Rocketry Video utilizing a Strap-on Camera Mount
Amateur rocketry is great fun! 5-4-3-2-1 Launch! The motor ignites, the rocket accelerates upward toward the sky and it's soon well out of sight hundreds, if not thousands, of feet into the air. For a great many rocketry enthusiasts, this would be enough; however, I soon found myself pining to see what I could not — the view from the rocket's point of view. I found numerous on-board rocketry videos on YouTube made by other amateur rocketeers which prompted me to want to try my hand at doing the same. If you too should have an interest in video documentation of your own amateur rocket's flights, read on.The first thing, obviously, is that you will need an appropriate camera. My criteria were: Small, so that it could be mounted inside or affixed to the outside of a rocket without drastically affecting the stability of the rocket; Lightweight, so that it didn't dramatically affect the overall flight performance of a rocket; Relatively inexpensive, so that if there was a CATO or if the rocket should lawn dart taking out the camera, there wouldn't be a great monetary loss. Any camera I'd purchase would, of course, also need to also be Mac OSX or Linux compatible. I searched around for small, lightweight, and inexpensive digital video gear for some time. After searching the internet for several possible options, I came across what appeared to be a suitable item on eBay. It was described as a Mini USB spy camera and its price was only $9.99. It seemed it was worth giving it a try for a meager $10 plus its shipping charge from China.
When the camera arrived, I made a few test videos with it — not rocket videos — to check out its video quality. For $0, the video quality was quite impressive.
For my inaugural rocket video, I my plan was to attach this camera on-board my Estes Nike Smoke which can be launched on F and G class APCP propellant motors. This rocket stands close to 4 feet tall and it has a three (3) inch diameter airframe. I could have followed the lead of other video rocketeers by simply taping the camera to the rocket's airframe but I didn't want to ruin my rocket's finish; especially, after having spent countless hours sanding, painting, clear-coating and polishing it to achieve its mirror gloss finish. I decided that I'd fashion some sort of removable strap mount to hold the camera to the rocket; thus, allowing the camera to be easily attached and detached. I possess a large roll of 1.5 inch wide adhesive backed Velcro which came to mind immediately for use as a possible solution. However, I needed the adhesive backing only for affixing the Velcro to the camera. What I now needed was a band of Velcro that could wrap around the rocket's airframe. I set out to locate an already fabricated Velcro strap.
An internet search quickly landed a couple of possible leads for a suitable Velcro strap. One of the possible sources was, of all places, Walmart. I almost never frequent the local Walmart but, because I wanted to get this project completed, I made an exception. There, I found a package with two, 36 inch long, Velcro cinch straps. 3 feet was much longer than I needed but I figured I could fashion a shorter, more suitable, strap from these two longer straps.
Because the Estes Nike Smoke airframe is three (3) inches in diameter, I would need about 9.5 (3" • Π ≈ 9.5") inches of strap to encircle its airframe. I added an additional 6 inches to fold back over the camera and for Velcro adhesion, and one inch to wrap around the plastic loop buckle. I cut the length needed from the tapered end of the strap and cut the rest of the strap free from the plastic loop buckle. I then fastened the plastic loop buckle to the shortened strap with two-part 5-minute epoxy adhesive. The resultant strap is shown below.
The following two images depict the mounting of the camera using the aforementioned mounting strap. The first image is the strap wrapped around the Estes Nike Smoke with the camera affixed to the strap via adhesive Velcro strips. There is a cap which covers the camera's USB connector. There's a small strip of adhesive Velco on it as well; thus, allowing the cap to be removed but it also insures that the cap is secured when the camera is attached.
The photo below is showing the strap's 6 inch excess pulled back taught over the camera and attached to the Velcro strap itself.
The YouTube video featured below shows the camera being mounted to the Estes Nike Smoke with the fashioned Velcro cinch strap camera mounting strap as well as a full flight video aboard my Estes Nike Smoke. I can also be seen setting up communications with my Jolly Logic AltimeterThree — which I will discuss in another blog — in the video. Enjoy!
Post Scriptum
Attaching a camera to a rocket will affect both its CG (center of gravity) and its CP (center of pressure). To achieve a stable flight, the rocket's CG must be ahead of the rocket's CP. I have not done the aerodynamic mathematics to compute the CP contribution of the camera attached with its Velcro mounting strap but I would conclude that its contribution to the overall CP is relatively minor. However, the camera and its Velcro mounting strap do have mass; therefore, to minimize any affects on flight performance, I'd suggest that it be placed on the rocket forward of its known CG. This will move the overall CG forward maintaining the rocket's overall stability. This is why, in the video, so much of the rocket's airframe is seen. The only other way to address the CP/CG concern would be to add additional weight to the nosecone end of the rocket. I'm seeking to document altitude flights; therefore, the addition of nosecone mass would limit altitude achievement.
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