Purpose

Summer 2014 Introduction to Engineering Competition

Who We Are

First of all, this RC hovercraft is not a standalone DIY project. It is designed with the purpose of winning the summer 2014 Intro to Engineering competition for Team BAZOOKA. We are a group of engineers-in-training at University of Michigan - Shanghai Jiao Tong University Joint Institute (UM-SJTU JI), located in southwest Shanghai. That is why you are seeing rules for competition, limits on materials and, most exciting of all, videos of hovercraft racing competition. Follow me through the fun process of creating it.

The Competition

The competition is divided into two parts, timed-trial and tournament. In timed-trial, you basically need to go one lap within 3 minutes, proving the hovercraft is fast enough to have a shot at winning the tournament. Now the tournament is where it gets interesting. All teams gets randomly assigned to compete with each other, and the winning team gets promoted to the second round, competing with other winners. One champion arises after winning three rounds. Here is a video of our hovercraft winning the first round (we are the team on the right). Enjoy!

Rules

The rules for racing are quite intuitive: no blocking, short-cutting or purposeful crashing (which we violated once…), something like that.

But the rules for building the hovercraft are the ones that are tough. Let me list below

Overall weight below 800g (we really struggled on this)
Maximum size within 30 * 30 * 30 cm
Maximum two batteries with each below 12V
Maximum motor working voltage below 12V
Arduino control required

Now the rules are all clear, let’s get started!

Step 1: Arduino Control Circuit

Here is a diagram for the design concept and a list of all materials. Please note that

bluetooth module is connected to Arduino UNO through USB interface, no wiring necessary. Attached is the picture of bluetooth connected with Arduino.
in practice, motor & ESC are connected directly to Arduino, no breadboard or circuit is needed. They are put in the picture for better understanding of wires.
the use of brushless motor requires ESC (electronic speed controller) to convert battery DC current to motor AC current. The wires attached to the motor in the graph are actually attached to ESC. Then ESC introduces the signal along with AC current to motor.

The control logic is also attached. Have a look.

Step 2: Mechanical Component (Main Body)

The mechanical main body is separated into three parts

Bottom part is the one attached to the skirt. Cut a hole of the same size as the pump motor in the middle to allow air into the skirt. Since the skirt is made of thin garbage bag (haha), having a bottom layer means when the skirt gets broken, we can simply replace the bottom layer and leave all upper layers intact.
Middle part is the main platform holding all electronics. It has basically the same size and cut-out as the bottom part. Considering the power of the motor, it would be a good idea to come up with a structure that attaches the pump motor more firmly to the hole in the middle. So we are taking Kraftpaper (a very durable paper), rolling it up around the motor, and spread the rest like a flower pedal. Attach the “pedals” to the main body and we are good to go. The picture explains itself.
The upper part is where we fix the two powerful propulsion motors. Cut two holes of appropriate size should get us going. Now the only problem remaining is how to attach the upper part to the middle part. For that, we are using plastic triangle as mentioned in the material list. You can see from the picture here.

Finally, to make sure the three parts of the main body stays together, we are taping them all. The black stripes you see on the pictures are what it takes to make sure the hovercraft does not break into 3 pieces in the middle of a race.

Now the picture shows the view of all pieces together.

Step 3: Electrical Component

Mechanical part is almost finished. Now we are connecting the electrical wires.

First, motors are connected to ESC (Electronic Speed Controller) output. Find the matching colors and plug them together. That should be easy.
Then, make sure Arduino signals are properly transmitted to SEC input. Connect two wires from Arduino ports to corresponding SEC. This should be tricky. But follow the circuit diagram in step 1, it should work just fine.
Finally, connect ESC with the power source through T-interface. Be careful since motor might operate unexpectedly when you connect the power.
So where does Arduino draw its power? Luckily ESC has 5V power output meant for the control power. Connect Arduino power to one ESC 5V output and we are done.

Step 4: A Little More Friction

After testing, we found the original design too hard to control. See the video for yourself. The friction between hovercraft and the floor is too small for the hovercraft to be properly controlled.

So we are adding two polyfoam strips in the bottom. And result proves we are right. Hovercraft performs a lot more steady with the strips increasing friction. See for yourself in the video posted in the introduction part.