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241 Articles

R/C Whirlygig Is Terrifyingly Unstable

February 6, 2019 by 10 Comments

In the days during and immediately after World War II, aerospace research was a forefront consideration for national security. All manner of wild designs were explored as nation states attempted to gain the upper hand in the struggle for survival. The Hiller Hornet was one such craft built during this time – a helicopter which drove the rotor through tip-mounted ramjets. Unsurprisingly, this configuration had plenty of drawbacks which prevented it from ever reaching full production. The team at [FliteTest] had a soft spot for the craft, however, and used it to inspire their latest radio controlled experiment.

Initial experiments consisted of a modified foam wing from a model seaplane, with two left wings facing opposite directions, and joined in the middle. Two motors and props were fitted to the wings to provide rotational motion. After some initial vibration issues were solved, the improvised craft generated barely enough lift to get off the ground. Other problems were faced with centripetal forces tearing the propellers off the wing due to the high rotational speeds involved.

A second attempt started from scratch, with a four wing setup being used, with much higher camber, with the intention to generate more lift with a more aggressive airfoil, allowing rotational speeds to be decreased. The craft was capable of getting off the ground, but instabilities likened to the pendulum rocket fallacy prevented any major gain in altitude.

We’d love to see a redesign to solve some of the issues and allow the craft to sail higher into the air. If you think you know the solution to the whirly bird’s dynamic problems, be sure to let us know in the comments. It should be possible, as we’ve seen successful designs inspired by maple seeds before. Video after the break.

[Thanks to Baldpower for the tip!]

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The Design And Construction Of A Tribute To A Bomber Pilot

February 5, 2019 by 11 Comments

Decades ago, [wilmracer]’s grandfather was piloting a B-17 over the Rhine, and as it goes, aviation runs in families. Now, more than 70 years later [wilmracer] is deep, deep into remote controlled aircraft, and he’s building an exacting scale model of the B-17G his grandfather flew on his last bombing mission over Europe.

This is a scratch build, with the design taken directly from the plans and schematics of a B-17. [wilmracer] has already paid the money to go up in the preserved B-17 Aluminum Overcast to get a better idea of the layout, and now he’s deep into cutting foam and bending balsa sheets. The first part of the build was arguably the hardest, and the main landing gear was expertly constructed out of aluminum tube and linear servos. The horizontal stab follows traditional building techniques of foam and carefully sanded balsa sheets. The fuselage is impressive, with the formers built out of foam, and eventually covered in 1/16″ balsa and wrapped in fiberglass.

If you’re going to do a large-scale model airplane, that also means you’ve got to do detailing. That means steam gauges rendered in 3D printed parts. [wilmracer] is modeling the cockpit and the machine guns in 1:9 scale. This is going to be an awesome build, and yes, there will eventually be plans.

Of course, this isn’t the biggest small B-17 ever built. That record goes to the 1:3 scale Bally Bomber, a real, not remote controlled plane built over the course of two decades by [ Jack Bally]. This is a real plane with a 34 foot wingspan that weighs 1800 pounds. Yes, it flies, and it went to Oshkosh last summer. Remote control really is the way to go with something like this, though: you can appease the rivet counters, put more power on the props, and you don’t need to worry too much about pesky things like regulations and laws. We’re looking forward to see where this project goes, and to the sound of a great PLA overcast thundering over the treetops.

Brushless R/C Rocket Tests Different Flight Regimes

January 25, 2019 by 31 Comments

Quadcopters are familiar, and remote control planes are old hat at this point. However, compact lightweight power systems and electronic flight controllers continue to make new flying vehicles possible. In that vein, [rctestflight] has been experimenting with a brushless electric rocket craft, with interesting results. (Youtube, embedded below.)

The build uses a single large brushless motor in the tail for primary thrust. Four movable vanes provide thrust vectoring capability. To supplement this control a quadcopter was gutted, and its motors rearranged in the nose of the craft to create a secondary set of thrusters which aid stabilization and maneuverability.

The aim is to experiment with a flight regime consisting of vertical takeoff followed by coasting horizontally before returning to a vertical orientation for landing. Preliminary results have been positive, though it was noted that the body of the aircraft is significantly reducing the available thrust from the motors.

It’s a creative design which recalls the SpaceX vertical landing rockets of recent times. We’re excited to see where this project leads, and as we’ve seen before – brushless power can make just about anything fly. Even chocolate. Video after the break.

