Building A Bicycle Dropper Seat Post

A recent addition to mountain bikes is the dropper seat post. This invention is in the vein of office swivel chairs, allowing the seat height to be adjusted with a simple handlebar mounted lever. They are rather fascinating inventions ranging in complexity from simple mechanical systems, to electronic monstrosities actuated by Bluetooth. Inspired by the panoply of possibilities, [kane components] set forth to create such a home-built dropper post. 

Inspired by woodworking bar clamps, [kane’s] design utilizing angled plates binding against a rail inside the dropper post. Two pairs of plates sitting at opposite angles resist opposite forces from either the rider sitting on the post, or the return spring. A simple cable actuated cam moves the plates to a nonbinding position when the lever is actuated, and springs return the plates to a binding rest-state. The return is handled by an air spring pressurized against a piston at the bottom of the shaft.

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3D Printing A Usable Airless Tire

For decades now, companies like Michelin have been teasing us with futuristic-looking automobile tires that don’t use air. Instead, they use a polymer mesh of sorts which maintains the same pressure on the travel surface that a pneumatic tire does, with much less maintenance than their pneumatic counterparts. At least, in theory. There’s a reason that these tires live in the same mythical realm that Half Life 3 and the modern affordable Volkswagen do, and [Berm Peak] decided to discover those reasons for himself.

Of course, [Berm Peak] isn’t building these for his daily driver, an electric pickup truck featured in previous videos of his. He’s putting these on his mountain bike instead, a challenging environment for a tire like this in its own right. When mountain biking at the level he does, punctures and flats can become a real nuisance on the trail, so he set about experimenting with these designs with the 3D printer to see if he could make something rivaling pneumatic technology. After a few design iterations he settled on a TPU-based version with a compliant S-shaped spacing between the tread and wheel. The tire printed in sections that are installed by joining them together on the bike rim with a separate 3D printed rim interface.

At the end of this process [Berm Peak] ends up with a surprisingly capable tire that mostly holds up to his extreme off-road testing, an impressive feat for something 3D printed in his shop. Presumably a company specializing in bicycle tires could build something even more capable, but it turns out that a different technology has already solved all of the problems that airless tires solve. Mountain bikers today almost exclusively ride on tires with sealant, so punctures and flats are essentially a solved problem. But the neon-green airless tires were still a fun project for [Berm Peak] and quite the head-turner out on the bike trails.

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Tearing Down Aircraft Weather Radar Avionics

If you’re flying high in the sky, it’s useful to know if there’s turbulence, heavy rain, or other nasty weather ahead. Onboard weather radar is a useful tool that pilots use to scope out conditions ahead. [Thomas Scherrer] came into possession of a weather radar display from a vintage aircraft, and decided to tear it apart for our viewing pleasure. 

The unit in question is a Bendix PPI-1 plan position indicator. This particular 1971 example was scored from a McDonnell-Douglas DC9. [Thomas] only has the display itself, not the radar that would feed it or the power supply to turn it on. Still, even just the readout unit is super interesting to look inside. Right off the bat, there’s a neat dimming filter on the front, and the case itself is really beautifully designed for service. The design is very much of its time, full of neat wire harnesses and chunky through-hole components.  There are some neat surprises inside, too, like an interesting device shaped like a triangular prism whose purpose we won’t spoil here.

If you’re wondering what one of these units looks like in action, you can see such an example on YouTube. The display basically lights up in areas where there were stronger radar returns indicating weather to be avoided.

We love radars around these parts, and we feature them all the time. Video after the break.

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3D Printed Go Kart Designed To Fit In A Suitcase

[Ivan Miranda] is famous for his large-scale 3D printed vehicles. They’re pretty fun, but they’re also pretty big and heavy—which can make transporting them around rather impractical. Hence, when he had reason to travel with a 3D printed go kart, he went back to the drawing board to create something light enough to pack in regular plane luggage.

The build started with some major compromises compared to [Ivan]’s previous go kart build. Notably, there are only three wheels instead of four, and a simplified control layout that eschews a regular steering wheel. These decisions were made to save weight and allow the design to be more compact. The kart uses a set of handles either side of the rider to handle steering. Drive is via a brushless motor, with power supplied from a series of 18 V drill batteries. Parts were produced on [Ivan]’s massive printer which comes in handy on large-scale projects like these.

