Quieting the Brainstorm

Disclaimer: this is shameless self-promotion.  Cause I gotta eat too.

I’ve had to make a lot of decision lately. What should I do for my career? Where should I live? What do I eat for breakfast? Should I go hiking? It’s stressful stuff. I have my ways of making decisions. I like brainstorming a lot. But then I have to wait for those ideas to settle and that takes time. Sometimes I color while I wait for more ideas. I also like getting ideas from people that I admire. I combined all three into a coloring book. There are prompts for some creative brainstorming, beautiful mandalas for coloring between prompts while ideas are brewing and inspirational quotes by my favorite philosopher Socrates. If you need to make decisions and would like to do it the zen way, you might consider using my book. It would also help me out a lot and give me more time to continue blogging. It’s called Quieting the Brainstorm. There’s a link below if you so desire to click on it.

Quieting the Brainstorm: Coloring Workbook for Making Decisions With Socrates as your Guide


Wooden bike trailer


I live in a coop house. Coop is short for cooperative and the premise of these institutions is that living in a community is better than being isolated and that sharing is more efficient than not.

Part of coop-time is dinner time. We share the cost of food and do groceries for the entire house.  There is only one problem; we don’t have a car. We have been walking or biking to get small amounts of groceries.  Being economical I reasoned that a lot of small grocery trips is inefficient compared to a few large grocery trips.  We needed a bike trailer.

As a group, we agreed that we should buy a bike trailer but we couldn’t decide upon which one we wanted. We couldn’t figure out how to split the expenses and then one person preferred one trailer over another. Weeks dragged on and we still had no way to haul large amounts of groceries.

Frustrated, I decided to build my own bicycle trailer.  I went to the thrift shop and got a used princess children’s bicycle for $10.  Here’s a picture below of me doing a sweet bunny hop.


I happened to have some lumber in the basement, so went to town making the trailer.  Four hours later the sun was shining down on my face as I emerged from my shop with a completed bike trailer. It was actually dark outside but it sure felt like the sun was shining down. I needed to test it. Here is a pictures of my first grocery run.


In the end, the hitch wobbled a bit so I had to redesign it. Simply tying the trailer to my bike worked like a charm. This was by far the cheapest and easiest solution.

In the future I’ll likely use aluminum. The wood is light but it’s not nearly as strong.




A fluidic transistor that I designed and printed.

A fluidic transistor that I designed and printed.

This blog post is a temperature check for how interested the community would be in an open source, 3d printable, fluidics hardware platform. I want to make sure that this is something that the maker community wants because this isn’t for me, it’s for you. So if you won’t use it, I won’t make it.  First, let me wet your appetite by listing cool projects and applications of fluidics, most of which can be printed on a 3d printer and then I’ll tell you how it works and what I want to do with it.

Awesome projects:

Educational. Teach electronics and logic via the fluid/electric analogy which is extremely strong.

3d printable pneumatic stepper motor made from plastic parts only.

Rocket propulsion control systems.

Aircraft flight control systems.

Steam punk steam robot that can function while on fire.

Robust space travel.

Wood wind magic key piano that opens up a trap door with wind.

Programmable digital computer with no electronics.

Programmable fountain with no electronics that you can interact with.

Pulsating shower head. Your shower head already uses fluidics.

Microfluidics, biological control. This could be an open source project in its own right.

Smart meta-materials(speculative).

How it works:

The electric/fluid analogy is very strong. Electrons flowing in a wire is much like water flowing in a pipe and in fact, the two systems follow many of the same laws.  A pressure difference is like a voltage, a long narrow tube provides resistance, a membrane is like a capacitor and a coil of pipe is like an inductor. You can send power with electricity and also with fluids(i.e. hydraulic power systems). These are all analog components but the analogy between fluids and electric circuits goes even deeper.  Just like with electric circuits, you can make fluidic circuits digital.  The principle here is that streams of fluid interact with each other. That is, two streams will divert each other, not pass through, so that you can use a control stream of fluid to divert a power stream.  You can use this to build a fluidic amplifier/transistors, logic gates, flip-flops and even a digital computer.

