Make: Projects

GoPro Cannon Cam

Take astonishing videos from high above — and look out below.

cannon-cam-opener

The original Cannon Cam shell was one of the first custom 3D projects I made when I started working at Make Labs. Due to the design constraints of the Thing-O-Matic 3D printer, the idea was doomed from the start, but I printed it out anyway. (It looked cool and I was excited about 3D printing.) It sat on my workbench for 3 years, until my editor noticed it during a brainstorm session for new 3D-printed projects. I told him it would probably wobble in flight and shatter on the first crash landing. Intrigued by the concept, he asked if I could design a new one that would fly stable and survive a crash. Of course I said yes — I can’t pass up a design challenge. The result was this new GoPro Cannon Cam, and video from the unique perspective of a human cannonball.

Originally, to give it stable, roll-free flight I added an electromechanical gyro stabilization system in addition to 6 spring-loaded retractable fins. To help it survive landings I designed a shock-absorbing nosecone and a non-electronic time delay parachute deployment system, triggered by the inertia the projectile experiences when fired from the cannon. After spending days researching World War II torpedoes, warhead fuses with clockwork time delays used by the Nazis, and gyro cars from the 1900s, I developed a projectile with several “modules” that each had a different function.

A nose cone module featured a spring-loaded shock-absorbing tip to protect the rocket on impact. But the impact would be lessened by a parachute module; a fan would rotate a series of lugs and when they lined up, the rear section would break away and drag a parachute into deployment. Meanwhile, a camera module with a built-in window held the camera in place without disrupting the aerodynamics. The gyro module had a small motor, mounted on a one-axis gimbal, that powered a steel washer flywheel. The final section was the retractable fin module, which was rigged to break away.

To incorporate all those components required a “rocket” almost 2 feet long and weighing around 6 pounds. (I have a tendency to over-engineer things.) So I took a step back. I abandoned the gyro and parachute systems in favor of a small, lightweight projectile with the shock-absorbing nose cone, camera, and retractable fins. If the projectile was light but strong, I reasoned, it would survive landings at terminal velocity. After a quick destructive test of a 3D-printed part, I incorporated threaded rods running the length of the body to hold the parts in compression and help it resist delamination during violent impacts. All that was left to do was print it out and test-fire it.

Steps

Step #1: Print the components.

PrevNext
GoPro Cannon Cam
  • Print the nose cone impact head, fins, slip rings, and window frame (get files here) at 80 percent solid infill. Print the remaining parts with 30 percent infill.
  • Make sure all the major body modules printed correctly, then use three 8.75" lengths of 6-32 thread rods to hold things together temporarily.
  • Once you have lined everything up and made sure all the modules sit flat against one another, mark the parts with a black Sharpie to ensure the Cannon Cam is always assembled the same way.
  • TIP: If your printer doesn’t print evenly, line up the pieces so they lean the same way, to keep the modules from binding up.

Step #2: Assemble the spring-loaded fin module.

PrevNext
GoPro Cannon CamGoPro Cannon CamGoPro Cannon CamGoPro Cannon Cam
  • Cut 6 lengths of 1/8-inch brass rod to 5/8-inch long, and de-burr the ends. Drill out the holes in all the fins with a #30 drill. Take one torsion spring and place it with one of the legs resting in the slot on the fin. Trim this leg so it is flush with the fin’s body, about 1/4" long. Now trim the other leg to around 3/4". Slide the brass rod into the spring.
  • With the brass pin and torsion spring in place, insert the protruding 3/4" leg of the torsion spring into the small hole on one of the slots on the fin body cap, then lay the brass pin in the corresponding trough. Repeat with each fin.
  • Fit the body cap and fin assembly to the spring loaded fin body, holding the two parts firmly together, and test all the fins to make sure they don’t bind and get stuck in the grooves of the body. If they do, disassemble it and file the sides down until the part no longer binds. Once every fin retracts and springs out freely, fix the two parts together with three 8-32×1/2" screws.

Step #3: Build the camera module

PrevNext
GoPro Cannon CamGoPro Cannon CamGoPro Cannon CamGoPro Cannon Cam
  • Carefully peel off the label of the soda bottle, then cut off the top and bottom to leave a large clear cylinder. Place your window frame over the plastic and trace out the shape of the frame on it, including markings where the screws will enter the body. Cut the window out of the plastic, trimming the corners until it fits in the camera module body. Drill holes to accept the screws.
  • Trace a line along the window’s vertical edges where the all thread rods will pass through the body and cut off the extra material. Place the window in the body and use the 4-40×3/8" screws to attach the window frame to the camera module, sandwiching the window between the two.

Step #4: Final assembly

PrevNext
GoPro Cannon CamGoPro Cannon CamGoPro Cannon CamGoPro Cannon Cam
  • In preparation for firing, start by assembling the nose cone module. Take the impact head and put the large spring in the hole in its base, then slide both into the hole in the bottom of the nose cone body. Screw the three 6-32×8.75" all thread rods into the small holes in the bottom of the nose cone body and add the first slip ring, making sure your tick marks are lined up.
  • Make sure your GoPro has a fully charged battery and an empty memory card, and slide it into the cavity in the camera module, then screw the cover on using the remaining 8-32×1/2" screws. Slide the camera module assembly onto the all-thread rods, making sure it is right-way up. Add the second slip ring, followed by the fin assembly. Finally, thread three 6-32 Allen nuts onto the ends of the rods and tighten to hold the whole assembly together. Check that all your marks line up and all your fins spring open freely.