All in all, the final build weighed around 20 kg. That’s light enough to be broken down across checked luggage and carry-on for a typical flight. We’d consider the project a success on that basis, even if quite a bit of assembly was required upon arriving at the destination. [Ivan]’s other builds in this realm are pretty fun too, from the printed scooter to the ride-on tank.

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A Train Departure Board For The Home

Trains are a great way to get around. You just have to make sure you’re across the schedule if you intend to get where you’re going in a timely manner. Train departure boards exist for that very purpose. As a train fan, [Jon] always wanted such a thing, so decided to build one for himself. 

The build started, as so many do, with a Raspberry Pi 4, with [Jon] deciding on the 1GB model. Hooked up to either an Adafruit RGB Matrix Bonnet, or an Electrodragon 3-port RGB Matrix board, it’s then possible to get the Pi running three to four HUB75E LED matrixes. Each matrix consists of 128 x 64 pixels, so stacking up a bunch of them can make a nicely-sized departure board that’s easily readable. [Jon] was sure to hook up a nice, juicy 5-amp 5-volt power supply to ensure there wouldn’t be any surprise brownouts under normal usage conditions. From there, it’s simply a matter of having the Pi query the Rail Data Marketplace in order to get the relevant schedule data to display on the board.

If you want to get information on your local rail services at a glance, or just want to impress your fellow foamers at your next railfan gathering, a build like this is a great way to go. We’ve seen similar builds before, too. Video after the break.

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A black pickup sits in front of a snow-capped mountain range in the background. It has a white camper shell with a sci-fi looking "01" emblazoned on the side in black text. An orange, wedge-shaped tent pops up above the campershell and truck roof.

A Pop-Up Truck Camper For Less

We live in a veritable Cambrian Explosion of camping options, ranging from a tarp on the ground to multi-million dollar RVs. Somewhere around the middle is the pop-up truck camper, but [Further Fabrication] wanted to build his own.

As is often the case, he saw the cool pop-up truck campers on the market, but balked at the cost. To make matters worse, the options out there weren’t really available in his country. After getting a solid set of measurements from the truck and some materials, he set to work.

The most interesting part of this build is probably the aluminum/plywood sandwich [Further Fabrication] chose for building the main structure of the camper shell. While many would’ve chosen a tubing space frame for the build, he decided to sandwich two layers of plywood around plywood beams and large rectangular aluminum tubing. These were affixed with a combination of construction adhesive and screws to create a lightweight yet sturdy enclosure.

The tent portion uses a 600-denier PVC-coated waterproof polyester fabric, sewn with nice YKK zippers, and features large windows with screens for excellent ventilation. The roof consists of two sections of aluminum composite sandwich, and the side panels were made from cutoffs of the roof material. Instead of the standard cam-lock used on most camper shells, [Further Fabrication] chose a solenoid-actuated system and more conventional grab handles.

We’ve covered campers several times, including a solar-powered RV, a truck camper that expands lengthwise rather than up, and several bike-based campers.

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Open-Source Mid-Drive E-Bike Motor Has Lots Of Promise, And Hyphens

[Pedro Neves] has a mid-drive e-bike, but he doesn’t own it — not truly, since he can’t repair the motor unit. For a hacker to be in that position, there are only two options: crack the old one and make it your own, or build your own from scratch. [Pedro] built his own and is open-sourcing it on his website for everyone to play with. Right now, that’s .step files and a BOM, so you’ll need to watch the design/build video on YouTube below to get the full picture.

His choice of a motor from an old battery-powered angle grinder is both thrifty and environmentally friendly, so we approve. His goal of 25 km/h seems like a reasonable speed limit, but may still be too fast for some countries’ regulations— so do check the local rules if you’re going to build this. Making the most of 3D-printed components is also a choice that makes the project more accessible, but don’t worry — the bearing surfaces are all metal. That includes the clutch bearing that will let you pedal home if the battery dies or the motor craps out. Well, unless the printed plastic axle gives up the ghost, but that got replaced with a CNC version, so it’s all good. Unless you’ve got legs like Hercules, it ought to hold.

If that’s not DIY enough, you could always build the motor yourself. This mid-drive is also part of a larger project [Pedro] is working on for a whole cargo bike, as he details in his video, which is a worthy project we’ve seen other examples of before.

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