Beginnings of a Whole Car

As reported in earlier blog posts, I've recently started selling "Mechanical Gifs", highly stylized acrylic models of simple mechanisms designed to illustrate how the things work—the same way an animated gif would, but in physical form.

The models currently for sale are one mechanism at a time: A lock, an engine, etc. But I've got a lot of other designs in my back pocket waiting to come to life (and to the store). Here is a preview of the inspiration I had a few days ago to combine several models I have been working on into a complete working car. (Well, more like the skeleton of the most fundamental working parts of an imaginary radial-engine car.)

Here's what it looks like if you push it across a table. The mechanism is smooth enough that the whole drivetrain turns even though there is almost no friction between the smooth acrylic tires and the smooth varnished table top.

Here is a video showing how the radial engine (a slightly modified copy of the one for sale at mechanicalgifs.com) connects to the differential (an unfinished design not currently available). Yes, there is no transmission and no universal/CV joints. Simplicity is key here! This is essence of car, not reality of car.

Here is more of how the differential works. (I didn't have anyone to hold my phone, so I can' show you how it works when the driveshaft is turning and you hold one wheel. Which is the whole point of a differential.)

Here's a close-up of the rack-and-pinion steering mechanism in action (top and bottom views):

The differential and steering mechanisms are not final designs, but neither are they first-generation. Both of them have been through 4 or 5 cycles of design, laser-cut, build, improve. For example, notice the little wings on the sides of the green rack gear in the steering mechanism? They extend as far as the ends of the joints connecting the rack to the tie rods. Without those wings, the rack tries to twist out of parallel when it's turned all the way to one side or another. Of course I didn't realize it would do that before I built one without wings.

I have several ideas already how to improve this design. For example, I'm going to replace the flat table-top connecting all the parts with two vertical rails running down the sides of the model. This will save plastic and make the whole thing much stronger and stiffer.

I'm also pretty sure I'm going to add a 2-speed transmission before finalizing the kit. (I have a design for a transmission, and it sort of works, but it's definitely not ready for prime time yet.) I don't think I will add any kind of suspension or universal joints: these parts do not feel to me as fundamental as the engine, transmission, differential, and steering.

My goal in all of these mechanical gifs is to simplify down to the most essential aspects of the design, to focus attention on the principal motions. In this case I wanted to find the essence of an old-school internal combustion car (electric cars are a whole other can of worms).

Of course you can't have a car without an engine, so that's definitely in. Without a steering mechanism you can only go in a straight line, so that also seems pretty fundamental. And if you have only one engine, then you must have a differential, or you will tear up the tires and axles as soon as you try to go around a corner. 

The transmission you could live without, but all real cars have one, because internal combustion engines are only efficient in a fairly narrow range of rotational speed. You have to have gears to let the speed of the wheels vary over a wide range, while keeping the speed of the engine in a narrow range. (Electric motors don't have this problem, and they are small, so you can just put a separate motor on each wheel and get rid of both the transmission and the differential.)

The other nice thing about a transmission will be that it shifts the axis of the drive train, so I can move the axis upwards, allowing the engine to be in a more natural , higher position while the differential remains lower down.

Stay tuned, maybe in a week or two I'll have the transmission installed.... (Sorry, not much chance of this being for sale before x-mas.)

P.S. Brakes? We don't need no stinking brakes. Onward!

Actually Making Things! MechanicalGIFs.com Kits Began Shipping Today

My son Connor claims that I know how to do this because I've done it before, but I don't think so. I'm pretty sure I'm just making it up as I go along, because as far as I can remember I've never actually mass produced a product for sale. (I'm not counting quilts because they are made one-off, not in a production line way.) 

18 copies of the Radial Engine kit.

If you're one of the people who have ordered one of my Mechanical GIFs kits, yes they have actually started shipping, and most likely all current orders will have been shipped by the end of the day tomorrow. See, here is a picture with a box full of finished kits in their retail packaging! (The last potential delay cleared up last week with the delivery of 5000 springs for the Pin-Tumbler Lock model.)

The concept of 5000 springs raises many questions in my mind. Like "where do you get 5000 springs?" and "why do you get 5000 springs?" and "is that a big box of springs or a small box?". I mean, that's enough for a thousand Lock kits, and I didn't even know if people would order ten kits, let alone a thousand. Am I nuts ordering that many?