Fluidic amplifier

I’ve taught electronics labs before and let me tell you, electronics are not intuitive to most people. Fluid flow is much more intuitive. One of my main motivations for an open source fluidics project is to make educational kits for high school and college students so that they can gain strong understanding for how electronics work by understanding how the more intuitive fluidic systems work.

Electronics are awesome. I love my computer and I love my Arduino.  But there are some applications that semiconductors are bad for. In particular, you can’t light your laptop on fire and expect it to function. Fluidic computers work just fine when on fire, provided the fluidic device is made of something like ceramics or metals and the fluid is something like gas or oil.  Indeed, you can make your power stream be rocket thrust, very hot, and use a perpendicular small control stream to divert the power stream, thus being able to steer a rocket! Nasa has a nice blurb about his here.

Rocket control

Fluidic rocket control.

Generally fluidics is practical in harsh conditions. Yet another example is space travel.  There are tons of charged particles and other radiation flying around in space that damage semiconductors.  Indeed, semiconductors have to be radiation hardened to withstand these harsh conditions. Because fluidics use fluids instead of electrons for their operation, they can be more reliable in such situations.

Fluidics is just plain cool. The number of steam punk applications are endless. You can make a robot that moves and thinks with steam, just steam! There was someone who made a desk that would play notes via a pipe organ when the drawers were opened. If you open the drawers in the right sequence, a trap door would open. It was made entirely from wood with no electronics. Cool huh?

Fluidic pipe organ desk with a secret compartment

Fluidic pipe organ desk with a secret compartment

Fluidic pipe organ desk with a secret compartment

Fluidic pipe organ desk with a secret compartment

One speculative application that’s on the forefront of science that I’m particularly interested in is digital meta-materials.  Digital meta-materials are materials that are made of bits of matter, put together like legos to make something that is functionally more powerful than each individual block.  In this case, I’m imagining fabric with a vascular system that responds to temperature and pressure  via fluidic logic.  I don’t think that 3d printers can beat traditional manufacturing in what traditional manufacturing does well already but I do think that 3d printers can win, hands down, when it comes to complex intricate objects like printing an intricate fluidic vascular system. The philosophy here is that we should be looking for applications of 3d printers that were not possible before.

What I want to do:

I’d like to start an open source fluidics project. Something like Arduino, easy to use, but with fluids. Maybe we could call it the Fluiduino? My primary motivations are educational and inspirations.  I want students to have a deep understanding of electronics and I want makers and hobbyists to easily be able to make rocket control systems, steam robots and programmable fountains. What I want from you is feedback as to whether an open source fluidics platform is something you’d be interested in playing with in the future? I’m not doing this for me, I’m doing this for the community as whole so if you’re not interested, I won’t do it. If however, you feel as inspired as I do, I’d love to find people to work with on this project.

-Sebastian Spiegel

Printing with Taulman 618 nylon filament

I used my Solidoodle 2, which took three months to get in the mail, 1.5 months longer than was quoted, to print with nylon today and wanted to report on my experience. Fist off, the nylon wouldn’t stick to my print bed. So I clipped paper to the print bed and printed on that. Seemed to stick fine but then kind of warped a lot later in the print and half way came off of the print bed.

Printing nylon with a paper base.

Printing nylon with a paper base.

Ventilation. Print with ventilation today and live to print with ventilation another day.  Some websites, and here,claim that within proper temperatures that nylon and ABS is safe. However, when I first received my 3d printer, I printed without ventilation in ABS and had a mighty sore throat and head ache. At home it’s hard for us to know exactly what temperature we’re printing at so to be safe, let’s just assume nylon can emit toxic fumes. I used a duct with a computer fan as well as a large room fan pointed at the window for ventilation and I still wish I had more ventilation. I didn’t smell any fumes but I don’t want to risk it.  In the future I plan to put my Solidoodle in a case and have the duct go completely outside. I could see some smoke come up through the vent which brings me to my next point. I printed at 190 Celsius. I’ve heard rumors that Solidoodle understates it’s temperature and that this is closer to 220 Celsius on other machines. My thermocouple read 180 \pm 10 Celsius but then again, half of it was exposed to the air so I’m not sure how accurate that is as well.


