3D Printed RC Jet Boat Gets Up To Speed

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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Hard Drive Gives Its Life to Cool 3D Prints

[Mark Rehorst] has been on the hunt for the perfect 3D printer cooling fan and his latest take is a really interesting design. He’s printed an impeller and housing, completing the fan using a hard drive motor to make it spin.

We should take a step back to see where this all began. Many 3D printers us a cooling fan right at the tip of the extruder because the faster you faster you cool the extruded filament, the fewer problems you’ll have with drooping and warping. Often this is done with a small brushless fan mounted right on the print head. But that adds mass to the moving head, contributing to problems like overshoot and oscillation, especially on larger format printers that have longer gantries. [Mark] just happens to have an enormous printer we covered back in January and that’s the machine this fan targets.

CPAP fan and duct tubing

Make sure you give [Mark’s] Mother of all print cooling fans article a look. His plan is to move the fan off of the print head and route a flexible tube instead. He tried a couple of fans, settling on one he pulled from a CPAP machine (yes the thing you wear at night to combat sleep apnea) found in the parts bin at Milwaukee Makerspace. It works great, moving quite a bit more air than necessary. The problem is these CPAP parts aren’t necessarily easy to source.

You know what is easy to source? Old hard drives. [Mark] mentions you likely have one sitting around and if not, your friends do. We have to agree with him. Assuming you already have a 3D printer (why else do you want to print this fan?), the only rare part in this mix is the ESC to make the motor spin. Turns out we just saw a BLDC driver build that would do the trick. But in [Mark’s] case he found a rather affordable driver that suits his needs which is used in the video demo below.

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3000W Unicycle’s Only Limitation Is “Personal Courage”

Electric vehicles are fertile ground for innovation because the availability of suitable motors, controllers, and power sources makes experimentation accessible even to hobbyists. Even so, [John Dingley] has been working on such vehicles since about 2009, and his latest self-balancing electric unicycle really raises the bar by multiple notches. It sports a monstrous 3000 Watt brushless hub motor intended for an electric motorcycle, and [John] was able to add numerous touches such as voice feedback and 1950’s styling using surplus aircraft and motorcycle parts. To steer, the frame changes shape slightly with help of the handlebars to allow the driver’s center of gravity to shift towards one or the other outer rims of the wheel. In a test drive at a deserted beach, [John] tells us that the bike never went above 20% power; the device’s limitations are entirely by personal courage. Watch the video of the test, embedded below.

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A Faster Grave Digger For Your Child

Children love speed, but so few of those electric ride on toys deliver it. What’s a kid to do? Well, if [PoppaFixit]’s your dad, you’re in luck.

This project starts with an unusually cool Power Wheels toy, based on the famous Grave Digger monster truck. During the modification process, it was quickly realised that the original motor controller wasn’t going to cut the mustard. With only basic on/off control, it gave a very jerky ride and was harsh on the transmission components, too. [PoppaFixit] decided to upgrade to an off-the-shelf 24 V motor controller to give the car more finesse as well as speed. The controller came with a replacement set of pedals, both accelerator and brake, to replace the stock units. On the motor side, a couple of beefier Traxxas units were substituted for the weedy originals.

Acceleration is now much improved, not just due to the added power, but because the variable throttle allows the driver to avoid wheelspin on hard launches. It also makes the car much more comfortable and safe to drive, thanks to the added controllability. Another way to tell the project was a success is the look of pure joy on the new owner’s face!

This was a fairly basic install, very accessible to the novice. These sort of electric vehicle hop-ups are commonplace enough that there are a wide variety of suppliers who sell easy-to-use kits for this sort of work. For that reason, we’ve seen plenty of hacks of this sort – like this modified scooter, or these Power Wheels set up for racing.

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How Current Shunts Work

Current. Too little of it, and you can’t get where you’re going, too much and your hardware’s on fire. In many projects, it’s desirable to know just how much current is being drawn, and even more desirable to limit it to avoid catastrophic destruction. The humble current shunt is an excellent way to do just that.

Ohm’s Law.

To understand current, it’s important to understand Ohm’s Law, which defines the relationship between current, voltage, and resistance. If we know two out of the three, we can calculate the unknown. This is the underlying principle behind the current shunt. A current flows through a resistor, and the voltage drop across the resistor is measured. If the resistance also is known, the current can be calculated with the equation I=V/R.

This simple fact can be used to great effect. As an example, consider a microcontroller used to control a DC motor with a transistor controlled by a PWM output. A known resistance is placed inline with the motor and, the voltage drop across it measured with the onboard analog-to-digital converter. With a few lines of code, it’s simple for the microcontroller to calculate the current flowing to the motor. Armed with this knowledge, code can be crafted to limit the motor current draw for such purposes as avoiding overheating the motor, or to protect the drive transistors from failure.

In fact, such strategies can be used in a wide variety of applications. In microcontroller projects you can measure as many currents as you have spare ADC channels and time. Whether you’re driving high power LEDs or trying to build protection into a power supply, current shunts are key to doing this.

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Here’s Why Hoverboard Motors Might Belong In Robots

[madcowswe] starts by pointing out that the entire premise of ODrive (an open-source brushless motor driver board) is to make use of inexpensive brushless motors in industrial-type applications. This usually means using hobby electric aircraft motors, but robotic applications sometimes need more torque than those motors can provide. Adding a gearbox is one option, but there is another: so-called “hoverboard” motors are common and offer a frankly outstanding torque-to-price ratio.

A teardown showed that the necessary mechanical and electrical interfacing look to be worth a try, so prototyping has begun. These motors are really designed for spinning a tire on the ground instead of driving other loads, but [madcowswe] believes that by adding an encoder and the right fixtures, these motors could form the basis of an excellent robot arm. The ODrive project was a contender for the 2016 Hackaday Prize and we can’t wait to see where this ends up.

Gorgeous Engineering Inside Wheels of a Robotic Trail Buddy

Robots are great in general, and [taylor] is currently working on something a bit unusual: a 3D printed explorer robot to autonomously follow outdoor trails, named Rover. Rover is still under development, and [taylor] recently completed the drive system and body designs, all shared via OnShape.

Rover has 3D printed 4.3:1 reduction planetary gearboxes embedded into each wheel, with off the shelf bearings and brushless motors. A Raspberry Pi sits in the driver’s seat, and the goal is to use a version of NVIDA’s TrailNet framework for GPS-free navigation of paths. As a result, [taylor] hopes to end up with a robotic “trail buddy” that can be made with off-the-shelf components and 3D printed parts.

Moving the motors and gearboxes into the wheels themselves makes for a very small main body to the robot, and it’s more than a bit strange to see the wheel spinning opposite to the wheel’s hub. Check out the video showcasing the latest development of the wheels, embedded below.

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