The frame materials arrived on Wednesday. We got 4 small delrin plates, 2.5"x2.5", and 20 or so 0.25"x0.25"x2.0" posts. I had ordered extra so that we would be able to screw up a few times without totally stalling the project.

We measured the posts at about 2.010 each, and very consistent, so those weren't a problem. The flat plates were off by about 0.040 on one axis, and 0.20 on the other, and we're not as consistent. Fortunately, we could pick out two (I ordered 4 just in case we screwed one or two up) that matched nicely, and used those.

The plan was to build a frame using 4 posts, where the servo motors would be connected to two posts on each side. The rough layout is a bit like this.

We drilled a 0.375" deep hole into both ends of the posts, as close to center as possible. We also drilled two holes in the side of the posts, one at 0.5" from the end, and the other at 0.895". The distances were based on measuring the spacing between the mounting holes on the servos. Fortunately, when using 4-40 screws, there is lots of slop in the mounting holes, so we didn't need to be too accurate.

The holes we drilled were 0.089" diameter, and we tapped each using a 4-40 tap. It took a while to tap the 16 holes, but Alex learned how to do the job pretty well, and that cut the time down a lot, since we were both able to tap at the same time. And there no broken taps, too. Not bad.

Finally, we drilled loose fit holes for the screws in the top and bottom plates, and assembled the whole thing.

I think it turned out very good. Those are the modified servo motors in the picture too. They are each mounted with the shaft nearest to one end, which means that they are opposite of each other, so the control pulses will need to be correspondingly reversed.

We were lucky too, all of the parts we made turned out perfect, so now we have enough materials to build a second robot later.

The next task is to wire the robot, and mount the Arduino.

Return to the robot project main page.