As for the print, I heard that nylon is softer than both PLA and ABS, which I can verify it is. It’s not quite elastic like a rubber band, but it does give.  I printed my one way valve with a flap. The flap blocks air in one direction and opens when blown in the opposite direction. A soft plastic makes a better seal, thus this is a perfect test item for my nylon filament.  You can download and print it here. The nylon had some oozing which made the flap stick to the wall. I had to cut this away with a knife. But once I did, the valve worked like a charm, blocking 80-90% of the fluid flow in the reverse direction.  I can’t wait to try this print out on elastic ABS and soft PLA!

Valve with a flap

Valve with a flap

Valve with a flap

Valve with a flap

Fluidic diode:trials and tribulations

Story, significance,

This story starts on wikipedia, where I discovered the Tesla valve, a one way valve for fluids with no moving parts.  I was so impressed that I designed a part in OpenSCAD and uploaded it to Thingiverse, here.  Unfortunatly, it didn’t work very well. I tried three different designs, all of which only kind of worked. So, I went back to the drawing board and kept designing.

Tesla valve

Printing my Tesla valve

But before I tell you about the designs, let me point out why this is important. Fluidics is the art of using fluids to do computation and control in the same way that electrical computers compute, but using a fluid instead. The Tesla valve is an example of what a Fluidicist, just made that up, would call a fluidic diode. You can also make the fluidic equivalent of transistor(fluidic amplifier), capacitor, resistors, inductors and more. Home 3d printers print in plastics which limits what they can do. In particular, they can’t print an electric stepper motor, one of the main components of an extrusion based 3d printer.  BUT extrusion 3d printers are awesome at printing solid parts like gears and pipes and such. With such elements, fluid stepper motors can be made along with fairly complex logic to control and drive it. In a way, fluidics could be a killer application of 3d printers because complicated ducts can be printed at no extra cost. In essence, you could print out complicated fluidic microchips at home. I should also point out that I’m not suggesting some untested crack pot wild scheme. Fluidics is a very well developed technology with a history that dates back to the 1950s and with applications that range from aerospace to biology.  For the more technical reader, I’ve collected some useful links at the bottom of the page.

Now back to the story.  So the Tesla valve wasn’t working as well as I wanted it to. I thought I’d do away with the “no mechanical parts” paradigm and include a flap that closes if air goes in one direction and opens when air goes in the other. This worked much better but still only reduced the air flow, by what felt like 30% or so, I’m guessing here. If the material was softer, I’m using PLA, I’m sure this would work much better. You can download and print it here.

One way valve

One way valve with flap:side view.

One way valve

One way valve with flap:bottom view.

One way valve

One way valve with flap:top view.

But then through my reading and on Thingiverse, I found out about the fluidic vortex diode. Sounds cool, huh?  It works the same way that draining a bath tub works. Huh? When you drain a bath tub, the water has  some angular moment and creates a whirl pool as it goes toward the drain. This whirl pool limits the speed at which water can drain. But going the opposite way, pumping from the drain, there is no whirl pool and so less resistance.   A fluidic diode works like this, only the angular momentum is maximized by pumping the fluid in perpendicular to the sink and by putting the whole contraption in a closed cavity.

I made two designs. The first one you can download here. It also only kind of worked. So I went to the drawing board and did some math.  It turns out that a spiraling fluid with no friction experiences a pseudo-potential barrier that varies inversely with the radius squared, meaning that if you double the radius of the vortex diode, it should take four times as much energy to overcome that centrifugal barrier.  So I designed a vortex diode with over twice the radius, which you can find here. It also didn’t quite work as well as expected. So now I’m calling out to the community, YOU, can you help me find a better fluidic diode?

