bicycles

2 Articles

PLA Gears Fail To Fail In 3D Printed Bicycle Drivetrain

October 10, 2025 by 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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Anti-Lock Brakes For Bike Might Make Rides A Little Safer

February 17, 2019 by 59 Comments

Crashing one’s bike is a childhood rite of passage, one that can teach valuable lessons in applied physics. Assuming the kid is properly protected and the crash is fairly tame, scrapes and bruises are exchanged for the wisdom to avoid sand and gravel patches, and how to avoid a ballistic dismount by not applying the front brakes harder than or before the rear brakes.

But for many of us, those lessons were learned long ago using a body far more flexible than the version we’re currently in, and the stakes are higher for a bike ride that includes braking mistakes. To help with that, [Tom Stanton] has been working on anti-lock brakes for bicycles, and in the process he’s learned a lot about the physics and engineering of controlled deceleration.

It seems a simple concept – use a sensor to detect when a wheel is slipping due to decreased friction between the tire and the roadway, and release braking force repeatedly through an actuator to allow the driver or rider to maintain control while stopping. But that abstracts away a ton of detail, which [Tom] quickly got bogged down in. With a photosensor on the front wheel and a stepper motor to override brake lever inputs, he was able to modulate the braking force, but not with the responsiveness needed to maintain control. Several iterations later, [Tom] hit on the right combination of sensors, actuators, and algorithms to make a decent bike ABS system. The video below has all the details of the build and testing.

[Tom] admits bike ABS isn’t much of an innovation. We even covered an Arduino-instrumented bike that was to be an ABS testbed a few years back. But it’s still cool to see how much goes into anti-lock systems.

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