We have been yearning for the hoverboard technology ever since it premiered in series like Back to the Future and Real Adventures of Johnny Quest. But, due to the complexity of the underlying technology, no hoverboards have yet been able to accommodate a real person during flight. It has largely been agreed that the future hoverboard’s levitation effect will come from the application of electromagnetic levitation rather than any propulsion. But in addition to the electromagnetism, the new board also uses liquid Nitrogen in some capacity. The new attempt at the hoverboard is called Slide and it can lift itself off the ground and carry a person. Not enough technical details regarding the board of our dreams are available, and the sole source of information is a video released by the Tokyo branch of Lexus, the company behind this invention. The project is a part of the Amazing in Motion campaign by the Lexus company that has produced an 11 foot tall android, a swarm of quadcopters and mannequins performing in Kuala Lumpur.
We see in the video (below) how a young man is getting off from his boring regular board and then moves towards the Slider board. It really seems to be levitating in thin air. It seems to be a remarkable feat of engineering and a long-awaited ride for us. Due to the brand image of Lexus, it is unlikely that it is an edited video. The video is real but to see an actual hoverboard is mesmerizing. I bet there are many technical difficulties to overcome before we can actually see it. There had been an attempt of making a working hoverboard before as Kickstarter attracted the Hendo hoverboard that could levitate and move across a floor of some conductive material to create a secondary field.
The Lexus spokesperson told the media that there won’t be any disclosure of information before the end of the month when the board could be unveiled for the cameras. However, we cannot help but feel suspicious about the whole thing. The electromagnetic levitation requires a particular type of surface to float on. In the video, the guy appears to be doing so on concrete, which doesn’t seem to make sense. Maybe there is a secret to the smoking sides of the hoverboard. They must contribute towards its function in some aspect.
Check out the video below and see what all the fuss is about!
Ferrofluid sculpture. Photo Credit: P.Davis, et al. (FYFD)
Today, Brian will be filling in for Ketton due to last minute scheduling issues, we apologize for the post delay.
Ferrofluids are quite complex fluids that display interesting behavior in the presence of magnetic fields. These ferromagneticfluids are created through the colloidal suspension of ferromagnetic particles of the nano-scale. What does this all mean? In simpler terms, you essentially take tiny (nano-scale, or on the scale of a nanometer/a billionth of a meter; think the size of the base width of a single strand of DNA) magnetic particles and disperse them homogenously (or evenly) throughout a carrier fluid in a way so that the particles are fully wetted (meaning that the particles surfaces are fully coated by the liquid, without other particles in contact with them).
Once the ferrofluid has been created, the next step is as simple as subjecting the fluid to a magnetic field, at which point the ferrofluid becomes magnetized. As the ferrofluid begins to be affected by the magnetic field, it wants to follow this field and comply with its geometry; basically, the fluid wants to become shaped like the field it is being subjected to, but there is a problem: the fluid has surface tension. Because the fluid has cohesive bonding between liquid molecules, the molecules are very strongly attracted to each other on the molecular scale. This should make sense to you, as when you run your hand through water (for example), you are able to readily cause bulk disturbances (you can split up the water on the large scale), but try as you might, you will not be able to split the water apart on a molecular scale (the smallest you can get water to by hand is tiny visible droplets, which are still collections of a ridiculously large amount of water molecules (on the order of sextillions, or thousands of thousands of thousands of thousands of thousands of thousands of thousands!).
Surface tension. Photo Credit: Wikipedia.org
Because of the aforementioned strong attraction between the liquid molecules, fully immersed liquid molecules are pulled on by other molecules in all directions, as shown above in the picture. However, the molecules on the surface are only pulled on by molecules around and below (but not above) them, leading to a breach in the equilibrium and causing the water to be pulled in the direction of the rest of the water (hence the curved water surface exhibited in the above diagram). So, armed with this knowledge of how surface tension works, we can revisit the ferrofluids and figure out what is going on.
