Bicycle Adds Reliability With Second Chain

February 3, 2025 by Bryan Cockfield 70 Comments

Ignoring the International Cycling Union‘s mostly arbitrary rules for what a bicycle is “supposed” to look like (at least if you want to race), there are actually reasons that the bicycling world has standardized around a few common parts and designs. Especially regarding the drivetrain, almost all bikes use a chain, a freewheel, and a derailleur if there are gears to shift because these parts are cheap, reliable, and easy to repair. But if you’re off grid in a place like Africa, even the most reliable bikes won’t quite cut it. That’s why a group called World Bicycle Relief designed and built the Buffalo bicycle, and the latest adds a second gear with a unique freewheel.

Bicycling YouTuber [Berm Peak] takes us through the design of this bike in his latest video which is also linked below. The original Buffalo bicycle was extremely rugged and durable, with a rear rack designed to carry up to 200 pounds and everything on the bike able to be repaired with little more than an adjustable wrench. The new freewheel adds a second gear to the bike which makes it easier to use it in hilly terrain, but rather than add a complicated and hard-to-repair derailleur the freewheel adds a second chain instead, and the rider can shift between the two gears by pedaling backwards slightly and then re-engaging the pedals.

Of course a few compromises had to be made here. While the new freewheel is nearly as rugged as the old one, it’s slightly more complex. However, they can be changed quite easily with simple tools and are small, affordable, and easy to ship as well. The bike also had to abandon the original coaster brake, but the new rim brakes are a style that are also easy to repair and also meant that the bike got a wheel upgrade as well. Bicycles like these are incredibly important in places where cars are rare or unaffordable, or where large infrastructure needed to support them is unreliable or nonexistent. We’ve seen other examples of bicycles like these being put to work in places like India as well.

Thanks to [Keith] for the tip!

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An Atomic Pendulum Clock Accurate Enough For CERN

January 28, 2023 by Dan Maloney 31 Comments

That big grandfather clock in the library might be an impressive piece of mechanical ingenuity, and an even better example of fine cabinetry, but we’d expect that the accuracy of a pendulum timepiece would be limited to a sizable fraction of a minute per day. Unless, of course, you work at CERN and built “the most accurate pendulum clock on the planet.”

While we’re in no position to judge [Daniel Valuch]’s claim, we’re certainly inclined to believe him, mainly because the 1950s-era Czechoslovakian pendulum clock his project was based on, the Elektročas HH3, was built specifically as a master clock for labs, power plants, and broadcast use. The pendulum of this mid-century beauty is made of the alloy invar, selected for its exceptionally low coefficient of thermal expansion. This ensures the pendulum doesn’t change length with temperature, but it still only brings the clock into the 0.1 second/day range.

Clearly that’s not good enough for a clock at CERN, the European Laboratory for Nuclear Research, where [Daniel] works as an RF engineer. With access to a 10-MHz timebase from a cesium fountain atomic clock — no less a clock than the one that’s used to define the SI second, by the way — [Daniel] looked for ways to sync the clock up to it. Now, we know what you’re thinking — he must have used some kind of PLL to give an electromagnetic “kick” to the bob to trim the pendulum’s period. Good guess on the PLL, but the trimming method is a little cruder — [Daniel] uses a stepper motor attached to the clock’s frame to pay out or retract a length of fine chain into a cardboard dish attached to the pendulum’s rod. The change in mass changes the pendulum’s center of gravity, which changes its effective length, and allows the clock to be tuned a couple of seconds per day.

It seems like [Daniel] is claiming that his chain-corrected clock won’t drift more than a second from the cesium clock for 158 million years. Again, we’ll take his word for it, but it’s a wonderfully ad hoc approach to tuning the clock, and we appreciate its simplicity.

3D-Printable Sculpture Shows Off Unpredictable Order Of Chains

September 25, 2022 by Donald Papp 7 Comments

[davemoneysign] designed this fascinating roller chain kinetic sculpture, which creates tumbling and unpredictable patterns and shapes as long as the handle is turned; a surprisingly organic behavior considering the simplicity and rigidity of the parts.

3D-printed, with a satisfying assembly process.

The inspiration for this came from [Arthur Ganson]’s Machine With Roller Chain sculpture (video, embeded below). The original uses a metal chain and is motor-driven, but [davemoneysign] was inspired to create a desktop and hand-cranked manual version. This new version is entirely 3D-printed, and each of the pieces prints without supports.

According to [davemoneysign], the model works well with a chain of 36 links, but one could easily experiment with more or fewer and see how that changes the results. Perhaps with the addition of a motor this design could be adapted into something like this chains-and-sprockets clock?

You can see [Arthur Ganson]’s original in action in the video embedded below. It demonstrates very well the piece’s chaotic and unpredictable — yet oddly orderly — movement and shapes. Small wonder [davemoneysign] found inspiration in it.