5000 springs doesn't look like much: This is all of them, together weighing less than a pound.

The answer to the first question, in this case, is the W. B. Jones Spring Company in Wilder, Kentucky. They are price-competitive with Chinese suppliers in the range of quantities I was looking at, with far shorter lead times. Yes, we in America can still manufacture things!

Why 5000? Because the economics of the situation push towards the maximum remotely plausible quantity. Purchased individually, these springs are $3.70 each. The five in my Lock model would be $18.50, which is of course nuts! But in units of 5000, they are 6.5 CENTS each, over fifty times cheaper (making the total $0.32 per model). By looking at the slope and intercept of price quotes for 1000, 2000, 3000, and 5000 units, it's easy to see that the formula for anything over a thousand units is $170 plus 3.1 cents/spring (total of $325 for 5000). In other words, there's a $170 setup fee for them to configure the machine to make that particular spring, and after that it costs 3.1 cents each to make them (including their profit). For small quantities they presumably either have a bit of stock on hand, or they lose money making enough to cover the order, plus some more to put into stock for the next small order.

It's not unlike the economics of color offset printing of books and posters. The first one costs a fortune because of setup time, but after that, they are just pennies a piece. So you should order as many as you can justify, to avoid paying the large setup costs again.

So I ordered a lot of them. I'm also pretty sure that I'm going to need similar springs in other models I have planned for the future, so unless the whole concept is a miserable failure, I do expect to use these up over time.

This is what 1000 tiny screwdrivers looks like.

I mention Chinese suppliers because for many things they are not actually the cheapest option. They are the only option. For example, suppose you want a bunch of those tiny disposable screwdrivers you get in some kits, and which I wanted to include in all my kits? It took me a while to figure out the right search terms, but eventually I found them for 8.3 cents each in quantity one thousand ($83 for a thousand, shipping included).

It was, of course, from a Chinese supplier. I don't know this for a fact, but I would be surprised if there are any US manufacturers of tiny disposable screwdrivers. I certainly didn't encounter any in my googling.

In the past my main problem in getting these screwdrivers would have been how to spend only $83 with a wholesale supplier who is literally half way around the world. If I wanted a million tiny screwdrivers for $80,000 there would be all sorts of ways, but in the past, the answer for such a tiny order was "you don't". It simply was not practical because of the high cost of finding and doing business over such distances. 

Today, the answer is alibaba.com or aliexpress.com, the outside-China focused websites of the giant Taobao (淘宝网) marketplace owned by the even more giant Alibaba group. At aliexpress.com you can buy small wholesale lots from countless thousands of small merchants, who in turn buy from the real manufacturers and resell with very little markup. It's basically a virtual version of the vegetable-stall style of industrial supplies market I talk about in this blog post. At alibaba.com the focus is on larger quantities of serious industrial equipment (but many merchants there will also deal in smaller quantities).

The more I think about it, the more I am convinced that the existence of aliexpress and its relatives is an important step in the restoration of industrial innovation and small-scale manufacturing in the United States. Yes, we need Chinese suppliers to be able to do industry in the US.

The thing about manufacturing is that it only works, in a competitive way, when each company is part of an ecosystem of suppliers and customers. For example, there used to be an ecosystem like that in Detroit to make cars. They could make cars faster, cheaper, and better in Detroit than anywhere else in the world, because everything needed to do it was just down the road. If one of the big companies needed a new kind of headlight, they could just go a mile over and talk to the engineers at the headlight manufacturer, who in turn could talk to the glass molding outfit next door, and so on. That's all gone now, or rather it's moved.

When I first started making quilts I thought about how we needed to price them, and whether we could consider going after mass markets. The answer is "not if we make them in America". This has nothing to do with labor costs, it's because we would be competing against factories in parts of the world where there are integrated manufacturing ecosystems for textile products. We would have to get fabric and batting shipped to us from far away. They can get supplies from next-door factories. They are also next door to the companies that make the machines that make the quilts. (We have one of these machines. There are thousands in China surrounding the companies that make them.)

