Portsmouth has a pretty cool Halloween parade that's been going on for ~20 years. My local makerspace, understandably, gets busy around the holiday; I think costume-making brings out the inner maker in us all.
I've been fostering a minor fixation with aluminum extrusions as a construction component since I got into 3D printer and CNC building. They're so darn versatile and they look cool. I though that using them to make a mechanism instead of a static frame would be interesting. I was hunting around for a costume idea anyway, so that's how I got on the track of building a set of articulated wings.
Now, I'm no engineer. I took physics in high school and I've been building and fixing things for a long time but when it comes to mechanics more complicated than levers and gears, I either have to do a lot of research, or wing it. My concept was to use a collapsible parallelogram linkage so the wings could fold up on my back, or open up. I drew a couple of sketches and then jumped into prototyping using the easiest method available to me - strapping and wood screws:
That worked out pretty well, but it wasn't going to map directly to the aluminum frame build. I wanted smooth motion without metal-on-metal contact to cause interference or wear. So my next thought was to come up with a hinge or pivot design. I found some hardware from the aluminum extrusion supplier that allowed for joining of two segments with an arbitrary angle, but it didn't seem designed for constant movement. I also couldn't find anything appropriate online, so I busted out SketchUp and made my own part.
3D printing to the rescue. Thick-plastic carriers holding skate bearings, held captive by retaining plates. All standard hardware, and sized to bolt right up to 20mm square profile extrusion:
I ordered the aluminum in lengths that were proportioned to my prototype, but a little bigger. The last segment was bent to a curve that I found visually appealing and more organic.
I also added gas shocks to carry the weight of the mechanism when open, and added some rare earth magnet closure catches (salvaged from scrap hard drives)
I wrapped them in a gauzy fabric I found at the local fabric store in the Halloween section. It seemed appropriately spooky and ethereal. The wings attached to an aluminum back plate with shoulder hooks, not unlike a marching drum (come on, I know you guys were band nerds in high school too).
I was pretty tired of construction by the end of all this, so the rest of my costume was a simple black robe.
The proportions of the wings were arbitrary, but I went BIG. Looking back, I went too big, and if I ever revise the design I'll scale it down. Awkwardness of motion - folding, collapsing, even just walking - increases exponentially with length of the segments.
One last shot of me haunting Portsmouth on Halloween night.