Ferrofluid and magnet, separated by glass. CLICK TO EXPAND TO SEE THE SPIKES BETTER! Photo Credit: Wikipedia.org
The magnetic field wants to push the ferrofluid outwards, but the ferrofluid itself wants to pull itself back inwards towards the liquid base due to the surface tension, all while gravity is also resisting the spike formation (this kind of interaction is explained through the normal field instability). At some point all of these forces equate and the fluid is said to be in equilibrium. The result of this? Really cool looking spikes in the ferrofluid as shown above. This gets even cooler when sculptures are created (as in the top picture) by using shaped bases and manipulating the shape of the magnetic field. It should be noted that art is most definitely not the only application for these fluids; in fact, ferrofluids also find application as: liquid seals around the shafts of spinning hard disks/drives, as a convective heat transfer fluid for wicking away heat in small scale and low gravity application, as an imaging agent in some medical imaging techniques (especially magnetic resonance imaging, MRI), as friction reducing agents, as mass dampers to cancel out vibrations, and even as miniature thrusters for small (nanoscale) sattelites!
So there you have it, another awesome engineering phenomenon! Please tune in Sunday for Ketton’s last Open Mind post and remember to continue following us at EngineeringAFuture.com when Engineering A Future (EAF) launches on Monday, July 13th! Enjoy the video below, created by altering the magnetic field in a ferrofluid sculpture!
Summer is here and with it brings barbecuing season. While the average charcoal BBQ may seem like a pretty simple appliance there is some solid engineering behind its design.
First let’s look at the charcoal briquettes. An engineer took chunks of wood and organic matter and heated it up in the absence of oxygen to produce an energy dense fuel that is fairly clean burning. This process is called pyrolysis and it removes all the moisture and fumes so that the avid BBQ enthusiast will be able to cook their food without coating it in a black smoke of tiny particles.
The BBQ itself is designed to control the combustion process. By opening and closing vents the user is able to regulate the flow of oxygen to the fuel. This directly affects the combustion rate, the rate at which energy is released in the form of heat.
And, as with any cooking process, heat transfer is an important consideration. When the coals are glowing hot they are emitting a lot of their heat as radiation. Radiation requires a direct line of sight and this is what causes one side of your food to get a nice sear on it before you flip it. When the lid to the BBQ is closed the air inside heats up and this allow for some natural convection, heat transfer from the hot air moved by its change in buoyancy (hot air rises). There is also some conduction, from relatively still hot air and the heated metal components that compose the grill (not to mention conduction through the food itself). Each one of these modes of heat transfer provide a different aspect to the grilling process. Radiation causes the sear, conduction is responsible for the grill marks and convection is responsible for the even heating and temperature of the food.
A deeper understanding of any process can lead to better results and engineering gives perspective into many of these processes. As far as grilling goes most of it can be picked up from experiences, but isn’t it more fun to know why these things happen! Happy Father’s Day to all the dads out there, no matter who does the grilling!
Last week, I had one of the best educational experiences of my life: a whole day of teaching 6th graders about STEM (Science, Technology, Engineering, and Math)! My lovely girlfriend is a 6th grade, Math and Science teacher and was constantly asked by her students as to when I would visit her class. With the build of DORY in full swing and wrapping up my undergraduate degree, I just couldn’t make time for a visit during the school year. In the last few months, my interest in teaching has grown, especially teaching about science, technology, and engineering. I knew I would take the opportunity to speak to her kiddos the first chance I could get.
A self-balancing wing my controls team made for class.
My girlfriend and I made plans for me to visit the second to last day of their school year. Her kids and I couldn’t be more excited. I made a presentation about STEM and how it applies to our everyday lives. I appealed to their interests by highlighting: famous people and how they use technology, popular electronics and how they wouldn’t be around without STEM, and popular social apps and how they came to existence using STEM. I also showed them famous celebrity engineers such as Ashton Kutcher, Rowan Atkinson, and Michael Gambon. I then continued to show them projects I worked on in my undergrad such as an obstacle avoiding cart and DORY, as well as a live demonstration of a self-balancing wing. They had so many questions with some that showed real engineering intuition. Seeing the excitement in their eyes and the “light bulbs” turn on was a fulfilling moment for me.
Homopolar Motor. Photo Credit: yourepeat.com
At the end of my presentation, I gave them a little background on electrical motors and brought materials to help them make their first simple motor. With a couple of magnets, a battery, copper wire, and a bit of patience they all made a homopolar motor. One team even had their motor spin for 14 minutes before the wire fell off. We even had time to make paper bridges which turned into a very competitive activity!