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Radio Control Buggy Gets V10 Power

January 12, 2019 by 12 Comments

Amongst the more difficult machining tasks in the world are those involved in the production of internal combustion engines. Thanks to the Internet, it’s now possible to watch detailed videos of master craftsmen assembling tiny desktop V8 and V12 engines in home workshops with barely a CNC in sight. However, up until now, most of these builds have been left on the test stand to bark and wail away. No longer – [Keith] has decided that needs to change.

We’ve seen [Keith]’s work before – particularly, his 125cc V10 build, featuring fuel injection, dual overhead cams, and even a supercharger. With several micro engines under his belt now, it was time to put them to work – the V10 is getting a new home in a 1/3rd scale RC buggy.

We’re not sure [Keith] has heard the phrase “off the shelf” – even the suspension dampers on this build are custom machined. Currently up to part 5, the chassis is coming together and there are plans for a hybrid powertrain, too. Carbon fiber and anodized parts are in abundance – this build is truly a work of art.

We can’t wait to see this V10 monster tearing up the dirt – It’s an ambitious build, but if anyone can pull it off, it’s [Keith]. Video after the break.

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RC Controller Becomes XInput Controller

January 5, 2019 by 4 Comments

XInput is an API that is used by applications to interface with the Xbox 360 Controller for Windows. The 360 controller became somewhat of a “standard” PC gamepad, and thus many games and applications support the XInput standard.

[James] is working on an entry for a robotics competition, and wanted a controller to use with their PC that was more suited to their build. They took an RC controller, and converted it to work with XInput instead.

The controller in question is the JJRC Q35-01, a trigger-type RC controller available for under $20. The conversion is executed neatly, with the original STM microcontroller being removed from the board, and the PCB traces instead being connected to a Teensy 3.5 which takes over running the show.

The conversion is remarkably complete, with the team not stopping at just reading the buttons and steering potentiometer. A USB logic analyzer was used to figure out how to control the LCD, and a calibration mode implemented just in case.

[James] has shared the work on Github so it’s reproducible for the average maker. We’ve seen plenty of builds in this space, like this tilt controller from [Electronoobs]. Video after the break.

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Fail Of The Week: Hard Lessons In 3D-Printed Bushings For A Giant RC Car

December 25, 2018 by 18 Comments

Can you turn 47 pounds (21 kg) of PLA filament into a gigantic working 3D-printed RC car? No, no you can’t — at least not if you eschew proper bearings in favor of printed bushings.

That’s the hard lesson that [Joel Telling] learned with his scaled up version of the OpenRC F1 car, an RC car that can be mostly 3D-printed. The small version still has its share of non-printed parts, mainly screws and bearings. In his video series documenting the build of the upsized version, [Joel] elaborates on some of the reasons for going with printed bushings rather than bearings, which mainly boil down to hoping that the graphite lubricant powder he added would reduce friction enough to prevent the parts from welding themselves together.

The car came out looking great, and even managed to scoot about nicely for a few seconds before its predictably noisy and unhappy demise. But what was unexpected was the actual failure mode. The plastic-on-plastic running gear seemed to handle the rolling loads fine; it was the lateral force exerted on the axle by the tension of the drive belt that was too much for the printed bushing to bear.

As [Joel] rightly points out, it’s only a failure if you fail to learn something, so kudos to him for at least giving this a try. And all that PLA won’t go to waste, of course — everything else on the car worked fine, so adding one bearing should get it back on the road. He should check out our primer on bearings for a few tips on selecting the right one.

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Go Up A Creek Without A Paddle

December 4, 2018 by 31 Comments

Kayaks are a some of the most versatile watercraft around. You can fish from them, go on backpacking trips, or just cruise around your local lake for a few hours. They’re inexpensive, lightweight, don’t require fuel, and typically don’t require a license or insurance to operate. They also make a great platform for a solar-powered boat like this one with only 150 watts of panels and a custom-built motor with parts from an RC airplane.

[William Frasier] built his solar-powered kayak using three solar panels, two mounted across the bow of the boat using pontoons to keep them from dipping into the water, and the other mounted aft. Separating the panels like this helps to prevent all three of them being shaded at once when passing under bridges. They’re all wired in parallel to a 12V custom-built motor which is an accomplishment in itself. It uses custom-turned parts from teak, a rot-resistant wood, is housed in an aluminum enclosure, and uses an RC airplane propeller for propulsion.

Without using the paddles and under full sun, the kayak can propel itself at about 4 knots (7 kmh) which is comparable to a kayak being propelled by a human with a paddle. With a battery, some of the shading problems could be eliminated, and adding an autopilot to it would make it almost 100% autonomous.

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