Introduction: Hovercraft - Bluetooth RC

Hovercraft are also know as air cushion vehicles. Floating on a cushion of air allows for near friction-less movement, especially and flat, smooth surfaces. Control (or the lack thereof) is not so dissimilar from spacecraft that must provide their own counter control to stop any motion they start. This makes driving both fun and exciting. You need to plan ahead to keep this craft under control and _moving_ in the direction you want, and not just pointed in the right direction but sliding sideways.

In this Instructable we'll be building a hovercraft using foam insulation and some simple electronics and motors with Bluetooth control. To control the craft you can either use a Windows PC or and Android device.

For Windows with Bluetooth built in or a Bluetooth dongle, you can download Serial Commander, a small program that lets you control your bot with the standard WASD keys.

For Android users you can download the app Joystick Bluetooth Commander from the play store. This will allow you to use a touch joystick style interface.

The files and shapes for the body in this Instructable work well, but it's worth investigating other shapes and designs on your own.

Step 1: Gather Tools and Materials

Tools:

  • White Glue
  • Toothpicks
  • Soldering Iron
  • Solder
  • Hot Glue Gun
  • Small phillips screwdriver
  • Android phone or Windows PC

Foam Body Parts (from bottom to top):

  • Plenum Shield (Deflector)
  • Plenum Skirt
  • Plenum Top Plate
  • Fan Duct
  • Fan Mount
  • Fin Guide
  • Fin Guide Cover
  • Fins (2x)
  • Arrow Shaft (not foam)

Solderable Electronics:

  • Printed Circuit Board
  • 4.7k Ohm resistors (2x)
  • MOSFET
  • 1x6 Chip holder
  • 1x6 female headers
  • 1x4 female headers
  • Power distribution wires (3x - Red, Black, Blue)
  • JST female pigtail connector
  • Lift fan motor
  • Lift fan wires (2x - red, black)
  • Drive fan motors
  • Drive fan wires (4x - 2 red, 2 black)


Other Important Bits:

  • PIC 16Fxxx Micro-Controller
  • HC-06 (or HC-05) Bluetooth module
  • L298N Dual H-Bridge Stepper motor driver
  • Lithium Polymer Battery (2S Lipo 370mAh)
  • Lift fan blades
  • Drive fan blades
  • SVG Files (attached to this step)

Step 2: Glue the Foam Pieces

The Plenum Chamber is often the body of the hovercraft. This is where the air that the lift fan blows in gets distributed so that it may equalize before venting out below to provide lift for the hovercraft.

The foam we use can be found in the insulation section of your regular large DIY store. We have three thicknesses in this design: 1/4", 1/2", and 3/4". Usually only one side of the foam insulation has markings. Pay attention to which side of each piece of foam will be on the outside of the finished hovercraft so you can hide the markings.

Line up the plenum skirt piece (or pieces) with body/plenum top and place a thin line of glue around the perimeter of the body and the perimeter of the electronics bay (rectangle), but NOT the fan circle.

Line up the parts using corners as a guide and use toothpicks to hold the parts and prevent them from slipping and sliding while the glue dries.

Step 3: Glue More Foam Pieces and Decorate

This really one of the more time consuming pieces of the build. There is a lot to glue together. Take your time, and line things up. Don't let air leak out. Make sure that the fan blades aren't going to hit the foam due to bad alignment. And...

Decorate. As you're putting these parts on you can use markers, glitter glue, tape, whatever to make your hovercraft your own. Watch the weight though, you do want it to get off the ground. But this is a good time to personalize since some of the parts will be difficult to reach once other parts are glued down. And still other parts, like the top plate are a wee bit fragile after you glue them down, but they're very easy to work with alone on a flat surface

Keep building up the hovercraft in layers. The technique remains essentially the same. Put a thin line of glue around the perimeter of the smaller piece and if available some glue in where firm contact will be possible.

You can glue the the alignment shafts (an arrow shaft cut down to size) to the plenum (but NOT higher up than the fan duct), and use it to help align the pieces as you glue them in place.

You will definitely need to use toothpicks on the fins/wings. And a tiny bit of hot glue helps things set up in short order.

Step 4: Make a Custom PCB

Or use jumper wires on a protoboard.

Step 5: Assemble the Electronics Package

With the custom electronics PCB soldered it's time plug all the other parts in and to screw in the power terminals.

Start by inserting the PIC into the chip holder with the dot on the chip holder on the same side as the dot on the PIC. If the chip holder is bigger than the chip make sure that you line up the chip with the traces on the PCB that are connected.

