3D Printing A Water Jet Drive

April 30, 2019 by Lewin Day 16 Comments

[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.

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Brushless R/C Rocket Tests Different Flight Regimes

January 25, 2019 by Lewin Day 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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Designing Tiny Motors Right Into The Robot’s Circuit Board

January 1, 2019 by Mike Szczys 10 Comments

Motors are not overly complex, but this one is downright simple. Carl Bujega has been working on a motor design that heavily relies on the capabilities of the printed circuit board (PCB) fabrication processes. His talk at the 2018 Hackaday Superconference covers how he built a brushless DC motor and speed controller into a PCB. You can watch the newly published video after the break.

There are two main parts of an electric motor; the stator is stationary while the rotor spins on bearings. Electromagnetic forces are used to cause that spinning action. In this case, Carl has built the electromagnets as coils on a 4-layer circuit board (six coils on each layer). When electrified, a magnetic field is generated that pushes against the rare-earth magnets housed in the rotor.

A couple of things are really interesting here. First, those coils are usually made of “magnet wire” (enamel covered wire that is very thin) wrapped around an iron core. Using the circuit board instead saves both physical space, and the time and expense of wrapping coils of wire in the traditional way. Second, Carl has been designing with manufacture in mind; you can see in the image show that his motor design is dead-simple to assemble by inserting a 3mm bearing in the PCB, inserting magnets into the plastic rotor and snapping it into place. The end goal is to make robot actuators that are part of the circuit board itself.

The genesis of this idea came from Carl’s interest in drone design, in fact, he jumped right into a drone startup immediately after finishing his EE. The company didn’t last, but his thirst for interesting designs is ongoing. When looking at reducing the total parts necessary to build a quadcopter he happened on the idea of PCB-based coils and he’s followed it to this motor design, and beyond to some very interesting flexible-PCB robot design work which you can check out on his Hackaday.io page, YouTube, and Twitter.

There are of course some trade-offs to this. The motor is low torque since it uses an air core and not an iron core. And he’s had trouble implementing a sensor-less Electronic Speed Controller (ESC) as the back-EMF from the coils appears to be too weak. Not to fret, he added a hall sensor and has succeeded in designing an ESC that measures just 14mm by 8mm. In fact, he’s holding up the ESC and motor in the image at the top of this article!

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Brushless Motor Thrust Stand Provides Useful Data

December 16, 2018 by Lewin Day 16 Comments

When designing model aircraft of any shape or size, it’s useful to know the performance you can expect from the components chosen. For motors and propellers, this can be difficult. It’s always best to test them in combination. However, with the numbers of propeller and motor combinations possible, such data can be tough to come by. [Nikus] decided it would be easier to just do the testing in-house, and built a rig to do so.

The key component in this build is the strain gauge, which comes already laced up with an Arduino-compatible analog-digital converter module. Sourced for under $10 from Banggood, we can’t help but think that we’ve got it easy in 2018. A sturdy frame secures motor and propeller combination to the strain gauge assembly. An ATMEGA328 handles sending commands to the motor controller, reading the strain gauge results, and spitting out data to the LCD.

It’s a cheap and effective build that solves a tricky problem and would be a useful addition to the workshop for any serious modeler. We’ve seen other approaches in this area too, for those eager to graph their motor performance data. Video after the break.

[Thanks to Baldpower for the tip!]

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Using Motors As Encoders

September 13, 2018 by Brian Benchoff 8 Comments

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.

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3D Printed RC Jet Boat Gets Up To Speed

September 5, 2018 by Tom Nardi 9 Comments

In one of those weird twists of fate, there’s currently a very high chance that anyone who owns a 3D printer has made a boat with it. In fact, they’ve probably printed several of them, so many that they might even have a shelf filled with little boats in different colors and sizes. That’s because it’s a popular benchmark to make sure the printer is well calibrated. But if you’re going to spend hours printing out a boat, why not print one that’s got some punch?

This 3D printable jet boat designed by [Jotham B] probably isn’t a great print to check your desktop machine’s calibration on, in fact you’re going to want to make sure you’ve got everything dialed in before taking on this challenge. If the classic “Benchy” is the beginners boat, then this is certainly for the 3D printing veterans. But if you’ve got the skills to pull it off, and some RC gear laying around to outfit it with, this could be a great project to end your summer on.

Unless you’ve got an exceptionally tall printer, the 460mm long hull will need to be printed in several pieces and then grafted back together. You could potentially use glue, but something a bit more robust like welding the parts together with a soldering iron is a better bet to make sure your printed boat doesn’t do its best Titanic reenactment out on the lake.

[Jotham] recommends printing the impeller at 0.15mm layer height, as you’ll want all the detail you can muster to provide a smooth surface. You’ll also need to use supports, so expect to spend a fair bit of time cleaning it up post-print. The rest of the model can be printed at 0.3mm, which is going to save a lot of time on the hull. All told, it will take about half a roll of filament to print all the parts for the boat (assuming no mistakes), which puts the pre-electronics cost at around $10 USD.

Speaking of electronics, you’ll need a RC receiver, a servo for steering, an electronic speed controller (ESC), and a suitable motor. [Jotham] used a 3674 brushless motor with a 120A water-cooled ESC, but notes that the setup is way overpowered. In the video after the break you can see the boat spends as much time airborne as it does in the water, which might look cool, but isn’t exactly efficient.

If you want to round out your 3D PLA fleet, we’ve also seen a printed FPV lifeboat as well as a hydrofoil that “flies” through the water.

[Thanks to Aidan for the tip.]

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RC Boat Goes Brushless For Speed & Reliability

August 24, 2018 by Lewin Day 17 Comments

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.

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