Large fluidic vortex diode

Large fluidic vortex diode

Fluidic vortex diode

Fluidic vortex diode

Links and further reading:


1967 report by the military summarizing fluidics

Fluidic stepper motor


Lecture at the Broad Institute about microfluidics

Fluidic logic

IMG_0771 IMG_0790

I recently made a blog post about the analogy between fluid flow in pipes and analog electric circuits.  Of course, I’m not the first to think of this. It’s called the hydraulic analogy.  But it’s not just analog circuits for which this analogy carries over, the analogy works for digital electronics as well. That is you, can do logic gates hydraulically. This is called fluidics and there already happens to be designs for how to construct hydraulic amplifiers. With hydraulic amplifiers, you can do logical operations.

How does it work? A very small stream of fluid deflects a very large stream. First I’ll show you how to do a NOT gate, then an AND gate and together NAND.

NOT gate:Simply take the left outgoing tube as your output. Done.

AND gate:To do an AND gate, take the output of the first amplifier, the right side, and feed it into the large stream of the second amplifier. Now the second amplifier will only have a stream in the right hand side if both control streams are on. BOOM! An AND gate.

Together, you can make a NAND gate and NAND is universal for logic which basically means you can make a computer if you can make a NAND gate.


The RepRap project was how I first learned about 3d printing. It has the remarkable mission, in that I’m remarking about it, of printing all of the parts to make another printer. Wow. Well, in principle, all of the circuits can be replaced with pneumatic ones. And also, you know, it might make a cool theme for a sci-fi flick. Just imagine a 3d printer printing with a background of hydraulic valves, pumps and hoses. Generate a pressure difference with steam and you’ve made a steam punk wet dream.

Now I’m not suggesting that we start running our 3d printers this way. The point is, if push came to shove, 3d printers could print out much more of their parts than they currently do without the need to resort to printing new materials.

In honor of the RepRap project, I designed a printable version of the fluidic amplifier. You can find it on thingiverse here. You can test that it works using your mouth.

Instructions:Just print it out twice and hold it together, tape it together, screw them together or glue them together. Doesn’t matter how you do it. Just make sure they stay together. To test them, you only need to hold them together with your hands and blow through the power port and one of the output ports. I just tested it and between 70-90% of the air went through the right output port. Considering that I was holding them together with my hands and using my mouth, that’s pretty freakin’ good. 🙂

I should also point out that this thing was already patented in 1974.


Tesla valve:print in one piece

Tesla valve is a one way valve with no moving parts that gives a preferential direction of air/liquid flow.  It’s exciting because most one way valves have a flap that closes are a ball that blocks flow in a particular direction.  But not the Tesla valve. It uses air itself to block air from passing.


Today I decided that I wanted to print a Tesla valve but all the designs I’ve seen require you to print it in two parts and then use screws to hold it together. That seems like too much work so I decided to design a Tesla valve that prints all in one piece.  You can download it here. This is all part of a bigger project which I plan to unveil in the future 😉

My first design was  kind of wonky. Blowing in one direction you would get smooth air flow and in the other, turbulent air flow but still quite a bit of flow.  added the fins in as well but the airflow is still substantial. I guess I’ll have to get back to it some other time.

Here’s my printer printing this Tesla valve:



I love wind turbines but people think they look terrible

I was talking to my friend Gabe today and Gabe is from a New England community that had down voted a wind turbine being installed in their neighborhood. I had read in articles that some people didn’t like the way they looked or the way they sounded but I had never imagined that those factors would be enough to drive a community to vote against installing wind power.  This all made me a little sad because  I realize how important it is that we move towards clean energy generation.

We continues talking for some time. I showed him pictures of various wind art and pointed out that wind turbines could be quite beautiful. That’s what I want to show you, the reader, in this blog post. Examples of beautiful wind art that sadly is not usually hooked up to a generator.  Now I’m not saying that we should use exactly these designs for energy generation. I’m saying that we should be inspired by them to make both beautiful and efficient turbines.

Better electric generator design and my shake generator

Background on generators for beginners:

It turns out that if you move a magnet past a wire loop, an electrical current will be created around the loop.  This is how generators work.  Going the other way, if you have an electrical current in a loop, it cause a magnetic field which will exert a force on the magnet. So while the magnet is causing a current in the loop, the current is causing a magnetic field that exerts a force on the magnet in the opposite direction of its motion. What is happening is that while the magnet is getting slowed down, that energy is being transferred to the current in the wire. This partially explains why perpetual motion machines don’t happen in electromagnetic systems. Energy can only be converted from mechanical to electrical energy and back but never created.