Plug the bluetooth module into the backside headers of the custom PCB (if you didn't already solder it in place).

Loosen all the screw terminals on the H-Bridge motor driver board. Insert the drive motors into terminals on either side of the board. Then screw the terminals down so the wires don't slip out. Do NOT over tighten. You don't want to break or twist the terminals.

Screw the JST battery connector/PCB power wires into the H-Bridge board. The red wire is raw power from the battery. The terminal for the red wire should be labeled or VCC or 12V. The black wire is ground and is labeled GND on the terminal. The blue (or some other color) wire is 5V regulated output from the H-Bridge, this terminal should be labeled 5V. None of these wires should cross going to the custom PCB.

Flip the the Custom PCB upside down and plug female headers onto the H-Bridge male headers so that the custom board is over the H-Bridge.

Hot glue the two drive motors onto the front of the fins and Press fit the Lift motor into the bottom side of the motor mount and you should be good to go.

Step 6: ​Stuff It All Together

Place the electronics package into the electronics bay in the hovercraft body. Make sure the battery wire is easily accessible and everything else is out of the way. Make sure that you can also fit the battery into the electronics bay as well. You may have to fiddle to get everything in with the wires and all, but be gentle, the foam and glue can only take so much stress.

Slide the Fin Assembly/electronics bay cover over the electronics bay leaving the battery connectors out and accessible. Make sure the Lift Fan is centered in the fan duct with good clearance all around and then secure with a two pair of tooth picks (two each - front and back) angled at 45 degrees into the thick plenum skirt layer (not just the plenum top plate). Make sure the Fan Mount doesn't slide out of position and allow the Lift Fan Blade to contact the sides of the Fan Duct (if it hits and gets stuck it will quickly burn out the motor).

The lift fan motor needs to be precisely centered over the hole in the top of the plenum chamber. If the fan blades are too close to the sides of the hole, they may bind on the sides when the hovercraft bumps into other objects. This could cause the blades to bind and the motor to burn up. If the hole is too big you won't have enough pressure to lift the hovercraft. A snug fit with precise alignment is the key.

Step 7: Fire It Up

DANGER: These fan blades move fast and will hurt if they hit you. I have touched both at speed and it hurt a lot and left my fingers tingling for a long time after. While it did not draw blood from my stubby digits, there is not guarantee that it won't completely remove yours. Do NOT touch! Also make sure any small children or pets nearby are kept away from the spinning blades or any blades the could potentially spin up. This is especially true of the Lift Fan Blade. It's beefy - so no touching!

WARNING: Also a stalled/stopped motor can burn up quickly so if there is a problem kill the throttle or remove the power immediately.

With fingers, small children, and pets safely out of the way... plug it in. If everything is wired right and working all the motors should twitch briefly and then stop. Unplug your battery until you're ready for the next step.

WARNING: Unplug your battery when not in use. Never operate a LIPO battery that is low, it will permanently damage the battery (usually starting a nasty fire that is very difficult to put out the next time you attempt to charge it). The voltage cutoff code can't turn itself off so if you leave the battery plugged in, even if the motors won't turn on, you will still kill your battery. UNPLUG your battery when not in use!

Step 8: Connect to Remote Control

You have a couple of choices at the moment for remote control. Our favorite way to control Bluetooth RC vehicles is the android app Joystick Bluetooth Commander. This free and open source app allows you to configure and send may commands to your RC vehicle. We'll only be using simple X and Y controls for hovercraft, but it's a great general purpose Bluetooth RC app, and since it's open source you can change it to meet your needs. There is also a bit of documentation and support available on the developers forum site. Just install the app and pair with Bluetooth like normal. The HC-05 modules will naturally report with the ID HC-05. If you happen to be in a room with several hovercraft you may need to look at the MAC Address of the HC-05 module to figure out which one to pair with. After pairing you can connect the app and use the joystick to drive the hovercraft. Practice makes perfect.

Also available is a custom coded Windows program (just for this hovercraft project) Serial Commander supporting a basic keyboard control over Bluetooth using the same protocol as Joystick Bluetooth Commander. It's a bit more basic for the moment, but it will allow anyone with a PC and a Bluetooth dongle to connect and control their hovercraft. Just download the program and run the setup and pair to your Bluetooth module as above. You will need to know which COM Port Windows has selected to use for this Bluetooth connection. Open Device Manager and select COM Ports. It should be the last one added (sometimes windows adds COM Ports in pairs, so it may be one of the last two - failing that you can always just try them all). Select the appropriate COM Port in Serial Commander and set the strength slider to a mid value and then use the WASD keys to control your hovercraft.

