Using A Cheap DC Motor To Make A Go-Kart Go

November 4, 2026 by Maya Posch 8 Comments

Where Archimedes said that he could move the Earth given a large enough lever and a suitable fulcrum, [Current Concept] decided that he could give his own spin on this quote by swapping the lever and fulcrum for a tiny $1 DC brushed motor and a very large gearing ratio.

In addition to 3D printing a compound gearbox with the requisite 1,243:1 gear ratio, the video also covers the joys of getting a ‘Craigslist special’ go-kart for about the same price as the electric motor and having to undo many very special modifications.

With that done, the newly printed gearbox was installed, along with the single DC motor to drive it all. This actually managed to propel the go-kart, at a pace that would impress even a snail, so for the next phase instead of a single motor a total of fourteen were used, all adding their tiny bit of torque into the gearbox.

Although one has to keep in mind that the gearbox and chain mechanism will also take its slice of the provided energy along with other inefficiencies, one still cannot beat the laws of physics. Much like Archimedes’ lever powered by a piddly human, the conversion of RPM into torque for these small motors was never going to get you that zippy go-kart experience.

Which isn’t to say that someone shouldn’t totally put some BLDC motors to the task and see how fast a go-kart can be made to move using those and an optimized gearbox.

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PLA Gears Fail To Fail In 3D Printed Bicycle Drivetrain

October 10, 2025 by Tyler August 33 Comments

Anyone who has ever snapped a chain or a crank knows how much torque a bicycle’s power train has to absorb on a daily basis; it’s really more than one might naively expect. For that reason, [Well Done Tips]’s idea of 3D printing a gear chain from PLA did not seem like the most promising of hacks to us.

Contrary to expectations, though, it actually worked; at the end of the video (at about 13:25), he’s on camera going 20 km/h, which while not speedy, is faster than we thought the fixed gearing would hold up. The gears themselves, as you can see, are simple spurs, and were modeled in Fusion360 using a handy auto-magical gear tool. The idler gears are held in place by a steel bar he welded to the frame, and are rolling on good old-fashioned skateboard bearings–two each. (Steel ones, not 3D printed bearings.) The healthy width of the spur gears probably goes a long way to explaining how this contraption is able to survive the test ride.

The drive gear at the wheel is steel-reinforced by part of the donor bike’s cassette, as [Well Done Tips] recognized that the shallow splines on the freewheel hub were not exactly an ideal fit for PLA. He does complain of a squeaking noise during the test ride, and we can’t help but wonder if switching to helical gears might help with that. That or perhaps a bit of lubricant, as he’s currently riding the gears dry. (Given that he, too, expected them to break the moment his foot hit the pedal, we can’t hardly blame him not wanting to bother with grease.)

We’ve seen studies suggesting PLA might not be the best choice of plastic for this application; if this wasn’t just a fun hack for a YouTube video, we’d expect nylon would be his best bet. Even then, it’d still be a hack, not a reliable form of transportation. Good thing this isn’t reliable-transportation-a-day!

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3D Printed “Book” Demonstrates Mechanical Actions

September 24, 2025 by Tyler August 22 Comments

A book of mechanical actions is a wondrous thing — mechanically inclined children have lost collective decades pouring over them over the generations. What could possibly be better? Why, if the mechanisms in the book were present, and moved! That’s exactly what [AxelMadeIt] produced for a recent video.

Being just four pages, you might argue this is but a pamphlet. But since it takes up a couple inches of shelf space, it certainly looks like a book from the outside, which is exactly what [AxelMadeIt] was going for. To get a more book-like spine, his hinge design sacrificed opening flat, but since the pages are single-sided, that’s no great sacrifice.

At only 6 mm (1/4″) thick, finding printable mechanisms that could actually fit inside was quite a challenge. If he was machining everything out of brass, that would be room for oodles of layers. But [Axel] wanted to print the parts for this book, so the mechanisms need to be fairly thick. One page has a Roberts linkage and a vault-locking mechanism, another has planetary gears, with angled teeth to keep them from falling out. Finally, the first page has a geneva mechanism, and an escapement, both driven by a TPU belt drive.

All pages are driven from an electric motor that is buried in the last page of the “book”, along with its motor, battery, and a couple of micro-switches to turn it on when you open the book and off again when you reach the last page. Rather than a description of the mechanisms, like most books of mechanical actions, [Axel] used multi-material printing to put lovely poems on each page. A nice pro-tip is that “Futura”, a font made famous by flying to the moon, works very well when printed this way. If you just want to watch him flip through, jump to 8:00 in the video.

This reminds us of another project we once featured, which animated 2100 mechanical mechanisms. While this book can’t offer near that variety, it makes up for it in tactility.

