Giant PC fan

3D-Printed Parts Let You Assemble Your Own Biggest Fan

It’s getting close to the time of year when we need to start carefully vetting projects here at Hackaday. After all, nobody likes to get punked by an early April Fool’s joke. But as silly as this outsized PC fan looks, it sure seems like a legit build, if a bit on the pointless side.

Then again, perhaps pointless is too harsh a word to use. This 500-mm fan is by [Angus] over at Maker’s Muse, and it represents a lot of design work to make it buildable, as well as workable and (mostly) safe. Using both CNC-cut MDF and printed parts, the fan is an embiggened replica of a normal-sized case fan. The fan’s frame had to be printed in four parts, which lock together with clever interlocking joints. Each of the nine blades locks into a central hub with sturdy-looking dovetails.

And sturdy is important, as the fan is powered by a 1,500 Watt brushless DC motor. With a 4:1 reduction thanks to a printed gear train, the fan spins at around 3,300 RPM, which makes a terrifying noise. There’s a little bit of “speed-wobble” evident, but [Angus] managed to survive testing. The fan, however, did not — the 3D-printed gears self-destructed after a full-speed test, but not before the fan did its best wind tunnel imitation. And the RGB LEDs looked great.

This one reminds up of something we might see [Ivan Miranda] come up with. In fact, his super-sized 3D printer might have been just the thing to shorten [Angus]’ print times.

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What do we want? Monowheel!

Monowheel Mayhem: When Good Gyroscopic Precession Goes Bad

Since the dawn of the age of the automobile, motorheads have been obsessed with using as few wheels as possible. Not satisfied with the prospect of being incompletely maimed by a motorcycle, the monocycle was born. Gracing the covers of Popular magazines and other periodicals, these futuristic wheels of doom have transfixed hackers of all kinds. [James Bruton] is one such hacker, and in the video below the break you can see his second iteration of a 3d printed monowheel.

[James]’ wonderful monowheel is beautifully engineered. Bearing surfaces, gears, idlers, motors, and yes, twin gyroscopes are all contained within the circumference of the tire. The gyroscopes are actuated by a rather large servo, and are tied together by a gear that keeps their positions in sync. Their job is to keep the monowheel balanced at all times.

But as [James] discovered, the chief difficulty of only having one wheel isn’t lateral balancing. Ask any monocyclist and they’ll assure you that it’s possible. The real trick is balancing the machine fore and aft. Unlike a two wheeled velocipede, the monowheel has nothing to exert torque against save for a bit of gravity.

As [James] found out the hard way, it was within this fore-aft balancing act that the gyroscopic precession reared its ugly head. The concept is explained well in the video. We won’t spoil the surprise ending because the explanation and conclusion are quite good so make sure to watch to the end!

If you’d like to look at [James]’ first version, we covered it here. And if you’re the daredevil type, perhaps we can interest in you in a two stroke human sized monowheel that will probably end in an ER visit. At least they wore a helmet. Thanks to [Baldpower] for the tip!

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Modified Car Alternator Powers Speedy DIY E-Bike

Your garden variety automotive alternator is ripe for repurposing as is, but with a little modification, it can actually be used as a surprisingly powerful brushless motor. Looking to demonstrate the capabilities of one of these rebuilt alternators, [DIY King] bolted one to the back of a old bicycle and got some impressive, and frankly a bit terrifying, results.

We should say up front that the required modifications to the alternator are quite extensive, so before you get too excited about building your own budget e-bike, you should check out the previous guide [DIY King] put together. The short version is that you’ll need to machine a new rotor and fill it with the neodymium magnets salvaged from hoverboard motors.

A custom built alternator rotor is the key to the project.

Once you’ve got your modified alternator, the rest is relatively easy. The trickiest part of this build looks like it was cutting off the bike’s rear wheel mount and replacing it with a plate that holds the alternator and a pair of reduction gears pulled from a 125cc motorbike. Beyond that, it’s largely electronics.

Naturally, you’ll also need a pretty beefy speed controller. In this case [DIY King] is using a 200 amp water-cooled model intended for large RC boats, though interestingly enough, it doesn’t seem he’s actually running any water through the thing. He’s also put together a custom 1,500 watt-hour battery pack that lives in a MDF box mounted under the seat.

To test out his handiwork, [DIY King] took to the streets and was able to get the bike up to 70 km/h (43 MPH) before his courage ran out. He thinks the motor should be able to push it up to 85 km/h, but he says the bike started wobbling around too much for him to really open it up. In terms of range, he calculated that while cruising around at a more palatable 30 km/h (18 MPH), he should be able to get 100 kilometers (62 miles) off of a single charge.

If you like repurposed motors and suicidal bike speeds, you’ll love this build that uses a washing machine motor to push a rider to a claimed 110 km/h. If you’re not worried about speed or range, then this supercapacitor e-bike is certainly worth a look as well.

