help me make a hovercraft!! (changed name from need a fan...)

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
i need a fan for a special project that uses very little voltage, is light weight, but puts out a lot of air. basically if you turned it on it could give itself lift into the air.

is this possible to find?
 

CTho9305

Elite Member
Jul 26, 2000
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can you go into more detail? how big of a fan do you need? is high current drain at low voltage acceptable? how much air do you need to move? for a small hovercraft, you can use 2 80mm case fans powered by a remote power source...
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
woah what are you talking abour remote power source?

that is exactly what im trying to do...a small hovercraft...


no fan size in particular, but it just needs to be moving plenty of air to support itself in the air as well as a little more weight.

what i need to do is get 6 or 8 fans in a circle all blowing a different direction....well not different, but they are all blowing a direction...

for example, if i used 8 fans, they would be positioned like a stop sign and all would be blowing away from the center. they, however, would not be blowing forward or backward, but instead north, northeast, east, southeast, south, southwest, west, and northwest.

those 8 fans would keep it suspended in the air and i think all of them would cancel out the others force. this is what im aiming for. get the object to stay in the air wherever i put it. i hold it at eye level, turn it on, and hopefully it will stay at eye level. then i want to put a fan in the center on a servo from a RC car or something and that be the directional fan.

does any of this make sense?

what i need:

6 or 8 small powerful and energy efficient fans
1 center fan, also powerful and efficient
material to mount them in a circle that is strong enough but very light
some kind of power source...i have no idea what to use for power
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
i did some research on remote power source, but i couldnt find anything. maybe i misunderstood what you meant. can anyone clarify?
 

Retro2001

Senior member
Jun 20, 2000
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My only guess for a remote power source would be high intensity light and photocells, or something of that nature. That or something along the lines of a Tessla Coil.

Peace,
will
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
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how do you make a tesla coil? how far would it shoot to make the power source remote and keep the hovercraft in the air?
 

Retro2001

Senior member
Jun 20, 2000
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Sadly, Electro-Physics is out of my league. As far as the distance, you should be able to calculate that based on the resistance of the air and the voltage differential between your distant coil and your craft. As far as I know, the type of device that I am talking about could be created by connecting any source of a huge voltage differential (probably in the 10's of k's range of volts) to a conducting rod. Then ground your device and place them near each other. Boom, instant weighless voltage source. Granted I'm probably wrong about everything I just said, its late, and I'm working from a dim memory of an intro to physics course. Good Luck.

Peace,
will
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
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how would i ground a floating craft? hang a bunch of thick wire from it? that would defeat the purpose of being almost weightless so it could fly...

 

Retro2001

Senior member
Jun 20, 2000
767
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To ground something you wouldn't nessisarly need a huge wire, (a smallish one would probably do) connecting the craft to an infinate sink (ie. a pipe running into the earth). I guess you could work a system with some capacitors so that you could make excursions away from the coil and the ground and then come back home to recharge. There may well be better ways, like using photocells and big lightbulbs. Actually you might be better off ditching electricity altogether. Gasoline has a much much higher power/weight ratio than any battery. You could get a bunch of little model engines (like .049's) and make a ring of fans powered by them running of a central fuel tank.

Peace,
will
 

blahblah99

Platinum Member
Oct 10, 2000
2,689
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I havn't posted as much in this forum lately.. so here's my take :)

If your going to use low voltage, then you will be pushing high currents through that fan. A typical 80mm fan (the kind you see everywhere on computers) uses like 4 or 5 watts of power, so solar cells and batteries are out of the question. I'd do what retro said and run it off a gasoline engine, with a rotating disc to keep the craft balanced, kinda like how a gyroscope balances itself when its in rotation.

You can also use induction to power the hovercraft, but they craft would be confined to the area covered by the inductors. Works the same way as induction-charging shavers and stoves.
 

CTho9305

Elite Member
Jul 26, 2000
9,214
1
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rolleye.gif
by "remote power source" I meant a power source that isn't actually on the hovercraft - like an ATX power supply or maybe batteries that you hold in your hand and follow the hovercraft around with that is connected by wires. its weight isn't carried by the hovercraft. :D

I'm not sure about your stopsign layout.... just have all the fans attached to a piece of cardboard blowing downwards and make a skirt around it from duct tape of plastic bags or something. 2 fans will hold up a 6"x12" cardboard hovercraft and can hold a little weight (probably enough to hold a few 9V batteries, but I didn't test this)
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
retro i really like your gas engine idea. what kind of engine is that? where can i get it? and how would i attach fans to them?

can any of you guys draw schematics in paint or something so i can get a visualization....you guys are really hitting this project on the nose on exactly how i need to do it.

thanks so far...
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
blahblah i dont know what you mean by all of that. sorry im not excellent with electronics yet, but i really want to know how to make this work.
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
i have a remote control car that uses gas power. could i use the engine on it? i dont understand how i would keep the craft suspended in the air though...could it spin a few fans fast enough to keep it airborn?
 

