Hardware - Moving parts are moving

A project log for A functional Stargate

It won't transport me, but it will transport something across vast distances

shlonkinshlonkin 04/17/2014 at 13:480 Comments

For the last couple weeks I have been doing battle with the rotating ring. I was expecting it to be a challenge, and it sure is, but it's finally coming together. At this point the internal ring does rotate and the chevrons light up.

The internal ring has to rotate precisely and reliably to put the right symbols in the right place. This means either a stepper or a servo. I chose a stepper because I have a box of salvaged ones waiting to be used and I am more familiar with them. But then I have to figure out how to couple the motor to the ring. The following picture shows my solution.

Yes, those teeth were cut by hand with a utility knife. There are hundreds of teeth. It was a painful and maddening process. There are a couple places where the teeth were just slightly too big and the motor does not mesh well, but tests have shown that it still still rotates without much skipping.

I then needed a way to keep the motor in contact with the ring. The obvious answer was to remake the gate so that the motor could be mounted directly to it. This cutting board was chopped up to make a new back layer with a tab for mounting the motor.

I then wanted to improve the bearing surface against which the rotating ring will press. I tossed the inner spacer and made a new one in a very different way. First I used scissors cut thin strips(3mm and 7.5mm) of 1.2mm polypropylene. I then wrapped them into circle placing the ends together like so.

Then I used my handy homemade foam cutter to melt the ends together, welding them. This produced a very smooth, round ring for the rotating ring to press against.

Oh, and here's the foam cutter if you wanted to see it. I had to go beyond the foam cutting settings to get hot enough for this plastic.

Once I had the pieces all made, I stuck them together and fought with it for a few days to get it moving. Here it is without the front layers attached. Notice that the rotating ring is painted.

To keep the gears meshed nicely, a spring pulls the motor up and one of the mounting screws rides in a slot.

Well, that wraps up this log. I know I mentioned that the lights are working, but I have to go to bed, so you will have to wait a day or two for that update.