Scratch-Built Ornithopter: Here’s How I Flapped My Way to Flight

One of humankind’s dreams has always been to fly like a bird. For a hacker, an achievable step along the path to that dream is to make an ornithopter — a machine which flies by flapping its wings. An RC controlled one would be wonderful, controlled flight is what everyone wants. Building a flying machine from scratch is a big enough challenge, and a better jumping-off point is to make a rubber band driven one first.

I experimented with designs which are available on the internet, to learn as much as possible, but I started from scratch in terms of material selection and dimensions. You learn a lot about flight through trial and error, and I’m happy to report that in the end I achieved a great little flyer built with a hobby knife and my own two hands. Since then I’ve been looking back on what made that project work, and it’s turned into a great article for Hackaday. Let’s dig in!

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Mechanisms: The Lever, It’s Everywhere

Levers are literally all around us. You body uses them to move, pick up a pen to sign your name and you’ll use mechanical advantage to make that ballpoint roll, and that can of soda doesn’t open without a cleverly designed lever.

I got onto this topic quite by accident. I was making an ornithopter and it was having trouble lifting its wings. For the uninitiated, ornithopters are machines which fly by flapping their wings. The problem was that the lever arm was too short. To be honest, as I worked I wasn’t even thinking in terms of levers, and only realized that there was one after I’d fine-tuned its length by trial and error. After that, the presence of a lever was embarrassingly obvious.

I can probably be excused for not seeing a lever right away because it wasn’t the type we most often experience. There are different classes of levers and it’s safe to say that most people aren’t even aware of this. Let’s take a closer look at these super useful, and sometimes hidden mechanisms known as levers.

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Cat Plays the Silver Ball for Treats

It’s pretty easy to train a dog to do things for treats. They’re eager to please. But a cat? Most cats have better things to do than learn tricks no matter how many treats are involved. But if you make an autonomous game out of learning a trick, they just might go for it.

That’s the idea behind Touchy Fishy, a pinball machine for cats. It’s the newest iteration of treat-dispensing machines that [Kim] made for his cat, MIDI. The previous version was shaped like a dog’s head with a joystick for a nose. MIDI was so adept at pulling the joystick toward herself that [Kim] decided to try a new design using a lever.

Humans like challenges, too, and [Kim] wanted to make something purely mechanical this time around. The final product is mostly springs and laser-cut acrylic. MIDI pulls the spring-loaded lever downward, launching a pinball upward in an arc. At the top of its trajectory is a spinner enclosed in a circle. When the pinball hits the spinner, it sweeps a treat toward an opening, and the treat falls down where MIDI can eat it. The best part? The spinner also returns the captive pinball to its starting point, so MIDI can play until [Kim] gets tired of dropping treats into the hole. Watch MIDI claw her way to the high score after the break.

Most of the cat-related projects we’ve seen were built to keep hungry cats from sitting on their owner’s chests at 3AM, demanding to be fed. Here’s one that goes a step further by putting the cat to work collecting wiffle balls which it uses to pay for small amounts of kibble.

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Repairs You Can Print: Racing the Clock for a Dishwasher Fix

No matter how mad your 3D printing skills may be, there comes a time when it makes more sense to order a replacement part than print it. For [billchurch], that time was the five-hour window he had to order an OEM part online and have it delivered within two days. The race was on — would he be able to model and print a replacement latch for his dishwasher’s detergent dispenser, or would suffer the ignominy of having to plunk down $30 for a tiny but complicated part?

As you can probably guess, [bill] managed to beat the clock. But getting there wasn’t easy, at least judging by the full write-up on his blog. The culprit responsible for the detergent problem was a small plastic lever whose pivot had worn out. Using a caliper for accurate measurements, [bill] was able to create a model in Fusion 360 in just about two hours. There was no time to fuss with fillets and chamfers; this was a rush job, after all. Still, even adding in the 20 minutes print time in PETG, there was plenty of time to spare. The new part was a tight fit but it seemed to work well on the bench, and a test load of dishes proved a success. Will it last? Maybe not. But when you can print one again in 20 minutes, does it really matter?

Have you got an epic repair that was made possible by 3D printing? We want to know about it. And if you enter it into our Repairs You Can Print Contest, you can actually win some cool prizes to boot. We’ve got multiple categories and not that many entries yet, so your chances are good.

Retrotechtacular: We’re Gonna Have Manual Transmissions the Way My Old Man Told Me!

archimedesSimple machines are wonderful in their own right and serve as the cornerstones of many technological advances. This is certainly true for the humble lever and the role it plays in manual transmissions as evidenced in this week’s Retrotechtacular installment, the Chevrolet Motor Company’s 1936 film, “Spinning Levers”.

This educational gem happens to be a Jam Handy production. For you MST3K fans out there, he’s the guy behind shorts like Hired! from the episodes Bride of the Monster and the inimitable Manos: The Hands of Fate. Hilarity aside, “Spinning Levers” is a remarkably educational nine-ish minutes of slickly produced film that explains, well, how a manual transmission works. More specifically, it explains the 3-speed-plus-reverse transmissions of the early automobile era.

It begins with a nod to Archimedes’ assertion that a lever can move the world, explaining that the longer the lever, the better the magic. In a slightly different configuration, a lever can become a crank or even a double crank. Continuous motion of a lever or series of levers affords the most power for the least work, and this is illustrated with some top-drawer stop motion animation of two meshing paddle wheels.

gearsNext, we are shown how engine power is transferred to the rear wheels: it travels from a gear on the engine shaft to a gear on the drive shaft through gears on the countershaft. At low speeds, we let the smallest gear on the countershaft turn the largest gear on the drive shaft. When the engine is turning 90 RPM, the rear wheel turns at 30 RPM. At high speeds using high gears, the power goes directly from the engine shaft to the drive shaft and the RPM on both is equal. The film goes on to explain how the gearbox handles reverse, and the vast improvements to transmission life made possible through synchromesh gearing.

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Mechanical engineering primer

So you’re master of electrons; able to program multiple chip architectures without batting an eye. Good for you. The only problem is that blinking LEDs gets boring after a while and you’re going to want to do something else. Here’s a chance to expand on your physical construction skills. Make: Skill Set is sharing the first chapter from the book Making Things Move by [Dustyn Roberts].

This chapter, which comes in PDF form, covers simple machines. It’ll guide you through the three different types of levers, including examples of how you use these in your everyday life. Next it’s on to pulley systems, wheels and axles, inclined planes and wedges, screws, and gears. [Dustyn] rounds out the chapter by talking about how these concepts are combined into machines like the Rube-Goldberg device seen above. Take some time to look this chapter over and then put it on the holds list from your public library if you’re interested in reading more.