HobbyKing Cheetah: Building Running Robots from Hobby Motors

[Ben Katz] is building a running robot from hobby level brushless motors, all on his blog under the tag, “HobbyKing Cheetah.

One of the features of fancy modern industrial motor and controller sets is the ability for the motor to act as a mass-spring-damper. For example, let’s say you want a robot to hold an egg. You could have it move to the closed position, but tell the controller you only want to use so much force to do it. It will hold the egg as if there was a spring at its joint.

Another way you could use this is in the application of a robot leg. You tell the controller what kind of spring and shock absorber (damper) combination it is and it will behave as if those parts have been added to the mechanism. This is important if you want a mechanical leg to behave like a biological leg.

[Ben] had worked on a more formal project which used some very expensive geared motors to build a little running robot. It looks absolutely ridiculous, as you can see in the following video, but it gives an idea of where he’s going with this line of research. He wanted to see if he could replace all those giant geared motors with the cheap and ubiquitous high performance brushless DC motors for sale now. Especially given his experience with them.

So far he’s done a very impressive amount of work. He’s built a control board. He’s characterized different motors for the application.  He’s written a lot of cool software; he can even change the stiffness and damping settings on the fly. He has a single leg that can jump. It’s cool. He’s taking a hiatus from the project, but he’ll be right back at it soon. We’re excited for the updates!

Boost Around Town with This 3D Printed Bicycle Assist

[MechEngineerMike]’s bike boost is just a pleasure to look at, and, we’re certain, a relief to use. While it’s not going to rocket you down the street, it will certainly take some of the pain away. (Just like the professionals!)

It’s one thing to design a device that can fit one bicycle. It’s quite another feat if it can support multiple frames. On top of that, it’s even simple. It attaches at one point and transfers the power to the wheel easily. There’s even just one wire to connect, an RCA cable, to engage the boost.

We really like the clever way [Mike] used the rotating shell of an outrunner motor as the surface that presses against the wheel. We wonder if a cast polyurethane rubber tire for the motor would help, or just help overheat the motor?

The parts for the device are 3D printed and pretty chunky. They should hold up. Check out the video of it boosting [Mike] to the grocery store, where he can, presumably, buy less with all the calories he saved after the break.

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Strandmaus, Small R/C Strandbeest

[Jeremy Cook] has been playing around with strandbeests for a while, but never had one that walked until he put a motor on it and made it R/C controlled.

These remote controlled strandbeests can’t be too heavy or they have trouble moving. He didn’t want to get too complicated, either. [Jeremy] decided his first idea – hacking a cheap R/C car – wouldn’t work. The motors and AA batteries in these cars are just too heavy. Then he realized he had a broken quadcopter lying around. The motors were all burnt out, but the battery, controller, and driver board still works. On a hunch, he hooked up beefier motors to the front and left rotor control, and found that it worked just fine.

The rest of the work was just coupling it to the mechanism. The mechanism is made of wood and metal tubes. [Jeremy] found that the strandmaus had a tendency to fall down. He figures that’s why the original strandbeests had so many legs.

For his next iteration he wants to try to make it more stable, but for now he’s just having fun seeing his little legged contraption scoot around the floor. Video after the break.

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Hand Gestures Drive Car

There are a number of ways to control an automobile without using the pedals, and sometimes even without using the steering wheel. Most commonly these alternative control mechanisms are installed in vehicles whose owners are disabled in some way, but [Anurag] has taken this idea of alternative control one step further. He has built a car that can be driven by hand gestures alone.

On a remote controlled car, a Raspberry Pi 2 was installed that handles processing and communication. A wireless network is created on the Pi, and a laptop connects to the Pi over the network. The web camera on the laptop regularly captures frames at 15 fps to check for the driver’s hand gestures. The image is converted to gray scale, thresholded, contours are obtained, and the centroid and farthest points are obtained.

After some calculations are done, a movement decision is taken. The decision is passed to the Pi, which in turn, passed that to the internal chip of the car. All of the code is available on the project’s github page. [Anurag] hopes that this can be scaled up to full sized cars in the future. We’ve seen gesture-based remote controls before that rely on Sonar sensors, so it’s interesting to see one that relies strictly on image processing.

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Automating RC Motor Efficiency Testing

Small brushless motors and LiPo batteries are one of the most impressive bits of technology popularized in recent years. Just a few years ago, RC aircraft were powered by either anemic brushed motors or gas. Quadcopters were rare. Now, with brushless motors, flying has never been easier, building electric longboards is simple, and electric bicycles are common.

Of course, if you’re going to make anything fly with a brushless motor, you’ll probably want to know the efficiency of your motor and prop setup. That’s the idea behind [Michal]’s Automated RC Motor Efficiency Tester, his entry to the 2016 Hackaday Prize.

[Michal]’s project is not a dynamometer, the device you should use if you’re measuring the torque or power of a motor. That’s not really what you want if you’re testing brushless motors and prop configurations, anyway; similarly sized props can have very different thrust profiles. Instead of building a dyno for a brushless motor, [Michal] is simply testing the thrust of a motor and prop combination.

The device is very similar to a device sold at Hobby King, and includes a motor mount, microcontroller and display, and a force sensor to graph the thrust generated by a motor and prop. Data can be saved to an SD card, and the device can be connected to a computer for automatic generation of pretty graphs.

Brushless motors are finding a lot of uses in everything from RC planes and quadcopters, to robotics and personal transportation devices. You usually don’t get much of a data sheet with these motors, so any device that can test these motors will be very useful.

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The Ultimate 1:1 BB-8 Build Guide

BB-8 is not only a cute little droid but also presents dandy of a challenge for hackers ’round the globe to try and recreate in the garage. Nonfunctional models are a dime a dozen and the novelty has long worn off the Sphero toy. This brings us to a legit full-scale BB-8, seen in action in the video after the break.

Lucky for us, [Ed Zarick] has written up a blog post that’s as impressive as the build itself. [Ed] has drawn some inspiration and shared knowledge from several online groups focused around recreating the BB-8. He also provides some thorough Solidworks assemblies that look painfully detailed.

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Fire Breathing Animatronic Waterfowl, Just Because

Unless you’re a collector or a hunter, waterfowl decoys are pretty boring. Radio controlled decoys that can putt around are kind of cool. But a radio controlled animatronic fire-breathing decoy? That’s the very opposite of boring.

This is another one of those projects from the “Why the Hell Not?” files, and [David Windestål] is pretty clear that there’s no practical purpose for a flame-throwing, floating fowl. This doesn’t stop him from including 100-plus pictures as well as the video below in his detailed build log, and there are actually some tips to be had here. The remains of an RC racing boat that can hit 30 km/h are used for the floating gear; sadly the decoy superstructure reduces the speed by a factor of 10, so if you’re hoping for a high-performance decoy you’ll be disappointed. The rotating head and evil glowing LED eyes make up for that, though, as does the articulated beak. But the butane flame thrower, with laser-cut acrylic frame and servo flow control, really adds to the menace of the Duck from Hell. Or goose. Whatever.

As with most projects of this type, this is clearly a “do not try this at home” build, but it looks like a bunch of fun. For more ill-advised fun check out this mini RC flame thrower or the Doof warrior ukulele.

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