Mini Hovercraft DIY: Build an 8''x3'' Craft with 9-Volt Batteries

[alex caps]

I picked up 2 4-AA cell holders today, some batteries, a soddering iron (with sodder), some hook up wire, a 5a switch, and I am waiting for the motor and propeller to come in the mail. I have a piece of wood about 8x4'' or so but might go out and get one a little larger. I am planning on just having a switch to turn it on, having it merely hover above the ground, and if all goes well.. I will start adding some stuff to propel it forward. If this all goes well I am probably going to eventually do another project much like the one swither is doing, so that I can control direction and speed and such. Good luck with yours and I will keep you posted on how mine is going..

 

[swither]

i'll probably build mine next month, really don't have the time at the moment. But i'll post some pictures, maybe even a video when I'm done!

 

[pack_rat2]

Are there any direct problems with this design?

I think the skirt should drop down much lower, so the air being injected can more easily travel around to maintain the internal pressure.

 

[swither]

I think the skirt should drop down much lower, so the air being injected can more easily travel around to maintain the internal pressure.

how much do you recommend it should drop down?

 

[ceptimus]

Don't extend it too much , or the hovercraft won't be stable. It will wobble about on a deep flexible skirt, and maybe even fall over. For operation over a smooth surface, the cushion only has to be about two inches deep, and you don't need a flexible skirt at all.

Try to keep the heavy items as low as you reasonably can. The thrust motor is the main problem, as it has to be mounted high enough to allow propeller clearance.

If you're going to operate over rougher terrain, it's a compromise between stability and ground clearance. The flexible skirt needs to be tall enough to ride over the largest bumps you're likely to hit, and the fan/propeller should be high enough to prevent any chance of it grounding.

 

[pack_rat2]

Don't extend it too much , or the hovercraft won't be stable. It will wobble about on a deep flexible skirt...

Not so. Remember, it's the air pressure inside that keeps it up. You can use flabby rubber from a balloon, without any support, and that would work--it would collapse when the motor shut down. I don't recommend that approach, though. I think a skirt that's 2-3 inches would be good. By the way, many people have built hovercraft, both small models and ones that can carry a person. I read an article in an old "Popular Mechanics" that had a project for making a one-person hovercraft. Why don't you search the Web and see what others have done, and have found successful?

 

[alex caps]

a question on wiring

The 5a switch has 3 spots to attach the wire. The cell holder has 2 extruding wires and the motor has spots for 2 wires. I used a soldering iron and soldered the red wire from the cell holder directly to the motor. I then soldered the black wire from the cell holder to the 5a switch. Then I took a separate piece of hook up wire and touched it to one of the empty spots on the 5a switch, and the other end to the other spot in the motor.. nothing happend. When I took one end of the hook up wire to the motor and touch the other directly to the black cable from the cell holder, the motor spins. I have tried connecting it to the 5a switch while it was switched in either direction and neither seemed to work. Any ideas on how to get this to work?

 

[alex caps]

never mind i got it

 

[alex caps]

Does anyone know how I could figure out rpm?

 

[Ivan Seeking]

In case you all missed this one.

http://www.hovercraft.com/UH-18SPW_Hoverwing.wmv

 

[alex caps]

some help needed for lift

Ok, I got a box about 6''x5'' and the motor is 400v, the propellor has a diameted of 5'' and it is wired to a 5a switch and a 4 AA-cell holder with 4 AA batteries in there. All the wiring is correct and works. The box has a base, then walls going up it, but no bottom. So I cut a hole in the base in the middle and put the motor in there, it is farely secure. I put the battery pack on top of the base and the 5a switch up there and rest the whole thing on the table, so the propellor is face down and the walls of the box act as a skirt, or atleast hold the whole thing up so the propellor doesn't hit the table. When I hit the 5a switch, the propellor spins but it acts alost as a vacume, pulling the whole thing down to the table and basically suctioning itself there. I remember some one saying a skirt was not needed, and it seemed heavy, so I cut off the walls of the box and was left with just the base of the box with everything still attached. Of course now I run into the problem of the propellor hitting the table, so I put 4 little pieces of cut off cardboard on the corners to hold it up. Now when I turn it on, it spins but will not lift. Does anyone have any ideas? I can't figure out how to lose weight due to the 4-AA cell holder being so heavy. I tried one where I held the 5a switch and batteries and then hit the switch but all it did was spin, it did not lift. Please help me and let me know if you want any pics.

