1/16 RC Hovercraft

[wibblywobbly]

Just a test run of a Hovercraft I am building

http://www.youtube.com/watch?v=6kD4-UEq13k

[Wildboar44]

Holy Schmoley..... is there no end to your talent ? . ...

[The Tank Man]

Wow that's fantastic Rob you going to show us some pictures of the internals and fans that make her tick!!!

[blimp]

Great stuff Wibbles ! more ! more !

[wibblywobbly]

It was quite easy really, I spent weeks trying to find info on the web, but there isn't any detailed advice anywhere, just a whole load of people asking the same questions, and getting incredibly complex answers.

I decided that the only way to do it was to build something at minimal cost, so if I had to junk it, all was not lost.

Weight is the key. The first prototype was a disaster. I bought four PC laptop cooling fans, the small ones with a rotary blade. I cut two holes in a sheet of very thin plasticard and taped two fans over them. Stuck some bin liner around it, and yes it floated but no power in the lift at all. That method was obviously not going to work, even if I used 20 of those fans.

So, what would provide lift?

Plane props should do it as they shift a lot of air, but I needed a loading deck without holes in it?

More searching and I looked at ducted fans, but they were ultra expensive, especially those with brushless motors. If I went that route I would also need brushless esc's. Big money all round, and I didn't know whether it would all work, so I was not keen on that approach.

More searching and I found Mtroniks sold ductless fans without motors, £10 each? That was worth a gamble, so ordered two.

I then went to B&Q and found polystyrene insulation panels, 1250x450. Perfect. Even a pack of them weighed nothing.

First off I experimented with one sheet.

I measured a centre line and then cut holes front and rear, the same diameter as the duct casings.

This was where it got interesting, and I learnt a bit more about electronics (and a bit about cheap components.. ).

The fans needed assembly, I used a pair of Jamara 480 HS BB motors that had been in my spares box for years, they had melted the esc's on my first Elmod board about 4-5 years ago, so were still brand new. When I ran the first fan one of the blades snapped off, the clearances between the fan blade tips and the case were two tight, so one trashed fan.

The other one was sanded prior to use, and was ok.

I mailed Mtroniks, and they sent me a replacement fan. Great customer service, no questions asked.

Once I had two fans, I simply pushed them into the holes in the styrene, they are only a friction fit. I then rigged up some wiring, a switch and a battery, and again used a bin bag for a lashed up skirt.

Fired it up and it floated, huge lift power. I couldn't even push it down with my hand.

I then realised that the wiring, battery, and switch was getting too hot to touch?? Then the esc kept cutting out??

Hmmm...what is going on here, I have new motors, an 80amp esc, all the wiring is secure etc?

Bought 2 metres of 16 amp wiring and tried that, still red hot. Replaced the switch with a heavy duty one, still the same?

Swapped motors and esc's, bingo, one combo ran cool. Took the hot esc apart and resoldered some dodgy Chinese joints, but still the same?

That left one source of the problem, one of the motors, sure enough, one motor ran cool, the other red hot. I now know why the Elmod board fried all those years ago, one of the motors was faulty.

I swapped the motors for HL ones, but they didn't rev fast enough, there wasn't enough lift. I then tried pairs of motors from my spares bin and found two that revved higher, they did the trick, and everything ran cool.

Ok, now I had lift. Next problem was, that the height of the duct fans with motors was a lot more than the thickness of a sheet of insulation, so hot glued three together, and cut duct fan holes through. Now I had a platform that didn't flex, and the top surface was level with the top of the motors.

Snag was, if I stuck on plasticard for a loading deck, then it would seal the air inlet for the fans.

Out with the kitchen knife and I cut channels in the top of the foam to the outside edges, this allowed air to travel under the styrene to the duct fans. That worked well, so I cut out sections of foam for the battery and all of the wiring, esc's, rx etc.

I then hot glued the styrene to the polystyrene base (you can use bathroom sealant or No More Nails, anything that doesn't contain a solvent or the polystyrene will melt). The styrene sheet adds some stiffness to the desk as well.

During a further test run, a small piece of styrene got sucked into a duct and snapped another blade, so I ordered two more duct fans, and an extension for the receiver wire. Mental note to put mesh over the holes.

What you see in the video, is just about where I am now.

Ripstop nylon is on its way so that I can make a proper skirt.

For propulsion I tried a duct fan, but they don't provide enough thrust. So bought a pair of cheap plastic motor mounts, a pair of 3 blade 6" props, and used HL motors. I have made a raised mount for the rear, and I am literally 50% of the way through getting these mounted properly. I won't know if they work until I mount them. To protect fingers from the rotating props I will use Asda microwave meal bowls, they are the perfect size.

Then I will be able to build the superstructure and make it look more like a military hovercraft.

It's been an interesting project, not expensive to do, I will post some more pics when I get the chance.

[wibblywobbly]

Fitted rear propulsion and tested it. No steering as yet.

This set up eats batteries though... As soon as the power drops off the lift motors it starts to struggle.

http://youtu.be/oEUTOaeylpI

[wibblywobbly]

Someone asked for pics of the build so here are the latest ones.

I have now installed a ramp, started facing up the hull with styrene sheet, and sorted out the rear propulsion fans.

It seems that there is a drought in the styrene industry, as I can't get hold of any A3 or A2 sheets anywhere? I may have to order A4 and use seperate strips for the sides.

I hope the pics show the type of fans I used, how they are mounted, and where the esc's and batteries etc are located.

The only drawback with this design is that any load on the deck has to be balanced down the centreline, as the two duct fans create a pivot point down the middle. This may become less of a problem if I can get the skirt design sorted out.

[wibblywobbly]

Just to show that work is still proceeding, managed to make a pair of rear duct surrounds and rudders. I am awaiting delivery of some more styrene sheet so that I can finish it off ready for some paint.

I found some magnetic A4 sheets on Fleabay, so I will use those to hold the superstructure on down each side of the deck. This will make access to the batteries and electrics very simple.

Rob

[wibblywobbly]

Not a lot of progress on this hovercraft, it is very tedious and I lose patience far too quickly.

I am building up the superstructure, started off by hot gluing three pieces of insulation panel together, then cut it to the shape that I wanted with a carving knife. One snowstorm later I had the basic shape.

I then cut out facing panels from styrene sheet and hot glued these on, and then had to go around all the edges filling and sanding to get a smooth edge. I am also building vents to allow air to get sucked down into the lower hull for the duct fans. I have never made my own louvres before, so they aren't perfect, though I am learning all the time.

Rob

[Wildboar44]

Still blown away with your scratch build skills....