Paper bridge. Photo Credit: tallbridgeguy.com
Although the day was filled with laughter and excitement, it didn’t come easy! Often times we (meaning my girlfriend!) would have to correct the kids when they would get too roudy or speak out of turn. By the end of the day, we were both so exhausted. I have a new appreciation for middle school teachers and am glad I had the chance to try out the position. It is one difficult career! Teaching 11 year olds may not be in my future, but teaching STEM classes could definitely be!
Electric motors are used in many applications from robotics to children’s toys. Although many of these motors are DC motors, Homopolar motors are the simplest of motors and are easy to show students in a classroom setting. All it takes to build your first simple motor are three common materials you can probably find around the house: copper wire, a AA battery, and neodymium magnets.
Common heart shaped approach. Photo Credit: electronics-micros.com
Constructing the motor is simple but getting it to work can take trial and error as well as a bit of patience. Here’s how to do it:
1) Attach the magnet to the negative side of the battery. 2) Strip the copper wire completely or for safety, in the middle and at the two ends. 3) Bend the wire so that one end touches the positive terminal and the other end touches the magnet. A common approach is a heart shaped wire for better stability. 4) Watch: As the copper wire touches the magnet, the wire will begin to spin.
Current (blue) flows from the positive terminal to the magnet at the negative terminal. The current flows in the presence of a magnetic field (red). This causes a force perpendicular to those directions (in the page on the left of the battery and out of the page to the right of the battery). This force causes the wire to spin. Photo Credit: Physics Central
How does it work? Well the theory can get as detailed as you want it to be but to keeps things simple, I will explain the homopolar motor briefly. The copper wire connects the positive terminal to the magnet at the negative terminal. This completes the circuit, allowing current to flow through the circuit (and the wire). Due to the magnet, the current is flowing in the presence of a magnetic field around the battery. When current flows in a magnetic field, it will experience a force called the Lorentz force. This force acts perpendicular to the magnetic field and the flow of the current (and the wire). Consequently, the perpendicular force pushes the wire around the battery.
Once you get a working motor, you can change the shape of the wire to any shape you want! Have fun!
We’ve all been taught that water freezes at 32F (0C) but in actuality water can remain liquid below this temperature, under special conditions. Imagine you’re sitting on your couch after a long day, you’re tired and you’re starting to feel a bit hungry, but the fridge is so far away. Eventually you get hungry enough to get up, go to the fridge, and satisfy your hunger. Water can relate. When the temperature of the water drops below 32F it would prefer to be a solid, but it takes energy to change from a liquid to a solid. As the temperature gets lower the water gets “hungrier”, it wants to be a solid even more, eventually it wants to be a solid enough to overcome the energy barrier, the “walk to the fridge”.
When water wants to become a solid there are two ways it can go. It can either grow on a surface, like condensation on a cool drink or around a dust particle like rain, or, if it has enough energy, it can grow little spheres of solid within the liquid, without the help of a surface. The amount of energy required for this phase transformation is directly related to the amount of surface created. When the transformation is happening on, say the inside surface of a water bottle, the liquid only has to support the area of a dome, the bottle takes care of the rest. When there is no bottle to work with, or the liquid is far from the surface of the bottle, it has to have enough energy to support the surface area of a whole sphere.
If you’re trying to replicate the video above it’s crucial to have very clean water. This means there are no little particles that the water can use to lower the amount of energy required to freeze, it has to save up enough to grow the spheres without any help. The water also needs to be cooled slowly and handled gently because any significant energy changes, thermal or kinetic, can give the water enough energy to start freezing. This is why hitting the bottle will start the reaction. When the bottle is hit, it finally gets the “oomph” it needs to get to the fridge (freeze).
These phenomena (heterogeneous and homogenous nucleation) are also responsible for the famous Mentos and Coke experiment, why bubbles in carbonated drinks seem to come from specific points in the glass, and how engineers make aircraft aluminum strong enough to keep planes in the sky.
