Fail Of The Week: Machining Bismuth

[David Cook]’s summary below the write-up of his experiences working with a bismuth ingot is succinct.

I wasted a weekend learning why elemental bismuth is not commonly used for metal parts.

It’s a fair assessment of his time spent growing unspectacular bismuth crystals, casting a bismuth cylinder that cracked, and machining bismuth only to be left with a very rough finish. But even though he admits the exercise was unsuccessful, he does provide us with a fascinating look at the physical properties of the element.

This is what [David] wanted to make. Alchemist-hp + Richard Bartz with focus stack. (Own work) [CC BY-SA 3.0], via Wikimedia Commons
This is what [David] wanted to make. Alchemist-hp + Richard Bartz with focus stack. (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Bismuth is one of those elements you pass by in your school chemistry lessons, it has applications in machining alloys and as a lead replacement but most of us have never knowingly encountered it in the real world. It’s one of the heavy metals, below antimony and to the right of lead on the Periodic Table. Curious schoolchildren may have heard that like water it expands on solidifying or that it is diamagnetic, and most of us have probably seen spectacular pictures of its crystals coated in colourful iridescent oxides.

It was a Hackaday story about these crystals that attracted [David] to the metal. It has a low enough melting point – 271.5 °C – that it can be liquified on a domestic stove, so mindful of his marital harmony should he destroy any kitchen appliances he bought a cheap electric ring from Amazon to go with his bismuth ingot. and set to work.

His first discovery was that cheap electric rings outdoors aren’t very effective metallurgy furnaces. Relocating to the kitchen and risking spousal wrath, he did eventually melt his bismuth and pick off the top layer once it had resolidified, to reveal some crystals.

These are the bismuth crystals he made.
These are the bismuth crystals he made.

Unfortunately for him, instead of spectacular colors and huge crystals, the sight that greeted him was one of little brilliance. Small grey crystals with no iridescence. It seems the beautiful samples are made by a very slow cooling of the liquid bismuth, followed by a quick pouring off of the remaining molten metal. Future efforts, he assures us, will involve sand-insulated molds and careful temperature monitoring.

Undeterred, he continued with his stock of bismuth and embarked on the creation of a cylinder. Early efforts with a clay mold resulted in cracked cylinders, so in desperation he cast the entirety of the metal in an aluminium baking tray and cut the resulting ingot to a rough piece of stock for turning.

Poor finish on machined bismuth.
Poor finish on machined bismuth.

With the bismuth in the lathe, he then came face to face with what he alluded to in his conclusion above, why machined bismuth parts aren’t something you’ll encounter. His cylinder came out with significantly rough patches on the surface, because bismuth is both crystalline and brittle. He suggests improvements could be made if the metal could be solidified with fewer crystals, but it’s obvious that elemental bismuth on its own is not a winner in the turning stakes.

We suggest you take a look at [David]’s write-up. It may be presented as a Fail of The Week here, but in fact it’s more of a succession of experiments that didn’t work than an unmitigated disaster. The result is an interesting and well-documented read that we’re sure most Hackaday readers will gain something from.

Aside from the bismuth crystals linked to above, we’ve featured bismuth a few times here at Hackaday. A low-temperature soldering process used it in an alloy, and we’ve even featured someone using it in another alloy to print using a RepRap.

Thanks [nebk] for the tip.

Lego-Like Chemistry and Biology Erector Set

A team of researchers and students at the University of California, Riverside has created a Lego-like system of blocks that enables users to custom build chemical and biological research instruments. The system of 3D-printed blocks can create a variety of scientific tools.

The blocks, which are called Multifluidic Evolutionary Components (MECs) appeared in the journal PLOS ONE. Each block in the system performs a basic lab instrument task (pumping fluids, making measurements or interfacing with a user, for example). Since the blocks are designed to work together, users can build apparatus — like bioreactors for making alternative fuels or acid-base titration tools for high school chemistry classes — rapidly and efficiently. The blocks are especially well suited for resource-limited settings, where a library of blocks can create a variety of different research and diagnostic tools.

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Homemade EDM Can Cut Through Difficult Materials Like Magnets With Ease

Many years ago [ScorchWorks] built an electrical-discharge machining tool (EDM) and recently decided to write about it. And there’s a video embedded after the break.

The build is based on the designs described in the book “Build an EDM” by Robert Langolois. An EDM works by creating lots of little electrical discharges between an electrode in the desired shape and a material underneath a dielectric solvent bath. This dissolves the material exactly where the operator would like it dissolved. It is one of the most precise and gentle machining operations possible.

His EDM is built mostly out of found parts. The power supply is a microwave oven transformer rewired with 18 gauge wire to drop the voltage to sixty volts instead of the oven’s original boost to 1.5kV.  The power resistor comes from a dryer element robbed from a unit sitting beside the road. The control board was etched using a hand traced schematic on the copper with a Sharpie.

The linear motion element are two square brass tubes, one sliding inside the other. A stepper motor slowly drives the electrode into the part. Coolant is pumped through the electrode which is held by a little 3D printed part.

