical hooks.  (Those vertical hooks are rather weak, and should be assembled carefully.) 

We created this truss design as a small part of a National Space Grant funded collaboration with several NASA centers working on modular robotic construction, and our Aurora Robotics Lab / Automated Construction and Advanced Materials Lab.  The grant is X-Hab Modular Robotic Construction.  

These files are released as public domain, but I'd like to see what you make with them!