… Scientific Illustration, by Asa Smith.
Last week I posted a story from kestrel about her rescue of a hummingbird. A few days later, this video crossed my desk, and it explains why the bird was likely so calm – torpor, which is a bit like going into a coma when you sleep. The video also covers a lot of general information about hummingbirds, focusing on their perfectly adapted and unique tongues. This channel is a bit irreverent, but their videos are humorous, engaging and well researched.
My goal in mcgyvering a vacuum pump was to remain under 100,-€ – which I did – and get better results than I have achieved with my shop-vac setup – which I did too. Still, I do not know whether to be disappointed or satisfied.
I wanted to utilize things that I already have, which includes several water pumps that are used to water bonsai trees and vegetable beds in summer and pumping water out of the cellar in the winter and some spare piping from house renovations. So I had to buy only the things for making the vacuum pump itself – in combination with a water pump, the best option seemed to be something based on the venturi principle.
So I went and bought these parts:
The parts were connected to each other more or less in the order as they are laid out on the picture. The black plastic hose connector was fitted into the brass one to lower its inner diameter. The brass hose connector right next to the right side of the chrome T junction is the inlet nozzle – I have glued an old tip from a silicone sealant tube (not depicted) in it to get the position and size of the nozzle correct. Into the upper brass hose connector was glued the white plastic 6 mm hose connector for the air suction.
So water comes in the T-junction from the right, gets squeezed through a nozzle which sprays into a slightly bigger opening in the outlet left, behind which is again a big pipe. The spray drags with it the air surrounding the nozzle and that way achieves suction through the top of the T-junction.
I am not able to write-up complete how-to, but this is the final product up and running in a vat of water.
The bubbles show it is working. When I connected the suction tube directly to a new vacuum manometer, I got a suction of whopping 0,6 bar, which did really impress me. Unfortunately, I do not get anywhere near that when I connect everything to the jar. After a few minutes, it stabilizes at this.
0.22-0.25 bar is still a bit more than what the shop-vac could achieve (which was 0.2). So it is usable and it is a definitive improvement because unlike the shop-vac it can run non-stop with zero risks of overheating anything, and it also makes nearly no noise, so a win there too. But when it achieves this, it still bubbles, so it still draws air. And when I close both ball-valves on the lid (one ball-valve is for pressure release, one for the suction), I start losing pressure in the jar really quickly. That tells me that the jar is not properly sealed and this here is not the maximum this setup can achieve, but an equilibrium between the pump and the improper sealing.
I had to make a new lid from five layers of plywood for this, with two ball-valves and the manometer, so there was a lot of potential for failure. But I did use water/airtight plastic sealant for everything and I went over all connections once more, yet I still cannot identify the leak(s). If it was a pressurized container, I might find the leaks with help of soapy water looking for bubbles, but I do not know how to check vacuum tightness.
So this is where I am now and this is where I leave this be for a few days at least. It has occupied me for three days already, time to go back to making knives.
When I was hardening the blades two days ago, I have tossed in there six cut-offs as well and I have used different methods to quench them. After that I had still one piece left so I have heated that up to the 1050 °C and let it cool in the forge. Then I performed some tests and the results are very interesting.
These are the samples and methods used (marked by the number of notches on the edge):
0 – left to cool in the forge
1 – untreated
2 – left to cool in the air
3 – quenched between Al plates only
4 – oil
5 – water
6 – AL plates + water + Freezer fro 2 hours
None of the samples were subsequently tempered, so they should be at peak hardness.
With the sample size just 1 piece per method I cannot of course perform too many tests. The idea was to polish the samples – which I did. And already during the polishing, I have noticed that all samples seem to be hardened, except #1.
The next step was supposed to be to etch the surface and look at the structure under a microscope. Well, that did not work at all, and the reasons are a mystery to me. Just as it happened with the knives last time, it happened again here – the electrochemical method worked on some samples perfectly, but completely failed on others. I was unable to solve the problem. Another thing was that my microscope apparently does not have big enough magnification to see a difference between the original steel and the quenched one. I could re-build it and improve it about ten times, but I am still not sure if that would be enough and I do not want to get sidetracked to that now, it would be probably more than one day of work and I have already spent two days having fun instead of working.
So I did what I could with samples of this geometry. First trying to scratch them with my hardness measuring gages .
sample # 1 could be scratched by the lowest 38 HRC gage, which was to be expected.
All samples except # 1 could not be scratched by the 62 HRC gage, so they are at hardness 62 HRC or more. Which is something I did not expect, especially not of # 0, which was left to cool in the forge – and that took definitively several hours. I was expecting this sample to be harder than the new steel, but not hard enough for a knife – but it evidently is more than enough hard for a knife, hardness 62 is in fact quite excessive.
