Ginning Up Some Cotton

We had a bountiful harvest of cotton here in the land of too-short-a-growing-season-for-cotton! My back 1/40th acre cotton field yielded about 25 pounds of raw, dried cotton bolls (counting seeds and "lint" or fiber, but not husks). This works out to about 800 pounds per acre, which would be a respectable yield if not for the fact that cotton yields are measured by the amount of lint only, not counting seeds. Since the bolls are over half seed by weight, my final yield will be under 400 pounds per acre, which is bad. But, I'm just happy I got any at all, and frankly even this is rather more than I know what to do with.  SO MUCH COTTON!

Here it is being dried on my make-shift forced air drying rack (powered by a large propane-fired greenhouse heater I have left over from a previous life). Hot air comes in the large duct on the bottom left and the plastic wrap forces it to exit from the top, after passing through all the shelves of cotton.

The central problem with American upland cotton (known as short-staple cotton because its fibers are relatively short compared to the longer fibers of Egyptian cotton) is separating the seeds from the fibers.

Cotton fibers grip very firmly to their seeds! Pulling apart cotton bolls by hand and picking out the seeds, I was able, with some practice, so separate about 330 seeds per hour. At that rate this batch would have taken literally months to separate. Fortunately I had previously constructed an entirely transparent cotton gin. Here we see it in front of the job to be done (cat for scale).

Here is the gin in action, separating seeds over 20 times faster than by hand (over 7000 seeds per hour). Apparently in historical times the first cotton gins were about 50 times faster than hand-separating. I think my 20-fold speed up is not bad considering that all parts of my machine, including the circular saw blades, are made of clear acrylic, and I only ever meant it to be used for getting some photos and videos of the process, not to actually gin all the cotton. (I didn't have a plan for that.)

I am using child labor for authenticity.

We're about 2/3 done with the job after about a week of on-and-off ginning operations. One day of production was almost entirely lost to a cat infestation.

Nice review of Reactions in Nature

My books generally aren't "serious" enough to get reviewed in serious places, so it's nice to see a proper review of Reactions In Nature  (perhaps the most serious scientific journal of them all). It's got some very nice quotes, which my publisher describes as "selling", as in likely to help sell the book (which goes on sale Oct 17th, 2017, and is available for preorder now, in case the quotes work in selling you on it).

a gorgeous gala of reactions
a lavishly illustrated tour of this molecular battleground, full of wit and wonder.
Gray’s enthusiasm shines in Reactions. The text is peppered with dry asides, and a grumpy disdain for anything unscientific.

I would like to say, by the way, that I'm not grumpy about all unscientific things. For example, I like kittens whose litter box someone else has to clean. I'm only grumpy when people lie about what they are doing, claiming it is based on science (i.e. reality) when in fact it's nonsense based on wishful thinking or intentional fraud. That I hate, much like a litter box I have to clean.

Of course, a proper review must always include some complaints (otherwise it isn't serious). You can go ahead and ignore those parts while I agonize over them and decide that I'm an imposter who has no business trying to write books. (I'll be agonizing over the bit about lack of narrative, but not about the places where he complains about one thing or another I didn't cover. I could make a list twice as long of the things *he* didn't cover in listing what *I* didn't cover. Seriously, who expects every important topic—even every headline topic—in chemistry to be covered in a 240 page picture book? That won't even get you past the first chapter in a typical organic chemistry textbook.)

OK, that was my obligatory negative bit about what is otherwise a very pleasing review. Even the (obviously British) reviewer admits that complaining is "churlish". See this lovely paragraph that immediately follows the regrettable ones. (It also includes our word of the day, "chiaroscuro", which is further evidence of the erudite nature of this review.)

Still, it feels churlish to gripe about this love letter. Mann’s photography transforms chemical samples into art, and captures the thrill of Gray’s demonstrations. Many photos recall the works of eighteenth-century artist Joseph Wright, using chiaroscuro to frame the glow of a reaction with a background of deep shadow. Others are playful: in one, chlorine gas combines with sodium metal to create a billow of sodium chloride, which rises to vaporously salt a net full of popcorn.

Nick has now officially been compared to one of the great painters of the Enlightenment, which he should definitely put on his resume. 

I was particularly pleased that the reviewer picked up on Chapter 4, On the Origin of Light and Color, which includes what I think are some of the nicest diagrams I've made in a long time.

the most attractive chapter, on the chemistry of light, draws a beautiful analogy between sound waves and musical notes, and electromagnetic wavelengths and colour.

