Bicycle Gearbox Does It By Folding

If you’ve spent any time on two wheels, you’ve certainly experienced the woes of poor bicycle shifting. You hit the button or twist the knob expecting a smooth transition into the next gear, only to be met with angry metallic clanking that you try to push though but ultimately can’t. Bicycle manufacturers collectively spent millions attempting to remedy this issue with the likes of gearboxes, electronic shifting, and even belt-driven bikes. But Praxis believes to have a better solution in their prototype HiT system.

Rather then moving a chain between gears, their novel solution works by folding gears into or away from a chain. These gears are made up of four separate segments that individually pivot around an axle near the cog’s center. These segments are carefully timed to ensure there is no interference with the chain making shifting look like a complex mechanical ballet.

While the shift initialization is handled electronically, the gear folding synchronization is mechanical. The combination of electronic and mechanical systems brings near-instant shifting under load at rotational rates of 100 RPM. Make sure to scroll through the product page and watch the videos showcasing the mechanism!

The HiT gearbox is a strange hybrid between a derailleur and a gearbox. It doesn’t contain a clutch based gear change system or even a CVT as seen in the famous Honda bike of old. It’s fully sealed with more robust chains and no moving chainline as in a derailleur system. The prototype is configurable between four or sixteen speeds, with the four speed consisting of two folding gear pairs connected with a chain and the sixteen speed featuring a separate pair of folding gears. The output is either concentric to the input, or above the input for certain types of mountain bikes.

Despite the high level of polish, this remains a prototype and we eagerly await what Praxis does next with the system. In the meantime, make sure to check out this chainless e-drive bicycle.

A New Kind Of Bike Valve?

If you’ve worked on a high-end mountain or road bike for any length of time, you have likely cursed the Presta valve. This humble century-old invention is the bane of many a home and professional mechanic. What if there is a better option? [Seth] decided to find out by putting four valves on a single rim.

The contenders include the aforementioned Presta, as well as Schrader, Dunlop and the young gun, Clik. Schrader and Dunlop both pre-date Presta, with Schrader finding prevalence in cruiser bicycles along with cars and even aircraft. Dunlop is still found on bicycles in parts of Asia and Europe. Then came along Presta some time around 1893, and was designed to hold higher pressures and be lower profile then Schrader and Dunlop. It found prevalence among the weight conscious and narrow rimmed road bike world and, for better or worse, stuck around ever since.

But there’s a new contender from industry legend Schwalbe called Clik. Clik comes with a wealth of nifty modern engineering tricks including its party piece, and namesake, of a clicking mechanical locking system, no lever, no screw attachment. Clik also fits into a Presta valve core and works on most Presta pumps. Yet, it remains to be seen whether Clik is just another doomed standard, or the solution to many a cyclists greatest headache.

This isn’t the first time we’ve seen clever engineering going into a bike valve.

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A bike computer sits on a wooden background. The back of the bike computer has a 3D printed attachment with two white translucent zip ties running through the back.

Repairing A Bike GPS With 3D Printing

We love hacks that keep gadgets out of the trash heap, and [Brieuc du Maugouër] has us covered with this 3D printable replacement mount he designed for his bike GPS.

One of the most frustrating ways a gadget can fail is when a small, but critical part of the device fails. [du Maugouër] combined a 3D printed back and four M2x6mm screws to make a robust new mount to replace the broken OEM mount on his handlebar-mounted GPS. Slots for zip tie mounting are included in case the replacement mount breaks before yet another replacement can be printed. Apparently [du Maugouër] agrees with Chief O’Brien that “in a crunch, I wouldn’t like to be caught without a second backup.” [Youtube]

It’s exciting that we’re finally in a time when 3D printed replacement parts are living up to their potential. This would be a lot easier if more manufacturers posted 3D printed design files instead of getting them pulled from 3D file platforms, but makers will find a way regardless of OEM approval.

We’ve covered a lot of bike hacks over the years including DIY Bike Computers and GPS Trackers. Do you have a project that keeps something from becoming trash or might save the world another way? There’s still time to enter the Save the World Wildcard round of the Hackaday Prize (closes October 16th).

Down The Fabrication Rabbit Hole To Build A Recumbent Bike

‘Tis the time of the year to find as many reasons as possible to shut off the smartphone and get yourself outside. [Rich Olson’s] newest excuse is a recumbent bicycle he built from at least three donor bikes. Of course we’ve seen any number of bike mods over the years (the tall bikes that integrate a ladder to climb up to the saddle have always held a special place in our hearts), but [Rich] left us a nice trail of bread crumbs on how to get into this yourself without breaking the bank.

He worked from a set of open source plans, with additional instructions laid out by [Brian in Ohio] in a bicycle hacking series on the Hacker Public Radio podcast. We learn in the first installment that you can get your hands on a torch that uses oxygen and MAP gas to braze the pipe joints — a quick Duck Duck Go search turns up kits that have the torch and both gases for about eighty bucks. Ask around your neighbourhood and you’re likely to find some bike frames from the disused and broken cycles lurking in dark garage corners. That first podcast page even has images that show you how to lay out fishmouth cuts where the tubes will meet.

But what really grabbed our attention is the tube bending for the recumbent seat. This is a speciality part that you’re not going to be able to salvage from traditional bikes. [Rich’s] project shows off this image of a bend template and the two main rails he used from the seat; but how did he make those bends? The third episode of [Brian in Ohio’s] series covers the one simple trick that electricians don’t want you to know. Those rails are made out of electrical conduit and you can easily buy/rent/borrow a commonplace conduit bending tool which has the handy advantage of including angle guides.

You’ll find [Rich’s] video after the break which begins with a slideshow and ends with a demo ride. That lets us see the lacing on the back side of the seat fabric that keeps it taught, yet comfy in a way a standard bike saddle just can’t be.

If this still hasn’t convinced you to pick up a torch, you can also build a recumbent with a wooden frame.

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Square Bicycle Design

Building A Square Bicycle

Inspired by [Michael Ubbesen Jakobsen’s] BauBike design, [Aaron Seiter] decided to try building his own.

The entire frame was made out of 1″ square steel tubing and welded together in no time at all. Actually intending to ride this bike, he had to make a few changes to the original BauBike design. Most importantly, he raised the seat up to allow for proper leg extension while pedaling.

The funny thing is most people on Reddit thought it wasn’t going to work, so shortly after posting the gallery to imgur, [Aaron] also uploaded a short video to YouTube to prove, yes, he can actually ride it. Stick around after the break to see it in action.

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