Nerf gun office war. Photo Credit: hrsolutionsinc.wordpress.com
Prompt: You are in an office and the annual Office War is about to begin. You have less than an hour, a desk (w/ pullout drawers), rolling chair, computer, keyboard, mouse (old roller-type), mouse pad, stapler, staples, three hole puncher, desk lamp (old fashion bulb), rubber bands, paper clips, pushpins, envelopes, printer, printer paper, clicker pens, No. 2 pencils, a white eraser, highlighters, 15 ft. Ethernet cable, scientific calculator, engineering pad, corded desk phone, a gallon water jug, a tin of Altoids, a hot cup of coffee (in a ceramic mug), and a frozen 4 lb. steak. It’s either you or them, and remember you are a mechanical engineer, not a tinkerer. Go!
NOTE: DO NOT try or create any of these ideas at home. This is purely for fun and we will not be held responsible for your actions! Enjoy!
The alarms have sounded, the office war has officially begun. You wipe the citrus flavored energy drink from the edge of your mouth and put the computer on standby mode. Confidence oozes from your pores like hot molasses, you stare at the closed door in your office and announce without fear, “Come at me brethren!” Footsteps suddenly stop, and redirect towards your position. You put your plan into action.
The Trap: You grab the hot mug of coffee and let its bitterness energize your blood stream. Looking for a cloth to wrap the mug, you decide the shirt on your back will do. Taking the metal 3 hole punch you smash the wrapped mug into jagged shards and sprinkle them at the entrance of your fortress (office) along with push pins facing up. And finally using the telephone cord to create a trip wire for any of your mates who will be bursting from your door.
CQC (Close Quarters Combat): Eventually the bodies will pile up at the door and initial trap will prove to be ineffective, you need to ready to defend and attack directly. With the lamp shining bright you break the bulb filling the room with darkness. This will hinder the incoming attackers vision and allow you to use the faces of enemy’s as the resistance to complete open circuit of the lamp. Quickly you empty the drawers from your desk and disassemble them for a large wooden slab making for a wooden shield that can be strapped to your forearm with your computer mouse’s wire.
The Steak Flail: You can’t stay plugged into the wall forever, you grab the frozen steak and tie it to the end of the 15 foot Ethernet chord and swing it like a medieval flail. For added protection, you take the Altoids tin and plastically deform it into a shiv to drive into the hearts of your enemies. Now armed with a long and short distance weapon and a shield, you work your way over all the bodies in your office and out the doors to victory.
Hopefully an office purge will never happen but my wish is that this article may somehow help you strategize and survive if it does. What would you do? Comment below, let me know.
Rock climbing is becoming more and more popular as gyms pop up all over Southern California. This sport, like all sports, has many components that have been analyzed and optimized by engineers. Rock climbing brings its own unique challenges, most of all the balance between safety and weight. The more safety gear a climber uses the heavier they are and the more likely they will get tired and make a crucial mistake.
Climbing ropes are the major staple for safety gear. A climbing rope must be strong enough to catch a falling climber, tough enough to withstand almost constant rubbing against rough rocks, and still stretch enough so that the climber isn’t injured by a quick stop from a long fall. This is quite a bill for any rope to withstand but climbing rope does the job incredibly well. For a class project, standard nylon rock climbing rope was tested and compared to nylon 550 paracord and standard polypropylene utility rope. The differences were very apparent. While the paracord and utility rope broke fairly easily the climbing rope withstood more weight and stretched beyond the range of the testing machine. Try as we might we could not break the climbing rope within the range of motion that we had. This rope had a few interesting properties that led to its great success. First there was a protective casing of a tough material that could resist abrasion very well, then within, in the load carrying section the fibers had a special weave. This weave allowed the rope to stretch very far without breaking and slowly load the fibers that made up the rope. Some engineer did their job very well.
The very act of rock climbing can be helped by a brief engineering analysis. First off is conservation of energy. A climber’s muscles have a limited amount of energy in them so that energy needs to be saved for actual motion on the rock. When a climber is hanging on the rock, looking for the next hold or clipping in the rope their arms are fully extended allowing the weight of their bodies to be held by their bones, a rigid structure, rather than their muscles, an energy devouring structure. Another concept is as simple as balance, when a climber can just hang on a rock rather than resist swing or spin they are in a low energy state, even if this means that they are horizontal to the ground. A trick for this is being aware of your own center of mass as a climber and ensuring that it is perpendicular to the hold surface.
