Designing - Brackets

With the arms build and glued together I could finalize the design for the brackets. In all the models I made the arms were held together by some sort of brackets attached to a spine. The brackets would have to be fairly strong as they would bear the entire weight of the panels, as well as contain the forces needed to extend the panels.

I figured that the best way to make the brackets strong was to minimize the amount of glued joints. I thought about steaming strips of plywood and then laminating them into U shapes, however, I had previously tried laminating strips together and while it did work, the results weren't very accurate or consistent. Since I wanted 4 U shapes of pretty much the exact same dimensions that option was out.

This is the design I was considering for most of the design phase.

The problem with the above design is that the brackets attach to the spine with very little surface area and the majority of the weight from the panels will be applied at the end of the brackets. Even with a strong epoxy, this would snap off pretty easily. It's also larger than I wanted, the wooden piece at the end of each bracket adds a fair bit of width that won't be covered by the retracted panels. It wouldn't have looked very nice.

Eventually, I realized that rather than trying to attach 4 brackets to the spine I could make 2 bracket assemblies and join them together, ensuring that the weakest points were in the least critical areas.


 The above design is much stronger in the places that matter. The weight of each panel is balanced out by the weight of the panel on the other side. Since the bracket is a single piece of wood there isn't a chance of it snapping. The joints between the brackets and the spine have a much larger surface area for the epoxy to bond to and won't take nearly as much force. And rather than having wood spacers at the end of each bracket I'll be using steel rods.

The arrangement I have the arms in for every design up to this point doesn't work. When the drive arm (the longest one) rotate upward to extend the panel it moves but it doesn't move anything else. You can see it quite clearly below.

Below is what I wanted, the axle that the panel is mounted to needs to extend all the way out.

So after playing around a bit with the positions of the end piece is fusion I figured out that by having the arm in a bit of a zig-zag pattern I could ensure they would extend. This also makes the spacing between the axles slightly smaller, which was a very good thing.

With the idea finalized I could draw up a proper design in Fusion. To figure out the exact spacing between the drive axle and the end rod I build a simple jig to test it. I drew the approximate shape of the arm onto the wood behind the arm.

Here's the design I settled on.

To make sure all the joints between the brackets and the spine pieces were strong enough I added a piece of plywood on the top and bottom, running the entire length of the spine. It'll be epoxied on once everything else is together.