Secondly, I have tried scratching the samples against each other, and the results became even more interesting. All samples could scratch # 1, as expected. But none could scratch #4 and #4 did scratch all, whilst the remaining five could not scratch each other, so they are all of the same hardness.
Thirdly I have put the sharpest angle of the triangle approx 10 mm into a vise and break it off. #1 has bent easily, as expected, all others have snapped off.
What can I deduce from this? Several things.
It would be interesting to see what is the exact influence on toughness/strength once tempered. I could not find it, so I will have to test it myself. But for that, I will need another sample geometry. So maybe next time.
All in all, the N690 seems to be pretty remarkable steel. It does not have the label (and price tag, otherwise I could not use it) of “super steel”, but it is no wimp either and apparently is not very fussy about the heat treatment, apart from the requirement to heat it above 1050°C.
Our current prime minister has been in the past often criticized as akin to Donald Trump re: conflict of interests and use of state resources to enrich himself and his family. And rightly so in my opinion, I cannot stand the man personally and politically.
However, when SARS-CoV-2 hit the Czech Republic, he, unlike Donald Trump, has done the right thing. In response to the pandemic, he has left decisions on the policy to actual epidemiology experts from the very beginning. Thus when CZ had mere 116 cases, 12 days after the first three on March 1., he declared a state of national emergency and just two days later virtually everything was put on hold except the absolute bare minimum (grocery stores, delivery services, apothecaries and some more). It was criticized by the opposition (our equivalent of US conservatives) as needless panic-making and fearmongering and the measures as needlessly draconian and a PR for himself and his party. Especially the order of mandatory face masks (home-made and improvised masks are allowed) was met with scorn.
On March 18. I have taken the data of confirmed cases so far, plotted them on a graph and calculated the best-fit exponential curve. It was at a daily increase of 39%, an effective doubling every two-three days, approsimately the same trajectory it has had all over Europe. This growth meant we should have over 140.000 cases today, but we, luckily, do not. We have less than 5.000. Howso?
Look at this graph:
The red curve is the actual cumulative cases as reported every day at midnight. The blue curve is the exponential best fit that I have calculated on March 18. And then there is the orange curve, which is also an exponential best-fit but only for the last week from March 28. to April 3. You can see that the two best-fit lines intersect on March 21.-22.
That is, in my opinion, the day when the enacted measures started to have a visible effect – eight to ten days after they were enacted. I do not know whether I am doing the right thing here mathematically – I have dabbled in statistics at work, but not in epidemiology – but it does seem right to me.
The new rate of growth is still exponential, but instead of 38% daily it is 8% daily. And although the difference between multiplying the cases daily by 1,08 instead of 1,39 does not intuitively look like much, it means the doubling of the cases is prolonged from mere 2-3 days to 10-11 days. Still not enough for an illness that can take up to 6 weeks to heal and kills 1% of infected people, but a very noticeable drop.
And AFAIK that drop is not due to insufficient testing. Testing has grown proportionally, although still not as much as it perhaps should have. But the ratio between positive/negative tests is getting lower, and that indicates that the drop in overall cases is real.
Now there is certainly much more to it than this oversimplified graph. For example, Germany took longer to enact strict active measures, relatively speaking. That is, CZ government enacted nation-wide strict measures when we had just several hundred people ill, whilst the German government did leave many decisions to individual states and instead of strict orders tried to control the situation with recommendations only at first. This has led to a bit of inconsistent reaction and different measures being enacted (and ignored by people) in different states. It worked, but not as much as was desired. Strong nation-wide measures started being implemented only when there were several thousand people ill already- at about the same time as in CZ. And at about the same weekend the curve began to break in Germany as well.
It was similar in Italy too, there the curve began to break at around March 15. (only estimated, I did not calculate the fit curves for Italy, I am doing this in OpenOffice and that is not the best program for this kind of work), about two weeks after the most-hit municipalities were put on lock-down.
Another quick analysis that can be done just by looking at the numbers – In Italy, it took 22 days for the cases to grow from about 100 to 20.000. In Germany, it took 24 days, in Spain 18 days, in UK and France 25 days and in the USA 20 days. The Czech Republic is now 24 days from its 100th case and we are nowhere near 20.000.
So even these amateurish and quick&dirty analyses show that quick reaction, regardless of what the nay-sayers say, is essential in avoiding the worst in case of an epidemic. The enacted measures work as intended. I only hope that our government and our people do not relax too soon.
Stay safe, stay at home whenever possible, and fingers crossed for you and your loved ones.
