OK, I lied. The Machine isn't green. But this is still a fun project which only takes a few minutes to make with household materials. It does make smoke rings, and can keep people entertained for hours.
Warning- This does involve fire/hot things, so please be careful, use common sense and good judgement, and supervise children. Remember, I am not responsible for accidents, resulting from stupidity, bad judgement, or otherwise.
Also, I got the general concept from Daniel Beard's The American Boy's Handy Book (Copyright 1882). However, I came up with the specific model.
So, let's begin.
Step 1: Materials
For this instructable, you'll need regular printer paper, wax paper or some other thin membrane, rubber bands, something to supply smoke (incense, cigar, cigarette, matches etc. Please don't start smoking just for this.) and a toilet paper roll or some other kind of solid tube that's open on both ends. I've even seen this done with a trash can (hole on one end, tablecloth with a plastic covering over it on the other, filled with fog from a smoke machine), so feel free to experiment with size.
Step 2: The End Piece
Take the paper, make sure it's wide enough to cover the end and still overlap by about the diameter on all sides. Poke a hole directly in the middle of the paper wide enough to fit your pinky through. Cover the end of the toilet paper roll, pull the paper taught, like a drum head, make sure the hole is in the direct center, and then pull all the sides down and put the rubber band over it, to hold it in place.
Step 3: The Trigger
Do the same thing on the other side, only without the hole. I doubled up a piece of wax paper, because the first time I did it, the wax paper tore. It worked just fine. Make sure it's as tight as a drum head. In fact, I hit it and it made a rhythmic noise, like a drum.
Step 4: Load
Fill it up with smoke. Put the match or incense in the hole (taking care not to let the hot end touch the walls or end) or breath smoke into it. I always find it good to grab the wax paper and pull it down, since the rubber band doesn't do much to hold it down. Let it fill up all the way.
Step 5: Fire!
Tap the wax paper with your finger or palm. If it's a trash can, simply pull it back and bang the membrane against your chest. You can do lots of fun things with the rings. You can launch them one at a time and let them dissipate before launching the next one. You can launch one softly and then try to aim at it and hit it with another one. I heard of a man who made a box out of cards with a hole in one end and then won himself a hotel room by betting he could make 100 smoke rings with one puff of his cigar. He won. (Remember, gambling is illegal in most places. I am not responsible for any trouble you get in.)