Giant Trackball

This is a really big trackball.

I was out for a walk, thinking about input devices for a photo display kiosk that J and I were thinking of making to go with a photo booth, when I spotted this bowling ball in a give-away pile on the sidewalk. What could be more fun than a giant bowling-ball trackball? I took the ball home and made a quick and dirty prototype.

I took apart an old Apple optical mouse, removed the circuit board, and set it into a piece of scrap wood. Its button was a simple switch, so I soldered leads to it and ran them out to a big arcade button. Then I set three transfer bearings into the wood to support the ball.

And, strangely, it just worked. The mouse expects a certain distance between its sensor and the surface it's tracking, but a little tweaking got it to the right depth.

I find it very amusing to use. It's nice to use two hands on an input device, and the inertia is satisfying. We didn't end up developing it any further for a few reasons. First, it's heavy, and the photo booth needs to be portable. Second, since the mouse is upside down the vertical axis is reversed. I'm sure it could be switched in software if I ever find a good use for the thing.

One problem that I was surprised not to have was the bearings falling into the finger holes in the bowling ball. You don't have to turn the ball very far to navigate around a computer screen, so the holes never get far from the top, at least in a short session.

Just recently I saw a post on Make blog that someone had made a similar giant trackball as a dedicated controller for a video game about rolling a ball (called "Katamari Damacy"), which I bet is a lot of fun.