Better generators:

What is the ideal generator? First you have to figure out what you’re trying to optimize for. What I want is a high power output given a constraint on the number of magnets that I have. I’m assuming that wire is unlimited.  If I were being more thorough, I would look at the cost of each material and optimize the power with respect to the cost.

Before I get to better generator design, let me tell you how I got started on this. I had this image in my head of little tiny units of energy generation. Little generators that would create voltages when they vibrated. They’re called shake generators and I posted about this previously. I imagined hanging them from trees or placing them in a stream or really anywhere where there is a lot of shaking going on. I tried this out by taking a tube, actually a pen, and wrapping a whole bunch of coils around it. The diameter of the pen was about 5mm.  By the time I finished wrapping 1000 times, my coil had a diameter of 20mm. Horrible.  Even then my neodymium magnets only produced a tiny voltage when I shook it really really hard. Fail. This was also happening at 2am which probably left my roommates wondering what the hell I was doing in my room.

Here are the problems with small generators:

1. If I want to keep the radius of the loops small, I have to use thin gauge wire which means more resistance.

2. The voltage around a loop is proportional to the area times the rate of change of the average magnetic field within your coil.   V_{loop}=-A\frac{dB_{avg}}{dt}. So small loops mean a small voltage.

3. Bigger loops with bigger magnets lead to less resistance for the larger generated voltage and hence to a higher power output.

To explain point three, that bigger loops with combined magnets is better, imagine that you had 2 square magnets and two square loops of the same size and that the loops are in series so that the voltages add.  I’m assuming the magnets are moving to the left over the top of the coils.


There are 2 squares, each square has 4 sides and so there are 8 sides. By combining the two square magnets and making a bigger loop, you get rid of one of the sides,  reducing the length of the wire which then reduces the resistance..  Plus the combined magnets produces a larger magnetic field and thus a higher voltage. Though I wonder how much each magnet demagnetizes the other when placed side to side?

So I’ve come up with some principles to work by in making my shake generator.

1. I need wider magnets with bigger coils and so a larger shake generator.

2. The magnet needs a weight attached to it so that it can carry more kinetic energy. Depending on cost,  I might just use a very large magnet.

3. I should try to convert slow mechanical motion, the shaking, to very fast motion, which would increasing the rate of change of the magnetic flux and thus increase the voltage. I might do this mechanically with gears and levers. I was also thinking of putting a magnet on a wire and using torsion or vibration to create a high frequency vibration..

Finally, if anyone sees any mistakes or improvements that can be made, please let me know.

3 improvements that could be made to 3d printers

Oh, how I wish I had more than one life to live. Then I would have the time to do all the things that I want to instead of just talking about them.

Most recently, right now, I came up with a few wishlist items that would improve additive 3d printers tremendously.  For all I know someone is already doing these things or maybe YOU, the reader already are. In which case, please let me know because that would be pretty cool. If enough time goes by, I might even attempt to do these three things myself. Without further ado, here they are:

1. Use 5 axes rather than 3 axes.

Support material sucks.  I mean, it’s great because it allows you to build up complex structures, but it’s expensive and it leaves marks when you break it away. If you could rotate the work piece, you could always be adding on top instead of from the side.  Certainly some support material might still be needed in cases where the printer head simply does not fit, but being able to rotate the work piece would certainly reduce the amount of support material.

2. Use feedback via a camera or laser to detect errors. 

3d printers are rather dumb right now. If it screws up, it just keeps on going and going and going until you come back from having your tea and realize that you have gobbly goop left.  Wouldn’t it be nice if your 3d printer actively scanned your work piece and compared it to your 3d model?

3. A router bit to correct errors.

Given that you can detect errors from point 2, why not correct them? A rotary cutter would allow you to remove mistakes and smoothen the work piece. You might need a vacuum system to go with this so that scraps don’t get in the way.

If any of my readers know of an example of these three things being done or ever do these things, please please let me know so that I can tell you how cool you are.

-Sebastian Spiegel