 

[ceptimus]

If the system is working as a vacuum, swap the wires over on the motor (or where they go to the batteries if that's easier) You need to get the current flowing in the other direction through the motor, so it spins the opposite way.

You may have to reverse the propeller on the motor shaft too. Reversing the propeller alone won't make it blow the other way, but if the propeller is on back-to-front, it won't be as efficient. The concave (hollow) side of the blades should face into the hovercraft air cushion, so the convex side will face upwards. With the Gunther propeller, you'll find it's easy to reverse the white plastic part on the same (black) hub.

It ought to have enough lift to raise the whole thing, including the batteries, providing the propeller is spinning the right way round and the propeller is facing the right way.

 

[Quantum_Prodegy]

Just a thought, if you made the hovercraft circular, it would be more stable, especially if you are only using one source of power and propeller. I built a hovercraft in school with some friends, a bit bigger, it was circular, 4 ft in diameter, and could carry a person. It was powered by 2 leaf blowers (lol) and used the school's power through a recepticle and an extension cord...it was sweet man.

 

[Lostpoet]

Low voltage HC

I built a hovercraft with only 3v of power and it works just fine! Whys everyone think you need a power house to run one? I constructed mine out of paper thin fiber glass. It's mainly in the design and getting the most of your power source and motor.

 

[Ararat77]

I'm building a miniature hovercraft for my high school Science Fair Project. I'm just getting started and I'm not quite sure where to begin. I want to test how high it can go depending on the temperature it is in. Do you think you could give me a step-by-step for how to build one and what materials I will need. I'm thinking of using a micrometer to measure it's height. Will that work?

 

[Danger]

I want to test how high it can go depending on the temperature it is in.

The temperature is irrelevant to a hovercraft, unless it's cold enough for air to freeze. Unlike an aeroplane, which is sensitive to air density, a hovercraft traps the air cushion under itself. Low-density (warm) air might take a wee bit longer to inflate the cushion, but after that nothing will change. How high it will go is just slightly higher than the cushion depth (unless, as ceptimus pointed out, you make it so tall that it falls over).

 

[Ararat77]

Okay, well, I've changed my project so that it doesn't involve temperature. I've created a hovercraft with a ground-hugging skirt that's 4 feet by 4 feet. I now need a thrust fan but don't know where to get one. Do you have any suggestions for cheap new or used hovercraft fans? I'm hoping to find something $50 or less. I need it as soon as possible. I don't need a very powerful one, just one that will take me at 5 or 10 mph.

 

[Danger]

Somewhere along the line, I've lost track of what voltage you're running. If you have 12 available, I'd think about getting a heater fan motor from a junked car and replacing the impeller with the blades from a 12-14" household cooling fan. It won't have a lot of thrust, but probably enough for a few mph.

 

[kleinjahr]

If all you want is a simple demonstration of the air lift effect, tis easy. A circular flat plate of iron about 1/4 to 3/8 thick, 1/4" tapped hole with nipple, valve and quick disconnect in the center. Connect to an air hose and open the valve. Won't lift very high, but it does lift.

Ever hear of the Avrocar? Check out some of the old films on it and you'll see the problems with stability.

 

[midnite13]

Sorry to dig up old threads, but I'm curious to see how these projects turned out...

 

[Danger]

Don't be sorry. I lost track of this sucker myself, and I'm still interested in what's going on.

 

[midnite13]

For those who find R/C hovercrafts interesting, I recommend you check out this video entitled "R/C Boat+Plane+Hovercraft" ...

http://video.google.com/videoplay?docid=9219568793902200741&q=hovercraft

I must say, the seemingly simplicity of the design baffles the mind. Can somebody please explain the logistics behind its design?

 

[Danger]

They look like neat toys, for sure, but they're definitely not hovercraft. I surmise that they're hydroplanes with built-in ground effect capability. From the way that they fly, I'm also pretty sure that they have close to 1:1 thrust to weight ratio. The title should give you a hint; they're made out of foam plastic. A hovercraft can't do any of the things shown in that video other than straight line travel. You certainly can't make one manoeuvre like that or become airborne.

 

[Imop45]

Ground effect

THats little R/C is cool! You said it's not a hovercraft, but ground effect. What is ground effect, and can you make a machine that uses ground effect for personal use instead of a Hovercraft? And be cann, I mean is it possible for someone with little experience to make it, like a HC?

