OK, here's the basics of how to make a non-stop vomiting monster. I'll give as much detail as I can, but a lot of this stuff was trail and error. As time goes on, I'll post more detailed instructions.
First get yourself a monster. What? You don't have a monster, well just build yourself one.
Here's the best way we've found to build a monster. Get some 2x3 or 2x4 lumber. Have someone assume the pose of the creature you would like to make. Then just take a tape measure and start measuring from joint to joint. This is how Ralph and NAM were built. The proportions on them are correct to the human body, so when they are clothed, they look like real people. I had several people ask me who the guy puking in the cafeteria was!

We measured our model from the middle of his ankle to the middle of his knee to the middle of his hip, to his shoulders, etc. to get all of the lengths right. From that point, it's a matter of cutting your angles correctly. This is done by holding the two pieces of wood next to the actor in the pose and marking them when they are in the correct position.

Once you have the shape of the monster built out of wood, grab some 1" chicken wire. They sell it in a couple of different hole diameters. The 1" tends to hold it's shape better. Build the body shape out of the chicken wire, stapling it to the wood skeleton with a staple gun.

That's the basics of building his shape.
Install the puking plumbing.
What we did for the plumbing was use some 3/4 inch PVC and some flexible tubing that fit around it. The tubing is some kind of fairly thin, flexible stuff we found at Home Depot. I think we got it because it was the cheapest they had that would fit around the PVC and the pump. Did I mention the pump yet? You'll need a sump pump. Ours is a boat model, so it runs on 12 volt. We use a car battery charger to run it.

To fit the PVC on the frame, dry fit the mask on then start hacking up the PVC until it fits and the tube ends where the mask's mouth is.

We used a mask I found at Bad Planet (check out the closeouts section. There's some good deals in there.) This one is called "Trench Mouth." Once you get the pipe positioned correctly, stuff the mask with plastic bags (don't use paper - it WILL get wet) then staple the mask down to the shoulder boards. One step you may also wish to take is to install some eyes in the mask. The eyes in Ralph are from the Anatomical Chart Company. If you don't know about the place, you should! The eyes are good from afar, but far from good, but they're cheap and in the dark no one can tell anyway! They're just some cheapo round plastic eyes with pupils painted on them. Anyway, if you want, cut out the eyes on your mask and hot-glue in some plastic ones. I find that they give the mask a lot more believability.

After you've got all that, attach the flexible hose to the PVC and the sump pump. You may want to spray paint the tube black so it's not so visible.
The electronics.
There are several components to the electronics. They are:
  • Sound
  • Pump
  • Relay
  • Digital Timer/Loop

Let's tackle the easy one first!

The Pump:

The pump is actually the easiest part of this guy. All you need is either a sump pump or a fountain pump that is strong enough to lift the water from the barrel to the mouth. We used a boat pump that runs on 12 volt, so that neccessitated the use of a car battery charger to act as a converter for us. A regular "wall wart" transformer doesn't have the amperage to drive the pump. Just take the pump and throw it in the barrel. If you don't want it to break you can place it in the barrel. It's up to you! We ran the leads up the side of the barrel so we wouldn't have to worry about leakage around a hole for the wiring and tube. If you want to get real fancy you can do that. We painted the tube and the wiring black and ran them up the inside of his arm under his trench coat and it worked out fine.

The Sound:

Sound is a little more complicated. We wanted the sound to be on board in one nice, neat package, so we opted for a set of computer speakers. We simply screwed the into the inside of his torso. Nothing fancy. The big advantage with using computer speakers is they are self powered. No need for an amp or anything like that, plus they are fairly cheap. While the quality may not be great, it's just for a puking noise, so big deal.

The sound itself is supplied by a hacked Radio Shack 10 second digital recorder. There are lots of plans around for how to hack these, so I won't go into detail here. If you are interested, email me or check out the Monster List. The sound quality is not great on these, so you may want to opt for something fancier. There are some plans out there using a CMOS digital board that probably gives you a lot better quality than this. Unfortunately, we ran out of time again this year already, so we're going to stick with this for now. The board is hacked in a couple of places. First, I soldered in some leads off the speaker output and ran those to the computer speakers. Second, by trail and error, I found a place that I could jump the button to activate the board and ran that to a relay. So far so good.

The Relay:

The relay is also fairly simple. It's a standard relay that runs on 12 volt power. Nothing fancy. On this particular prop, the only thing the relay controls right now is the triggering of the sound board. However, we used a relay to give us some flexibility to use lighting and whatever else may occur to us.

The Digital Timer/Loop:

The digital timer is the heart of Ralph. It's got two control pots on it. One is the time on and the other is the time off. When the timer is on, it supplies power to the sump pump as well as to the relay that triggers the sound board. Because there is a delay between when the pump starts and the water actually comes out of his mouth, we recorded a few seconds of silence before the puking sound so they were synched.

The timer kit is called an "Adjustable Interval Timer", part number MK111 and is made by a company called Velleman. I found mine at a local electronics store - Marvac. If I remember right, it was about 15 bucks. It's not too tough to put together, it should take about an hour to solder everything together with a decent soldering iron. I have a terrible one that is NOT made for small electronics works so it took me about 2 hours to put together - with lots of swearing!
Final steps.
The final steps are to get some clothes, we used a trench coat and an old pair of jeans, and a barrel. Stick some plastic prop hands on your monster, paint them green or whatever color your mask is, lean him up against the barrel and plug him in! He's a load of fun for about the first 4 or 5 hours. After listening to him puke non-stop for that long though has been known to cause insanity.

That's about it. If I've missed anything here or you want more details just let me know. Good luck!