Saturday, September 25, 2010

AUTOMATA - "DiggerBot" Pt.5

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, 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. )

Saturday, September 18, 2010

"Yosemite and Lake Tahoe" Pt.2

I'm taking a break from working on my "Digger Bot" project this week. I am enjoying a visit from my Mother-in-Law, and will be spending time with family. So I thought I'd share a few more images from my recent trip out to Lake Tahoe and Yosemite National Park. Some of them are composite panaramas that combine several shots. Hope you can make a trip out just don't do it justice. The first few are of Yosemite.

Jen was on this trail to show us the tents where she and Brad lived when they worked summers at Yosemite. Moments after this, we met "Ranger Charlie" who let us know that we'd be fined $1,500 if we continued up that trail, since it was closed due to rock fall in the camp. It would have been nice if there had been any signs telling us that first!

Leaving Yosmite...

Here's an industrious young fellow creating a pile of rocks at Tanaya Lake. These are similar to markers called "cairns" in the world of climbers and hikers...they indicate direction of a trail in a treeless area (thanks to Brad for that little bit of info).

This is a composite of Mono Lake in California...very high in alkaline and mineral salts.

A dried up hot spring source, in Sierra Nevada.
And this little trickle is the new source.

The valley view as we got closer to Lake Tahoe...

A very windy and cold day at Lake Tahoe...a bit too much to fully enjoy the song Brad played for Jen and I on the mandolin. But we both appreciated his efforts!

Here's my one and only trip to a casino. This little horse race game is a favorite of Jen and Brad's. Brad won $6 that night!! I had way more fun later that evening at an "all you can eat" sushi restaurant.

And speaking of's Las Vegas!! (from the airport anyway...)
That's it for this trip!

Saturday, September 11, 2010

AUTOMATA - "DiggerBot" Pt.4

I'm making some progress on the final "DiggerBot" parts. Here is how I made the bucket and arms.

I used the flat bucket shape from the prototype model as a template, then traced it onto a piece of 2"x4". I added a bit of length to the front of the bucket for the "teeth". Then cut it out with my band saw, and sanded it smooth on a belt sander.

Next I cut out the sides of the bucket from some bass wood, then glued them onto the bucket.

I had to modify the bucket a bit to allow for the full range of motion when connected to the arms. I had not accounted for this problem with the flat bucket model. So I cut out a section, then glued on a little extension, drilled it and sanded to the circular shape.

Here's how I made the "couplings" that go on the dowels for the arms. You may note that nothing is exactly squared-up and precise. I don't think I can do that if I tried...I definitely show the "hand of the artist" on these projects. Adding the paint job at the end hides a lot of those imperfections.

Here is how this new bucket will move. The lower arm is probably going to look different than what is shown here, but you get the basic idea.

Sunday, September 5, 2010

AUTOMATA - "DiggerBot" Pt.3

Welcome back to the "DiggerBot" in process. It's nice to have a long Labor Day weekend to work on this a bit more. Above is the two-armed prototype that I made to help me figure out some more of the mechanical components. I will change this quite a bit later, design-wise...but it was very helpful to build a rough version.

I'd like to take a brief moment to give some credit to my Mom's "sketchin' buddy", APRIL, for sending me some ideas to improve the engineering of the arm movements. It's been fun collaborating with someone who has a better brain than mine for these things. Thanks, April!

Below are the bits that make up the "bike pedal" action for the top axle. The Bot-arms will attach to this part. I like to use dowel pegs and a bit of Elmer's wood glue, instead of nails and screws, to put all of this together. The tight fitting pegs will hold things in place until I'm sure things work.

I temporarily attached the arm bits, to see if the axle rotation produces the effect I want.

Next, I made the gear box, so I can figure out the drive mechanism that will be underneath. I had to add a little block of wood to the base of the axle housing, because I had cut off too much earlier. These things happen. Again...this is quick and dirty, just for figuring out if this will really function.

Now you'll see the series of "failures" before I found a workable solution. My first idea was to use one of my daughter's "ponytail holders" to attach to the drive shaft underneath. Too stretchy...not enough tension. Next I tried a bit of twine, since it was rougher. But it slipped on the wood axles. So I ground in some grooves with my dremmel tool. Still didn't work. Then I made a little "cuff" of sticky-backed foam rubber. That seemed to help. I then made a larger "gear" for the lower drive shaft, to give more tension...the string still slipped on that, too. Finally I added some foam to the worked! Sort of...the string would slide off the rubber part and snag up on the sides of the axles.

Finally, I thought of making a true "belt drive" for this. I had some "fake leather" material, cut a long strip the right length...super-glued the ends together...and added a little duct tape for good measure. Worked just right!!

I made a duplicate arm for the opposite side of the Prototype TestBot, and...VOILA!
Things will slow down a bit from here on, because I will be designing more complex shapes for the final "DiggerBot". I'm also thinking about adding some other moving parts (like the Bot's mouth opening and closing). Stay tuned!!