The more a climber can think about the physics of climbing the more energy they will be able to conserve and the better technique they will have.
Stacked Shields on an Arduino. Photo Credit: robotshop.com
Arduino boards are very helpful and powerful tools to help connect the electronics world to the real world around us. Like I said in Part 1 of my Learning Arduino Series, they can read inputs and control outputs very quickly; faster than any human can do manually. With that said, an Arduino board, such as my handy UNO R3, can only do so much. After an “Arduinonian” has experimented with all the things in their beginners pack, they often want to venture out to more complex and demanding projects. Want to drive more than one motor? Want to drive two DC motors and 2-3 Servos? Want to connect your board to the internet or save data and images to an SD card? There’s a shield for that!
Robot Shield. Photo Credit: OpenElectronics
Shields are commonly made for microprocessors like the Arduino UNO R3 to inject it with extra functionality. They are designed to piggyback directly on top of your logic board, through the use of stacking headers, which can allow the use of pins not already in use by the shield itself. Some shields allow programmers to pull more amperage for driving bigger, hungrier motors while others add GPS or Bluetooth capabilities. There are WAY too many shields out there to describe in one post, so i will share with you some of the ones I have used and some that I plan to use in the near future.
1) Arduino Motor Shield R3
Arduino Motor Sheild. Photo Credit: Arduino.cc
The important thing about shields is that you want to make sure they are stackable with your specific board. For example this motor shield is called R3 because it fits perfectly on top of the UNO R3 but wouldn’t fit on the earlier R2. I bought this motor shield to do a few different projects that required me to use much stronger motors than the UNO R3 can handle. With the shield installed, a programmer can pull up to 4A, 2A per channel, safely with operating voltages up to 12V. It’s designed to drive relays, solenoids, DC motors, and stepper motors. In fact, it can drive two DC motors independently or one stepper motor with speed and direction control for either case. The shield can be powered by the same power supplied to the logic board (i.e UNO R3) or it can be powered by an external source through the VIN and GND terminals on the shield.
I found this shield to be very easy to use especially with everything already soldered on, even the headers. Working with the supplied library was also a breeze and allowed me to get my projects up and running in no time. I would totally recommend this shield for a beginner or even a professional looking to power up to 12V motors for its low price and easy implementation.
Power Boost 500 Shield. Photo Credit: Adafruit.com
Power Boost 500 Shield. Photo Credit: Adafruit.com
This shield is the latest shield I have worked with. I soldered up the headers and the on and off switch just yesterday! This shield by Adafruit is potentially going to be used in our Senior Project design granted it performs well in testing. The idea behind this shield is to take a single cell battery outputting 3.7V and boost the potential to 5V. This allows a single cell battery to power up your 5V Arduino project on the go! It also has a recharging circuit built in so that the LiPo battery can be charged via microUSB. All the indicators for ON, Charging, Done, and LOW are there to let you know that state of the battery. Another major plus is that depending on the size of the battery, it can fit nicely within the width and height of the stacking headers! So far testing has turned out great with 5V being supplied to my project with the use of only a single cell 3.7V 2,000mAh battery. This will save us plenty of space and take care of charging in one small stack-able package. Like most shields out there this one needed to be soldered before use and for that reason, I would recommend this shield to anyone as long as they can solder or know someone who can.
Click here for more information about this Adafruit shield.
The link above lists some cool shields to get you all started but don’t be afraid to look around for new and unique shields. Sparkfun, Adafruit, and other suppliers are constantly coming out with new stuff. To be honest, the possibilities of what you can do with an Arduino are endless especially when shields can be stacked on each other! Look out for my next Learning Arduino post about breakout boards and things I have needed to collect since starting this hobby!
As always thank you to everyone who has supported us and continue to share our posts and GoFundMe site. We really appreciate it!
