I bought a couple of these exclusively for hacking. Because the standard shipping unit of these devices is two per-box, you can get two sent to you for the usual 5 bucks shipping... so that's 12.50 a unit!
They came today and I opened one up immediately because it wasn't rolling too well. The quality is decent, in terms of the trackball.... they are acceptable, but not arcade quality. What hurts them is the lack of bearings. The posts that hold the encoder wheels (which are VERY thin btw) just fit into a plastic housing, no bearings at all. The springs inside that push them towards the bal are rather weak as well.
That being said, I discovered the cause of the bad rolling and after I fixed it, the trackball worked amazingly well for the cost! You see many of the plastic posts that held the rollers in place had "flash" inside. I removed it by scratching with my finger and it was good to go.
Inside the housing you'll find that the encoder pcbs are merged into a single pcb that is screwed to the bottom of the trackball housing. All that this pcb handles is the encoding... the pins are clearly marked and have individual wires leading to the game pcb. The chopper wheels are quite small, maybe a step up from those you would find in a ps2 mouse, but they do the job. It should be quite straight-forward to hack this into a mouse and the non-arcade encoder pcb means that the whole thing could probably be usb powered and self-contained!
Not only that, but it would probably be possible to wire the mouse in-line so that you could still play the game. Mind you I don't know why you'd want to... but hey...
The bottom of the trackball has a standard looking trackball base. There isn't one for the top, rather it screws directly to the top of the housing... so keep that in mind. I LIKE the housing though. It's just slighty smaller than the cp for a cocktail cabinet, and that's what I bought it for.
I think these trackballs could be beefed up in quality considerably by putting in stiffer springs and adding bearings to the encoder wheel shafts. These shafts are quite thin, so a smaller type of bearing could be used. Small bearings are generally much cheaper.
Now the trick will be to find a usb-powered ball-mouse in this day and age.
