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Every other week, MAKE's awesome interns tell about the projects they're building in the Make: Labs, the trouble they've gotten into, and what they'll make next.
By Steven Lemos, engineering intern
For a school project in my AutoCAD class, my group and I decided to design and build a hovercraft. At first we were planning a full-size, ride-on hovercraft, but after meeting and brainstorming it was clear we didn't have enough time to build one. So we decided to build a smaller version, using R/C controls. This was made possible by a friend's surplus supply of assorted R/C airplane parts, including motors, receivers, and controllers.
The hovercraft took one month to design using Autodesk Inventor software, two months to build working mostly on weekends and some school nights -- and 1 afternoon with the MAKE interns to wreck! Check out the video:
This was the first time we'd run it at full speed, and it flipped because we tried to turn it at too high a speed. We can't really fix that without a redesign, the base is just too long and thin. But so what, we've just established its maximum speed!
Construction is mainly 1/16" birch wood and some 1/8" basswood supports, with carbon fiber stripping used to secure high-stress parts such as the motor mount. We're using an O.S. Max .40 FP motor (a dinosaur of a R/C plane engine, but hey, it was free), attached to a 3-blade propeller with a total vehicle weight of 3.7lbs. The skirt is made out of ripstop nylon, mostly used for kites, and is secured using velcro.
It took some tinkering to get it to fly right. At first the skirt was droopy and the air distribution was not good; it would float on smooth surfaces but had a hard time with rough surfaces. The engine is also being pushed hard with the 3-blade prop and has a tendency to get hot if not cleaned after each use.
For more information on R/C hovercrafts, please check out rc-hovercrafts.com; this is where I got a lot of my information and ideas on the project.
Your hovering intern,
Steven, signing off
Nice looking craft. You might try turning the engine around the air from the prop is forced back over the engine to provide some extra cooling.
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also you could have some sort of counterweight that moves towards the inside of the turn so that its less likely to roll over? idk
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That is definitely good advice! It would have increased the drive time and reliability by alot!
However the reasons we did not go that route;
Center of mass, we wanted to keep the center of mass in the center of the craft, and the placement of the engine was very important in this equation (the engine being the heaviest one item going onto the craft), and because we had only one engine, we had to keep that weight in the center.
Structure of original design, The back plate we had designed did not appear strong enough to take the abuse of this motor.
Controls, because of the placement of a pull motor, we would have to design different rudder system than we already had(which wouldn't be a bad thing, if you don't factor in that we have 2.5 months to do this, while being a full time student and an intern at Make)
We overcame the the cooling problem by running helicopter fuel, which we were told had more oil so it burned slightly cooler, and had a benefit of keeping the engine well oiled.
On my next hovercraft build I plan to run 2 engines, an electric motor for lift, and a nitro motor for thrust, and this time the engine will be a pull motor, instead of a pusher.
For the counterweights: I have seen it done with a miniature figure driver that leans in turns which i thought was pretty cool. However we had not thought we would have this flipping problem. We were also trying to keep the weight down as much as possible, but counterweights could definitely help keep it more stable.
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That is really interesting.
I just finished building my R/C car. It took a long time to finish my R/C car. Anyways I bet building that R/C hovercraft was really hard to build though. Did you have fun doing it? But that is really cool though.
Hope to see another post soon.
Bye!
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