In the book my diagrams for light and sound have blocks of text and pictures inset into them, so I'll put them here clean and unencumbered. First, this diagram of the visible range of light. Note the wavelength scale: each color is represented by a wave of the appropriate wavelength:

Here is the equivalent for sound over the range of a piano (which is about half of the typical human hearing range):

I think the most striking thing is just how much wider the range is for sounds than for colors. We can hear sounds over a nearly thousand-fold span of wavelengths, but see colors over less than a factor of two.

Next I talk about how musical notes and colors of light can be created. One way is additive: emit the light, or the sound, you want. For example, to get light of a green color, you could create a device of some sort that emits wavelengths of light only in the green range:

To get sound of a particular "color" you could similarly create a device that emits sound of only certain wavelengths. For example, you could play these three notes on a piano to get a pleasing chord:

But there's another way to achieve the same result: create light, or sound, of all wavelengths and then block, or filter out, all the ones you don't want. Imagine for example sunlight, which contains all frequencies of visible light, hitting a special wall that lets only the green wavelengths through:

That must be some pretty special material this wall is made of, right? Actually it's just green paint. Or green-tinted glass, or a green leaf, or anything else that looks green under sunlight. That's what it means for something to be green: It blocks (absorbs) all the frequencies of light that aren't green. (In the book I also talk about how you can do the same with sound, though it is somewhat less common than with light.)

Well, I've gone on long enough, so to end this review of a review, I will gratuitously post the spectrum of a fluorescent light that I put in the book. There is very little justification for drawing spectra this way, with wavy lines, but I think it's very pretty so I did it anyway.

Reactions! Actual Copies Arriving! Pre-order Now Possible (and Highly Recommended)!

My new book, Reactions is actually a reality now! I have a handful of copies in hand, and it's loverly!  (No, not enough to send you one, not even if you're related to me, come on, I've only got like three of them.)

Reactions is the sequel to Molecules, which is the sequel to The Elements. Together they form a trilogy that covers all of chemistry. (To the extent that any of my books can be said to "cover" a topic, since they are mostly pictures and stories, not some kind of textbook exposition. You get my books if you want to find out what's interesting about a topic, not if you want a substitute for taking a class on the subject.)

The official on-sale date is October 17th, but you can pre-order copies of Reactions right now, either an autographed copy from me, or a regular version from any of the major online booksellers (that link is to the publisher's website, where you will find a popup menu listing all the different sellers).

Right now there is a second option for getting a pre-autographed copy. Several months ago, before the books were printed, they chained me to a desk and forced me to sign hundreds and hundreds and hundreds of sheets of paper, which were then shipped back to the printer to be bound into copies of the book. Those are now for sale, with the most copies available from Barnes & Noble while their stock lasts. (They're selling autographed copies cheaper than I am, because they are much more efficient at packing and shipping stuff, since that is actually their business. But if you order from me, you can request a custom inscription, so there's that.)

Appearance In, and Report From, Beijing

Next Friday at 7PM I'll be speaking at what is described as a TED-like monthly lecture series at the Beijing Haidian Culture Treater (海淀文化小剧场). The event is open to the public, but some kind of ticket is required, which you get in some kind of complicated way that involves a lot of Chinese I don't understand. Here is a link to the event description:

In the mean time, here is a small update from Beijing. First, hotels—at lease my hotel—have robots to deliver small packages to guest rooms. I'd ordered a replacement for the Apple Pencil I forgot at home, and when I went to pick it up from the desk, the bell captain kindly agreed to send it by robot so I could follow it to my room....

When it gets on the elevator it says "I'm a little girl and I'm very nervous about getting on this elevator! Please give me the space in the middle!". There are many questions. For example, how does it push buttons on the elevator? When it got on, it asked, in its nervous-little-girl voice, for someone to please push floor 15, but no one did (including me because I wanted to see what it would do). The answer is that it is actually in telepathic communication with the elevator, because floor 15 pushed itself moments later. Perhaps it's just asking because people like to be helpful, and it's trying to endear itself to passengers (while demanding, in a cute way, that everyone get out of the way).

