DIY Bike Wheels Welded With Rebar

[Liebregts] is working on a trike design, and needed a pair of wheels to go up front. Regular bicycle wheels wouldn’t do, as they’re not designed to work with a single-sided support. They also wanted to be able to mount disc brakes. Thus, they set about building a set of custom wheels to do the job.

The build began with a regular set of 20″ bike wheel rims with all the spokes taken out. A ring of steel rebar welded on the inner perimeter gave the rims more strength. A set of hubs and axles were then fabbed up with a welder and lathe, with provisions for bolting on disc brake components. Lengths of rebar were then welded in as non-adjustable spokes. Next, it was time for a coat of paint. Finally [Liebregts] mounted the tires and brakes, and called the job done.

Obviously, it is possible to buy wheels specifically for trike builds. However, [Liebregts] found it difficult to find exactly what they wanted, particularly where the disc brake option was concerned. The best option was a custom build.  The resulting wheels are obviously much heavier than traditional bike wheels, but they’re also likely a fair bit stronger, too. If you need to weigh down a tarpaulin, for example, these wheels might just do the trick.

We’ve seen some other crazy wheels on trikes before, too! Oh, and who says wheels need to be a full circle, anyway? Creativity will never cease to amaze!

Giant Wheels Make For Exciting Powered Rollerskates

Roller skates are fun and all, but they’re pretty well limited to rolling on relatively smooth surfaces. [Fireball Tool] wanted something a little more rugged, so set about a build of his own. 

The challenge of the design was to build these skates using as many wheelchair parts as possible, including the wheels. Roughly 22″ tall, the wheels have great bearings inside and are designed to run on a single-sided axle support, perfect for the skates. A metal bracket is then used to attach a snowboard boot binding so the wheels can be fitted to the wearer’s feet. Training wheels were fitted to the rear to make it easier for the rider, while a chainsaw engine was pressed into service to provide some welcome propulsive force.

In a short test on a flat workshop floor, the wheels performed ably. The hope is that the large diameter wheels should do better than traditional roller skates would on rough surfaces like grass or dirt. We look forward to seeing that test in action as a comparison to other powered skates we’ve seen. Video after the break.

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3D Printing Omni-Balls For Robot Locomotion

Wheels are all well and good for getting around, but they only tend to rotate about a single axis. Omni-wheels exist, but they’re still a little too pedestrian for [James Bruton]. His latest project involved 3D printing custom omni-balls which roll in all directions. (Video, embedded below.)

The omniball concept comes from earlier work by Osaka University, which also produced a treaded tank-like vehicle by the name OmniCrawler as well. The spherical design, fitted with an axle and casters as well, allows rotation in multiple directions, allowing for a platform fitted with such omni-balls to easily rotate and translate in all directions.

[James] set about creating his own version of the design, which relies on grippy TPU filament for grip pads to give the 3D printed hemispheres some much needed grip. There’s also bearings inside to allow for the relative rotation between the hemispheres and the internal castor, necessary to allow the wheels to move smoothly when sitting on either pole of the hemispheres. Skate bearings were then used to assemble three of the omni-balls onto a single platform, which demonstrated the ability of the balls to roll smoothly in all directions.

While it’s just a demonstration of the basic idea for now, we can imagine these balls being used to great effect for a robot platform that needs to navigate in tight spaces on smooth surfaces with ease. The mechanical complexity of the omni-balls probably negates their effective use in dirtier offroad contexts, however.

We’ve seen [James]’s work before too – such as his compliant leg design for walking robots, and his active gyroscope balancer last week. When does [James] sleep?

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Hackaday Links: May 16, 2021

With the successful arrival of China’s first Mars lander and rover this week, and the relatively recent addition of NASA’s Perseverance rover and its little helicopter sidekick Ingenuity, Mars has collected a lot of new hardware lately. But while the new kids on the block are getting all the attention, spare a thought for the reliable old warhorse which has been plying Gale Crater for the better part of a decade now — Curiosity. NASA has been driving the compact-car-sized rover around Mars for a long time now, long enough to rack up some pretty severe damage to its six highly engineered wheels, thanks to the brutal Martian rocks. But if you think Curiosity will get sidelined as its wheels degrade, think again — the rover’s operators have a plan to continue surface operations that includes ripping off its own wheels if necessary. It’s a complex operation that would require positioning the wheel over a suitable rock and twisting with the steering motor to peel off the outer section of the wheel, leaving a rim to drive around on. JPL has already practiced it, but they predict it won’t be necessary until 2034 or so. Now that’s thinking ahead.

With all the upheaval caused by the ongoing and worsening semiconductor shortage, it might seem natural to expect that manufacturers are responding to market forces by building new fabs to ramp up production. And while there seems to be at least some movement in that direction, we stumbled across an article that seems to give the lie to the thought that we can build our way out of the crisis. It’s a sobering assessment, to say the least; the essence of the argument is that 20 years ago or so, foundries thought that everyone would switch to the new 300-mm wafers, leaving manufacturing based on 200-mm silicon wafers behind. But the opposite happened, and demand for chips coming from the older 200-mm wafers, including a lot of the chips used in cars and trucks, skyrocketed. So more fabs were built for the 200-mm wafers, leaving relatively fewer fabs capable of building the chips that the current generation of phones, IoT appliances, and 5G gear demand. Add to all that the fact that it takes a long time and a lot of money to build new fabs, and you’ve got the makings of a crisis that won’t be solved anytime soon.

From not enough components to too many: the Adafruit blog has a short item about XScomponent, an online marketplace for listing your excess inventory of electronic components for sale. If you perhaps ordered a reel of caps when you only needed a dozen, or if the project you thought was a done deal got canceled after all the parts were ordered, this might be just the thing for you. Most items offered appear to have a large minimum quantity requirement, so it’s probably not going to be a place to pick up a few odd parts to finish a build, but it’s still an interesting look at where the market is heading.