 

[russ_watters]

http://www.se-technology.com/wig/index.php

Ground-effect is an aerodynamic phenomena where, essentially, the wing squeezes air between itself and the ground, allowing the craft to lift a small distance off the ground at relatively low speed (yeah, it is actually more complicated than that). There has been talk of making massive craft for transoceanic transport. They'd be faster than boats, but more efficient than planes. Trouble is, at 50 feet altitude, a big wave (not to mention a mast) could still knock one down.

I first heard about them in a Popular Mechanics article a decade ago - it was a one-seater.

 

[FredGarvin]

http://www.se-technology.com/wig/html/main.php?open=showpic&code=&pic=21

http://www.se-technology.com/wig/html/main.php?open=showpic&code=&pic=14

 

[arthuritus]

Hummm, I'm doing a hovercraft for my science fair project too. The idea is to make a self-contained hovercraft capable of lifting a person. I'm going to be using an electric leaf blower, electric because they are MUCH cheaper than petrol ones of the same power to weight ratio. The only thing is, I'm not sure if the leaf blower is going to be able to lift it up. Sure, it's powerful, but it has a small fan and goes for airspeed rather than volume. Is this going to affect my pressure in the skirt? Is my goal realistic? I'm also trying to figure out what deck area would be the most efficient BEFORE I start hacking into my precious plywood. I understand how to work out how much pressure is needed to lift a given weight, but I have no idea how to figure out what the pressure is.

 

[arthuritus]

I want to know how changing the area of the base is going to affect how much weight it can lift.Would I be right in saying that to calculate velocity pressure in N/m squared you use the formula VP=0.6xV^2? In my case, VP = 0.6x77.7^2 = 3622.37 N/m^2 Is this the right formula to be using for what I'm after?

 

[Danger]

I don't know from formulae, but I have a personal relationship with hovercraft. How the curtain area affects the lift potential is direct; the more area you have, the more lift. Whatever pressure your source can obtain is evenly spread over the entire area. If your leaf blower can put out, say... 20 psi, then it will lift 20 x [area] lbs., but the larger the area is, the longer it will take to pressurize it. Your source must be able to keep up to the curtain leakage to maintain that pressure.

Great link, Fred.

 

[arthuritus]

Yep, that seems to figure. I was amazed; I made a rough prototype today with a .75m^2 circlular base, and it could comfortably lift my 80 kg brother. I think my leafblower was churning out about .3629 N/cm^2, which means with a 1m^2 base it should be able to lift about 360 kg?, provided there's no unwanted leakage etc. I though that was ridiculous, maybe it was meant to be 35 kg? But it could lift 80 kg plus it's own weight, so... It shall be interesting to see how much it can lift with a decent skirt and stuff. Amazing. Bring on the big beasties : )

 

[arthuritus]

Also, you know how that if you make the base bigger it'll be able to lift more, but won't float as high off the ground? Is the amount of floatiness measured from the bottom of the skirt or is it the total air cushion? Is there any way of calculating how much your float hight is going to change with a given base area increase/discrease?

 

[Danger]

I'm not quite sure where that came from. The lift height shouldn't be in any way reliant upon the cushion area, unless the attendant weight gain from the extra material overcomes the lift pressure. Adding weight, such as passengers, will initially raise the pressure, but the excess will almost immediate bleed out. That is dependent upon the skirt design, though. Something rigid, such as a single long strip of rubber, will hold more pressure than the preferred multiple 'mini-skirt' type. Regardless, the pressure will always equalize automatically. Too much will leak out; not enough just won't lift. The lift height is typically measured from the lowest 'solid' part of the machine, since the skirt is always in contact with the ground. That solid part can be the bottom of the frame, or the upper part of the skirt that isn't flexible enough to move easily. The measurement is essentially an indicator of how large an object the craft can pass over without hanging up, like the ground clearance of a car.

 

[kach22i]

Trouble is, at 50 feet altitude, a big wave (not to mention a mast) could still knock one down.

WIG's ......like airplanes, never fly higher than you are willing to fall.

My hovercraft flies only six inches off the ground/water, plow-in or grounding out can still get nasty.

Overall hovercraft are the safest form of transportation ever invented (WIG's excluded).

 

[arthuritus]

Hmm, I've just figured out that all my calculations were wrong. Perhaps I should be working with m^3 instead of m/s?

 

[Danger]

I'm not sure which calculations you're referring to. M^2 is how you figure out your lifting capacity, because it's area x pressure. To know the volume of air that needs to be initially supplied, then M^3 is appropriate. For figuring out curtain leakage, you use the perimeter, so that's just M. Your sustained airflow is based upon the leakage.
And before you ask, I don't have the formulae at hand. They're around somewhere, but I can't remember where.