The key is a modified design based on the Kresling pattern, with each actuator having a specially-designed section (the colored triangles in the image above) that are designed to pop out under a certain amount of positive pressure, and remain stable after it has done so. This section holds its shape until a certain amount of negative pressure is applied, and the section pops back in.
Whether or not this section is popped out changes the actuator’s shape, therefore changing the way it deforms. This makes a simple actuator bi-stable and capable of different movements, using only a single pressure source. Stack up a bunch of these actuators, and with careful pressure control, complex movements become possible. See it in action in two short videos, embedded just below the page break.
Old wives’ tales, folk knowledge, common sayings, and even cliches and idioms are often taken as givens since they form an often unnoticed part of our vocabulary and culture. There’s so many examples that it’s possible to fill a 17-season TV show busting potential myths like these, and even then there are some that slipped by. For example, the saying “you can’t put toothpaste back in the tube” which, as it turns out, is not as impossible as we might be led to believe.
This video is the product of [Tyler Bell] who has taken this idiom on as a challenge. To figure out if it was possible he first got to work building a vacuum chamber, which turned out to be a little easier than he thought it would be. After cutting a piece of polycarbonate tube and sanding it down, all that was needed were some rubber gaskets and fittings for the vacuum pump.
From there, the theory was to put an empty toothpaste tube into the vacuum chamber, pump all of the air out, and let atmospheric pressure “push” the toothpaste back into the tube. During [Tyler]’s first run he thought that it had worked successfully but it turned out that he had just inflated the empty toothpaste tube like a balloon. Further iterations were able to return some of the toothpaste to the tube, but each time some air would eventually work its way into the toothpaste which would immediately fill the remaining space in the tube with air rather than toothpaste.
While not completely successful, he was able to get some toothpaste back into the tube with a relatively small bill of materials. It’s not likely that this experiment will result in a change of this particular idiomatic expression, but it was interesting to put it to the test nonetheless. For other instances of toothpaste and its relationship to tubes, both inside and out, be sure to check out this recent piece on various methods of toothpaste storage.
Atmospheric pressure is all around us, and capable of providing a great deal of force when used properly. As Otto Von Guericke demonstrated with his Magdeburg hemispheres over 350 years ago, simply removing air from a chamber to create a vacuum can have astounding results. More recently, [Tom Stanton] has used vacuum to power a small 3D-printed dragster.
In the dragster build, a typical plunger syringe is plugged at the end, and the plunger pulled back. Atmospheric pressure acts against the vacuum, wanting to push the plunger back towards its original position. To make use of this, a string is attached to the plunger, causing it to turn a gear as it moves forward, driving the rear wheels through a belt drive. With the correct gear ratio on the belt drive, the dragster is capable of spinning its tires and shooting forwards at a quick pace.
The work is a great follow on from [Tom]’s earlier vacuum experiments, using syringes as small rockets. It reminds us of the classic CO2 dragsters from high school competitions, and would be a great project for any science class. Video after the break.
As a general rule, you probably shouldn’t be getting your Personal Protective Equipment (PPE) from the party store. But these are exceptional times, and rather than potentially depriving medical professionals the equipment they so desperately need on the front lines, the team at [Robots Everywhere] has been looking into improvised PPE. We’re not sure things are at the point where you would need to don this DIY Positive Pressure Suit (PAPR), but it’s certainly an interesting look at what’s possible when you think outside the box.
At the most basic level, a PAPR is a mostly air-tight garment that is continuously pumped full of filtered air. As long as the pressure inside the suit is higher than outside, there’s no way airborne bacteria and viruses can get in without traveling through the filter first.
For this project, the folks at [Robots Everywhere] took an inflatable astronaut costume and replaced the dinky original air pump with a much larger 12 V unit designed for inflating air beds. Upgrading the pump not only increased the internal air pressure of the suit, but also made it easier to add a HEPA filter to the inlet. As long as the suit is inflated and there are no leaks in the hose, the wearer will be surrounded by a bubble of filtered air.
Presumably, you don’t want to be tethered to the wall though, so the write-up briefly touches on how the pump system can be made more mobile with the addition of an RC-style battery pack. With the pump and batteries secured in a pouch attached to the suit, the wearer is free to venture outside the confines of their self-isolation bunker and go about their dystopian daily business.