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Quirky Complicated Clock Piques Constructor’s Curiosity

July 19, 2022 by Ryan Flowers 2 Comments

The Clock that served as inspiration for the garberPark Clock

Have you ever observed the project of another hacker and thought to yourself “I have got to have one of those!”? If so, you’re in good company with hacker [garberPark], the maker of the unusual chain clock seen in the video below the break.

While on a stroll past the Chicago Avenue Fire Arts Center in Minneapolis, MN, [garberPark] was transfixed by the clock seen to the right here. In the clock, two motors each drive a chain that has numbers attached to it, and the number at the top displays the current time. It wasn’t long before [garberPark] observed his own lack of such a clock. So they did what any hacker will do: they made their own version!

Using an ESP8266, and Arduino, and some other basic electronics, they put together a horizontal interpretation of the clock they saw. Rather than being continuous rotation, limit switches keep things in line while the ESP8266’s NTP keep things in time. Salvaged scanner stepper motors provide locomotion, and what appear to be bicycle cranks and chains work in harmony with cutoff license plates to display the current time- but only if there’s somebody around to observe it; A very nice touch and great attention to detail!

If you enjoyed this, you’ll love the Sprocket and Chain clock we featured a few months back.

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Sprockets And Chains Drive This Unique Mechanical Digital Clock

March 1, 2022 by Dan Maloney 17 Comments

When it comes to mechanical timepieces, we’re used to seeing mechanisms stuffed with tiny gears and wheel, often of marvelous complexity and precision. What we’re perhaps less used to seeing is a clock that uses chains and sprockets, and that looks more like what you’d find on a bicycle on your typical bicycle.

We can’t recall seeing anything quite like [SPE]’s “Time Machine” before. It’s one of those builds that explains itself by watching it work, so check out the video below and you’ll see where this one is going. The clock has three loops of roller link chain, each of which has a series of numbers welded to the links. The loops of chain are advanced around sprockets by a trio of geared-down motors, with the numbers standing up straight at the top of each loop. A microcontroller keeps track of the time and starts the clock advancing every minute, but a series of microswitches that are activated by the passing chain do all the rest of the control — sounds like a perfect time to say, “Could have used a 555,” but we still think it’s great the way it is.

Surprisingly, [SPE]’s clock seems like it wouldn’t be that hard to live with. Many unique electromechanical clocks that we feature, like a clock that’s nothing but hands or The Time Twister, are a little on the noisy side. While “Time Machine” isn’t exactly silent, its whirring isn’t terrible, and even though its clicks are a little loud, they’ve got a satisfying mechanical sound to them.

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RC Snowmobile Makes Tracks On Ice

February 18, 2022 by Bryan Cockfield 7 Comments

With all the futuristic technology currently at our disposal, it seems a little bizarre that most passenger vehicles are essentially the same thing that they were a century ago. Four wheels, a motor, and some seats would appear to be a difficult formula to beat. But in the 3D printing world where rapid prototyping is the name of the game, some unique vehicle designs have been pushed out especially in the RC world. One of the latest comes to us from [RCLifeOn] in the form of a single-wheeled RC snowmobile.

While not a traditional snowmobile with tracks, this one does share some similarities. It has one drive wheel in the back printed with TPR for flexibility and it also includes studs all along its entire circumference to give it better traction on ice. There are runners in the front made from old ice skates which the vehicle uses for steering, and it’s all tied together with an RC controller and some lithium batteries to handle steering and driving the electric motor.

There were some design flaws in the first iteration of this vehicle, including a very large turning radius, a gearing setup with an unnecessarily high torque, and a frame that was too flexible for the chain drive. [RCLifeOn] was also testing this on a lake which looked like it was just about to revert to a liquid state which made for some interesting video segments of him retrieving the stuck vehicle with a tree branch and string. All in all, we are hopeful for a second revision in the future when some of these issues are hammered out and this one-of-a-kind vehicle can really rip across the frozen wastes not unlike this other interesting snowmobile from a decade ago.

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Putting 3D Printed Chain Through Its Paces

May 15, 2021 by Lewin Day 15 Comments

One of the more frustrating things facing makers in decades past was the problem of power transmission. Finding things like belts, pulleys, sprockets, and chain for your projects could be difficult, particularly if you lived far from the shipping radius of suppliers like McMaster-Carr. These days, there’s no need to fuss, because you can simply 3D print whatever you need, as [Let’s Print] demonstrates by whipping up some chains.

The chains are a mixed design, combining plastic inner and outer links with bolts and nuts to fasten them together. [Let’s Print] tries out several combinations of ABS, PLA, and PETG, running them on 3D printed sprockets and determining that they are all functional, albeit at minimum load. The chains are also put through tensile testing by attaching a heavy brake disc to a length of chain and dropping the weight to see at which point the chains snap.

We’d love to see more 3D-printed chains; all-plastic snap-together designs, or even those that print pre-assembled are particularly tantalizing ideas. We’d also enjoy more testing done with the chain under some proper torque loads, rather than just spinning freely.

We’ve seen work from [Let’s Print] before, too – in the case of this awesome water pump. Video after the break.

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