Second question: How is it going to knock on the door to my room? At the very end of the video you can just about hear the answer: It is also in telepathic communication with the phone system. A few seconds after arrival, the phone in my room rang. Unfortunately my room key was messed up so I couldn't get in to answer the phone, but I'm going to assume that it would have been a kindly robot mom saying "Hello nice hotel room occupant, my very nervous daughter-robot is at your door to deliver a package, could you please open the door and pat her on the head? Er, I mean, push the button on top to open the delivery compartment?"

China is very kid-friendly in many ways. For example, I had lunch outside Beijing with laser cutter engineers in a huge restaurant attached to some kind of bizarre children's paradise. You know those pretend backhoes they have in playgrounds for kids to dig with? The ones made of just a few metal bars that are entirely kid-powered? Well, here they are real power shovels with working hydraulic systems. God how I want one of these. They also have a sketchy-looking zipline and a large area that looks a lot like a paintball range, except it's a playground.

Back in town the next day, I was finally directed to the proper set of buildings for Beijing's electronic components market. (I tried to find these buildings last visit but only found nearby ones that were not quite right.) It's two buildings, one 4-story, one 6-story, filled entirely with farmer's market style vegetable stalls, except all the vegetables are capacitors, resistors, connectors (SO MANY CONNECTORS), chips, LEDs, potentiometers, heat sinks, power supplies, and so on forever. 

I had been warned by the laser cutter engineers that I would probably not find stepper motors, and we did in fact walk around for a good hour without seeing any. (I told my translator that this is what it's like when a girl takes a guy clothes shopping. It just seems like hours and hours of endlessly pointless walking around not buying anything. Actually there is a deeper logic to the activity.)

As time was running out, we finally hit the jackpot: A stepper motor vendor who had a sign saying he was closing his shop soon, everything on sale!

I didn't take a picture of them, but I got a super deal on six of exactly the stepper motors I wanted, plus over-sized drivers. I had calculated that I wanted about one Newton-meter of torque, but since my excellent translator is non-technical, this was a bit difficult to communicate. Finally I heard the guy saying "new me" and I leapt on this to ask, through the translator, how many new me's the motor had. One! Perfect. $145 for six motors, controllers, and pulleys, maybe 1/3 what I'd expect to pay from a proper supplier in the US.

Why do I need six stepper motors? Because I have a six-heddle loom that I want to automate. I'll mount them above with strings going down to lift each frame. Connor will be pressed into service to make an Arduino controller that will step through the desired pattern sequence.

Here's a couple pictures of how I was warping the loom just before leaving for China, complete with high-stakes cat:

It has what is called a sectional beam, and the thing I made to hold the yarns is called a warping rack. Combs (literal hair combs) guide the yarns to the beam. 24 yarns fill a 2-inch wide section of the beam (12 yarns-per-inch).

Here are videos of both ends of the yarn path:

24 yarns makes 2 inches, do that 12 times and you have a 288 yarns over a 24-inch width. Unfortunately I miscalculated and only had half as much yarn as I needed, so I only got half way and will have to finish with more yarn when I get home.

3-Week Laser Cutter Update

I’ve had my new laser cutter for three weeks now, and I continue to be very impressed with its capabilities. I’m currently in China (see picture of crazy intersection outside my window) visiting the manufacturer, mainly to learn more about it and their other models. So I thought I would make an omnibus blog post showing the things I’ve been able to make so far.

At this point I have four mostly complete, smoothly operating mechanisms, shown here in my hotel room in Beijing. (Some of these have been in previous blog posts, others are new.)

First, this lock mechanism is slightly improved from previous editions, with pin numbers (so you know what order to put the pins in when assembling it) and an acrylic chain link holding the insert to the other end of the lock. The springs are still fake. Not shown is a matching lock picking tool for leaning how to pick locks.

Next up is the improved spring scale. This version is reliably smooth in operation, and has a dial that goes up to 11. The acrylic springs break when they are stretched about twice as far as the design allows them to, so I think it should be pretty robust.

This is the real spring scale from which the design of my acrylic version is taken (loosely). I've replaced all the outer covers, the weighing platform, and the dial with laser cut/engraved duplicates, so you can see the mechanism inside. But you still can't see it as clearly as in the diagram. My hope is that when people see the real thing side-by-side with the acrylic model, everything will be obvious.

I don't have an acrylic model of it yet (and may not make one), but here is the much bigger, and much nicer Toledo scale, which uses a counterbalance system in place of springs. It too has laser-cut replacement covers and dial.

