Monthly Archives: October 2009

Gigantic Floating Eyeballs, Part 4

Ruth was the first to suggest that the video screens looked like breasts. I didn’t see it, which is shocking, but I was focused on the end result and always had seen the screens with the image of an eye even when the projector is off. Now it is obvious: round and firm, yet supple with perfectly centered…

Enough of that. But the first thing my neighbor said when he saw them was “Going pornographic this year?” Now the pressure is really on. Even if I can get this thing to work, there is a chance that I will mistakenly crossover from scary to erotic.

One more thing to do: design and build the motion control system. I left this to the last minute since I work with software every day. The plan was to create a pseudo-random set of movements for the two pneumatic cylinders. Now I am out of time.

I was going to scrap the whole motion thing, but then it struck me that I don’t need software at all. Each input to the cylinders has their own speed control. If I just add a simple on/off timer, the cylinders can be set to move in and out at slightly different speeds, thus creating three dimensional motion. It looks like this:

I know… messy. But try to remember we are in panic mode. Time to put this thing up on the roof.

How to Assemble Your Gigantic Floating Eyeball Kit

Step 1: Place base (with lift mechanism) in desired location.

Step 2: Attach center bar (with mounted projector) to base.

Step 3: Attach video screen assembly to the front of bar.

Step 4: Attach mirror assembly to the rear of bar.

Step 5: Enjoy!

Gigantic Floating Eyeballs, Part 3

My first mechanical Halloween project was made out of PVC pipe. PVC is strong and easy to assemble because it can be glued together and there are ready-made elbows available that make angles easy.

There is a drawback to using pipe: It’s round. Inevitably you need to attach something flat to it. A flat surface screwed to a curved surface will wobble and wobbling is bad.

This brings us to the question, “How does one mount two large round surfaces to the end of a pole?” Well… like this:

I wish I could tell you that this was the result of years of experience in mechanical design or, better yet, computer aided design (as a throwback to ’90’s car commercials). The reality is that I started by attaching one piece of aluminum and it wobbled. So I attached another piece and it got stiffer. A dozen pieces later we have a nice rigid frame that can be attached to the end of a pole.

So, we’re done, right? No.

Remember the aforementioned mirror at the other end of the pole? The mirror assembly weighs about 15 lbs. The screens also weigh about 15 lbs. When you put one of each at the end of a 6 foot pole…?

That’s right. The pole twists. Especially if the pole is made out of aluminum. When the mirror moves the screen does not move with it. I’m screwed.

There are many solutions to this problem, most of which I have not the time or money to implement. What I do have is aircraft cable. The structure will either submit or destroy itself. Start the betting now.

Gigantic Floating Eyeballs, Part 2

When the people in Maine told me the acrylic domes had shipped, they left out two important details: They were made in Canada and were being shipped to Maine not from Maine. Yes, the people in Maine outsourced their acrylic forming. This apparently leaves Maine with potatoes and tourism as their only economic engines.

When will I receive them? Soon, they say. Being more specific might somehow break the Ch’i.

I can’t blame all my problems on Canada as so many have tried. It turns out that the minimum distance needed to focus the video projector is about 10 feet. The roof on which this sitting is only 8 feet deep. That would be two feet too long.

Before I describe the solution, please allow me to stress the importance of testing the viability of your ideas, especially things designed on the back of a napkin or, in this case, the back of a bar napkin.

I could have checked the focal length at any time in the last four months, but I assumed that because the projector’s specifications said “5 feet” that meant “5 feet the way you are using it.” You really can’t assume anything… except for an incredulous look  from your wife when you suggest a run down to Staples to drop $1200 on a new projector.

The solution: A Mirror

I’ll be the first to acknowledge that this is not the most elegant solution. The mirror needs to be 32 inches wide. That’s a lot of weight to be torquing around on the end of a six foot pole. I thought of (and had it suggested to me that) changing the optics of the projector would be the most straightforward approach.

The projector, I must say, is a marvel of mechanical design. To take it apart and, more to the point, to put it back together seemed like an insurmountable task. The mirror I can have cut locally for $28 plus a couple hours of my time to mount it. Bada bing!

So, a change in the design will be needed: The mirror-end of the assembly will no longer move. It will pivot, but it will not move horizontally or vertically. That will simplify the lift system to include two pneumatic cylinders rather than three. The eyes will more right, left, and look up. They will not be able to peer down over the edge. Easier, but less impressive.

Coming up: Assembly.