Most of us can remember the days in elementary school where we learned to make paper cranes, flowers, boxes and all manner of things just by folding paper. I was never one to master the art of origami but I can make a pretty nice paper air plane! This technique of folding paper has generated a lot of interest in the engineering world. The National Science Foundation has provided a grant to a few top universities to research this. The goal is the creation of materials that can fold up into very small places and then unfold when needed. Imagine a solar collector that could unfold like a flower in sunshine then collapse again at night or when power is not needed. Read a full article about it on the American Society of Mechanical Engineers’ website here: https://www.asme.org/engineering-topics/articles/design/engineering-meets-art
Newton’s 3rd Law of Motion. Photo Credit: Buzzle.com
Prompt: Boston Dynamics is a company that specializes in producing robots that can really do the unimaginable. Take Sand Flea. Sand Flea weighs 11 lbs and can jump to heights of up to 30 ft. Such a feat represents a very attractive design goal across all industries for the coming years: the ability to store massive amounts of energy and release it very quickly. Considering that these high energy-density type systems are in fact the way of the future, using what you know about energy come up with either at least 3 ways of storing/quickly releasing a large amount of usable mechanical energy or come up with one way and describe at least 3 ways to look at your solution.
There are countless applications for these kind of high energy-density storage, quick release type systems; however, in this post, we will simply be looking at a few design considerations that a mechanical engineer would have to account for if he/she wanted to design a robot capable of jumping to great heights by taking advantage of the expansion associated with the release of compressed gases.
As shown above, Sir Isaac Newton’s 3rd Law of Motion essentially states that for every action, there is an equal and opposite reaction. This simple statement has profound complex consequences in the real world. If you have ever seen a spaceship lift off, felt the recoil from a firearm, had a hammer bounce back at you after hitting a nail, or wanted to see what would happen if you were to use a fire extinguisher as a booster while sitting in a rolling chair, you have seen the phenomena that Newton’s 3rd Law of Motion is referring to.
Fire extinguisher + rolling chair = fun. Media Credit: Brooklynn99Insider.com
Now in reality, things get much more complicated as there are many inter-dependencies that affect these reactions (i.e. the reaction of air resistance on the skin of the spaceship, the rerouting of gases in automatic weapons to chamber the next round and reduce recoil, the elastic properties of the steel head of the hammer, the rolling friction of the chair wheels or that associated with the bearings of the wheels, and the list goes on…).
So getting back on topic, what would we need to consider if we wanted to design a robot that used compressed fluids to jump?
Fluid Mechanics As a class of fluids, gases are much more compressible than liquids; this fact, in combination with the tendency of gases to fill the shape of their containers (or flow paths) makes them ideal for use in high-compression fluid storage to be used for imparting large amounts of kinetic energy to objects via momentum transfer from their expansion kinetics. By storing a large volume of gas under heightened pressure within a properly suited pressure vessel (PV), large volumetric expansion ratios/rates can be realized when the gas is released. This gas expansion leads to massive amounts of energy being released very quickly from these areas in which massive amounts of fluid can be stored in a very compact space (thus high energy density storage and fast release). The energy and momentum associated with this gas can be used to propel our robot up and into the air, but know what? Did we intend to design our robot to be single use or do we want it to be able to jump again? We need to find a way to refill the system.
The means by which these systems are refilled or “recharged” is most often dependent on the kind of gas being used. In order to replenish your energy stores in an air-based system, you could simply pull the air from the atmosphere using an air compressor (although this becomes significantly harder when you are for example 500m under the ocean’s surface). Another complication associated with this method is the fact that an air compressor may not be ideal for our application on the basis of size, weight, vibration, noise, power requirements (as the air compressor will up the robot’s power requirements and thus decrease its run time for the same amount of power supply or even necessitate the use of all new control circuitry), etc.
This situation is complicated even further when the gas being used is not air, as now you have to store all of your gas reserves unless you can find out some way of extracting the gas you need from the atmosphere, which is simply not feasible, especially on such a small scale. So how do we get around these limitations?
