3D Printing RC Airplanes that Fly: An Engineer’s Chronicle

In the past, creating accurate replicas of models and fantasy objects was a task left to the most talented of cosplayers. These props need not be functional, though. [Steve Johnstone] takes replica model-building to the next step. He’s designing and building a model airplane that flies, and he’s documenting every step of the way.

Armed with a variety of 3D printing techniques and years of model-building experience, [Steve] is taking the lid off a number of previously undocumented techniques, many of which are especially relevant to the model-builder equipped with a 3D printer in the workshop.

As he continues his video log, [Steve] takes you through each detail, evaluating the quality of both his tools and techniques. How does a Makerbot, a Formlabs, and a Shapeways print stand up against being used in the target application? [Steve] evaluates a number of his turbine prints with a rigorous variable-controlled test setup.

How can we predict the plane’s center-of-gravity before committing to a physical design? [Steve] discusses related design decisions with an in-depth exploration of his CAD design, modeled down to the battery-pack wires. Though he’s not entirely finished, [Steve’s] work serves as a great chance to “dive into the mind of the engineer,” a rare opportunity when we usually discover a project after it’s been sealed from the outside.

3D printing functional parts with hobbyist-grade printers is still a rare sight, though we’ve seen a few pleasant and surprisingly practical components. With some tips from [Steve], we may complete this video journey with a few techniques that bump us out of the “novelty” realm and into a space where we too can start reliably printing functional parts. We’re looking forward to seeing the maiden voyage.

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Tiny R/C P-51D Mustang Tips the Scales at 3 Grams

Commercial R/C aircraft have been getting smaller and smaller with each passing year. In the early 2000’s, a palm-sized plane or helicopter was the dream of many an R/C enthusiast. Today, you can pick them up for around $20 USD at the local mall. The smallest models however, are still built by an elite group of modelers. Weighing in at a mere 3 grams, [Martin Newell’s] P-51D mustang model certainly puts him into that group. While the P-51’s 11.6 cm wingspan may not make it the smallest plane in the world, its many functions make it incredible.

The Mustang is an 8 channel affair, with elevator, throttle, rudder, ailerons, flaps, navigation lights, working retracts, and flashing cannon lights. That’s Wright, we did say retracts, as in retractable landing gear on a 3 gram model.

All the Mustang’s flight surfaces feature fully proportional control. However, there are no closed loop servos involved. The flight surfaces use magnetic actuators, consisting of a tiny neodymium magnet surrounded by a coil of magnet wire. We’re not sure if the signals to these actuators is straight PWM or if [Martin] is varying the frequency, but the system works. The retracts use heat-sensitive Nitinol “muscle wire” along with a bellcrank system to make sure the landing gear is up and locked after takeoff, and comes down again before a landing.

We don’t have any in-flight video of the Mustang, but we do have footage of an even smaller 1.2 gram plane [Martin] has been flying lately. Click past the break to check it out!

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A Remote Control, Swing Wing F-14

Anyone can build a remote control airplane with a sheet of foam, some glue, and a handful of servos. Building an F-14, complete with the swing wing mechanism? [Thomas] found built one that’ll take you right into the danger zone.

This was [Thomas]’ first go at scratch building a RC airplane, and wanted a lot of electronics inside. His choice of airframe was the venerable F-14 Tomcat, complete with wings that swing out for landing and swing in for high-speed flight. This isn’t just taking off-the-shelf receivers and putting them in a fancy airframe, either: [Thomas\ is reading the PWM signals from the receiver with a small electronics board, mixing the elevons with his own code, and implementing an auto stabilization system with an accelerometer.

Most of the work on the airframe was done by [Maybz] over on the RCGroups forums. That’s an impressive thread spanning seven years of posts. [Thomas] doesn’t see his F-14 as an end goal, though: he’s using this as a stepping stone to learn about building unstable planes for a more complex UAV.

Videos below, with a warning to headphone users.

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Controlling a Quadcopter with Gestures

[grassjelly] has been hard at work building a wearable device that uses gestures to control quadcopter motion. The goal of the project is to design a controller that allows the user to intuitively control the motion of a quadcopter. Based on the demonstration video below, we’d say they hit the nail on the head. The controller runs off an Arduino Pro Mini-5v powered by two small coin cell batteries. It contains an accelerometer and an ultrasonic distance sensor.

