Home-made transportation is a thriving area for makers to flex their skills. Looking to shorten their university commute, [doublecloverleaf] modded his penny board by adding a motor that can have him zipping along at 40 Km/h!
The electric motor is mounted to the rear truck and delivers power to the wheel gear using a HTD 5 m pulley belt. Finding the deck too flexible to mount the battery pack under, [doublecloverleaf] strengthened it with a pair of carbon-fiber tubes bracketed on the underside. A few custom PCB boards connect ten 5 Ah LiPo battery cells in series to create two, five-cell packs which are kept safe by a thick housing mounted between the board’s trucks. [doublecloverleaf] calculates that they could make up to a 15 km trip on a single charge.
This collaboration between ETH and the Disney empire’s research arm is a ultra-light robot that can roll across horizontal surfaces and also transition and climb walls.
The robot has four wheels with one steerable set, but its secret sauce is the two propellers gimbaled on its back. Using these propellers it can move itself across the ground, but also, when approaching a wall, provide enough thrust to overcome the gravity vector.
Naturally, the lighter the robot, the less force will be needed to keep it on the wall. That’s why the frame is made from carbon fiber corrugated sandwich panels. The motors, batteries, and controllers are all also light and small.
We liked how the robot was, apparently, using its propellers to provide additional stability even while on the ground. There is a video after the break, and more information can also be found on the Disney Research webpage.
Don’t let the friendly smile on this RC cart fool you, it will take your strawberries away — though that’s kinda the point. It’s an RC car that [transistor-man] and a few friends modified for carrying freshly picked strawberries at strawberry fields so that you don’t have to.
They started with an older Traxxas Emaxx, a 4-wheel drive RC monster truck. The team also bought a suitable sized water cooler at a local hardware store. A quick load test showed that 5lbs collapsed the springs and shock absorbers, causing the chassis to sink close to the ground. The team had two options: switching to stronger springs or locking out the springs altogether. They decided to replace one set of shocks with metal plates effectively locking them. After that it was time for some CAD work, followed by the use of a water jet to cut some aluminum plate. They soon had a mounting plate for the water cooler to sit in. This mounting plate was attached to 4 posts which originally held the vehicle’s Lexan body. A bungee cord wrapped around the cooler and posts on the mounting plate holds the cooler in place.
Some initial testing showed that the vehicle moved too fast even in low gear and tended to tip over, as you can see in the first video below. Some practice helped but a 3:1 reduction planetary gearbox brought the vehicle down to walking speed, making a big difference. A trip was arranged to go to local strawberry picking field at Red Fire Farms, but not without some excitement first. At 1AM the UNIK 320A High Voltage Speed controller emitted some magic smoke. A quick check with a thermal-camera found the culprit, one of the MOSFETs had failed, and after swapping it with one that was close enough they were back in business.
As you can see in the second video below, testing in the strawberry field went very well, though it wasn’t without some tipping. Kids also found it a fun diversion from picking strawberries, alternating between mock fright and delight.
[ossum] had a stack of Amazon and Shapeways credits lying around after winning a few competitions. He had this dream of building an R/C car for a while, and decided now was the time. After ordering all the needed parts from Amazon, he made an extremely nice model of the car in Fusion 360. The CAD model is a great learning resource. If you want to learn how to use reference photos, parts, and more to build a detailed and useful CAD model we recommend downloading it as a Fusion archive and scrubbing through the timeline to see how he did it.
Some of the parts were sent off for laser cutting. Others were 3D printed. The rest he made himself. Thanks to his model, they all went together well. You can see his R/C rod racing in the video after the break.
BB-8 is the much loved new droid introduced in the 2016 movie Star Wars: The Force Awakens, though in my case from the very first trailer released in 2014 I liked it for the interesting engineering problems it posed. How would you make a robot that’s a ball that rolls along, but with a head that stays on top while the ball rolls under it?
BB-8 in 1st Star Wars: The Force Awakens trailer
Hamster in hamster wheel
To make the ball roll, the answer most people found obvious at first was to use the analogy of a hamster wheel. The hamster running inside makes the wheel turn. In the BB-8 building world, which is quite large, the drive mechanism has come to be called a hamster drive, or just a hamster.
For the head, it seemed obvious that there would be magnets inside the ball, perhaps held in place near the top of the ball by a post extending up from the hamster. Corresponding magnets in attraction would then be attached to the underside of the head, and balls (also mounted under the head) would keep the head moving smoothly over the ball.
The magnet approach for the head has turned out to be the method used by all BB-8 builders that I’ve seen. However, the hamster has turned out to be only one of multiple solutions. Since the original debut many different methods have been used in builds and we’re going to have a lot of fun looking at each separate approach. It’s almost like revealing a magic trick; but really it’s all just clever engineering.
Note that for the actual movie, a combination of 7 or 8 props and CGI were used. The official working BB-8s that are shown at various promotional events were built after the movie was made and as of this writing, few details of their construction have been released. One notable detail, however, is that they aren’t using hamster drives.
Below are details of all the different BB-8 drive systems I’ve seen so far that have been built along with how they work.
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!
[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.