Daisy Red Ryder BB Gun. Photo Credit: ehstoday.com
Many air-based systems use air-pistons in order to recharge their compressed gas reserves as anyone who has ever had to pump a BB gun or water gun has experienced. The mechanism for actuating this piston is not always something as obvious as the lever action on your Daisy Red Ryder BB gun (remember to always practice proper gun safety, lest you shoot your eye out…referencing the movie A Christmas Story). Some systems may have a protruding pin that (when depressed) cycles a small pump compressor or reciprocating piston to recharge thy system. In some applications, exhaust gases may be re-routed and used to actuate the compressing mechanism. Technological creativity knows no bounds and, as such, it is more realistically finding a way to recharge a system comes down to design time, costs, and other system-level tradeoffs. Would it not be easier if we simply did not allow the gas to ever leave the system in the first place?
We could create a closed-system by using a highly elastic material to cover the exit nozzles of our robot, so that when we released the gas, it would rapidly balloon out and propel our robot through the elastic collision interaction mechanics between the gas-filled elastic material and the ground (think Newton’s 3rd Law of Motion) without expelling the gases to the atmosphere. To better understand this, visualize taking one of those squeeze toys where the eyes bulge out (see below) placing the toy with the eyes against the ground and then filling the eyes with a ton of gas really rapidly and watching the thing fly up in the air! This is just one example of the open-minded nature of engineering problem solving. The only bummer would be that in reality, this feat would likely be far more difficult than stated here and would likely require the development of a custom material with the proper amount of elasticity or “stretch”, tensile strength, strain-recovery time (how fast the material returns to its original size/shape), and would likely need include stiffer/more rigid pads where contact would be made with the floor so that the material could transfer more of the gases kinetic energy to the ground (rather than simply absorbing all of the gas’s energy through the material’s ductility).
Thermodynamics/Heat Transfer In order to bring this article to end sooner rather than later (sometimes I get carried away and don’t realize how much I’m writing, so my apologies!), I will quickly move through this subject for consideration as well as the 3rd one.
Most gases would experience significant thermal energy generation under large compression ratios and thus the surrounding system would likely require cooling to prevent damage to the electronics or to the user; this cooling could be accomplished by passive controls such as extended surfaces/fins or forced heat transfer by way of a fan – the cheapest active thermal control. You have likely seen both of these types of systems mounted to your computer’s CPU.
Fan mounted to extended surfaces on a CPU. Photo Credit: Wikipedia.org
Mechanics of Materials A very noteworthy consideration in this application would be the strength of the pressure vessel (PV). Depending on gas used, compression ratio, allowed temperature rise and transmittance of impulse (high energy transfer over small time period) to the PV, hoop stresses (circumferential) can become significant and therefore require thicker PV sidewalls, use of stronger material for the PV, or rib reinforcement of the PV.
Pressure within a pressure vessel (in this case a CO2 canister). Photo Credit: science-of-speed.com
So anyways, there is a long-winded look into just a few of the many, many things a mechanical engineer might consider in their design of a robot capable of jumping to great heights using compressed gas. One of the many beauties of mechanical engineering is the fact that it is such an incredibly open-minded field that requires creativity, intelligence, determination, and the realization that there is never one right answer.
The idea of 3D printing is spreading around into all kinds of different disciplines, from cooking to make up. In engineering the idea of 3D printing has been around for a while now. But more recently it has become accessible to the average consumer. Some organizations made 3D printer designs open source, meaning that they published their designs on the internet free of charge. This allowed anyone with some know how to make their own. Once the average hobbyist could invest in the technology it began to get more interest and eventually has become the thing that it is today. As an additive manufacturing method for prototypes, or single production runs, where strength isn’t a huge concern 3D printers open up a huge world of design to the interested population.
LED Sign Example. Photo Credit: animationlibrary.com
Welcome back for another round of learning Arduino! I just want to take a moment to thank those who are continuing this journey with me. For those just joining us, please take a look at Part 1, Part 2, and Part 3 to clear up any questions! I personally have come a long way since my start in Summer and have worked on some really awesome projects this past quarter. Through the use of my personal Arduino starter kit, I have been able to build an obstacle avoiding car, a temperature controlling HVAC system, and a self-stabilizing wing. These projects were completed for a Control of Mechanical Systems class I took this past quarter and I can’t wait to share them all with you.
In Part 3, we were able to build a simple circuit and breakdown the code to control the circuit. It was a nice intro project that showed how to setup an Arduino code and upload it to the board. This time around the task will be slightly more involved but will show you important coding practices to make future projects more manageable. We will be controlling multiple LED’s and manipulating their states at any given time. Let’s get to it!
