How—And Why—To Avoid Tolerance Stacking In Your Technical Drawings

July 25, 2018 by Cameron Coward 49 Comments

If you want to have your part designs fabricated, you’re going to need to provide the manufacturer with a technical drawing. Yes, 3D printers and many modern machine tools rely on toolpaths created from 3D models. But, there is a good chance the manufacturer will be recreating the 3D model in their own system, instead of using the one you provided. Or, they may use traditional manual machining and not touch a 3D model at all. More importantly, the technical drawing gives them vital information on how closely they need to adhere to your dimensions in order for you to accept the parts.

On a technical drawing, the dimension that you want is called the nominal. But, no manufacturing is ever perfect, so you have to allow some wiggle room in what you’ll accept. That wiggle room is called tolerance. Maybe your part could be a little longer than specified and it wouldn’t affect the functionality. Maybe it could be a little shorter—or either. Specifying a tolerance is necessary, because it tells the manufacturer exactly how much wiggle room you’re giving them.

But, tolerances can introduce unforeseen consequences if you’re not careful. The wiggle room provided by tolerances is absolutely necessary, but if you don’t use them properly you can easily end up with unusable parts, even if the manufacturer followed your instructions to the letter. That usually happens because you have multiple tolerances being added together, which is called tolerance stacking.

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Edwin Armstrong’s Battle For FM Radio

July 24, 2018 by Al Williams 50 Comments

Chances are you have at least one radio that can receive FM stations. Even though FM is becoming less used now with Internet and satellite options, it still is more popular than the older AM radio bands. FM was the brainchild of an inventor you may have heard of — Edwin Armstrong — but you probably don’t know the whole story. It could make a sort of radio-themed soap opera. It is a story of innovation, but also a story of personal vanity, corporate greed, stubbornness, marital problems, and even suicide. The only thing missing is a long-lost identical twin sibling to turn it into a full telenovela.

Early Days

Armstrong grew up in New York and because of an illness that gave him a tic and caused him to be homeschooled, he was somewhat of a loner. He threw himself into his interest in electric and mechanical devices. By 1909 he was enrolled in Columbia University where professors noted he was very focused on what interested him but indifferent to other studies. He was also known as someone more interested in practical results than theory. He received an electrical engineering degree in 1913.

Unlike a lot of college graduates, Armstrong didn’t go work for a big firm. Instead, he set up a self-financed independent lab at Columbia. This sounded good because it meant that he would own the patents on anything invented there. But it would turn out to be a two-edged sword.

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Learn To Count In Seximal, A Position Above The Rest

July 20, 2018 by Tucker Ervin 42 Comments

Believe it or not, counting is not special. Quite a few animals have figured it out over the years. Tiny honeybees compare what is less and what is more, and their brains are smaller than a pinky nail. They even understand the concept of zero, which — as anyone who has had to teach a toddler knows — is rather difficult to grasp. No, counting is not special, but how we count is.

I don’t mean to toot our own horn, but humans are remarkable for having created numerous numeral systems, each specialized in their own ways. Ask almost anyone and they will at least have heard of binary. Hackaday readers are deeper into counting systems and most of us have used binary, octal, and hexadecimal, often in conjunction, but those are just the perfectly standard positional systems.

If you want to start getting weird, there’s balanced ternary and negabinary, and we still haven’t even left the positional systems. There’s a whole host of systems out there, each with their own strengths and weaknesses. I happen to think seximal is the best. To see why, we have to explore the different creations that arose throughout the ages. As long as we’ve had sheep, humans have been trying to count them, and the systems that resulted have been quite creative, if inefficient.