The controller allows the quadcopter to mimic the orientation of the user’s hand. The user holds their hand out in front of them, parallel to the floor. When the hand is tilted in any direction, the quadcopter copies the motion and will tilt the same way. The amount of pitch and roll is limited by software, likely preventing the user from over-correcting and crashing the machine. The user can also raise or lower their hand to control the altitude of the copter.

[grassjelly] has made all of the code and schematics available via github.

Mechanical Bird Actually Flies by Flapping its Wings

Turns out you don’t have to be a multi-million dollar corporation like Festo to create a remote controlled, flapping bird robot. [Kazuhiko Kakuta] is a medical Doctor of Allergy, and in his free time he likes to build flying mechanical birds with his son.

It has just over a meter wingspan, weighs 193 grams, and it flies by flapping its wings. The majority of its components are 3D printed. If that’s not impressive enough for you as is, consider this. It it has no sensors, no gyroscopes or anything — it’s all manually controlled by [Kazuhiko].

And this isn’t even the only ornithopter he’s done. He’s also created something out of an anime film, Castle in the Sky. He even sells the designs for one of them, to be printed via Shapeways.

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Extrinsic Motivation: Smart Antenna Tracker for R/C Aircraft

Long distance FPV (First Person View) flying can be a handful. Keeping a video feed alive generally requires a high gain directional antenna. Going directional creates the chore of keeping the antenna pointed at the aircraft. [Brandon’s] smart antenna tracker is designed to do all that automatically. What witchcraft is this, you ask? The answer is actually quite simple: Telemetry! Many flight control systems have an optional telemetry transmitter. [Brandon] is using the 3DRobotics APM or PixHawk systems, which use 3DR’s 915 MHz radios.

The airborne radio sends telemetry data, including aircraft latitude and longitude down to a ground station. Equipped with a receiver for this data and a GPS of its own, the smart antenna tracker knows the exact position, heading and velocity of the aircraft. Using a pan and tilt mount, the smart antenna tracker can then point the antenna directly at the airborne system. Since the FPV antenna is co-located on the pan tilt mount, it will also point at the aircraft and maintain a good video link.

One of the gotchas with a system like this is dealing with an aircraft that is flying directly overhead. The plane or rotorcraft can fly by faster than the antenna system can move. There are a few commercial systems out there that handle this by switching to a lower gain omnidirectional whip antenna when the aircraft is close in. This would be a great addition to [Brandon’s] design.

THP Entry: The Everything RC Transmitter

OSRC With few exceptions, most of The Hackaday Prize are things we really haven’t seen much of before: base-3 computers that have been relegated to the history books, extremely odd 3D printers, and fancy, new IoT devices are the norm. The OSRC is not a new project to us. (UPDATE: Looks like they deleted their project page. Here is a snapshot of it from the Internet Archive) We saw it once in 2011 and again a year later. What makes the OSRC an interesting project for The Hackaday Prize isn’t the fact that it’s the most advanced RC transmitter ever created. Creating that was evidently the easy part. The OSRC could use a big financial kick in the pants, and if [Demetris] wins, we’d guess he wouldn’t be taking that ride to space. Rather, he’d be taking the cash prize to get his ultimate transmitter into large-scale manufacturing and out into the wild.

While at first glance the base model OSRC seems expensive at about $6-700 USD, consider this: a six-channel transmitter from an excellent brand costs about $120 USD. Nine channels will run you about $400. The OSRC is a forty channel radio. The sticks are capable of force feedback, and of course the ‘pro’ model of the OSRC has that wonderful screen, capable of displaying video from an FPV camera, a GPS/map overlay, or an incredibly extensive telemetry display. There are multi-thousand dollar avionics for real airplanes out there that have a smaller feature set, and that’s not hyperbole.

A few months ago, [Demetris] was interviewed by the awesome people at Flite Test. That (highly suggested) video is embedded below.

SpaceWrencherThe project featured in this post is an entry in The Hackaday Prize. Build something awesome and win a trip to space or hundreds of other prizes.

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