The EDM works well, and he has a few example parts showing its ability to perform difficult cuts. Things such as a hole through a razor blade., a small hole through a very small piece of thick steel, and even a hole through a magnet.

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Copenhagen Suborbitals Launches Impressive Amateur Liquid Fueled Rocket

Copenhagen Suborbitals just launched their latest amateur liquid fuel rocket. Why? Because they want to strap someone to a bigger amateur liquid fuel rocket and launch them into space.

We’ve covered them before, but it’s been a while. While they make a big deal of being amateurs, they are the least amateurish amateurs we’ve come across. We’ll forgive a lot as long as they keep making great videos about their projects. Or posting great pictures of the internals of their rockets.

The Nexø I rocket they recently launched claims to be the first guided, amateur, liquid-fueled rocket. There is a nice post on the guidance system. It was launched from a custom built barge off the shore of Denmark, which allows them to escape quite a few legal hurdles around the launch. The rocket flew beautifully. That is, it went only away from the ground; no other directions. Also, it didn’t explode, which is a lot to expect from even the biggest players in the field.

Copenhagen Suborbitals continues to do amazing work. Hopefully their next rocket will be even more impressive… for amateurs, that is.

Make Your Own Transparent Wood

Want to bring your fine antique furniture into the 21st century? Make it clear with transparent wood. That’s what [blorggg] is doing over on Hackaday.io, and it looks cool enough to have a some interesting and novel applications besides small, clear test pieces.

The recipe for transparent wood is surprisingly simple, and all the ingredients are readily available from a drug store or home supply store. First, the wood is soaked in a bath containing lye and sodium sulfite for several hours. The wood is then bleached in a bath of hydrogen peroxide. After this, the wood is transparent, but very weak. Infusing the wood with epoxy resin strengthens the wood.

We first heard about this process back in May when the the paper [blorggg] based his recipe on came to light. the lye and sodium sulfite are frequently used in the paper industry to dissolve the lignin in wood. By removing the lignin, the microscopic structure of a piece of wood becomes just a series of tubes and thin cell walls. After bleaching, adding the epoxy shores up the now exceptionally weak structure of a block of wood.

While the original researchers only made two pieces of transparent wood – end grain and cross grain basswood, inexplicably referred to as R-wood and L-wood – [blorggg] is taking this much further. He’s using plywood to great effect, and the process is simple enough to expand to woods a bit weirder than basswood. If you have some scrap walnut, burl, or some exotic wood, this might be something to try out.

The Dubious Claim of a World Helium Shortage

If you’ve been reading the news lately, you doubtless read about the find of a really big new helium gas field in Tanzania. It’s being touted as “life-saving” and “game-changing” in the popular media, but this is all spin. Helium is important for balloon animals, scientists, and MRI machines alike, but while it’s certainly true that helium prices have been rising steadily since 2000, this new field is unlikely to matter all that much in the grand scheme of things.

helium_uses
Source: USGS

The foundation of every news story on helium is that we’re running out of the stuff. As with most doomsday scenarios, the end of the world’s supply of helium is overstated, and we don’t just mean in light of the new Tanzanian field. Helium is the second-most abundant element, making up 24% of the total mass of the universe. And while the earth has a disproportionate amount of heavier elements, helium is in rocks everywhere. It’s just a question of getting it out, and at what price that’s viable.

So while we’re stoked that the era of (relatively) cheap helium can continue onwards for a few more years, we’re still pretty certain that the price is going to continue to rise, and our children’s children won’t be using the stuff for something so frivolous as blowing up party balloons — it’ll be used primarily, as it is now, where it’s more valuable: in science, medicine, and industry.

Let’s take this moment to reflect on the economics of second-lightest element. Here’s to you, Helium!

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You Can Learn a Lot from a Candle

Beginning in 1827, [Michael Faraday] began giving a series of public lectures at Christmas on various subjects. The “Christmas Lectures” continued for 19 years and became wildly popular with upper-class Londoners. [Bill Hammack], aka [The Engineer Guy], has taken on the task of presenting [Faraday]’s famous 1848 “The Chemical History of a Candle” lecture in a five-part video series that is a real treat.

We’ve only gotten through the first episode so far, but we really enjoyed it. The well-produced lectures are crisply delivered and filled with simple demonstrations that drive the main points home. [Bill] delivers more or less the original text of the lecture; some terminology gets an update, but by and large the Victorian flavor of the original material really comes through. Recognizing that this might not be everyone’s cup of tea, [Bill] and his colleagues provide alternate versions with a modern commentary audio track, as well as companion books with educational guides and student worksheets. This is a great resource for teachers, parents, and anyone looking to explore multiple scientific disciplines in a clear, approachable way.

If there were an award for the greatest scientist of all time, the short list would include [Faraday]. His discoveries and inventions in the fields of electricity, magnetism, chemistry, and physics spanned the first half of the 19th century and laid the foundation for the great advances that were to follow. That he could look into a simple candle flame and see so much is a testament to his genius, and that 150 years later we get to experience a little of what those lectures must have been like is a testament to [Bill Hammack]’s skill as an educator and a scientist.

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