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What To Expect When You’re Expecting – A Trademark

July 18, 2018 by Bob Baddeley 18 Comments

A trademark represents a brand, so it can be words like “Apple”, including made up words like “Kleenex”. It can be symbols, like the Nike swoosh. It can also be colors, like UPS brown, and even scents like the flowery musk scent in Verizon stores. Filing a trademark in the United States is surprisingly easy. With a couple hundred dollars and a couple hours, you can be well on your way to having your very own registered trademark and having the right to use the ® symbol on your mark. You don’t need a lawyer, but you should know some of the hangups you might run into. The USPTO has a fantastic primer on trademarks, but we’ll TL;DR it for you. Continue reading “What To Expect When You’re Expecting – A Trademark” →

Françoise Barré-Sinoussi: Virus Hunter

July 17, 2018 by Steven Dufresne 13 Comments

It was early 1983 and Françoise Barré-Sinoussi of the prestigious Pasteur Institute in Paris was busy at the centrifuge trying to detect the presence of a retrovirus. The sample in the centrifuge came from an AIDS patient, though the disease wasn’t called AIDS yet.

Barré-Sinoussi and Montagnier in 1983, Image source: Le Globserver

Just two years earlier in the US, a cluster of young men had been reported as suffering from unusual infections and forms of cancer normally experienced by the very old or by people using drugs designed to suppress the immune system. More cases were reported and US Centers for Disease Control and Prevention (CDC) formed a task force to monitor the unusual outbreak. In December, the first scientific article about the outbreak was published in the New England Journal of Medicine.

By May 1983, researchers Barré-Sinoussi and Luc Montagnier of the Pasteur Institute had isolated HIV, the virus which causes AIDS, and reported it in the journal Science. Both received the Nobel prize in 2008 for this work and the Nobel prize citation stated:

Never before have science and medicine been so quick to discover, identify the origin and provide treatment for a new disease entity.

It’s only fitting then that we take a closer look at one of these modern detectives of science, Françoise Barré-Sinoussi, and what led to her discovery.

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Let’s Talk About Elon Musk’s Submarine

July 17, 2018 by Tom Nardi 223 Comments

When word first broke that Elon Musk was designing a kid-sized submarine to help rescue the children stuck in Thailand’s Tham Luang cave, it seemed like a logical thing for Hackaday to cover. An eccentric builder of rockets and rocket-launched electric sports cars, pushing his engineering teams and not inconsiderable financial resources into action to save children? All of that talk about Elon being a real life Tony Stark was about to turn from meme into reality; if the gambit paid off, the world might have it’s first true superhero.

With human lives in the balance, and success of the rescue attempt far from assured (regardless of Elon’s involvement), we didn’t feel like playing arm-chair engineer at the time. Everyone here at Hackaday is thankful that due to the heroics of the rescuers, including one who paid the ultimate price, all thirteen lives were saved.

Many said it couldn’t be done, others said even saving half of the children would have been a miracle. But Elon’s submarine, designed and built at a breakneck pace and brought to Thailand while some of the children were still awaiting rescue, laid unused. It wasn’t Elon’s advanced technology that made the rescue possible, it was the tenacity of the human spirit.

Now, with the rescue complete and the children well on their way to returning to their families, one is left wondering about Elon’s submarine. Could it have worked?

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Getting The Lead Out Of Lithium Battery Recycling

July 16, 2018 by Dan Maloney 74 Comments

When that fateful morning comes that your car no longer roars to life with a quick twist of the key, but rather groans its displeasure at the sad state of your ride’s electrical system, your course is clear: you need a new battery. Whether you do it yourself or – perish the thought – farm out the job to someone else, the end result is the same. You get a spanking new lead-acid battery, and the old one is whisked away to be ground up and turned into a new battery in a nearly perfect closed loop system.

Contrast this to what happens to the battery in your laptop when it finally gives up the ghost. Some of us will pop the pack open, find the likely one bad cell, and either fix the pack or repurpose the good cells. But most dead lithium-based battery packs are dropped in the regular trash, or placed in blue recycling bins with the best of intentions but generally end up in the landfill anyway.

Why the difference between lead and lithium batteries? What about these two seemingly similar technologies dictates why one battery can have 98% of its material recycled, while the other is cheaper to just toss? And what are the implications down the road, when battery packs from electric vehicles start to enter the waste stream in bulk?

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