My personal view of the coronavirus is that outside of China, the mortality rate might significantly rise above what it has now (which is already several times higher than influenza), just as it did with the swine flu pandemic in 2009 (which my sister barely survived, but luckily nobody else in the family got). My reasoning for this is – people in China were probably at least somewhat exposed to the said virus in its non-human-infectious form, or some of its less dangerous relatives, which would give them at least partial immunity. Once the virus spreads to populations that have no immunity to its or to viruses similar to it, it will become much worse.
Since it is a pulmonary disease, our whole family is especially susceptible and in danger, since all of us have asthma, my parents are elderly, my sister has already damaged lungs and my brother is a heavy smoker. I certainly hope not to encounter it, I already had viral bronchitis this year for two weeks and I did not enjoy it in the least.
Last time I was working on this project, I had some very bad results from quench. This week I have finally managed to test one idea of correcting the problem and maybe prevent it from ever happening again in the future. And I am glad to say that it did work. Not perfectly, but the new process is definitively worth to use instead of the old one.
Here is first the comparison of the three worst blades before and after. As you can see, there are still some curls in there, but they are noticeably less pronounced and one blade is almost completely straight. They will still come smaller than intended out of the polishing process, I will still have to remove some material from the edge until I get to the straight part, but I estimate it to be about 1/2-1/3 of what it was before. On the worst blade, the curls went about 10-15 mm from the edge towards the spine, whilst now it is about 3-5 mm. That is a significant improvement, and I think that had the blades been quenched from a straight form, they would never have curled in the first place.
As I alluded to previously, the process that I wanted to use for correcting the blades is called plate-quench. It cannot be used for simple carbon steels. Only so-called deep hardening steels can be thus quenched, and N690 is such steel, according to some articles I found on the internet. Nevertheless, it is better to not have the internet at all than to believe everything you can read on it – the manufacturer recommends oil quenching.
So I have tested the process first on one blade that I accidentally broke when correcting an ever so slight banana-bend. When the broken blade hardened properly – which I have confirmed not only by scratching with my gauges, but also by breaking off a tiny piece of it – I went on with the curly ones. On one of these, I confirmed the hardening too by breaking off a tiny piece of the tip, with the remaining two I was satisfied with the scratch test only.
For the plate-quench are used two flat plates from either alluminium or copper. These two metals have very high heat conductivity and thus can cool down some steels fast enough for them to turn into martensite. Luckily I got quite a few nice slabs of alluminium on hand. And because I wanted to make the process a bit faster (despite not making time-measurements this time), I have made a simple prototype quench-jig.
It consists of two identical pieces of alluminium with a small hinge, and locking pliers. The hot blade went out of the forge between the plates with the edge towards the hinge. Then it was firmly clamped by the pliers to hold it straight. When it stopped glowing near the tang – indicating a temperature well bellow 600 °C – I dunked the whole thing in a bucket of cold water just to be sure. And just as last time, because it costs nothing, I have put the blades into a freezer straightway for a few hours before tempering them. None of the three blades cracked.
It worked reasonably well and quick. I will definitively improve it and build a proper jig when the weather is nicer and I do not freeze my nuts off in my workshop. I will add a more stable hinge(s) and maybe even screw one of the plates to the pliers.
Another advantage of this process is no burnt oil gunk on the blade, no flames and no stinking oil fumes.
I often listen to podcasts when I walk Jack, and I’ve found a new one that I think you’d really like, too. It’s called ‘Ologies’ and the host Ali Ward is an Emmy award-winning science journalist. She’s worked on such shows as ‘Brainchild’ (Netflix), ‘How to Build Everything’ (Science Channel) and ‘In The Wild’ with co-host Adam Savage of Mythbusters.
Alie Ward is a charming and humorous host, and every week, she interviews a scientist from a different ‘Ology’ or specialty area, and questions them on what their field is all about. She approaches each subject with a genuine sense of curiosity and wonder. What you hear as the end product is a bunch of scientists who are passionate about their work telling stories and talking about what they love. Each interview ends with a lightning round of questions sent in by her patrons. One of her mottos is, “Never be afraid to ask a smart person a stupid question.” Or a smart one, either – Alie, herself, has a science background and prepares well for each interview, so the conversations are compelling and intelligent with a pleasant touch of humour. As an interviewer, she allows each guest space and time to tell their best stories in that passionate way of nerds.
‘ Ologies’ is Alie’s own brainchild, something that she thought about doing for many years before finally putting it together. There are currently over a hundred ‘Ologies’ available and Alie intends to keep going. She also makes a donation on each show to the charity of the Ologists choice and then features the charity on her website. I’ve been binging on it for about 2 weeks, and I’m hooked. Give it a listen. This is the website for the show, and you should be able to find it via most podcast players.