ericman - the blog

This is my blog about designing and building my MAME cabinet.  It is the perfect project for me - it combines all my favorite hobbies:  woodworking, computers, video games, hanging out in the garage MacGyvering, designing stuff and frequent trips to Home Depot.

FYI - this blog is upside down.  You'll find newer content at the bottom of the blog.

I started by sketching a few concept drawings to see what I liked and then used Google Sketchup to make a 3D model.  Here is the virtual ericman that I designed and used as a model:

and here is an actual photo of the finished result:

I put the name "ericman" on the model as a placeholder thinking I'd come up with a cooler name later, but after a picture of the model with the ericman marquee hung on the refrigerator for a few months, it kind of stuck.

There are two really cool features that aren't immediately evident in the photo.

First, ericman has a rotating control panel with three sides, each with a different set of controls (a single 4/8-way classic balltop joystick; dual 8-way fighter joysticks; and a trackball and spinner).  This gives the authenticity of an arcade control panel, but also has enough controls to play lots of different games.

Second, ericman has a rotating monitor that is switchable between horizontal or vertical.  This allows you to play portrait games like Frogger, Pacman, Donkey Kong, Centipede and Galaga; as well as landscape games like Robotron, Defender, Asteroids, Marble Madness and Joust.

Fitting both a rotating control panel and a rotating monitor in the same cabinet took some thought and a lot more time to design and build, but were definitely worth the effort.

The Combinations

With the rotating monitor and the rotating control panel, there are lots of combinations:

Vertical, single joystick	Horizontal, single joystick
Vertical, dual joysticks	Horizontal, dual joysticks
Vertical, trackball	Horizontal, trackball
Vertical, spinner	Horizontal, paddle

Touching up the paint and creating some bezel and control panel art are next on my list.  I'm also thinking of replacing the black buttons with a different color.

Rotating Monitor Mechanism

My rotating monitor design was pretty easy to build out of commonly available parts and so far has worked awesomely:

(click image for full size version)

The rotating mechanism is basically a bicycle rim that rides on roller blade wheels attached to a 2x4 frame. The roller blade wheels fit nicely inside the bicycle rim. Since the roller blade wheels ride on ball bearings and the inside of the bicycle rim is perfectly round and polished, the whole thing spins smooth as glass (even with a heavy monitor in it).

The 2x4 frame is 26" square (the inside of my cabinet is 26" wide). Just for the fun of it, I used half lap joints so the 2x4 frame lays flat but that was probably overkill and isn't really necessary. The roller blade wheels are mounted on carriage bolts that go through the 2x4s, with a flat washer on both sides of the wheel and a lock nut on the back.

Before mounting the rim, I traced it twice onto a 2'x4' piece of 3/4" plywood - one tracing of the inside and one tracing of the outside. I then cut out both circles with a jig saw. The two plywood circles are attached to each other, centered, with wood glue and screws. A large rectangle is cut in both circles for the monitor. The smaller plywood circle fits snugly inside the bicycle rim and is held in place by a few screws through the spoke holes into the edge of the plywood.

The whole contraption is mounted inside the cabinet with drywall screws through the outside of the cabinet (countersunk with a little bondo and you can't even see they are there).

Mounting the Monitor
I removed the swivel base and took the plastic case off the back of monitor to exposie the metal chassis, which fits into the rectangle cutout in the plywood circles.  Two L-shaped angle irons fasten the monitor in place.

The whole thing fits together like this:

Despite the look of it, it is actually pretty well balanced since the bulk of the weight of the monitor is the glass CRT.  The plywood is 1 1/2" thick so it also provides a pretty good surface for the monitor case to rest on.

Rotating Monitor Photos

Here are some more detailed photos.  Some parts are more complicated than they should be because of a mistake I had to correct for: I perfectly centered the rectangle in the plywood circle assuming that the centers of the CRT and monitor chassis lined up.  They didn't, which caused the monitor to be off-center in portrait mode. I had to make some last minute quality adjustments to fix that by basically moving the rectangular cutout (enlarged it on one side and filled it in on the other).  This worked, but introduced a new problem: it unbalanced the monitor so when you put it in portrait mode, it would swing back to rest at a crooked position.  Attaching a counterweight to one side to balance it fixed it.

