Balloon-borne camera, part 9: Finally, success (and a final post)

I'm happy to report that after a lot of unhelpful weather got in the way, we finally have successful video! Before we get to that, I have a few more details to fill you in on. The first is that, emboldened by the success of our tiny $4 kite, we invested in what can only be described as Kite Kong, Lord of the Kites, with a whopping 9 square feet of surface area. We also bought 500 feet of 150-lb rated kite line. We went with a delta-shaped kite because they have a reputation as being easy to fly and very stable, although this parafoil kite was also an option due to a similar reputation for stability and good performance in low wind conditions. In the end, the real difference maker was that giant kites look way more awesome, so if a big parafoil kite had been available, we may have gone with that.

Anyway, with the help of one of the camp counselors, on Monday we had our first successful video-capturing flight! Here's a short excerpt from the video - as you can tell from the audio, we were having a little trouble getting altitude and needed a little help from the campers :)

Edit: Nix that for now, I'm having trouble

getting an excerpt from the video.

Will add it later.

Balloon-borne camera, part 8: switching to kites and fixing poor choices

Like I told you last time, we had to make a sad decision and give up on the balloons in favor of kites. This exposed some bad practices I described in earlier posts, which will be corrected as soon as I post the corresponding correct practices!

So it was with sadness in our hearts but determination in our eyes that we went and bought our first kite, from a nearby hardware store (yeah, a hardware store). In fact, it was this kite, and it was super inexpensive. I was a little apprehensive about how much weight this little kite could lift, given our previous troubles with the balloons, but man was I proven wrong. With a little help from the high winds of an oncoming storm (note: it is a pretty dumb idea to fly a kite in a storm), we got our camera way up on the first try! No pictures, sadly, but if you look at pictures from previous posts and replace the balloons with a small Canadian flag kite, you'll get the idea.

So it worked really well, except (there's always an except)...

Balloon-borne camera, part 2 - Building a stable camera platform

As I mentioned in my last post, the major problem we were having was how to stabilize the camera so you could get a decent video of it. A little searching online led me to kite aerial photography enthusiasts, who prefer the picavet as a way of suspending a camera from the kite line so that the camera naturally levels itself. I decided to construct one and see if it gave us any better results.

Two websites were particularly helpful to me and deserve special mention - Charles Benton's Kite Aerial Photography page and the KAPER Picavet page. This last one in particular had useful images and diagrams.

Briefly, a picavet is basically a cross suspended from the kite line (not from the kite itself) by a rope strung through the four corners of the cross. Each corner has an eye through which the rope runs, along which the picavet can slide. The camera is attached to the picavet from below. This rig uses its own weight to slide down to the bottom of the rope, where it hangs perpendicular to the ground. It continuously readjusts itself as the kite line moves. The principle on which it works deserves its own post, so I'll leave it at that for now.

This diagram from the KAPER site shows the major parts:

Picavet diagram. Points A and B attach to the kite line. The camera hangs underneath the cross.

We wanted to take a very low-budget approach using materials found around the museum. This picture shows some of what I collected:

String, washer, balsa wood, and glue gun

Cup hooks

On the top starting from the left, you see a spool of reasonably strong string (I can snap it by pulling, but I have to pull really hard), a tiny washer, two rectangular sticks of balsa wood (30 cm x 2 cm), and a hot glue gun. Other materials included some E-Z hang cup hooks for hanging things from walls (bottom), and (not shown) pliers and two cheapo carabiners like the ones you get in the checkout aisle at a convenience store.You'll see the pliers and carabiners in later pictures.

Note: If you plan on lifting a fancy camera that will be expensive to replace, I really suggest you use stronger materials, like aluminum for the cross, bolts to connect the cross pieces, sturdy kite line for the string, and real climbing carabiners. My approach works well for our 30 g picavet and 30 g camera, but doesn't really scale.

Alright, now we're ready to put it together. The first step is to make the cross out of balsa wood. I used a ruler to mark the center of each piece, and did my best to align them perpendicularly. I drew lots of guide lines on the wood to help me. Carefully holding the pieces in place, squirt glue from the glue gun down the edges where the pieces meet (all four edges - flip the cross over to get the last two). There are probably more secure methods of joining the cross-pieces, but this one works well enough for our light load and is quick and simple to do. Feel free to substitute your own glue, but I would be very hesitant to use arts and crafts glue. Stick to stuff meant for hardware, like cyanoacrylate-based adhesives.

