Designing - Arms Pt. 3

I started off with by figuring out exactly what the arms would look like. I drew up 3 different arm designs in TinkerCAD and, once again, ended up not using any of them.

These were designed to include a short piece of rope wrapping around each end. I wasn't sure how strong the bond between metal and wood would be and I thought maybe a piece of rope slathered with epoxy would add enough strength to the joint.

Straight Arm

Tapered Arm

Rounded Arm

I experimented with the last design.

I drilled with a larger bit first to make room for the lip the bearing has, then all the way through with a smaller bit.

Fits pretty perfectly.

I used Kroeger Quik-Cure 5 minute epoxy. It's supposed to have a better bond with both wood and metal compared to their 10 or 15 minute versions.

The bond was decent, but with a little sideways force it popped right off. The epoxy needs more surface area to get a strong bond.

Back to the drawing board. Rather than just having the wood end at the bearing I decided to make it wrap all the way around.

I drilled the 2 sizes of holes into this piece of wood. This piece was just wide enough to not be cut in half by the drill bit like before. Then I epoxied the bearing in place, I also added a short piece of 5/16" steel rod in the middle of the bearing to test the epoxy in a metal to metal bond.

I cut the wood around the bearing leaving a thin rim. Once the epoxy had cured I tried to break it like before and I couldn't. I got other people to try to break it, they couldn't either. This is how I did all the bearing joints in this project.

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Designing - The Cells

A distinction I should make before going any further is the difference between solar cells and solar panels. When I am talking about the solar cells I am talking about the individual square parts inside of the panel. The panel being the housing for the cells, some sort of stiff material for the back and a sheet of glass over the front. The cells produce power and the panel houses and protects the fragile cells. The first step of designing the solar panels was to get the actual solar cells I'd be using since literally, everything was dependent on their size. I was able to find some panels for fairly cheap on eBay, so I officially began the project with the purchase of 10 A Grade 4.8W 19.6% 156mm Mono Silicon Cells. Here's what that means: A Grade - Panels are completely intact. B, C, or D Grade will have increasingly large chips missing from the cells. Read more here. 4.8W - This is the power output. 19.6% - This is the claimed efficiency of the cells. ...

Update - Drive System

Right, so my suspicions about the bond between the drive arm and drive arm were correct. When I tried to extend the panels using a pair of pliers the epoxy joints cracked and the axle broke loose. The panels did not extend at all. I've drilled a hole through the drive arm and axle, I epoxied a nail into the hole and it seems to be holding. I can now extend the panel with pliers. It takes quite a bit of force to do it. I kinda doubt a servo will be able to handle it.

Building - Arms Pt. 1

Building the arms was by far the most time-consuming task. If only I had a cnc.... The rim of wood around the bearing was needed but I didn't like the really thick arm, I drew this up in Fusion, printed out the drawing, and stuck it down with a glue stick. The slot in the middle was an idea to make the arms lighter and look cooler. I tried it with one arm and then ditched the idea, it really didn't work and was a lot of work. All cut-out, at this point I didn't have access to a scroll saw so this was all done with a regular handsaw and files. It's pretty rough but I cleaned it up as best I could. Already looking much better. The next step was mass production, I needed 20 arms total. For this, I bought a used Craftsman Scroll saw. It was very, very useful. All cut and drilled out. Removing the paper was annoying, I used the top edge of a file to scrape it off. Since I put it on with a glue stick it wasn't very difficult to scrap...

Martens Solar

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