Not yet available is an IOS (iPhone, iPod, etc) app. We have to get enough polish on the app to get it through the Apple approval process. Check back often.

Comments

author
acklenx (author)2014-05-23

More random pictures of the build and process if you're interested: https://plus.google.com/u/0/+QuincyAcklen/posts/YMECnfEdBr3

author
michaelhein (author)2014-08-16

Hi

This looks perfect for at weekend with my grandsons, they will just love it ;-)

But is it possible tha you upload the layout of the PCB? and perhaps the SVG files in another format like DWG or PDF?

Thanks in advance

author
tomdubick (author)2014-05-31

This is sweet. Nice work.

author
Kiteman (author)2014-05-24

How did you make all the foam parts? Have you got a template?

author
acklenx (author)Kiteman2014-05-24

We made the parts on a laser cutter. When I started taking pictures I already had the parts cut, so it didn't occur to me to include "how we got these really important parts". I'll update the Instructable with the SVG files shortly.

author
Kiteman (author)acklenx2014-05-25

That's cool.

(Professional query: What kind of foam is it? Some kinds of foam emit fumes that damage the optics of a laser cutter.)

author
acklenx (author)Kiteman2014-05-28

We used extruded polystyrene foam (XPS). Not to be confused with expanded polystyrene (EPS). Most sites copy the same warning that Polystyrene is the #1 cause of laser fires. And while I can't find the resource at the moment (though I it was from ATX Hackerspace that also has the same warning) a group had actual experience and XPS was just fine and using lower PPI even helps with cut quality. Real world experience. With that we decided to test with a small cut, a deep breath first, and fire extinguisher in hand. We had no fire or fouling what so ever in 1/4" XPS foam so we tried more and then worked our way up to 3/4" foam (focused for 1/2" foam with 2" focal length lens). This seemed to work great. We had no noxious fumes and no fowling of the optics or even ugly smoke. If ever we did multiple passes (usually because we set intitial power wrong on new thicknesses) we encountered some odd melting patterns between the layers, but still no other adverse effects.

author
Kiteman (author)acklenx2014-05-28

Thanks.

I wasn't worried about fire, just chlorine compounds etching the mirrors.

author
acklenx (author)Kiteman2014-05-29

Universal Laser warns:

Some brands of foam board are made with PVC foam rather than polystyrene foam. Cutting PVC foam with a laser is not recommend. Always verify the core material before proceeding.

But doesn't warn against using true XPS. Oh I found the link... it's Kim Vellore that discusses using using lower PP on a sawmillcreek forum post with XPS (looks more like "depron" XPS):

http://www.sawmillcreek.org/showthread.php?187961-...

author
robinpaine (author)2014-05-26

There is a 700 page book, with 450 pictures called 'On a
Cushion of Air', (www.Amazon.com or www.thebookdepository.com
and Kindle), which tells the story of Christopher Cockerell's discovery that
heavy weights could be supported on a cushion of low pressure air, and the
development of the hovercraft by those who were there, from the very early days
through to the heyday of the giant 165-ton SRN.4, which crossed the English
Channel starting in 1968 carrying 30 cars and 254 passengers at speeds in
excess of 75 knots on a calm day. It was subsequently widened to carry 36 cars
and 280 passengers with an A.U.W. of 200 tones and was later lengthened to an
A.U.W of 325 tons and capable of carrying 55 cars and 424 passengers. The
amazing point was that from 165 tons to 325 tons only 400 extra hp was
required, although a bit of speed was sacrificed, proving conclusively that
Christopher Cockerell's theory was sound.

Sadly, for economic reasons, the service came to an end on
1st October 2000. In total 6 SR.4s were built and the two remaining ones are in
the Hovercraft Museum at Lee-on-Solent. See www.onacushionofair.com

author
acklenx (author)robinpaine2014-05-28

I just bought the book. Thanks for the recommendation. I would like more technical details of the skirt design/behavior/principles/etc. The preview on amazon "teased" well.

We (a bunch of us at Hackerspace Charlotte) played with a lot of different designed for the jetting out the bottom of the plenum. Only a few had skirts, since out our scale we had difficulty getting something with desirable performance characteristics. We he too much drag, not enough rigidity or way to much. A finger skirt seems to be the answer, just not for something this small. This is definitely one of the areas ripe for more investigation and experimentation.

author
bricabracwizard (author)2014-05-25

Could you post a video of this hovercraft in action?

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