Convenient and inexpensive, plastic beverage bottles are ubiquitous in modern society. Many of us have a collection of empties at home. We are encouraged to reduce, reuse, and recycle such plastic products and [Kaboom Percussion] playing Disney melodies on their Bottlephone 2.0 (video embedded below) showcases an outstanding melodic creation for the “reuse” column.
Details of this project are outlined in a separate “How we made it” video (also embedded below). Caps of empty bottles are fitted with commodity TR414 air valves. The pitch of each bottle is tuned by adjusting pressure. Different beverage brands were evaluated for pleasing tone of their bottles, with the winners listed. Pressure levels going up to 70 psi means changes in temperature and inevitable air leakage makes keeping this instrument in tune a never-ending task. But that is a relatively simple mechanical procedure. What’s even more impressive on display is the musical performance talent of this team, assisted by some creative video editing. Sadly for us, such skill does not come in a bottle. Alcohol only makes us believe we are skilled without improving actual skill.
But that’s OK, this is Hackaday where we thrive on building machines to perform for us. We hope it won’t be long before a MIDI-controlled variant is built by someone, perhaps incorporating an air compressor for self-tuning capabilities. We’ve featured bottles as musical instruments before, but usually as wind instruments like this bottle organ or the fipple. This is a percussion instrument more along the lines of the wine glass organ. It’s great to see different combinations explored, and we are certain there are more yet to come.
Obviously, if the air filters in your home HVAC system are dirty, you should change them. But exactly how dirty is dirty? [Tim Rightnour] had heard it said that if you didn’t change your filter every month or so, it could have a detrimental effect on the system’s energy consumption. Thinking that sounded suspiciously like a rumor Big Filter™ would spread to bump up their sales, he decided to collect his own data and see if there was any truth to it.
There’s a number of ways you could tackle a project like this, but [Tim] wanted to keep it relatively simple. A pressure sensor on either side of the filter should tell him how much it’s restricting the airflow, and recording the wattage of the ventilation fan would give him an idea on roughly how hard the system was working.
Now [Tim] could have got this all set up and ran it for a couple months to see the values gradually change…but who’s got time for all that? Instead, he recorded data while he switched between a clean filter, a mildly dirty one, and one that should have been taken out back and shot. Each one got 10 minutes in the system to make its impression on the sensors, including a run with no filter at all to serve as a baseline.
The findings were somewhat surprising. While there was a sizable drop in airflow when the dirty filter was installed, [Tim] found the difference between the clean filter and mildly soiled filter was almost negligible. This would seem to indicate that there’s little value in preemptively changing your filter. Counter-intuitively, he also found that the energy consumption of the ventilation fan actually dropped by nearly 50 watts when the dirty filter was installed. So much for a clean filter keeping your energy bill lower.
With today’s cheap sensors and virtually infinite storage space to hold the data from them, we’re seeing hackers find all kinds of interesting trends in everyday life. While we don’t think your air filters are spying on you, we can’t say the same for those fancy new water meters.
[Uri Shaked] is really into Latin music. When his interest crescendoed, he bought a trumpet in order to make some energetic tunes of his own. His enthusiasm flagged a bit when he realized just how hard it is to get reliably trumpet-like sounds out of the thing, but he wasn’t about to give up altogether. Geekcon 2018 was approaching, so he thought, why not make a robot that can play the trumpet for me?
He scoured the internet and found that someone else had taken pains 20 years ago to imitate embouchure with a pair of latex lips (think rubber glove fingers filled with water). Another soul had written about measuring air flow with regard to brass instruments. Armed with this info, [Uri] and partners [Ariella] and [Avi] spent a few hours messing around with air pumps, latex, and water and came up with a proof of concept that sounds like—and [Uri]’s description is spot-on—a broken robotic didgeridoo. It worked, but the sound was choppy.
Fast forward to Geekcon. In a flash of brilliance, [Avi] thought to add capacitance to the equation. He suggested that they use a plastic box as a buffer for air, and it worked. [Ariella] 3D printed some fingers to actuate the valves, but the team ultimately ended up with wooden fingers driven by servos. The robo-trumpet setup lasted just long enough to get a video, and then a servo promptly burned out. Wah wahhhh. Purse your lips and check it out after the break.
If [Uri] ever gets fed up with the thing, he could always turn it into a game controller a la Trumpet Hero.