Step #5: Launch it

PrevNext
GoPro Cannon CamGoPro Cannon CamGoPro Cannon Cam

Firing the Cannon Cam is pretty straightforward. Get yourself a spud gun with a 3-inch barrel. Turn on the GoPro and set it to record video. Tilt the muzzle to approximately 80 degrees, and slide the projectile in with the camera facing down. Launch it, collect it, and download your footage.

Dan Spangler

Dan Spangler

Dan Spangler is a freelance maker with a passion for fabricating speed, high voltage, and the things that go boom.


  • Dave Robinson

    Hi Dan,
    A great article and model. I have downloaded the files and are preparing to try a print.

    Looking at the camera module body, it looks like it needs to be printed with supports on. I took a look at the model through Makerware software and can see the circle and structure above seem to try and print in thin air. Did you use supports on your print? Or did you change the orientation on the print bed?

    • Dan Spangler

      Hey Dave, thanks for the compliments, I did have to use support material for the Camera Module Body which I printed in a vertical orientation. I used an Afinia 3D printer to make the part.

    • http://kkhausman.com/ Kalani K. Hausman

      @Dave Robertson,
      If you rotate the GoPro section so that the lens aperture ring is towards the bottom, it print well without support. All of the rest aside from the border is entirely supported by the material below.
      Kirk

  • http://kkhausman.com/ Kalani K. Hausman

    Dan, the linked spud gun “Night Lighter” has a 3″ combustion chamber, but only a 2″ barrel diameter. My teachers are asking if there a design with a barrel that fits this projectile’s requirements you could recommend? I can test upscaling to a 5″ combustion chamber and 3″ ID barrel, but suspect it would be faster to locate a measured configuration already tested.

    • Dan Spangler

      Hey Kalani, we have re-uploaded the files and the zip file now contains the slip ring model, thanks for the fix on thingiverse. In response to your cannon question, i would use a 4 inch chamber with the 3 inch barrel. 5 inch pipe and fittings is hard to find and expensive. jsut make the 4 inch chamber longer to create more volume. check out http://www.spudfiles.com/ for more info.

      • http://kkhausman.com/ Kalani K. Hausman

        Thank you for adding that, Dan. I see that your Slip Ring is slightly thicker than the one I posted up before. I will try to make the spud gun using a 4″ combustion chamber and a 3″ barrel to see how that works. The biggest challenge I am having now involves discharging what amounts to a fixed emplacement mini-cannon on campus – which is humorous because the University fires off a howitzer every time we score a touchdown in games! And I have one team of students working on a replacement for the GoPro section to hold an Arduino and pressure sensor to track vertical displacement during the time of ballistic flight. I will make sure to share that once the finish it.

        • Dan Spangler

          while not as impressive as the combustion style cannons, compressed air cannons can be an effect alternative, there quieter, offer more control over power and viewed as less dangerous by the general public (less likely to get in trouble). the arduino and pressure sensor module sounds awesome, cant wait to see the data.

          • Gregory Allard

            Also they are easier to disarm. they are no slouch with some of the larger ones having a nearly 1 mile range with a pumpkin.

  • http://kkhausman.com/ Kalani K. Hausman

    Dan, the slip rings do not appear to be included in the STL file archive.

    • http://kkhausman.com/ Kalani K. Hausman

      I created a slip ring for the cannon-cam (1/4″ thick) and uploaded it to Thingiverse here: http://www.thingiverse.com/thing:336517 Print two of these and they fit between the camera body and both nose cone and fin sections.

  • Dick Stafford

    Dan, this is an awesome design! I was wondering if the base of the fin unit was large enough to accommodate a 29mm hole (or 24mm?). I’d be interesting in using the fin section and nose cone in a model rocketry application. TIA, Dick

    • http://kkhausman.com/ Kalani K. Hausman

      @Dick Stafford,
      The fin unit’s three screws are mounted roughly 3.5cm apart, so a central hole should fit in the center while leaving enough plastic to retain the screws when installed.

  • Joe Dues

    I love the projectile and after printing, it gave me an excuse to build a big pneumatic gun. Here is the video of some test launches:

    It’s been dry and so I haven’t launched my GoPro yet – hopefully we’ll get some rain soon to soften up the field!

    • Studio M

      Joe: Can you say more about your cannon design? That’s unique.

  • Mike

    Is there somewhere I can have this printed that won’t cost me an arm and a leg? I don’t currently have access to a 3d printer.

  • C Bandy, Sr

    I just became aware of Make about a week a go. Our library is offering free 3-D printing for a while. I subscribed to Make today with the intent to download this file. How do I do it? Where is it located? Is there special software needed? Thanks for your help.

    • http://kkhausman.com/ Kalani K. Hausman

      @C Brandy, I am glad to hear your library has started supporting 3D Printing and Maker efforts – I work with several to get the same types of programs started, and can tell you that MAKE is an excellent resource for your participants – young and older. The files (STL format for 3D Printing) are available in the build directions (http://cdn.makezine.com/make/39/cannoncam-3d-files-new.zip) and can be created using your own 3D Printer or online using a service like Shapeways or iMaterialize if you didn’t have the necessary equipment. The software to prepare each file to print may be included with your printer (MakerWare for MakerBot printers, etc) or may be downloaded (Repetier or Pronterface) from online sources. Design of files and modifications to the existing files can be done using free applications like TinkerCAD (in-browser) or SketchUp easily. I am teaching those skills in the AggieSTEM summer camps at Texas A&M University right now in fact.

  • Alex

    Cannon cam? with Led lampen is cool too

  • andy tackett

    Did the clockwork parachute work,and do you have those files?

  • Utility Engineer

    would it be possible to attach multiple camera modules so you could have 360 degree coverage?