CTho9305

Elite Member
Jul 26, 2000
9,214
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Originally posted by: MrDudeMan
i have a remote control car that uses gas power. could i use the engine on it? i dont understand how i would keep the craft suspended in the air though...could it spin a few fans fast enough to keep it airborn?

yup. you could use bigger fans that way too if you can find blades.
 

Retro2001

Senior member
Jun 20, 2000
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Your going to also want to watch your rotational energy. You probably don't want this thing spinning like a top so be sure your canceling out the torque from your fans

Peace,
will
 

bizmark

Banned
Feb 4, 2002
2,311
0
0
how high do you want this thing to fly? A few inches, a few feet, 6 feet? I don't know how well bottom-mounted fans would work on something that floats more than a few inches off the ground. You'll have to have some mighty powerful fans for it to "stay in the air wherever you put it". I'm no engineer, but there's gotta be stability issues involved. If it tilts slightly to the side, it'll fall to the ground as the vertical force becomes horizontal force. I've never seen a hovercraft that hovers very high off the ground, and helicoptors have their rotors on top. If you're trying to build something useful (like to carry drinks or something), you may just want to try a model helicoptor kit, or a mini-blimp kit.

Come to think of it, hovercrafts don't hover in the air like a helicoptor at all. The skirt keeps the air around the bottom of the hovercraft. The skirt basically forms an inflated cushion without a bottom. Think if you had one of those inflatable chairs. Normally, when you sit on it, what's keeping you up? The air pressure inside the chambers. So imagine sitting on one of those but cutting a big hole in the side. Would you still be able to sit on it? You would, but only if you could provide enough air into the cushion to maintain air pressure despite the air constantly escaping through the hole.

Do you see what I'm getting at? A hovercraft doesn't work by providing lift from rotating its blades (which, in helicoptors, are essentially rotating airfoils). A hovercraft works by forcing enough air into a mostly-enclosed space that the air pressure inside is high enough to lift up the hovercraft. The fact that it uses giant propellers/fans to do this is mostly a coincidence. It could do it just as well with compressed air or some other source.

The problem with a gasoline engine is that it can't stay hovering indefinitely. It's gotta be refueled, and a bigger tank means longer flying time but more power needed to keep it flying. Plus it lets out nasty pollution, so you probably wouldn't want to use it indoors for your own health ;)
 

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
alright well i guess i could just make it more like a helicopter...

what i was aiming at though was something like a harrier jet

it can go straight up, and then fly around from there...


maybe this changes your ideas...anyone have a different take on this now?
 

glugglug

Diamond Member
Jun 9, 2002
5,340
1
81
Normal air pressure is 15 lbs per square inch -- the fan really does not need to move much air to lift itself off the ground. Almost any case fan or CPU fan would I bet. The problem is balance. You can have a fan with a power supply sitting above it, and it will lift up, but almost immediately tip to one side and no longer be floating. A trick you can do is to stick a large surface around the fan that the air has to flow under to escape, thereby preventing it from tipping to any one side. I would suggest a light foam board attached to the sides of the fan housing.
 

pm

Elite Member Mobile Devices
Jan 25, 2000
7,419
22
81
You could build a Biefeld-Brown Effect lifter a lot easier. Not exactly a harrier jet, but "flying saucers" are pretty interesting too. And a lot easier and cheaper to build. :)

A lifter is essentially a vehicle - in this case a model made out of balsa wood and aluminum foil - that levitates by (so the current thinking goes) an ionic air reaction caused by extremely high voltages and the corona discharge of the craft from a capactively coupled external power source. Follow the link if you want more information. Here's DIY instructions.

A little time with balsa wood and aluminum foil and a broken TV or computer monitor and you can make your own levitating flying saucer.

Edit: fixed link. Thanks for pointing it out.
 

bizmark

Banned
Feb 4, 2002
2,311
0
0
pm, your first link has a problem... two http://'s and a space. Very cool stuff though :)

edit: :Q:Q:Q that is amazing stuff. My jaw is dropped. This is DEFINITELY a project my roommate and I will take on, as we have several old broken monitors lying around.
 

Armitage

Banned
Feb 23, 2001
8,086
0
0
I don't think you want to do a helicopter or harrier type thing. The stability & control issues would hill you.
But an RC hovercraft with a gas model airplane engine would be fun!

A hovercraft is basically self stabilizing. If it starts to tilt, that raises the skirt on the high side, which lets out more air on that side, which reduces pressure and makes the high side drop. You would really only need 2 servos ... throttle, and one to operate a rudder that stick out into a stream of air diverted from the main fan (or a seperate propulsion fan).
 

GoodRevrnd

Diamond Member
Dec 27, 2001
6,801
581
126
Hovercrafts eh? That might be just the ticket to use my 120mm I accidentally ordered! :D