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Auto Ball Launcher Will Be Your Dog’s New Best Friend

If there’s one bright spot on the blight that is this pandemic, it’s got to be all the extra time we’re spending with our pets. Dogs especially love that we’re home all the time and want to spend it playing, but sometimes you need to get stuff done. Why not head outside with your laptop and keep the dog happy with an automatic ball launcher?

This is a work in progress, and [Connor] plans to publish a BOM and the STL files once it’s all finished. For now, it’s a working prototype that shoots a ball into the air and about 25 feet away, from the looks of it. Far enough to be fun, but not so far that it goes over the fence.

All [Connor] has to do is drop the ball in the top, which you know is going to lead to training the dog to do it himself. A proximity sensor detects the ball and starts up a pair of 540 R/C motors, then a servo drops the ball down the internal chute. The motors spit the ball out with great force with a pair of profiled, 3D-printed wheels that are controlled by a Turnigy ESC and an Arduino Nano.

In the future, [Connor] plans to print a cover for the electronics and enlarge the funnel so it’s easier for the dog to drop in the ball. Check out the brief demo and build video after the break.

All dogs should be able to get in a good game of fetch as often as they want, even if they happen to be blind.

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Shoot Above The Waves On This E-Foil Made From A Rifle Case

So you say you want to fly above the waves on an electric hydrofoil, but you don’t have the means to buy a commercial board. Or, you don’t have the time and skills needed to carve a board and outfit it with the motor and wing that let it glide above the water. Are you out of luck? Not if you follow this hackworthy e-foil build that uses a waterproof rifle case as the… hull? Board? Whatever, the floaty bit.

If you haven’t run across an e-foil before, prepare to suddenly need something you never knew existed. An e-foil is basically a surfboard with a powerful brushless motor mounted on a keel of sorts, fairly far below the waterline. Along with the motor is a hydrofoil to provide lift, enough to raise the board well out of the water as the board gains speed. They look like a lot of fun.

Most e-foils are built around what amounts to a surfboard, with compartments to house the battery, motor controller, and other electronics. [Frank] and [Julian] worked around the difficult surfboard build by just buying a waterproof rifle case. It may not be very hydrodynamic, but it’s about the right form factor, it already floats, and it has plenty of space for electronics. The link above has a lot of details on the build, which started with reinforcing the case with an aluminum endoskeleton, but at the end of the day, they only spent about 2,000€ on mostly off-the-shelf parts. The video below shows the rifle case’s maiden voyage; we were astonished to see how far and how quickly the power used by the motor drops when the rifle case leaves the water.

Compared to some e-foil builds we’ve seen, this one looks like a snap. Hats off to [Frank] and [Julian] for finding a way to make this yet another hobby we could afford but never find time for.

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Visualise ESC Problems With LEDs

For many in the RC community, blowing up an Electronic Speed Controller (ESC) means one thing: throwing it away and buying another one. However, if you’re regularly pushing the limits or simply hate waste, fixing failed units is an option. To assist in this task, [LouD] built an ingeniously simple ESC tester.

The board is designed to be wired in parallel with a brushless DC motor when hooked up to an ESC. The board packs two LEDs per phase, wired in opposite directions. Thus, current flow in both directions can be visualised on a phase-by-phase basis. If everything is operational, the red and green LEDs on each phase should glow evenly as the throttle is ramped up. However, if there are problems, it will be readily apparent as the blinking becomes erratic or one or more LEDs fails to light at all.

It’s a nifty little device that would prove useful when testing  a pile of possibly-defective units. It’s also a quick way to verify a fix. The project is up on OSHPark should you wish to order your own.

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Put More Scoot In Yer Scooter

We have a scooter hack that is odd for a couple of reasons. First, the vehicle in question is a Doc Green EWA 6000, a German clone of a Xiaomi M365, so Country stereotypes be darned. Second, it is about increasing the performance, and when we think of scooters, we get hung up on scoot. The link between these peculiarities is the speed limiter Germany requires on all scooters, which the Chinese model lacks. Despite the law, [Nikolaj] wanted a higher top speed and Bluetooth connectivity. Wireless unlocks advanced features, like cruise control, which are absent in the stock model.

The mainboard is responsible for speed control, but that is merely a component, and you can find third-party replacements. [Nikolaj] found a new part with a German forum member’s help, then recorded his work in English for our sake. The speed boost is nice, but the Bluetooth functionality is a massive improvement by itself. If you live in an area where the law doesn’t allow this sort of thing, think before you upgrade. Aftermarket parts aren’t always drop-in replacements, and in this case, the controller and display needed some finessing to fit, so measure twice and buy once.

If tearing into a brand new scooter isn’t for you, consider breathing new life into a retiree, and don’t forget that stopping is the other half of the battle.