The Frame
Here is a front view of the rotating monitor frame mounted inside the cabinet.  The frame is tilted backwards to match the angle of the cabinet.  The rough cuts on the inside of the frame are the result of more last minute quality adjustments with a jig saw, chisel and exacto knife.

The 2x4 frame is held to the sides of the cabinets with lots of wood glue and drywall screws.  The frame also sits on nailing strips on the bottom and back.  Here is a view from the back of the cabinet with the bicycle rim and plywood installed:

As you can see, the roller blade wheels are attached to the frame with carriage bolts.

The Rotating Parts

 

You can also see the wooden blocks and cabinet latches that lock the monitor in the horizontal position.

The bicycle rim and plywood rotate on the roller blade wheels.  The plywood disk is made of two concentric 3/4" plywood circles glued together and is attached to the bicycle rim with a few screws through the spoke holes:

Because the roller blade wheels fits inside the channel in the rim, the top pair of roller blade wheels have to be installed after the rim and plywood.

Mounting the Monitor

I removed the monitor from it's plastic casing before I mounted it:

This probably wasn't necessary, but it is much cooler than having a beige plastic monitor case showing. I was happy to find that the CRT and electronics were enclosed in a metal case, especially after reading all the warnings about people getting the crap shocked out of them messing around inside a CRT.  The monitor fits inside the large rectangle cut in the plywood disk and it is held in place with a couple of angle irons and screws.  Here is a front view of the top right corner of the monitor in the cabinet that pretty much shows everything:

The white piece on top is a counterweight so that the monitor is balanced in the circle in both directions.  It is a piece of leftover baluster from my deck railing filled with pennies and capped with wooden blocks on the ends so the pennies don't move or spill out when the monitor rotates.

Here is a rear view of the monitor mounted in the frame:

I originally was thinking of devising some way of rotating the monitor from the outside of the cabinet, but it is easy enough to just reach around and spin it with my hand that I think I am going to leave it as is.

Monitor Controls

One problem with a rotating CRT monitor is that if you rotate it when it is on, the colors get messed up because the magnetic field of the earth bends the cathode ray.  Really.   Fortunately, monitors have a degauss button for just this purpose.  Since my monitor has a dedicated degauss button, along with a dozen other buttons for various other adjustments, all I had to do was move them someplace where I could reach them once the bezel was installed.

Sounds easy in concept.  Then I did this:

Doh! I cut all the wires without labeling them so I had no idea which goes to which.  I'm not usually that stupid.  My excuse is that I am color blind and thought they were color coded.  I didn't find out until  I called Lori downstairs to help me match them and she broke the news.

I eventually sorted it out by deduction and soldered on a pair of DB25 connectors.  I ordered a 6' serial extension cable and mounted the monitor control circuit board inside the front of the cabinet where I could easily reach it.

The Bezel

In order to make it presentable, I needed a bezel - something to hide the monitor case and rotating stuff.  I started with the front of the original plastic monitor case.  I cut a slot in the side for the cable to the remote monitor controls.  I spray painted the visible parts of the plastic black.

Here are views of the monitor, in both the horizontal and vertical position:

 

The big white counterweight is necessary to keep the monitor from trying to spin back from the vertical position.

So that the bezel would completely cover everything except the monitor screen, I made it in two layers.  The inner layer is a circle attached to the plastic monitor frame and rotates with monitor; the outer layer is attached to the cabinet and does not rotate.  Both layers are made out of 1/4" hardboard and painted black.  I'm going to add bezel art soon.

Here are pictures of the front and back of the inner bezel.

The inside edge of the bezel is beveled to match the angle on the plastic monitor case.

The pieces of MDF fit on either side of the plastic monitor case.  Note the screws that protrude slightly through the MDF - they fit into holes drilled into the side of the plastic monitor case and hold it surprisingly firmly.

This is what the cabinet looks like with the inner bezel installed:

The outer bezel is a piece of 1/4" hardboard painted black with a rounded square, slightly wider and taller than the width of the monitor screen.  It is sorely in need of some cool arcade artwork:

The outer bezel fits into the monitor opening in the cabinet.  The inside edges of the monitor opening are notched to hold the outer bezel:

There is another notch to hold a piece of 1/8" plexiglass on top of the outer bezel.

OK.  Time for less blogging and more playing.

Rotating Control Panel

Coming soon.