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I'm a beginner in electronics. I tried making a hovercraft that looks like this:

The bottom looks like this: enter image description here

And the battery used is this:enter image description here

I have used a 9v motor, a 9v battery and a dual blade propeller. For now, I just temporarily connect the wires to the motor to see how it works. As soon as I connect the wires, the motor turns on and the propeller spins with a high speed. However, the entire craft just vibrates(not vigorously) and stays in its place. Sometimes, it displaces very slightly due to the vibration. Moreover, the speed of the motor decreases after a minute or so. Note that I'm not placing the battery on the hovercraft. I hold it while it is connected and try to move along with it when it moves. But the movement is too feeble.

1) Is the battery not good enough?

2) Is the skirt not well shaped?

3) Is the motor to heavy?

4) Is the air intake not properly designed?

What am I doing wrong here?

Vin
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    I'm voting to close this question as off-topic because the problem is only tangentially an electronic one. The question demonstrates a lack of research on the working principle of hovercrafts, so that it would be low-quality on other StackExchange sites, too, and can't be migrated. – Marcus Müller Sep 03 '18 at 17:38
  • @MarcusMüller: I agree, but I was having too much fun :-) – MartinF Sep 03 '18 at 17:44
  • @MartinF, fun or not, but your answer is methodologically misleading. The first thing - total luck of intake - must be solved first; the rest of your concerns about electrical stuff may or may not be true, these might be second-order effects and might not need any attention at all, especially if OP said that "the propeller spins with a high speed" for the whole minute. – Ale..chenski Sep 03 '18 at 18:10
  • @Ale..chenski: I kindly disagree. I answered his question in the order they were asked, using the same numbers in front. I wasn't looking to create an 'order of approach' in steps 1..4. I was merely answering his questions. As for the 'electrical stuff': OP also stated that the motor decreases speed after a minute or so, which indicates that the battery is running flat (unless he used an old battery, which I don't assume). – MartinF Sep 03 '18 at 18:16
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    In addition to everything else mentioned, the propeller is on backwards. And lift motors only lift, you need others to move. – Chris Stratton Sep 03 '18 at 18:20
  • Try the forums rcgroups.com but please spend some time reading existing hovercraft articles rather than dropping your current unworkable project on that community, either. Once you've learned a bit from reading you can get some ideas about how to start over with an idea that could actually work. And then if you have a problem *with a design conventional enough to plausibly work* you could ask them for help with that. – Chris Stratton Sep 03 '18 at 18:22
  • @MartinF, this EE site is mostly an educational site. If some junior has a bunch of misconceptions and formulates a set of question in order of his/her weak or incorrect understanding, it is a disservice to follow the wrong train of thoughts and formally answer unrelated question in their order. Running a toy for the whole minute is pretty normal for this "class of devices", and optimization of its runtime should be considered as a different question. – Ale..chenski Sep 03 '18 at 18:26
  • @Chris Stratton I have been working on this project for the past week. I did look up a few websites along the way. Here's the one I used for reference: https://youtube.com/watch?v=srwmY5v0KYo – Vin Sep 03 '18 at 18:31
  • I tried the solution proposed by @MartinF and the hovercraft does hover now! I just need to get better batteries with a higher current output now. Thanks again! – Vin Sep 03 '18 at 18:40

2 Answers2

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I have several ideas about your design:

1) The battery is indeed not good enough. Those 9V batteries are not made to supply 'relatively large' currents, like your motor will ask. So you need a better battery.

2) The skirt needs to be shaped differently indeed. The idea is that the air is 'held' underneath the hovercraft. The paper sheet would act like a barrier, that 'prevents' the air from escaping the bottom. So the skirt needs to be around the edges of the hovercraft, not covering like you did.

3) I don't know if your motor will be strong enough to lift the entire thing, including the (heavier) battery. But because the rest is pretty light, you can try. If you redesign the skirt, it might work.

4) There is no air intake at all. There must be a way to suck air in from the top. The 'circle' you used should be mostly open to allow air in.

Good luck!

MartinF
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  • Could you link a picture regarding the second point? Thanks! – Vin Sep 03 '18 at 17:44
  • Also, how big should the hole at the top be? – Vin Sep 03 '18 at 17:45
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    If you search online for 'hovercraft skirt' you'll get lots of great ideas. Because your design has edges like it has, it might even work without skirt - for testing. The hole should be the size of your propeller. – MartinF Sep 03 '18 at 17:47
  • Okay, and must there be a bigger skirt, for instance a garbage bag (but I'm worried about the weight). Also are AA batteries good for this model? – Vin Sep 03 '18 at 17:49
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    AA is much better, ideed. But to get 9V (like the battery you were using before), you'd need 6 of them in series. Do make sure you apply a voltage to the motor that it was designed for. Many of those motors need 3V, sometimes 12V. I've never seen 9V ones, but they might exist as well. Then again, applying 9V to a 12V motor is no problem at all. – MartinF Sep 03 '18 at 17:58
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The major principle of hovercraft is to suck air in, and force the air to escape along the hovercraft skirt. In your design the propeller is completely blocked, and no air flows in. This is aerodynamics, not electronics, especially if your electrical arrangement allows your propeller to "spin fast" for the whole minute.

"how big should the hole at the top be?" - It should match the size of your impeller. But you will be much better off if you use a smaller hole and smaller impeller size, about half or 1/3 of what you have now.

Ale..chenski
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