Speaking of learning from the marketplace, if you’re curious about what brands and models of hard drives hold up best in the long run, you could do worse than to look over real-world results from a known torturer of hard drives. Cloud storage concern Backblaze has published their analysis of the reliability of the over 175,000 drives they have installed in their data centers, and there’s a ton of data to pick through. The overall reliability of these drives, which are thrashing about almost endlessly, is pretty impressive: the annualized failure rate of the whole fleet is only 0.85%. They’ve also got an interesting comparison of HDDs and SSDs; Backblaze only uses solid-state disks for boot drives and for logging and such, so they don’t get quite the same level of thrash as drives containing customer data. But the annualized failure rate of boot SDDs is much lower than that of HDDs used in the same role. They slice and dice their data in a lot of fun and revealing ways, including by specific brand and model of drive, so check it out if you’re looking to buy soon.

And finally, you know that throbbing feeling you get in your head when you’re having one of those days? Well, it turns out that whether you can feel it or not, you’re having one of those days every day. Using a new technique called “3D Amplified Magnetic Resonance Imaging”, or 3D aMRI, researchers have made cool new videos that show the brain pulsating in time to the blood flowing through it. The motion is exaggerated by the imaging process, which is good because it sure looks like the brain swells enough with each pulse to crack your skull open, a feeling which every migraine sufferer can relate to. This reminds us a bit of those techniques that use special algorithms to detects a person’s heartbeat from a video by looking for the slight but periodic skin changes that occurs as blood rushes into the capillaries. It’s also interesting that when we spied this item, we were sitting with crossed legs, watching our upper leg bounce slightly in time with our pulse.

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3D Printed Wobbly Wheels Put Through Their Paces

When we talk about wheels, the vast majority of the time we’re talking about ho-hum cylindrical rollers as seen on all manner of human conveyances. However, there are all manner of wild and wacky shapes that roll, and having had some experience with them, [Maker’s Muse] decided to take a shot at having a robot drive on them. (Video, embedded below.)

The benefit of a 3D printer is that it makes producing these parts with strange geometries a cinch. The video shows a variety of designs, from the wobbly “Nightshades” to the entertaining “Prongle” wheels being put through a variety of tests. In an attempt to equalise the playing field, each design was matched in its surface area so as not to artificially bias the results.

While the wobbly designs look strange, they also come with some benefits over simple disc wheels, providing extra traction on both carpet and sand. Particularly impressive was the performance of the 8-spoke wheels on the beach, though as this design mimics real-world sand tyres, we’re not surprised at the results. We’ve seen similar 3D printed parts do the job for driving on water, too.

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ABS Mercedes Rims Push The Limits Of 3D Printing

While we’re big believers in 3D printing here at Hackaday, there’s no denying that some things just aren’t meant to be printed. For example, most of us would agree that it’s not the first choice for making rims for a passenger car. We imagine that [Jón Schone] from Proper Printing probably feels the same way, but that didn’t stop him from trying to do it anyway.

A couple of months ago [Jón] got a test subject in the form of an older Mercedes with 19-inch rims. The first two challenges are bed size and warping, so he modified a Creality CR10 S5 with a heated chamber capable of reaching 70 °C to reduce warping with the ABS filament he intended to use. Another challenge is the amount of filament required for the print, especially since [Jón] wasn’t keen on babysitting the machine to replace the spool every so often. His attempt at building a filament joiner ultimately didn’t work out, so in the end he simply sourced the filament in bulk size rolls.

Bolts hold the two halves of the rim together.

Eventually [Jón] managed to print a complete rim in two halves, bolted together around its circumference. Unfortunately, even with the heated chamber, the parts still warped all around the edges. This left a gap at the seam, but to fit a tubeless tire, the rim had to be airtight. So the entire inside surface was painted to close any small gaps, and the larger gaps were filled with sealant.

In the end it was still unable to hold pressure with a tire mounted, so it was test fitted to the car just to see if it would carry the weight. This test also failed, splitting on the thinnest part of the rim. [Jón] has headed back to the drawing board to try again in 2021. We probably would have moved on by now, but you have to admire his tenacity. We hope to see success in the new year.

Printing large parts brings its own set of challenges, but if you stick to good old PLA it’s not too difficult. [Ivan Miranda] has made a name for himself with massive 3D printed projects like a ride-able tank, and also built a supersized 3D printer for future projects.

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Really Useful Robot

[James Bruton] is an impressive roboticist, building all kinds of robots from tracked, exploring robots to Boston Dynamics-esque legged robots. However, many of the robots are proof-of-concept builds that explore machine learning, computer vision, or unique movements and characteristics. This latest build make use of everything he’s learned from building those but strives to be useful on a day-to-day basis as well, and is part of the beginning of a series he is doing on building a Really Useful Robot. (Video, embedded below.)

While the robot isn’t quite finished yet, his first video in this series explores the idea behind the build and the construction of the base of the robot itself. He wants this robot to be able to navigate its environment but also carry out instructions such as retrieving a small object from a table. For that it needs a heavy base which is built from large 3D-printed panels with two brushless motors with encoders for driving the custom wheels, along with a suspension built from casters and a special hinge. Also included in the base is an Nvidia Jetson for running the robot, and also handling some heavy lifting tasks such as image recognition.

As of this writing, [James] has also released his second video in the series which goes into detail about the mapping and navigation functions of the robots, and we’re excited to see the finished product. Of course, if you want to see some of [James]’s other projects be sure to check out his tracked rover or his investigations into legged robots.

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