So we make "fancy" quilts that sell for 3-5 times more than the ones you get at Walmart. Some of that extra price is because there's a lot more stitching, or they are custom designs, or just very cool, but some of it is just because we cannot possibly be as efficient making one or two at a time (compared to, for example, this factory which makes 1350 quilts a day using five of an earlier model of the same machine we have).

With the mechanicalgifs.com kits I'm trying to keep the cost as low as possible. It's more realistic to be competitive because the parts are much smaller, so shipping in components isn't as cost-prohibitive as with quilts. And I manufacture the highest-value-added parts in-house (using my large laser cutter) from raw stock (acrylic sheets) that I can get at a good price close enough (Chicago) that I can economically drive up there and pick up new stock in person from time to time.

If the kits are successful online, in museum shops, and through educational distributors, I think it is realistic to keep making them here in Illinois. But only because I have access to a wide range of wholesale parts through aliexpress/alibaba. It really is the difference between happening and not happening. It's an example of what people mean when they say the world is shrinking.

Some people dream of restoring the kind of geographically-concentrated, vertically integrated manufacturing regions we had in the past (like Detroit). But that's not going to happen, and it's not the right goal anyway. We should instead look towards the inevitable future where the whole world is that region, for everything. We could be leaders in the game of bringing together the best from everywhere by embracing rather that fearing the merging of our destinies with those of our friends across the ocean..

 

And Now for Something Completely Different: Transparently Obvious Models

After a decade of writing books only about chemistry, I have started on something completely new. I call them Mechanical GIFs, because they are a lot like animated GIFs, but they are real mechanical devices that you can hold in your hand—and that I will sell you kits of at my new website, MechanicalGIFs.com.

The name is also a play on the r/mechanical_gifs subreddit, which contains many actual animated GIFs of interesting mechanical devices. (Of course the animated images you see here are actual GIFs, but they are GIFs assembled from photographs of a real object doing exactly what it looks like it's doing. There is no CGI or Photoshop involved here.)

My original motivation for making these models was that I had started working on a new book, tentatively called Things, which will require a lot of illustrations of how various kinds of mechanisms work. (It's a sort of "Way Things Work" book done by someone—me—who is really in love with mechanical devices.) In the past my books have always been filled with real photographs of real things, and I wanted to keep it that way as much as possible.

The problem with real mechanisms is that most of them are completely opaque, both literally and figuratively. They are typically made of metal, wood, or opaque plastic. And they are very complicated because they are meant to be practical, and practical always means a bunch of distracting realities have to be taken into account.

What I wanted was real things I could photograph but which would be as easy to understand as a schematic drawing. So I decided that I would make simplified, abstracted, stylized versions of the mechanisms I was writing about, and take pictures of them. 

I spent some time thinking about how best to go about making these things. I knew they would have intricate, difficult-to-make shapes, so conventional hand craft methods would be tedious. The three obvious choices were 3D printing, CNC machining, and laser cutting.

20170916142959_48176.jpg.jpg

3D printing is immediately disqualified because a fundamental requirement for the designs is that they be transparent. Not just translucent, but optically clear like glass, so the inner workings are totally visible. You can't 3D print fully transparent parts (well, you sort of can using the incredibly expensive and slow resin curing method, but even those parts require tedious post-processing and are never really glass-smooth). Also 3D printed parts just always look ugly, sorry.

20170916142959_48176.jpg.jpg

CNC machining is disqualified because it too does not leave a glass-smooth surface, and it has limitations when making small, delicate parts out of glass-clear plastics (because the plastic is brittle, and the machine is whacking it very hard).

So that leaves laser cutting as the tool of choice. The big disadvantage of laser cutters is that they can fundamentally only make flat things. You start with a flat sheet of acrylic and you end up with another flat sheet of acrylic that has a different outline. Fortunately it turns out that this limitation is a desirable creative constraint.

A big reason real devices are hard to understand is that they typically fold their action into complex three-dimensional shapes. Moving parts are going in all directions, overlapping, going through each other, and so on. In a laser-cut re-imagining of the same mechanism, everything needs to be flattened out. The different parts of the machine need to be separated into geographically distinct regions, all in the same plane rather than stacked up in the third dimension.