The last step is to screw the cup hooks into each end of the cross. Before you do that, you need to close the hooks so that the end makes an eye (obviously, an alternative is to simply use eye bolts instead of hooks, but I used what I was able to most easily find). Just crush the hooks with pliers, like in the following two pictures. Crush them and crush them well, so the string won't slip out later when your camera is 50m in the air (you can also avoid this by using thicker string or rope).

Not crushed.

Crushed!

Screw one into each end of the picavet cross. When you're done, turn them all to face the same direction. It should look something like this:

 

Picavet cross, with eyes oriented left-to-right. You can also see where I glues the cross pieces together. Ignore the hole in the middle - that was a failed experiment! I promise to explain it later.

On a final note, feel free to replace these materials with anything else you feel is better or easier for you to obtain. Eye bolts, for example, would have been a good replacement for the cup hooks, but I found the cup hooks first so that's what I went with.

Congrats, the base of the picavet is finished! Next time: stringing it and hanging it from the kite line.

Disclaimer: Although I am a volunteer at the Canada Science and Technology Museum, the content on this blog in no way reflects an official communication of the museum. 

Balloon-borne camera, part 1 - Introduction

One of my projects for the Canada Science and Technology Museum (/Musee de la Science et de la Technologie du Canada) is to get their balloon-borne camera project working. This is going to be a summer camp activity where the campers use balloons to lift a camera high into the air and record some video. If you're coming here to find out how it was built, welcome! You're the reason for these posts, and I hope you find them useful. I'll just warn you that this will be more of a story than a how-to - I will probably have quite a few mistakes, dead-ends, and corrections as I go along. I'll do my best to update my posts when this happens, so you can skip ahead to working solutions.

The first attempt was the most straightforward - we hung the camera from underneath about 15 balloons. Here's the video from that first try:

As you can see, the camera had a tendency to swing pretty wildly. We chose the particular camera (a Digital Concepts 3-in-1 Micro Digital Camcorder) because we're still testing out the project and if we lost the camera it wouldn't hurt our wallets too badly. So, we aren't expecting HD quality video, but still we should be able to get a better video than that. It looks like the major problem is stability - we need to find a way to stop the camera from swinging.

 Where do I turn to when I need help? The internet! I discovered after some searching that this project is quite similar to kite aerial photography, an activity with a very active online presence. In KAP, as the name suggests, you use a kite instead of balloons to lift your camera into the sky. Apparently this technique is very popular with archaeologists who need a quick, inexpensive, and relatively uncomplicated way to get overhead photos of their dig sites. They have developed some nice tricks for getting good pictures.

Their preferred device for stabilizing a camera is called a picavet, developed shortly before the first World War by the French inventor Pierre Picavet. In the next post, I'll show (with lots of pictures!) how I built mine and explain how it works.

Disclaimer: Although I am a volunteer at the Canada Science and Technology Museum, the content on this blog is my own and only my own, and does not represent an official statement by the museum.

Update: Poland is over, on to new things!

A brief update on my status, because I'm planning on actually writing over the next few weeks and I need something to bridge the gap between posts!

My time in Poland has come to an end. I finished my MC-PAD fellowship and successfully defended my thesis, making me a Master of technical physics with a specialization in nuclear (really, particle) physics. I really loved Poland, but at the same time I'm happy to be moving on to the next step with my career.

I'm excited to say that in the fall I'll be starting the physics PhD program at Johns Hopkins University, in Baltimore, MD! They're a top program and they made me a great offer, which came with the added bonus that I finally wouldn't be an ocean apart from my girlfriend.

In the meantime, Katie invited me to come to Ottawa with her for the summer, where she is working with the Canadian government in a US-Canadian partnership program. To stay occupied until August, I've offered my services to the Canada Museum of Science and Technology. They have given me some really cool projects to work on for the summer camps and various other events, and in return I'm learning a lot about communicating science to the public. 

This blog will hopefully document the progress of those projects (since they mostly involve building cool stuff). Look forward to pictures and video from the June 5 transit of Venus across the Sun (if you are unfortunate enough to be on my email lists, I'm sure you've heard enough from me about it already), and how to lift a video camera with balloons. That's what I'm working on now, and future projects will also be posted here.