Here is a small child for scale (ha ha).

This is the new, much elaborated 7-cylinder form of the radial engine described in a previous blog post. Most real designs had an odd number of cylinders, so my previous 6-cylinder version was not ideal. This one also has engraving lines representing the cooling fins, and if you look closely, you can even see dummy valve stems and spark plugs. I thought about adding actual valves, cams, and lifters, but decided that would be insane

Finally, this rope machine is very pleasing to spin. I'm really quite surprised that it runs as smoothly as it does. I didn’t think laser cut plastic could be such a practical engineering material.

Moving on from machines to art, this is the laser-cut version of Nina’s $1000 bill (mentioned in my previous blog post and repeated here so I have one post with everything I've done so far…).

Here’s a video that shows just how fast the engraving works.

The main problem is keeping the power level low enough, and the head speed fast enough, to avoid going too deep. I have since learned, from the manufacturer’s engineers, that it would probably work better to engrave this in raster mode (where the beam does horizontal scan lines). This seems counterintuitive to me, so I’ll be eager to see how it comes out when I try it that way.

My hotel is very nice. This is what I had for breakfast.

Laser Money

Very quick post here because I'm about to leave for China in an hour, but I had to show y'all this because it's so neat. My new laser cutter, as it happens, accepts exactly the same DST files as the quilting machine. So what happens if you give it Nina's $1000 bill pattern?

Well, it works. This thing is fast!

Here's the final result:

More later.

6-Cylinder Radial Engine

Boy is this fun! Today's model is a 6-cylinder radial engine:

It's made with two layers of 1.44mm (rather thin) and one layer of 5.28mm (about 1/4" thick) acrylic. The pistons, link arms, and star-plate in the center are all cut in-place in operational arrangement (as in the CAD file above). In other words, you can simply slide it out of the laser cutter (being careful not to let any of the parts drop) and it works. Here is the main layer in raw form, with the protective film still on:

Getting the top and bottom plates screwed on is a bit tricky, but here it is all assembled:

The disk in the center is basically the crank shaft bearing. It's the rotation of the big disk within the cutout circle that keeps the crank shaft rotating about its center. The offset hole then caries the star plate around its orbit, operating the six pistons in order. (A certain wag who shall remain nameless complained that there were no operating valves, so I declared it to be a 2-stroke engine whose valves are just holes (not shown) in the cylinder walls.)

What blows me away is how smoothly this thing operates. I did not trim, sand, polish, or in any way manipulate any of the operating parts: everything is exactly how the laser cutter left it. All I did was add the nuts and bolts to hold it all together. Watch this!

Who needs a fidget spinner when you have a 6-cylinder spinner?

Although I had always been planning to make some engine models, I admit that the details of this one were inspired by this really cool cardboard version. Which reminds me that I need to add some engraved details around the cylinders.

Meanwhile, my cotton field is doing nicely. I weeded it this afternoon and it's looking good. A transparent cotton gin is next in the list of projects for the laser cutter.

Visible Lock

My purpose in getting a laser cutter was to make visible mechanisms, in order to make their operation clear. Here's the second example I've been working on: A visible pin-tumbler lock. With the key out, pins block the "core" from moving. But when the key is put in, the pins are all lifted to just the right height so that their tops line up along a "shear line". In a typical padlock, the core is then free to rotate, but in this version (as in some bike locks, for example), the core can instead slide out far enough to free a latch previously held in piece. Watch the video and it will all make sense (which is of course the whole point of making these things).

What the video doesn't show is that you can also pick this lock in the traditional way, by tensioning it (pulling gently on the core) and then using a thin tool to lift the pins one at a time until you find the one that is binding, then repeating until they all clear.

By the way, notice that the "springs" are completely bogus. In a real lock, springs push the pins down, but in this one the springs just act like small weights. The lock has to be held vertically so gravity can act in place of springs. Why did I do it that way? Because I haven't yet been able to figure out how to make acrylic springs that are weak enough to work for this situation. Everything I've tried has pushed way too hard, making it impossible to insert the key without a lot of wrangling. Acrylic is a terrible material to make springs out of, though I did get some extension springs to work pretty well in my previous mechanism.

