[Ivan Miranda] is always experimenting with 3D printing, and recently has been taking his work on the water. His latest creation is a racing paddle boat, but its performance left [Ivan] with a need for speed. Cue the development of the 3D printed water jet engine (YouTube link, embedded below).
The basic principle of operation is simple. Water is sucked through an inlet, where it is accelerated by a turbine driven by a brushless motor. This turbine, in combination with stator fins, forces the water through the outlet, propelling the boat forwards in the process.
The first prototype is printed in PLA. Tolerances are good, thanks largely to [Ivan]’s experience and well-calibrated printers. After assembly, the engine is fired up, to great results. After sourcing a series of larger tubs in which to test the device, the engine is finally run up to full throttle and appears more than capable of shifting a serious amount of water.
We’d love to see a proper instrumented thrust test, particularly one that compares the device to other water jet drives on the market. Brushless motors make a great drive solution for RC boats, so we’re sure [Ivan] will be tearing up the lake real soon. Video after the break.
Continue reading “3D Printing A Water Jet Drive”
[Adam Zeloof] (legally) obtained a retired electric scooter and documented how it worked and how he got it working again. The scooter had a past life as a pay-to-ride electric vehicle and “$1 TO START” is still visible on the grip tape. It could be paid for and unlocked with a smartphone app, but [Adam] wasn’t interested in doing that just to ride his new scooter.
His report includes lots of teardown photos, as well as a rundown of how the whole thing works. Most of the important parts are in the steering column and handlebars. These house the battery, electronic speed controller (ESC), and charging circuitry. The green box attached to the front houses a board that [Adam] determined runs Android and is responsible for network connectivity over the cellular network.
To get the scooter running again, [Adam] and his brother [Sam] considered reverse-engineering the communications between the network box and the scooter’s controller, but in the end opted to simply replace the necessary parts with ones under their direct control. One ESC, charger, and cheap battery monitor later the scooter had all it needed to ride again. With parts for a wide variety of electric scooters readily available online, there was really no need to reverse-engineer anything.
Ridesharing scooter startups are busy working out engineering and security questions like how best to turn electric scooters into a) IoT-connected devices, and b) a viable business plan. Hardware gets revised, and as [Adam] shows, retired units can be pressed into private service with just a little work.
The motors in these things are housed within the wheels, and have frankly outstanding price-to-torque ratios. We’ve seen them mated to open-source controllers and explored for use in robotics.
Some ideas are real head-scratchers from a design standpoint: Why in the world would you do it that way? For many of us, answering that question often requires a teardown, which is what [Ben Katz] did when this PCB motor-powered weed whacker came across his bench. The results are instructive on what it takes to succeed in the marketplace, or in this case, how to fail.
The unit in question comes from an outfit called CORE Outdoor Power. The line trimmer was powered by a big lithium-ion battery pack, but [Ben] concentrated on the unique motor for his teardown. After a problematic entry into the very sturdy case at the far end of the trimmer’s shaft, he found what looks like a souped-up version of [Carl Bugeja]’s PCB brushless motors. The rotors, each with eight large magnets embedded, are sandwiched on either side of a very thick four-layer PCB with intricately etched heavy copper traces. The PCB forms the stator, with four flat coils. The designer pulled a neat trick with the Hall-effect sensors needed for feedback; rather than go with surface-mount sensors, which would add to the thickness of the board, they used through-hole packages soldered to surface pads, with the body of the sensor nestled in a hole in the board. The whole design is very innovative, but sadly, [Ben]’s analysis shows that it has poor performance for its size and weight.
Google around a bit and you’ll see that CORE was purchased some years back by MTD, a big player in the internal combustion engine outdoor power market. They don’t appear to be a going concern anymore, and it looks as though [Ben] has discovered why.
[Jozef] tipped us off to this one. Thanks!
Betteridge’s Law holds that any headline that ends in a question mark can be answered with a “No.” We’re not sure that [Mr. Betteridge] was exactly correct, though, since 3D-printed stators can work successfully for BLDC motors, for certain values of success.
It’s not that [GreatScott!] isn’t aware that 3D-printed motors are a thing; after all, the video below mentions the giant Halbach array motor we featured some time ago. But part of advancing the state of the art is to replicate someone else’s results, so that’s essentially what [Scott!] attempted to do here. It also builds on his recent experiments with rewinding commercial BLDCs to turn them into generators. His first step is to recreate the stator of his motor as a printable part. It’s easy enough to recreate the stator’s shape, and even to print it using Proto-pasta iron-infused PLA filament. But that doesn’t come close to replicating the magnetic properties of a proper stator laminated from stamped iron pieces. Motors using the printed stators worked, but they were very low torque, refusing to turn with even minimal loading. There were thermal issues, too, which might have been mitigated by a fan.
