I decided to add a trackball, but the control panel is too small and shallow for a standard one.
I looked at DIY trackball setups, but couldn't find anything I liked.
This one looks like it functions great, but it uses a custom PCB and I couldn't find the STL files anywhere.
There is another video where he plays some classics, but no fast spin Golden Tee type stuff.
So the plan is to roll my own.
From the parts bin:
A pair of tiny industrial encoders with 6mm ID. Got a deal on them over a decade ago. Wanted to use them for rotating joysticks, but they turned out to be too much of a PITA to mount.
6mm rod
Opti-Wiz or KADE interface
Had to buy:
$7 cheap 6mm ID bearings
$10 red bumper pool ball (2 1/8")
$18 Molex Pico Blade connector kit for the tiny encoders.
Already approaching the cost of a used 2 1/4" trackball.
Skateboard bearings with 8mm rod and plastic encoder wheels would make more sense.....but anyways.....
Apparently there is a reason trackball rollers aren't straight shafts. Arranging things so the ball doesn't contact the bearings in the corner turned out to be a balancing act.
The ball has to sit low enough that the circumference where it contacts the rollers is large enough to clear the bearing in the corner. But the lower it sits the more of a PITA it will be to mount it in the CP while still having a proper amount protruding on top.
Prototyping in clear ABS because I'm not using it for much else. The final version will be black.
This is not even a preliminary design. It is just to get clearances and shaft lengths.
I wasn't sure how I would keep the shafts in place, but it turned out that they are oversized and don't fit in the bearings unless sanded.
So they basically ended up being press-fit and the bearing cannot travel any further inbound on them.
It will end up being about 3.5"x3.5"
Clearances are
tight, but there is clearance.
I've got no CAD skills, so I'm hacking this together in TinkerCAD.
The brown and blue blocks on the right represent the thickness of the control panel top and plexi.
I don't want to replace the CP artwork. I was hoping to get away with just drilling a 2.5" hole with a hole saw with the CP in place, but I see no way to pull this off without routing out an area on the backside.
No idea what the top part or mounting situation will look yet. It needs to be serviceable, but will probably end up being held in place with wood screws. I guess I might tolerate four recessed screws under the plexi, but definitely not ok with a big mounting plate on top.
I am still looking at other options, but this is the direction I'm heading for now.
Solutions that use an optical mouse talk about having to reverse the X axis in Windows, but MAME has the option to reverse an axis so it really isn't an issue unless you want to play trackball game outside of MAME or use the trackball as a mouse in Windows.
Experimenting with the mouse on my desktop, the ball has to be right up against the sensor for it to work reasonably well.