When professional engineers are giggling like kids, you know something interesting is about to happen. [Destin Sandlin] of [Smarter Every Day], [Jeremy Fielding], and a few other like-minded individuals have built a very impressive air cannon, capable of launching baseballs at supersonic velocities.
The muzzleloading canon consists of a large pressure chamber and vacuum chamber stuck together, with a plug and baseball separating the two. The barrel forms part of the vacuum chamber, and is sealed off at the muzzle end with plastic tape that ruptures when fired. The firing mechanism runs the entire length of the pressure chamber, exiting out the back where it is held in place by a large pneumatic sear mechanism. When the sear is released, it “pops the cork” between the two chambers, sending high-pressure nitrogen into the vacuum chamber, forcing the ball forward. This causes the plug rod to shoot out the back of the pressure chamber, where it is stopped by a pneumatic piston. The entire thing is permanently mounted on a trailer. A professional-looking control box is used to operate the beast from behind the safety of a steel blast shield.
Be sure to watch the videos after the break with subtitles turned on. The first is the highlights reel, and the second is a very entertaining hour-long behind the scenes look. To the surprise of the builders, they were able to shoot a baseball at Mach 1.38 (1050 mph or 1690 km/h) on the very first try, with only a partially pressurized system and a leaking vacuum chamber. When impacting the thick steel target, the ball disintegrates completely, imprinting its stitches on the target. [Destin] and co recorded the results with his usual high-speed cameras, but also included a Schlieren rig that allowed them to photograph the shock waves and Mach cones generated by the speeding ball. After a few shots, the bolts were stripped out of the pneumatic piston that stops the plug rod, which is no surprise judging by how much the steel frame flexes in that area. Continue reading “Making Baseballs Go Supersonic”→
Filming in slow-motion has long become a standard feature on the higher end of the smartphone spectrum, and can turn the most trivial physical activity into a majestic action shot to share on social media. It also unveils some little wonders of nature that are otherwise hidden to our eyes: the formation of a lightning flash during a thunderstorm, a hummingbird flapping its wings, or an avocado reaching that perfect moment of ripeness. Altogether, it’s a fun way of recording videos, and as [Robert Elder] shows, something you can do with a few dollars worth of Raspberry Pi equipment at a whopping rate of 660 FPS, if you can live with some limitations.
Taking the classic 24 FPS, this will turn a one-second video into a nearly half-minute long slo-mo-fest. To achieve such a frame rate in the first place, [Robert] uses [Hermann-SW]’s modified version of raspiraw to get raw image data straight from the camera sensor to the Pi’s memory, leaving all the heavy lifting of processing it into an actual video for after all the frames are retrieved. RAM size is of course one limiting factor for recording length, but memory bandwidth is the bigger problem, restricting the resolution to 64×640 pixels on the cheaper $6 camera model he uses. Yes, sixty-four pixels height — but hey, look at that super wide-screen aspect ratio!
Ski areas are setting formal policies for drones left and right, but what happens when your drone isn’t a drone but is instead a tethered iPhone with wings swinging around you like a ball-and-chain flail as you careen down a mountain? [nicvuignier] decided to explore the possibility of capturing bullet-time video of his ski runs by essentially swinging his phone around him on a tether. The phone is attached to a winged carrier of his own design, 3D printed in PLA.
One would think this would likely result in all kinds of disaster, but we haven’t seen the outtakes yet, and the making-of video has an interesting perspective on each of the challenges he encountered in perfecting the carrier, ranging from keeping it stable and upright, to reducing the motion sickness with the spinning perspective, and keeping it durable enough to withstand the harsh environment and protect the phone.
He has open sourced the design, which works for either iPhone or GoPro models, or it is available for preorder if you are worried about catastrophic delamination of your 3D printed model resulting in much more bullet-like projectile motion.
If you watch science fiction movies, the robots of the future look like us. The truth is, though, many tasks go better when robots don’t look like us. Sometimes they are unique to a particular job or sometimes it is useful to draw inspiration from something other than a human being. One professor at Johns Hopkins along with some students decided to look at spider crickets as an inspiration for a new breed of jumping robots.
The banner image above shows a bullet travelling through a set of matchsticks. [Destin] uses the sound of the gun firing to trigger the flash that captures the image. A piezeo transducer picks up the sound, triggering a precision pulse generator. That pulse generator then triggers the flash, adding a delay based on the settings. In this way, [Destin] can capture video by firing a bullet for each frame, but adjusting the delay period of the pulse generator to capture the image when the bullet is in a slightly different place from the previous frame. It’s an old technique, but after some post-processing it produces a high-quality output without sinking thousands of dollars into an actual high-speed camera. Check out the video we’ve embedded after the break.
Some researchers from Oxford University have come up with a way to produce high-speed video from a one mega-pixel camera. They’re calling the method Temporal Pixel Multiplexing. This method adds a digital micromirror device in line with the camera lens. These chips house over a million mirrors and can be found in home theater projectors. By placing one in front of the digital camera, a longer exposure can be used while the DMD redirects the light. This way, one high-resolution image actually contains multiple frames of lower-resolution video. The video is still decent quality and, at a far lower cost than common high-speed video equipment, this is a worthwhile trade off.