Custom Hybrid Drivetrain Powers Boat

June 28, 2026 by Bryan Cockfield 17 Comments

Offloading acceleration and braking to an electric motor in a hybrid configuration allows the less efficient combustion engine run in a more narrow set of RPM and torque ranges. In some cases the motor is decoupled from the mechanical drivetrain entirely and used simply as a generator, where it can run at a single speed all the time. And this concept isn’t limited to passenger vehicles, either. [rctestflight] put this premise to the test using a small knockoff Honda motor as a generator for an electric boat.

This project builds on a previous version where he used a much smaller hobby motor to see if it could generate usable power, and that system powered a small autonomous boat as a proof-of-concept. Those motors aren’t really designed to be used in this sort of application though, so this build upgrades the internal combustion engine and pairs it with an electric skateboard motor that’s configured to run as a generator. The setup is capable of producing almost 800 watts for as long as the gasoline lasts, provided that the 3D printed parts all hold together and the other parts don’t vibrate off of the assembly.

Out on the lake at full throttle, the small generator can get the boat up to seven knots (13 kph) but at this speed [rctestflight] reports that the generator is “quite unpleasant” due to the noise and vibration. Instead, he ran it on a test bench at several RPM and torque points and documented the efficiency of the motor at each one, and then operated the boat mostly at the point he found it to be most efficient. For a hybrid drivetrain, that not only decreases noise and vibration, but also maintenance and fuel efficiency.

Although the energy density of fossil fuels is much better than batteries, a fuel-free long-distance option is still available if you’d rather equip your boat with solar panels instead.

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Building The Most Simple Motor In Mostly LEGO

February 14, 2026 by Maya Posch 13 Comments

Although [Jamie’s Brick Jams] has made many far more complicated motor design in the past, it’s nice to go back to the basics and make a motor that uses as few parts as possible. This particular design starts off with a driver coil and a magnetic rotor that uses two neodymium magnets. By balancing these magnets on both sides of an axis just right it should spin smoothly.

The circuit for the simple motor. (Credit: Jamie's Brick Jams, YouTube) — The circuit for the simple motor. (Credit: Jamie’s Brick Jams, YouTube)

First this driver coil is energized with a 9 V battery to confirm that it does in fact spin when briefly applying power, though this means that you need to constantly apply pulses of power to make it keep spinning. To this end a second coil is added, which senses when a magnet passes by.

This sense coil is connected to a small circuit containing a TIP31C NPN power transistor and a LED. While the transistor is probably overkill here, it’ll definitely work. The circuit is shown in the image, with the transistor pins from left to right being Base-Collector-Emitter. This means that the sensor coil being triggered by a passing magnet turns the transistor on for a brief moment, which sends a surge of power through the driver coil, thus pushing the rotor in a typical kicker configuration.

Obviously, the polarity matters here, so switching the leads of one of the coils may be needed if it doesn’t want to spin. The LED is technically optional as well, but it provides an indicator of activity. From this basic design a larger LEGO motor is also built that contains many more magnets in a disc along with two circular coils, but even the first version turns out to be more than powerful enough to drive a little car around.

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Finding A Way To Produce Powerful Motors Without Rare Earths

January 13, 2026 by Zoe Skyforest 40 Comments

The electric vehicle revolution has created market forces to drive all sorts of innovations. Battery technology has progressed at a rapid pace, and engineers have developed ways to charge vehicles at ever more breakneck rates. Similarly, electric motors have become more powerful and more compact, delivering greater performance than ever before.

In the latter case, while modern EV motors are very capable things, they’re also reliant on materials that are increasingly hard to come by. Most specifically, it’s the rare earth materials that make their magnets so good. The vast majority of these minerals come from China, with trade woes and geopolitics making it difficult to get them at any sort of reasonable price. Thus has sprung up a new market force, pushing engineers to search for new ways to make their motors compact, efficient, and powerful.

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A Deep Drive Deep Dive Into A Twin-Rotor Motor

December 9, 2025 by Tyler August 45 Comments

Compromise is key to keeping a team humming along. Say one person wants an inrunner electric motor, and the other prefers outrunner. What to do? Well, if you work at [Deep Drive], the compromise position is a dual-rotor setup that they claim can be up to 20% more efficient than standard designs. In a recent video, [Ziroth] provides a deep dive into Deep Drive’s Twin-Rotor Motor.

This is specifically a radial flux permanent magnet motor, like most used in electric vehicles today — and don’t let talk of inrunners and outrunners fool you, that’s the size of motor we’re talking about here. This has been done before with axial flux motors, but it’s a new concept for team radial. As the names imply, the difference is the direction the magnetic field is orientated: axial flux motors have all the magnetism oriented along the axis, which leads to the short wide profile that inspired the nickname “pancake motors”. For various reasons, you’re more likely to see those on a PCB than in an electric car.

In a radial flux motor, the flux goes out the radius, so the coils and magnets are aligned around the shaft of the motor. Usually, the coils are held by an iron armature that directs their magnetic flux inwards (or outwards) at the permanent magnets in the rotor, but not here. By deleting the metal armature from their design and putting magnets on both sides of the stator coil, Deep Drive claims to have built a motor that is lighter and provides more torque, while also being more energy-efficient.