Good examples of what I mean by "stylized" and "separated into different regions" can be seen in this thing, which I call a Right-Angle Steam Engine

It represents an engine with a double-acting piston (it both pushes and pulls), and a spool valve (looks like a spool of thread). The job of the valve is to direct steam first to one side and then the other side of the piston, at the correct times to keep the engine spinning. (You can read more about the details of how this works on my page describing this model.) The point I'm making here is that this design completely "deconstructs" the working parts of the engine. The valve and piston are far apart (normally they would be right on top of each other to keep the steam path as short as possible). The connecting rods that link the crank arm on the flywheel to the piston and valve are as simple as they possibly can be. And the right-angle orientation between the piston and valve make explicit that the motions of these two parts are harmonic (follow a sine wave), and ninety degrees out of phase with each other.

I have several other designs of steam engine that move progressively closer to how real ones are laid out, but still retain the flattened, separated aesthetic.

The last one is actually operating on two layers (notice how the green and amber parts are on top of each other. This make it the most like a real engine, which would have a crank shaft with two out-of-phase crank arms. But the multiple layers also makes it the least easy to understand: It is best appreciated after studying the other two.

Steam engines are all about timing. You can't get an intuitive feel for them by looking at static images. And you can't (or at least I can't)  really "get" them by looking at animations. They are either going too fast, so you don't see how the valve and piston motions relate, or they are going too slow, so the dynamic nature of the interplay of movements is not clear. What you need is something you can move backwards and forwards at will, interactively. What you need is a physical model. 

Perhaps the best example of what I mean by the tagline Transparently Obvious is this model of a pin-tumbler lock. You can plainly and obviously see that there are a series of pins of different lengths which are blocking the movement of a sliding plate (which needs to move in order to release the catch). When the key is inserted, the different levels on the key are exactly right to align the tops of all the pins, allowing the plate to slide. This is exactly how all pin-tumbler locks work. (Except that they typically rotate into the third dimension rather than sliding, though there are a few that slide exactly like this one). 

Actually, it's not 100% obvious from the animation you see here. To be completely obvious, you have to have the physical model in your hand. Then you can feel the sliding plate, feel how the pins are blocking it, feel how the resistance of the key to being inserted goes up and down as it encounters more and more pins (which you will then start recognizing with real locks, allowing you to guess at the relative lengths of the pins without seeing any of them, just from the feel of the key).

So, deep breath....I am actually manufacturing and proposing to sell these models. I have a couple dozen designs worked out, of which I have chosen six to release for what amounts to initial test-marketing. For those I have retail packaging, efficient layouts for mass production, and a stock of parts.

I have no idea if people are going to like these things. I mean, I think they are very cool and fun to hold and play with. They really do what you see here (and in the more conventional videos on mechanicalgifs.com). Even my kids seem to like them, and they automatically think everything I do is boring.

I have the laser cutter, I have the plastic, screws, packaging, and the hundred other things needed to semi-mass produce the models. You, as my faithful Blog/Facebook readers, are getting a sneak peak at the MechanicalGIFs.com website: I haven't announced it anywhere else and don't plan to until next week. As I said, I have no idea if these will be popular or not. If they are, I can make probably a few hundred up to maybe a thousand in time for x-mas (it's a fast and powerful laser cutter). If they are not popular, well, I think they'll find a market in museum gift shops, and if nothing else I needed to design them for my book anyway.... 

Since you're going to be the first people looking at the website (I hope?), I would much appreciate any comments you have, like typos, broken links, this is stupid, go back to making Apps, or whatever comes to mind. Leave comments on this post or email me.

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
— http://www.nature.com/nature/journal/v550/n7675/full/550186a.html
a lavishly illustrated tour of this molecular battleground, full of wit and wonder.
— http://www.nature.com/nature/journal/v550/n7675/full/550186a.html
Gray’s enthusiasm shines in Reactions. The text is peppered with dry asides, and a grumpy disdain for anything unscientific.
— http://www.nature.com/nature/journal/v550/n7675/full/550186a.html

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.
— http://www.nature.com/nature/journal/v550/n7675/full/550186a.html

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.
— http://www.nature.com/nature/journal/v550/n7675/full/550186a.html

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:

        http://www.huodongxing.com/event/4396240870100

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.