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24hz-water-camera-trick

From this still image you’d think the hose dispensing the water is being moved back and forth. But watch the video after the break and you’ll see the hose is quite steady, as is the standing wave of water. It’s bizarre to be sure. Knowing how it works makes cognitive sense, but doesn’t really diminish the novelty of the demonstration.

This is the second time [Brasspup] has posted a video of this phenomenon. The newest version does a great job of showing several different patterns. But even the first segment from a year ago, which has over 4 million hits, shows the water moving against gravity. We also saw a similar rig in a links post a year ago.

We’d call it an optical illusion but it’s really more of a technological illusion. The water is falling past a sub-woofer speaker which is tuned to 24 Hz. At the same time, the camera filming the demonstration is capturing 24 frames per second. As was mentioned then, it’s much like flashing a light to freeze the water in mid-air. But the flashing of the frames is what causes this effect.

 

 

via Hack a Day http://hackaday.com/2013/03/14/camera-trick-lets-you-see-sound-waves-in-falling-water/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+hackaday%2FLgoM+%28Hack+a+Day%29

x-post by Jered Higgins

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retrotechtacular-mechanical-computer

The device that these seamen are standing around is a US Navy targeting computer. It doesn’t use electricity, but relies on mechanical computing to adjust trajectories of the ship’s guns. Setting up to twenty-five different attributes by turning cranks and other input mechanisms lets the computer automatically calculate the gun settings necessary to hit a target. These parameters include speed and heading of both the ship and it’s target, wind speed and bearing, and the location of the target in relation to this ship. It boggles the mind to think of the complexity that went into this computer.

The first of this seven part series can be seen after the break. The collection covers shafts,  gears, cams, and differentials. Sounds like it would be quite boring to sit through, huh? But as we’ve come to expect from this style and vintage of training film it packs a remarkable number of simple demonstrations into the footage.

 

See all seven parts of the series

 

via Hack a Day http://hackaday.com/2013/03/13/retrotechtacular-mechanical-targeting-computers/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+hackaday%2FLgoM+%28Hack+a+Day%29

x-post by Jered Higgins