inportb

I’d designed few alcohol burners in the past, and they’d all depended on using metal rods or shims to vaporize the fuel. One end of the metal would be submerged in fuel while the other end would be in contact with the flame, thus conducting heat back into the fuel and generating combustible gas in situ. A benefit of this approach is that much more power is generated due to the pressure and mixing with air. Because of this, the alcohol burner has become a useful part of my toolkit.

Recently I spent an hour or so reading up on Bunsen’s design of his gas burner. Though a Bunsen burner relies on pressure from the gas line rather than generating its own pressure, some of the concepts are nonetheless helpful in improving my own design. Incorporating some of Bunsen’s ideas, I came up with yet another alcohol burner design: this one allows fresh air to be drawn into the flame by the Venturi effect, thereby improving efficiency and power output. The result is a clean and non-luminous flame.

Here are a couple of pictures of the burner in action. In the first, it is burning 70% ethanol available at most pharmacies; in the second, it is burning 100% acetone. I also tried 100% ethanol, but the flame is barely visible; it works very well, but it is not worth photographing…

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Tyvek is a material made of high-density polyethylene fibers flashspun and bonded into a paper-like sheet. This lightweight and highly breathable plastic resists tearing, moisture, and chemicals, but can be folded and cut like paper. Tyvek is often used in protective clothing, backpacking groundcloths, CD sleeves, and mailing envelopes. It can also be used to make weather-resistant pouches for electronic devices. In this case, Tyvek from a used USPS Priority Mail envelope was engineered into a T-Mobile G1 smartphone pouch.

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Insects are a ubiquitous part of our lives. Some of the most versatile insects belong to the order blattodea. Cockroaches are amazingly quick and hardy critters. They can run a meter a second and change directions 25 times a second. Their small size and sleek form factor make them easy to work with and difficult to capture. Their tough exoskeletons allow them to survive harsh environmental conditions and their muscular limbs allow them to carry weighty loads. In other words, this lean little beast is a perfect platform for robotics.

Imagine a tiny harness containing measurement and remote control mechanisms that can be strapped onto a cockroach, turning it into a remote-controlled probe. Now let’s scale the scenario up to tens, hundreds, or thousands of mobile units. Each unit carries a tiny camera and can be directed to any location via radio signals. Together with a computer control center, the swarm could be used to rapidly map out areas that humans would be loathe to investigate. This is just one of the many applications of such technology. But how can such a system be designed?

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Okay, I was being sarcastic. But I ran into this today and had a good laugh:

nvidia 7800 wont work

i bought one of these and tried putting in my dell dimension 2350. my friend said that the shiny metal part on the bottom looks like it has lines because you cut at the lines if it doesnt fit. so i carefully cut off the bottom so that it fit into 1 of the slot things in my computer. now it doesnt work. did i cut it wrong? id post pics, but no camera. is there anyway i can fix this? thanks for any help.

ouch…
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The Stirling engine, invented in the 19th century as an alternative to the steam engine, is powered by the expansion and contraction of a gas as it is alternately heated and cooled. In a conventional Stirling engine, the heating and cooling is achieved by moving the gas between a hot chamber and a cold chamber. The result is an extremely efficient mechanism that can operate on very small temperature differentials (i.e. body heat vs. environment).

The lamina flow engine is a Stirling engine with a single chamber with a hot end and a cold end, insulated by a restriction in chamber diameter. Not only does it have a much simpler design, but it is also somewhat more efficient: the only moving part is the piston.

It would be interesting if lamina flow engines can be used to harness solar energy the same way these guys are doing in L.A. with traditional Stirling engines.

I will be constructing a simple model using a test tube and a glass syringe. Details will follow as they become available.

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I’ve been thinking about homebrewing a scanning tunneling microscope for a couple of years now, since finding out that it was possible. However, I did not have the engineering expertise to actually pull it off. Conceptually, the device is very simple. Basically, a sharp conductive probe is passed over a conductive sample, a voltage is established between the probe and the sample, and the tunneling current is constantly monitored. Using an STM, one can image a conductive surface down to the atomic level.

There are several challenges for the average hacker. The most daunting is that because nanotechnology is such a young field, one cannot just Google for this stuff and find usable plans for STM construction. I have found several potentially useful websites; since none of them describe workable projects with reasonable detail, I’ll be using them for ideas only. However, I intend to document this project as well as I can, for the benefit of future hackers of nanotechnology.

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The baby railgun was fired for the first time tonight. I was surprised that it actually worked, being so tiny. It’s also horribly inefficient. At the moment, it’s a hot rail type railgun, which means that the rails are energized before firing, and the projectile completes the circuit when injected into the barrel. Currently, I use a bamboo toothpick to push the projectile into the barrel. There’s a problem with that — because my hand is relatively slow, the moment any part of the projectile contacts the rails, that part is blown off, leaving the rest of it behind. I can certainly use compressed gas to inject the projectile, but that defeats the purpose of having a small and cheap demonstration railgun. The other choice is to use a neutral rail design, and use a switch to close the circuit. The switch would be exposed to sparks and arcs, so it would not last long.

That’s enough talk for now. On to the pictures!

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So… I broke another blade today. I really need a bandsaw… oh, well. But the beauty of this project is that it can be done without power tools, just not as quickly or neatly. I hacked out a couple of rails from an aluminum busbar, sandwiched them between microscope slides for heat resistance, and sandwiched the resulting unit between acrylic sheets for impact resistance. The whole assembly was held together using a couple of binder clips, so it can be taken apart easily and serviced.

The rails were 3.5″ x 0.5″ x 0.125″ and placed 1/16″ apart. The microscope slides were 3″ x 1″ and just enough to cover the rails and let 0.5″ stick out for the electrical connections. The acrylic sheets were 3″ long and wider than the microscope slides; this makes handling the barrel safer, because no metal is exposed at the sides.

Now the only thing I’m worried about is unwanted capacitance forming between the metal binder clips and the rails. We’ll see how it goes.

Its time for pictures!

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A railgun needs a pretty beefy power supply that’s able to dump loads of current across the rails. Trying to keep costs low, I decided to borrow the charging circuit of a disposable camera. I removed the capacitor, xenon flash lamp, and a bunch of nonessential parts. Then I soldered on some switches, resoldered the indicator LED onto longer wires, and added alligator clips that will lead to the capacitor bank. Obviously, the capacitors are also to come from disposable cameras.

Here’re some pictures.

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Happy New Year, all! And in the spirit of starting the year with a bang…

I felt like having some fun, so I started designing a tiny railgun. A tiny, kid-safe railgun. Eh, who am I kidding?

Anyhow, I imagine a small power supply based on the charging circuit in a disposable flash camera and a capacitor bank made from capacitors found in more disposable flash cameras. The rails would be short copper bars — somewhere in the range of three inches long, positioned about a millimeter apart. They’d be secured in a glass and plexiglas barrel using cheap clamps, and connected to the circuit using alligator clips. Unfortunately, there won’t be a real high voltage switch until I find something like an SCR rated for high currents; instead, I’ll just make do with a spark gap trigger.

What about the projectile? Ha. What projectile? The power supply should be able to dump 330V of high direct current across the rails for a split second. I imagine there to be just enough oomph to vaporize/ionize a tiny piece of aluminum foil and sling the plasma a couple of feet. Not bad for a baby model, eh?

The power supply’s pretty much done; now I just need to get me some copper bars and really thick copper wire…

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