Well, there's not much to show this week, except a messy workbench. But I do have some sketches of "problem solving". There were design issues that I had not yet figured out, so I needed to do some thinking on paper before I spent more efforts in wood.
One of the things I decided to add to the movements was the DiggerBot's mouth opening and closing. I had considered using a string or wire, which would pull on a hinge...but ended up with a simpler idea. The weight of the head will press down to keep the mouth closed. But a dowel in the neck will be pushed upwards by a lever, and gravity will pull the jaw open, as the head goes up.
I had cut out a more organic shape for the larger support arm. Originally the flat side was on the left, like an "L" (see sketch above). But I looked at modern diggers, and flipping the "L" was more like today's style. I had also made a circular end-piece for the lower arm. I now prefer the way I did the upper arm, so I'll have to modify them.
Once I had flipped the "L" shape, I was wondering about some other embellishments. On a modern digger, there are hydraulic arms that push and pull the main arm. Mine will be just for looks, since the support arm will be glued stationary.
Next, I just started sketching some variations on proportions and design. As I was working on some of the bits and pieces, my original prototype model started malfunctioning a bit. The earlier "belt drive" began to slip some, and the cranking motion wasn't working consistently. So I got a little concerned that my final version would have "issues". So I began to consider a gear driven mechanism. It seemed like it would be sturdier, and more dependable. I also spent a little time figuring out the cam-driven lever that would make the head go up and down.
It didn't take long before I was again handicapped by my lack of engineering skills. So I started sketching around with how I'm gonna make these wooden gears. Luckily, YouTube.com has some demos from woodworkers to give me some help.
So this last page has the basic gear-drive in place. I also thought that I should flip the triangular "tank tracks" around, more like early World War I versions. This approach would let me hide a second gear underneath, which would now become the axle used for the crank handle. The early model had a gear-box underneath...this way I can let the DiggerBot rest on a single base of wood.
That's it for this time...hopefully I'll make some progress on the construction next week. (I have to be honest here...this is moving slower than I want, and is not as much "fun" at this stage. I know I'll enjoy painting this guy...but that's a long way off. )