Of course you can’t use magnet wire if your coil is self-supporting, so instead they’re using hefty chunks of copper that could moonlight as busbars. In spite of needing magnets on both inner and outer rotors, the company says they require no more rare-earths than their competitors. We’re not sure if that is true for the copper content, though. To make the torque, those windings are beefy.

Still, its inspiring to see engineers continue to innovate in a space that many would have written off as fully-optimized. We look forward to seeing these motors in upcoming electric cars, but more than that, hope they sell a smaller unit for an air compressor so after going on a Deep Drive deep dive we can inflate our rubber raft with their twin rotor motor boater bloater. If it works as well as advertised, we might have to become twin-rotor motor boater bloater gloaters!

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This Rail Speeder Needs A Little Work

September 16, 2025 by Jenny List 30 Comments

If you take the wheels off a FIAT Punto, you might just notice that those rims fit nicely on a rail. [AT Lab] did, and the resulting build makes for a very watchable video.

Some of us have been known to spend a little too much time chasing trains, and there’s little on rails that won’t catch a railfan’s eye. That goes for rail speeders too, home constructed railcarts for exploring abandoned lines, and there are some great builds out there. We like the one in the video below the break, but we can’t help noticing a flaw which might just curtail its career.

It’s a simple enough build, a wooden chassis, a single motor and chain drive to one axle. All the wheel fittings are 3D printed, which might be a case of using the one tool you have to do everything, but seems to work. It rides well on the test track which appears to be an abandoned industrial siding, but it’s in those wheels we can see the problem and we guess that perhaps the builder is not familiar with rails. The Punto wheels have an inner rim and an outer rim, while a true rail wheel only has an inner one. There’s a good reason for this; real railways have points and other trackwork, not to mention recessed rails at road crossings or the like. We love the cart, but we’d cut those inner rims off to avoid painful derailments.

If you’re up for the ultimate railway build, take care not to go near a live line, and make sure you follow this video series.

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A photo for a motor and a meter on a bench.

Let’s Brief You On Recent Developments For Electrostatic Motors

August 20, 2025 by John Elliot V 28 Comments

Over on his YouTube channel [Ryan Inis] has a video about how electrostatic motors are breaking all the rules.

He explains that these days most motors are electromagnetic but suggests that may be changing as the age-old principles of electrostatics are being explored again, particularly due to the limited supply of rare-earth magnets and other materials (such as copper and steel) which are used in many electromagnetic motors.

[Ryan] says that new electrostatic motors could be the answer for highly efficient and economical motors. Conventional electromagnetic motors pass current through copper windings which create magnetic fields which are forces which can turn a rotor. The rotor generally has permanent magnets attached which are moved by the changing magnetic forces. These electromagnetic motors typically use low voltage and high current.

Electrostatic alternatives are actually an older design, dating back to the 1740s with the work of Benjamin Franklin and Andrew Gordon. These electrostatic motors generate motion through the attraction and repulsion of high voltage electric charges and demand lower current than electromagnetic motors. The high voltages involved create practical problems for engineers who need to harness this energy safely without leading to shocks or sparks or such.

[Ryan] goes on to discuss particular electrostatic motor designs and how they can deliver higher torque with lower energy losses due to friction and heat making them desirable for various applications, particularly industrial applications which demand low speed and high torque. He explains the function of the rotor and stator and says that these types of motors use 90% less copper than their electromagnetic alternatives, also no electrical steel and no permanent magnets.

For more coverage on electrostatic motors check out Electrostatic Motors Are Making A Comeback.

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Building The Feynman Motor That Fits Through A Sewing Needle’s Eye

January 27, 2025 by Maya Posch 19 Comments

The first attempt at replicating William McLellan's miniature motor. (Credit: Chronova Engineering, YouTube) — The first attempt at replicating William McLellan’s miniature motor. (Credit: Chronova Engineering, YouTube)

How small can an electric motor be without resorting to manufacturing methods like lithography? In a recent video, [Chronova Engineering] on YouTube tries to replicate the 1960 McLellan motor that fulfilled [Richard Feynman]’s challenge requirements. This challenge was part of [Feynman]’s 1959 lecture titled There’s Plenty of Room at the Bottom, on the possibilities of miniaturization. A $1,000 reward was offered for anyone who could build an electric motor that was no larger than 1/64th inch cubed (~0.0625 mm³), with the expectation that new manufacturing methods would be required to manufacture a motor this small.

As reported in the December 1960 issue of The Month at Caltech, [William McLellan] walked into [Feynman]’s lab with this tiny marvel that took him 2.5 months of lunch hour breaks to build. Weighing in at 250 micrograms and consisting out of 13 parts, it was constructed using a microscope, a watchmaker’s lathe and a toothpick. Surely replicating this feat would be easy today, right?

The main challenge is that everything is incredibly small. The rotor shaft is 90 micrometers in diameter, and the four coils require winding incredibly thin wire at scales where typical manufacturing methods do not apply. Suffice it to say that it takes massive amounts of patience, creativity and the best (stereo) microscope you can get, yet even with modern optics and materials this first attempt mostly failed.

At the end we’re left with SEM shots of this replication attempt and an immense amount of respect for the skills of [William McLellan] who made a working version in 1960 using much more basic tools during his lunch breaks.

Thanks to [J. Peterson] for the tip.

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