Playing With The Laser Cutter

In my last blog post I reported on the arrival of my new laser cutter.... Today some videos of the first day and a half of playing with it. First let me say, this machine is AWESOME. I was expecting at least a week of frustration before it did anything sensible, but it basically just started up and ran right out of the box. I have not even had to touch the laser alignment despite its having been shipped across the country, tipped on its side, etc, since it was first put together.

It was a good call putting this thing in our side-building (a former drive-through bank, basically a bunker with bullet proof glass and a completely separate ventilation system from the main office building). It came with a powerful blower to extract fumes, and this turns out to be really quite important. Burning plastic smells terrible! I'm paranoid about setting things on fire, so I replaced the supplied plastic ducts with metal ones. The box in the middle is a water cooling unit that circulates cold water through the laser tube. (The shelf above it is the former money drawer, for passing things to customers outside in their cars. Sadly it doesn't work anymore.)

There is a lot of stupidity with file formats trying to get patterns into the machine, but that's not the fault of the machine, it would be the same with any model. Remarkably, in some cases I have had to resort to using the DST file format to transfer a design from Mathematica into the software that operates the machine. Why? Because bugs in Mathematica's DXF export make that not work, and I happen to have an elaborate body of code for exporting DST files, developed for use with our quilting robot. Why is this silly? Because DST is a decades-old format originally implemented on punched tape. It's limited to 0.1mm resolution, which is not good enough, so I have to expand the pattern by a factor of 10, then shrink it back down again. Oh well, I'll get some workarounds in place eventually.

Anyway, here is a video of the first real thing I tried to cut, a model of a spring-dial scale:

The version being cut here didn't work, but after several iterations I got a working device.

Making springs out of acrylic is sketchy, because the stuff is very brittle. But with enough zig-zags, I got springs that are able to stretch as far as they need to without danger of breaking. The scale is not "calibrated" in any sense of the word, and is super inaccurate, but that's not the point. The purpose it to let you understand how the mechanism works with a simplified, cross-sectional sort of mechanism. (When placed side-by-side with photos/videos of a real spring-dial scale, everything will make sense, I promise.)

After making the model scale, I started cutting and engraving transparent replacement dials to go on a pair of real scales (one spring scale, and one huge no-springs Toledo scale). My idea is to replace as many as possible of the cover plates and the dial face with clear acrylic, so that we can photograph the scales in operation, but you can see how they work inside. Creating the pattern for this involved spending a couple of hours carefully measuring the original dial, and writing Mathematica code to recreate the tick marks and letters as closely as possible. (Toledo uses a very strange font, and they are currently looking to see if they can get me a version of their old corporate font to make the numbers closer to the original.)

This scale dial is huge! 60cm, or nearly 24 inches, in diameter. Interesting, I think, that all the dimensions of the dial are clearly in metric units, even though it was made in Toledo probably in the 1950s. How did that happen? I have a book on the history of the Toledo scale company that will hopefully explain things to me.

Here's a picture of the smaller spring scale with its transparent replacement dial temporarily in place. Sorry for the mess, it's my garage. We will clean up and repaint (the scale) before taking the real pictures. Notice how the mechanism inside mirrors the acrylic model from above, except it's harder to see how it works. In both cases there are a pair of springs, and a rack-and-pinion gear system to turn linear movement into rotation of the dial pointer.

Next I'm working on a lock mechanism, which isn't working very well yet.

Meanwhile, Connor is having fun not cutting all the way through a piece of 1/2" acrylic. This is a time lapse of his depth test, varying the laser power level. I'm surprised how consistent the depth is. I didn't think you could do this with a laser cutter:

It's HERE!

It's Here!

It has parts!

It's huge!

It fit through the door!

It has a nice big working area!

It has a laser!

And a cutting head!

Yes, you guessed it, I just got a laser cutter! I'm so excited! I have no clue how to make it work!

This is a GU Eagle Advanced Automation model BF-1309 laser cutter, basically the small end of large-style laser cutters (it is, in fact, the smallest model offered by GU Eagle). It has a 130W CO2 laser tube, a water chilling unit to keep the tube cool, and a big blower fan to suck away the smoke and fumes from cutting whatever you're cutting. (I got a good deal on it from meeting the CEO on a recent trip to China.)

Why did I get a laser cutter? I'm starting on a new book project and I "need" it to make what I've decided to call "mechanical GIFs". It's too hard to explain what I mean by that, but hopefully pretty soon I'll have a couple that I can post images of (assuming the whole concept ends up working out as I hope it will).