Its time to get back at some body work. I needed a little break from the internals for a while while I’m waiting for parts on order.
About my outer shell, as mentioned in a few posts earlier I’m using an outdoor garden (ball) lamp as the main material. It just so happens to match the actual size of the real BB-8. The plastic is HDPE High-density polyethylene, which is super strong and yet very light and easy(ish) to cut. A Dremel works perfectly on this for cutting and carving. The only issue with with kind of material is that it doesn’t like being glued in other words NO traditional glues work. I finally a tracked down a “Poly-bonder” adhesive that should work and I’m waiting for that delivery from the UK. The “Pie panels” will be totally cut out of the sphere but the paneling details will be carved in. The most tedious part of this process was to draw all the paneling on the ball first before cutting. I must have measured and remeasured a dozen times to get them lined up, so it took a few days to complete. Because I have a life, doing this kind of tedious process took a while but the drawings are done and I can begin cutting out the 2 actual (planned) working panels.
After working on my internal “buggy” in the the body I wasn’t getting the traction that I was hoping for so I’ve done a slight comprise to my construction. I’m reimplementing from my original design my fixed middle pivot point idea so the entire internal structure is mounted on that fixed pivot point with a high torque motor on one side and a hollow bar on the other side. The hollow bar in great for when I’m installing lights and working doors to the outer shell and not getting the cables twisted. Its hard to explain but the pictures show everything. I’m also using super strong plexi-glass on every part when possible to make visibility unobstructed. I did a test drive and it works as I hopped.
I’m waiting for a delivery of a new wind-shield-whipper motor that will spin the bottom weight. My next post will be about working on body shell itself.
He’s the video promised earlier. It’s sturdy, works as I had hoped and yes it all fits tightly but perfectly in the body. I’m very pleased!
The next hurdle was to design a way of controlling the the head movement. And before I get that far into that part of the build I needed to design a sort of “neck” structure that can support and tip the entire head in all directions. This is what I’ve done. Because of the tight enclosure I decided to use a 1/2 ballistics type plexiglass which is extremely durable. And at the same time give better visibility between the sections. A solid piece of wood or metal would have limited how much I could see on the inside. If (when) repairs are needed in the future I can see the internal workings better. The servos I’m using have a 40kg torque which are all metal gears. Anyway, here are a few pics. Video coming shortly…
This is my official first test run of the motors. It actually worked as I hopped. You’ll notice a few things that may look a little strange. I put a panel pie piece underneath the body to get at better idea of how the finish BB-8 will behave. As you can see the forward and back as well as the left and right movements work well. There was a little shakiness during the turns but that’s a simple tweak of the bottom weight, its a little off-center. The spinning movement of the bottom weight creates the left and right movement. Anyway, I’m pleased with results so far. Here’s the video. It isn’t the best quality but viewable:
The past few days I’ve been measuring, cutting, re-measuring and re-cutting to make sure the internal base-platform fits and is not bumping on the internal shell. To my surprise it finally fits and works perfectly. In the pictures below you can see I have an 8.5 kg centre weight that spins on a single axis. This spinning effect makes BB-8’s body turn both right and left. It works while its rolling and while he’s standing still. The weight also keeps the body from bobbing around too much. In case you’re wondering where I found a curved weight that happens to be 8.5 kg, its simple, it was originally the foot of a desk lamp ;-). The white HDPE board on top falls just below the middle point which is perfect for the head control mechanisms for which I’m planning to construct in the coming weeks. The “front” single wheel is a high torqued motor which runs at 37 rpm. I may change that out for a slightly faster one (ie 60 rpm) in the future but will run this one for the time being. Anyway, here are a few pics to give you glimpse of the progress. Ignore the wires…
I’ve now started working on the internal mechanisms and well it’s kind of like building a ship in a bottle where I construct on the inside a platform, mini scaffolding for moulding all the working parts, batteries etc. Its actually a fun challenge and equally important to get everything right the first time ;-)