What are lifters and how do they work? Good question. I'll show you what I know and how I built one, but for now check out this great article about lifters at Wired. You can also check out MythBusters episode 68 where they built their own, identical to the one I built.
Lifters work on the basis of ion thrust. If you've owned or seen Sharper Image's Ionic Breeze air purifier this is the exact same principal. By applying a high voltage to a thin wire, electrons will fly off the wire and charge the surrounding air molecules. The molecules then rush down toward a negative electrode producing enough air flow to lift the craft off the ground. Lifters were once claimed to be antigravity or "electrogravity" devices and can still be found as "antigravity fliers".
A friend and I built two triangle shaped lifters about one year ago but during the move into a new house they got stepped on and were no more. We did have some success and learned some do's and don'ts which I'll share with you.
Building a lifter is easy, below is a list of materials needed to build your own.
- 1/8" Balsa Wood Dowels
- Super Glue
- Lightweight tape
- 34 AWG or thinner wire
- Lightweight foil
- 1 old CRT color monitor or TV that has a working screen
- High wattage resistor (2W+, around 250 K Ohms) (optional)
- A few test cables with alligator clips (optional but very useful)
If you can't find balsa dowels (I couldn't), just buy square balsa and sand the edges to be round. The wire can be found as magnet wire at your local electronic component parts store. A few alligator clips can make the workspace a bit safer and a high wattage resistor, at least 2W, about 250 K Ohms will help to extend the life of your monitor. I recommend a color monitor as it will put out higher voltages then a monochrome monitor or B&W TV. You can often find old color monitors at thrift stores or even by people's dumpsters on trash day. Try to find one without automatic power saving technology as they may not work.
I started by building a simple triangle shaped lifter. It's the easiest to build and its triangle shape makes it strong. However, experiments have shown it to be the least efficient shape. A shape where the inside corners have a wider angle, such as an octagon, provide a higher thrust.
First cut 3 pieces of balsa about 10 inches in length. Then 3 more pieces about 4 inches in length. Next, glue each side to the middle of the 4 inch posts to form a triangle. After the glue dries, cut a strip of aluminum foil about 3 inches wide and long enough to wrap around the entire craft. Now wrap the foil over the frame and tape the ends together. The foil should look like an aircraft wing and no sharp edges should be visible. Now cut a few feet of your thin wire and remove the insulation from each end. A fine grit sandpaper works great or a sharp knife if you carefully scrape it off. Tape one end of the wire to your foil.
Take your wire and if it has insulation on it you need to remove as much of it as possible for the section that will be over the aluminum foil. The distance above the foil to place the wire will depend on your power source. Start with about 1.25 inches and adjust it from there. A good trick is to use plastic straws around the posts so you can slide the wire up and down. Glue one end of the wire to a post and wrap it around a few times and run it over to the next post. Keep the wire tight so it won't move during flight but be careful not to break your balsa supports. Go all the way around and now leave yourself several feet of wire so your lifter can get off the ground.
Next comes the dangerous part. You will be dealing with 30,000+ volts of electricity. Be very careful, and if you don't know what your doing, don't do it. Take your color monitor or TV and remove the cover. There will be a suction cup on the back of the tube; this is your HV output. Pull back the suction cup and attach an alligator clip to the connector. Then carefully put the suction cup back. There should be some springs or wires also wrapped around the tube. These are the ground straps, connect an alligator clip to one of those.
Now find a flat surface that won't build a static charge. Vinyl or carpet floors are bad as they build a static charge very easily. To keep your lifter from flying across the room and injuring someone or something, cut 3 pieces of dental floss and anchor the lifter down. Attach ground wire from your lifter to your monitor ground alligator clip. If you have a resistor, clip one end to your HV alligator clip and tape your HV wire to the other end. Make sure that during flight your ground wire and HV wires will not touch or come close to each other.
With everything complete stand back and plug in your monitor. Most monitors will be off by default requiring you to flip or press the switch. Carefully do so, and you should hear a loud hissing sound. If you get a lot of arching, making your lifter look like an electrical storm, turn off the monitor immediately. The arching will quickly damage your monitor and will cause the lifter to perform poorly or not at all. We noticed that the very first time a lifter was powered up it would arch a few times then settle down. This was probably caused by the foil oxidizing. If heavy arching occurs raise your HV wire a mm or two where the arching occurred. If the hissing sound is weak and the lifter shows no signs of lifting off the ground the HV wire will need to be lowered a mm or two. After turning off or unplugging your monitor it will still probably hold a high voltage charge for several hours. Before touching your lifter use a plastic or wood handled screw driver and short the HV and ground together.
It may take several tries and adjustments but once it is perfect invite all your friends over to marvel at your wizardry. Running the lifter will cause ozone to be produced and you should easily be able to smell it. While small amounts of ozone are found to be beneficial, large amounts can cause problems especially with those who have respiratory problems such as asthma. Proper ventilation might be required for long periods of running the lifter.