So not a stunning success, but still an interesting experiment. And seeing the layers in the printed stators gives us an idea: perhaps a dual-extruder printer could alternate between plain PLA and the magnetic stuff, in an attempt to replicate the laminations of a standard stator. This might help limit eddy currents and manage heating a bit better. Continue reading “Can You 3D-Print a Stator for a Brushless DC Motor?”
Electric vehicles of all types are quickly hitting the market as people realize how inexpensive they can be to operate compared to traditional modes of transportation. From cars and trucks, to smaller vehicles such as bicycles and even electric boats, there’s a lot to be said for simplicity, ease of use, and efficiency. But sometimes we need a little bit more out of our electric vehicles than the obvious benefits they come with. Enter the electric drift trike, an electric vehicle built solely for the enjoyment of high torque electric motors.
This tricycle is built with some serious power behind it. [austiwawa] constructed his own 48V 18Ah battery with lithium ion cells and initially put a hub motor on the front wheel of the trike. When commenters complained that he could do better, he scrapped the front hub motor for a 1500W brushless water-cooled DC motor driving the rear wheels. To put that in perspective, electric bikes in Europe are typically capped at 250W and in the US at 750W. With that much power available, this trike can do some serious drifting, and has a top speed of nearly 50 kph. [austiwawa] did blow out a large number of motor controllers, but was finally able to obtain a beefier one which could handle the intense power requirements of this tricycle.
Be sure to check out the video below to see the trike being test driven. The build video is also worth a view for the attention to detail and high quality of this build. If you want to build your own but don’t want to build something this menacing, we have also seen electric bikes that are small enough to ride down hallways in various buildings, but still fast enough to retain an appropriate level of danger.
Continue reading “Electric Drift Trike Needs Water Cooling”
If you have a brushless motor, you have some magnets, a bunch of coils arranged in a circle, and theoretically, all the parts you need to build a rotary encoder. A lot of people have used brushless or stepper motors as rotary encoders, but they all seem to do it by using the motor as a generator and looking at the phases and voltages. For their Hackaday Prize project, [besenyeim] is doing it differently: they’re using motors as coupled inductors, and it looks like this is a viable way to turn a motor into an encoder.
The experimental setup for this project is a Blue Pill microcontroller based on the STM32F103. This, combined with a set of half-bridges used to drive the motor, are really the only thing needed to both spin the motor and detect where the motor is. The circuit works by using six digital outputs to drive the high and low sided of the half-bridges, and three analog inputs used as feedback. The resulting waveform graph looks like three weird stairsteps that are out of phase with each other, and with the right processing, that’s enough to detect the position of the motor.
Right now, the project is aiming to send a command over serial to a microcontroller and have the motor spin to a specific position. No, it’s not a completely closed-loop control scheme for turning a motor, but it’s actually not that bad. Future work is going to turn these motors into haptic feedback controllers, although we’re sure there are a few Raspberry Pi robots out there that would love odometry in the motor. You can check out a video of this setup in action below.
Continue reading “Using Motors As Encoders”
Remote control boats can be great fun, and come in all manner of forms. There are unpowered sailcraft, speedboats that scream under the power of internal combustion, and of course, those that move under electric power. The brushless motor revolution of the past 20 years in particular has proven capable of creating some exciting RC watercraft, and [Matt K] decided he wanted to get on board.
[Matt] had owned a Kyosho Jetstream 1000 for several years, but found the nitro engine to be temperamental and not the most fun for high-jinx down at the lake. An old-school brushed motor setup with mechanical speed control similarly failed to excite. However, after experiencing the power of brushless in RC planes, [Matt] knew what he had to do.
Using an online calculator, [Matt] determined that his earlier nitro powerplant was putting out roughly 900 watts. When it came to going brushless, he decided to spec a Turnigy powerplant with twice as much power, along with the requisite speed controller. There was some work to do to integrate the new motor with the original propeller driveshaft and water cooling system, but in the end [Matt] ended up with a much faster boat that is a lot less hassle to set up and run.
Perhaps though, your RC boat needs brains, over brawn? Perhaps it’s time to look at autonomy…
Video after the break.
Continue reading “RC Boat Goes Brushless For Speed & Reliability”