Tagged: maker

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.

Tesla_valve_cross-section

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:

IMG_0741

IMG_0742

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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

I’ve got the AWG wire thickness blues

I’m thinking about making a vibration charger for my phone and so I need magnet wire, i.e. thin copper wire to wrap around a magnet. So I discovered, to my disgust, that AWG is the unit of wire thickness. For some reasons, the powers that be decided that it would be smarter to use a logarithmic function of diameter to measure wire thickness, instead of just, hmmm, using the fucking wire diameter to measure the wire thickness!

I decided to make a table of conversions for those of us that still strive for sanity. In terms of the AWG number, you can get the wire thicknessm, in millimeters, using this formula:

Diameter=0.127mm \ \times 92^{\frac{36-n}{39}}

I know someone is goint to respond to this post and say something like “they use that equation to make it a logarithmic scale”. The only reason you use a logarithmic scale is because the range of values are so vast that it becomes annoying to write out all of the digits. I question whether the range of values of wire thickness is vast enough to warrants the use of a logarithmic scale.

AWG Millimeters Inches Light years
-10 26.307 1.2331 0.00000000000000000278
-9 23.427 1.0981 0.00000000000000000248
-8 20.862 0.9779 0.00000000000000000221
-7 18.578 0.8709 0.00000000000000000197
-6 16.544 0.7755 0.00000000000000000175
-5 14.733 0.6906 0.00000000000000000156
-4 13.120 0.6150 0.00000000000000000139
-3 11.684 0.5477 0.00000000000000000124
-2 10.405 0.4877 0.00000000000000000110
-1 9.266 0.4343 0.00000000000000000098
0 8.251 0.3868 0.00000000000000000087
1 7.348 0.3444 0.00000000000000000078
2 6.544 0.3067 0.00000000000000000069
3 5.827 0.2732 0.00000000000000000062
4 5.189 0.2433 0.00000000000000000055
5 4.621 0.2166 0.00000000000000000049
6 4.115 0.1929 0.00000000000000000044
7 3.665 0.1718 0.00000000000000000039
8 3.264 0.1530 0.00000000000000000035
9 2.906 0.1362 0.00000000000000000031
10 2.588 0.1213 0.00000000000000000027
11 2.305 0.1080 0.00000000000000000024
12 2.053 0.0962 0.00000000000000000022
13 1.828 0.0857 0.00000000000000000019
14 1.628 0.0763 0.00000000000000000017
15 1.450 0.0679 0.00000000000000000015
16 1.291 0.0605 0.00000000000000000014
17 1.150 0.0539 0.00000000000000000012
18 1.024 0.0480 0.00000000000000000011
19 0.912 0.0427 0.00000000000000000010
20 0.812 0.0381 0.00000000000000000009
21 0.723 0.0339 0.00000000000000000008
22 0.644 0.0302 0.00000000000000000007
23 0.573 0.0269 0.00000000000000000006
24 0.511 0.0239 0.00000000000000000005
25 0.455 0.0213 0.00000000000000000005
26 0.405 0.0190 0.00000000000000000004
27 0.361 0.0169 0.00000000000000000004
28 0.321 0.0151 0.00000000000000000003
29 0.286 0.0134 0.00000000000000000003
30 0.255 0.0119 0.00000000000000000003
31 0.227 0.0106 0.00000000000000000002
32 0.202 0.0095 0.00000000000000000002
33 0.180 0.0084 0.00000000000000000002
34 0.160 0.0075 0.00000000000000000002
35 0.143 0.0067 0.00000000000000000002
36 0.127 0.0060 0.00000000000000000001
37 0.113 0.0053 0.00000000000000000001
38 0.101 0.0047 0.00000000000000000001
39 0.090 0.0042 0.00000000000000000001
40 0.080 0.0037 0.00000000000000000001

Hello world!

This is my maker blog devoted to sharing my projects and other peoples cool projects. I think stuff like this:


is pretty amazing.

Stirling engines are kind of awesome but at their best, they still under perform compared to combined gas-jet steam cycles. The benefit of Stirling engines though, is that you don’t need to build at an industrial level, as the person in the youtube video so clearly demonstrates.

I have so many questions, like is it cost effective to make a Stirling engine out of plastic rather than metal? The problem is that plastics tend to have thermal conductivity(i.e. how quickly they can give off heat) of between .19 to .5 \frac{W}{mK} whereas iron has a thermal conductivity of 80 \frac{W}{mK}. That’s about 400 times better than the best plastic, which is high density polyethylene. What this means is that to make a Stirling engine out of plastic with a similar power output as an iron engine, you would need 400 times the surface area between the working gas and the hot and cold reservoirs. 

But what if 400 times the material was still cheaper if it was made out of plastic? Plastic typically comes form oil and oil is currently trading at about $93/barrel. Each barrel has about 159 liters in it so the raw materials for plastic cost at least $0.58/liter.  By contrast, iron ore is trading at about $100/metric ton and a ton of iron has about 142 liters of volume.  That’s about $0.70/liter for iron ore. I’m sort of shocked by the outcome. Oil and iron ore are trading for close to the same price per volume. If this translates into the cost of producing a Stirling engine, and this is a big if, then that would mean that a plastic stirling would cost several hundred times more than an iron stirling for the same energy output. Warning! These numbers are so rough that they should hardly be believed. They’re only meant to give some intuitive insight into the cost effectiveness. 

There’s a lot that could be wrong with this picture. Plastics are easier to work with and you might require less plastic than metal, especially for low temperature stirling engines. There are so many questions and so little time!!!……..