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RC Hot Air Balloon

Propane Powered - Remote Controlled

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This is a collaboration project with a good friend of mine, Josh Thurman, to create an RC hot air balloon.

Total Weight: 27.6 lb
Canopy Weight: 9.4 lb
Basket Weight: 18.2 lb
Canopy Size: 2500 cubic feet (21' x 16')
Lift Capacity: 23.8 lb @ 89 degrees F (excluding balloon weight)
Range: 700-1000 meters
Max Air-Time: >1 Hour
Fuel: Propane
Fuel Capacity: 32.8oz
Cost: Around $400.00
*Canopy is by far the biggest expense at over 2/3 the total cost.



Operation

Operating the balloon is pretty simple since it’s really just an on/off thing. The colder the ambient temperature is, the more efficient the balloon will be. Setting up the balloon requires a fan to blow air into it to inflate the canopy. To get it to stand up, it helps to have a spare propane tank and weed burner to get hot air into the canopy to reserve the primary fuel for the flight. After it’s up, the main burner needs to be lit and the flame adjusted to a place where it will not go out, but not high enough to lift it. The weed burner is neat in this regard. It will allow enough gas to pass through to retain the flame when the handle is closed. It can be turned off to pass control to the handle as well. Having a separate small tank to feed a pilot light would be ideal, but is not necessary. In our testing, the flame only went out when our fuel supply ran out. To pack up, it helps to pop the top of the canopy to help collapse it. (Most canopy tops will be removable via Velcro.) The canopy we used was purchased, but could be hand sewn with the right material and tools.

Lift Capacity Calculation

To calculate lift capacity with the Ideal Gas Law and Net Buoyant Force we would need to know the temperature inside the canopy. Since we do not have this temperature reading, we measured it with a crane scale staked down to the ground at max thrust for a rough measurement.

ino - 1.35 kB - 07/07/2017 at 21:50

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Transmitter.png

Transmitter Diagram

Portable Network Graphics (PNG) - 305.26 kB - 01/05/2017 at 14:33

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Receiver.ino

New Version with failsafe added.

ino - 1.40 kB - 07/07/2017 at 21:50

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Receiver.png

Receiver Diagram

Portable Network Graphics (PNG) - 302.90 kB - 01/05/2017 at 14:33

Preview
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Hookup Guide.txt

Hookup guide for pins.

plain - 1.09 kB - 01/05/2017 at 13:46

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  • 2 × Audrino Uno
  • 1 × Savox SA-1231SG High-Torque Servo
  • 2 × nRF24L01+ Wireless Modules
  • 1 × Brush Burner Harbor Freight
  • 2 × Propane Gas Coleman Lantern Tanks

View all 16 components

  • Air Test 3 & Overview Video

    Matt Barr07/11/2017 at 05:14 0 comments

  • ​Data Updates & Canopy Details

    Matt Barr07/11/2017 at 02:58 0 comments

    I’d like to post some updates since the last flight. We added a failsafe/interlock to kill the gas in the event of connectivity issues, and made some fuel adjustments. Also, we have had quite a few questions from the Hackaday.io community about the canopy that I’d like to answer. For fuel, we have determined that we can get a lot more thrust by flipping the propane tanks upside down. The liquid propane on the bottom of the tanks generate much more power than the vapor you’d normally get by having them right side up. Using liquid, the burner is much more dynamic and the balloon does not need as much gas to fly, thus being more efficient. It does seem to be more prone to having the flame go out this way, so we intend to add a pilot light soon. It also makes the tanks very cold, as you can see in the last picture below. I also had a chance to take some pictures of the top of the balloon to show the vent to those who were interested. Our canopy has a vent on top like a regular balloon, but is not something we need to use in flight. It is mainly for making it easier to pack the balloon up. On a large-scale balloon, the tops can be popped to reduce altitude. Lastly, I had a chance to get a crude measurement of lifting capacity by measuring it with a crane scale. This and some other measurements can be found in the project details. The canopy width and height was a rough measurement with a tape measure after it was inflated and just before we got it upright.

  • Test #1

    Matt Barr01/06/2017 at 01:06 0 comments
  • RC System Build

    Matt Barr01/05/2017 at 14:46 0 comments

    The radio system is Arduino powered using the NRF24L01+ 2.4GHz radio modules. On the transmitter side, there is a master power switch, 10k pot, two led indicators, Ardunio, and 9V battery. Both switches provide a simple on/off function. The NRF24L01+ transmits the on/off state of the 10k pot. One led is a power indicator and the other is a gas on/off indicator. On the receiver side, there is a master power switch, Ardunio, two led indicators, and 9V battery. One led is a power indicator, and the other is a connectivity indication. There is an interlock/failsafe function in the receiver code that will turn the gas off should connection be lost. Two 9V lantern batteries, wired in series, provide power to the servo. There is a L7805CV 5V voltage regulator attached to the servo power line to reduce voltage to the servo. The Savox SA-1230SG servo is rated at 416 oz/in torque@4.8V. It can tolerate up to 6V. Any less than 390 oz/in is not enough torque to pull the handle. Having a little more than this, and providing a little less power than the maximum the servo can handle is a good compromise between having enough power without burning out the servo. Everything fits nicely inside some SparkFun project boxes.



  • Basket Build

    Matt Barr01/05/2017 at 13:16 0 comments

    The basket frame is built from lightweight aluminum angle, riveted in place. The sides of the basket are fitted with black foamcore panels trimmed to size. One sheet of foamcore from Hobby Lobby was enough to cut all the panels. The main burner is a simple propane weed burner from Harbor Freight. It is held in the basket with 20ga wire, and actuated with a high end (>400 oz/in) Savox servo. The servo attaches to the handle with some heavy gauge wire and a zip tie. Gas is provided by dual Coleman camping fuel tanks with a custom fitting to reduce a standard propane grill tank fitting to one that will fit the Coleman tanks. The burner comes with a pretty long hose with fitting attached, so it’s not too hard to connect.





  • Up and Running...

    Matt Barr11/30/2016 at 19:12 0 comments

    I started building the remote system with a Picaxe micro-controller. My programming board went out, so I switched over to Audrinos because they are more durable and easier to work with. The nRF24L01+ Wireless Modules are amazing, I highly recommend them. At this point the remote system is complete and working properly. We will now attempt to field test them, then move on to the balloon itself if everything checks out.

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  • 1
    Building & Assembly

    Acquire parts and follow the hookup guide in the files above for radio assembly. Then follow the project log to replicate what we have done to build everything.

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Discussions

Matt Barr wrote 07/07/2017 at 21:49 point

That is probably a good idea.  When the gas is killed up in the air, it really does not come down all that hard at all.  It more or less coasts down since we are not popping the top.  May be a good idea for safety though.  

  Are you sure? yes | no

manta103g wrote 06/22/2017 at 23:11 point

Matt, really excellent project  since Helium is highly expensive.

Hot-air is generated by your burner as in manned balloons.

Don't you think inflated bumbers attached at the buttom could provide safety measures to propane gas tanks in case of balloon failure (hope none).

  Are you sure? yes | no

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