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This Service Life Study Really Grinds Our Gears

July 17, 2025 by Tyler August 69 Comments

3D printing is arguably over-used in the maker community. It’s just so easy to run off a quick prototype and then… well, it’s good enough, right? Choosing the right plastic can go a long way to making sure your “good enough” prototype really is good enough for long term use. If you’re producing anything with gearing, you might want to cast your eyes to a study by [Mert Safak Tunalioglu] and [Bekir Volkan Agca] titled: Wear and Service Life of 3-D Printed Polymeric Gears.

Photograph of the test rig used in the study. — No spin doctoring here, spinning gears.

The authors printed simple test gears in ABS, PLA, and PETG, and built a test rig to run them at 900 rpm with a load of 1.5 Nm against a steel drive gear. The gears were pulled off and weighed every 10,000 rotations, and allowed to run to destruction, which occurred in the hundreds-of-thousands of rotations in each case. The verdict? Well, as you can tell from the image, it’s to use PETG.

The authors think that this is down to PETG’s ductility, so we would have liked to see a hard TPU added to the mix, to say nothing of the engineering filaments. On the other hand, this study was aimed at the most common plastics in the 3D printing world and also verified a theoretical model that can be applied to other polymers.

This tip was sent in by [Benjamin], who came across it as part of the research to build his first telescope, which we look forward to seeing. As he points out, it’s quite lucky for the rest of us that the U.S. government provides funding to make such basic research available, in a way his nation of France does not. All politics aside, we’re grateful both to receive your tips and for the generosity of the US taxpayer.

We’ve seen similar tests done by the community — like this one using worm gears — but it’s also neat to see how institutional science approaches the same problem. If you need oodles of cycles but not a lot of torque, maybe skip the spurs and print a magnetic gearbox. Alternatively you break out the grog and the sea shanties and print yourself a capstan.

Wire-frame image of gearbox, setup as a differential

Roller Gearbox Allows For New Angles In Robotics

May 22, 2025 by Ian Bos 18 Comments

DIY mechatronics always has some unique challenges when relying on simple tools. 3D printing enables some great abilities but high precision gearboxes are still a difficult problem for many. Answering this problem, [Sergei Mishin] has developed a very interesting gearbox solution based on a research paper looking into simple rollers instead of traditional gears. The unique attributes of the design come from the ability to have a compact angled gearbox similar to a bevel gearbox.

Multiple rollers rest on a simple shaft allowing each roller to have independent rotation. This is important because having a circular crown gear for angled transmission creates different rotation speeds. In [Sergei]’s testing, he found that his example gearbox could withstand 9 Nm with the actual adapter breaking before the gearbox showing decent strength.

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A chocolate coating machine works in the round to enrobe mint Oreos.

Chocolate-Coating Machine Mk. 2: The Merry-Go-Round

November 28, 2024 by Kristina Panos 17 Comments

This holiday season, [Chaz] wanted to continue his family’s tradition of enrobing a little bit of everything in dark chocolate, and built an improved, rotating chocolate-coating machine.

You may remember last year’s offering, aka the conveyor belt version. Although that one worked, too much chocolate was ultimately lost to the surface of the kitchen table. [Chaz] once again started with a standard chocolate fountain and bought a round wire rack that fits the circumference of the bowl at the bottom. He snipped a hole in the center large enough to accommodate the business part of the fountain and printed a collar with holes that he cleverly zip-tied to the rack.

[Chaz] also printed a large gear to go around the bowl, a small gear to attach to a six RPM motor, a motor mount for the bowl, and an air blade attachment for a portable Ryobi fan. The air blade worked quite well, doing the double duty of distributing the chocolate and thinning out the coating. Plus, it gives things a neat rumpled look on the top.

Want to make some special chocolates this year, but don’t want to build an enrober? Get yourself a diffraction grating and make some rainbow goodies with melted chocolate.

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Dispense 60 Bolts In 2.3 Seconds

March 21, 2023 by Michael Shaub 26 Comments

We’ve covered a number of projects that assist makers who need to fill orders for their small businesses, or kitting. [Helmke] has sorted thousands of pieces of hardware that they include with 3D printed parts sold online. They have been developing an alternative, a modular system for sorting and packaging specific quantities of parts.

After the break, check out the latest video from their small but growing channel for a very clear walk-through of the counting system they’ve been iterating on. The 2nd video in the series explores solenoids, Geneva drives, and ultimately a sprocket to dispense a variable number of bolts from the sorting machine. The approach gives consistent results, easily to vary quantities, and is fast! These videos are also rich with lots of small details you might want to explore on your own like magnetic part feeding, discussions of different sensors for detecting and counting parts, 3D printed gear box designs, and we love the use of stackable crates for project enclosures.

We hope to see more videos from [Helmke] in the series as the project matures for deeper dives into the existing mechanisms and new features they develop next. Hungry for more? We’ve brought you everything from cutting and stripping wire, to SMD tape, to resistors, to laser-cut parts. Continue reading “Dispense 60 Bolts In 2.3 Seconds” →