Make Physics Fun With A Trebuchet

What goes up must come down. And what goes way, way up can come down way, way too fast to survive the sudden stop. That’s why [Tom Stanton] built an altitude recording projectile into an oversized golf ball with parachute-controlled descent. Oh, and there’s a trebuchet too.

That’s a lot to unpack, but suffice it to say, all this stems from [Tom]’s obvious appreciation for physics. Where most of us would be satisfied with tossing a ball into the air and estimating the height to solve the classic kinematic equations from Physics 101, [Tom] decided that more extreme means were needed.

Having a compound trebuchet close at hand, a few simple mods were all it took to launch projectiles more or less straight up. The first payload was to be rocket-shaped, but that proved difficult to launch. So [Tom] 3D-printed an upsized golf ball and packed it with electronics to record the details of its brief ballistic flight. Aside from an altimeter, there’s a small servo controlled by an Arduino and an accelerometer. The servo retracts a pin holding the two halves of the ball together, allowing a parachute to deploy and return the package safely to Earth. The video below shows some pretty exciting launches, the best of which reached over 60 meters high.

The skies in the field behind [Tom]’s house are an exciting place. Between flying supercapacitors, reaction wheel drones, and low-altitude ISS flybys, there’s always something going on up there.

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A Very, Very Small IMU

The reason we’re playing with quadcopters, flight controllers, motion controlled toys, and hundreds of other doodads is the MEMS revolution. A lot is possible with tiny accelerometers and gyroscopes, and this is looking like the smallest IMU yet. It’s an 18mm diameter IMU, with RF networking, C/C++ libraries, and a 48MHz ARM microcontroller – perfect for the smallest, most capable quadcopter we’ve ever seen.

The build started off as an extension of the IMUduino, an extremely small rectangular board that’s based on the ATMega32u4. While the IMUduino would be great for tracking position and orientation over Bluetooth, it’s still 4cm small. The Femtoduino cuts this down to an 18mm circle, just about the right size to stuff in a model rocket or plane.

Right now, femtoIO is running a very reasonable Kickstarter for the beta editions of these boards with a $500 goal. The boards themselves are a little pricey, but that’s what you get with 9-DOF IMUs and altimeter/temperature sensors.

The Ultimate Tiny Altimeter

altimeter

While traditionally a project geared more toward the model rocket crowd, a lot of people are flying quadcopters these days, and knowing the altitude your RC aircraft reached is a nice thing to know. [Will] came up with a very nice, very small, and very lightweight altimeter that’s perfect for strapping to microquads, their bigger brothers, and of course model rockets. As a nice bonus, it also looks really cool with an exceedingly retro HP bubble display.

The components used in this tiny altimeter include a MEMS altitude and pressure sensor, HP bubble display featuring four seven-segment LEDs, an Arduino Pro Mini, and a tiny 40 mAh LiPo capable of powering the whole contraption for hours.

In the video below, [Will] shows off the functions of his altimeter, sending it aloft on a quadcopter to about 100 ft. There are settings for displaying the minimum, maximum, and delta altitudes, all accessed with a single button.

While it’s not the most feature packed altimeter out there, it’s still much better than commercial offerings available for the model rocket crowd.

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