What you need:
8 x LED’s (any color)
8 x 330Ohm Resistors (if you don’t know what you have, the color code is orange-orange-brown)
Arduino board
Breadboard
Assorted Jumpers
Friendly Note: We are not responsible for any misuse or risky behavior!
Photo Credit: Vilros Starter Kit Guide by Sparkfun
Place the LED’s anywhere on the breadboard, without plugging any two legs into the same rows. This can cause a short and you will experience unwanted circuit behavior. Also, take care in knowing which leg is the longer length (positive) and the shorter length (negative). You may want to place the LED’s in an organized fashion so that the light sequencing looks nice. Remember, we want to place a resistor in series with the LED’s to protect them from excess current. Next, place jumpers from the positive LED legs to the Arduino inputs such as digital inputs 2 -9. Finally, apply a 5V potential to the positive(+) column on the breadboard and a ground jumper to the negative (-) column. Take a look above for a better view of the circuit layout!
Code
The code below is VERY good at teaching what each part does. Instead of re-analyzing each part again, I will add to it in hopes of clarifying any questions. Simply copy and paste it into your IDE and upload it to your Arduino board. I have included a video demonstration below the code to give you a better visual of what to expect once you run it.
// for tips on how to make random() even more random.
index = random(8); // pick a random number between 0 and 7
delayTime = 100;
digitalWrite(ledPins[index], HIGH); // turn LED on
delay(delayTime); // pause to slow down
digitalWrite(ledPins[index], LOW); // turn LED off
}
Video Demonstration:
Here’s what you should expect to see in your circuit! Enjoy!
In future projects you will most likely need to use For Loops and Arrays to complete tasks efficiently and to consolidate writing space. These components of code show up in all different forms of script such as VBA and Matlab so learning it now will make you better prepared. Have some fun with the code above by playing with the timing of delays and with the mixing of functions. If you’re wondering what multiple LED’s are even used for just imagine a marquee display. They are made up of a bunch of LED’s that turn on and off independently to form a desired letter, symbol, or shape.
Thanks for reading Part 4 of my Learning Arduino series and don’t forget to visit our GoFundMe site to help us reach our fundraising goal!
A company called CyPhy Works has discovered a way to make UAVs that have “unlimited” run time! How is this possible you might ask?? Well it’s rather elementary.
If you think about it, all your household appliances use the same cutting-edge technology. A power cord. Or in this case, a microfilament that provides energy, direct communication, high definition video, and receives data from sensors quickly and reliably. But you might think that having this “tether” is a huge drawback as the microfilament could get snagged and that would be the end of the UAV. This problem has been carefully considered. The UAV actually dispenses the spool of microfilament as it moves so it will never be in tension to hold it down. And if worst comes to worst, if someone decides to cut the microfilament, the UAV can simply return to its point of origin on battery power.
Helen Grainer, founder of CyPhy Works, says that this is a solution that solves the problem that most UV’s have and that is loss of communication when employed for duty. UVs go into bunkers, inside a building, around a corner. All lose communication and by the time communication is restored it’s already too late. Too late to recover the UV itself or any information it might have stumbled upon. The latest of CyPhy Works’ projects is the Pocket Flyer UAV that has a battery life of 2 hours or longer, with a microfilament cable that can spool up to 76 yards, and has replaceable spools for the drone to use after completion of each mission. The point of having a UAV so small is so soldiers always have a drone on their person no matter the situation and it can be run using an OS on a smart phone or other similar devices. These UVs are ready for production to get them into the hands of soldiers who need them the most. Here’s the incredible video of the prototype, https://www.youtube.com/watch?v=rMdCnRg81qE
Intergranular crack propagation due to Stress Corrosion Cracking (SCC). Photo Credit: NASA.gov
In my opinion, the single most important course I’ve taken in my undergraduate curriculum at Cal Poly Pomona by far has to be…HRT 318 Wines, Beers, and Spirits. And I think anyone who has taken that course will agree. Cheers.
However, the most important course I’ve taken in my MECHANICAL ENGINEERING curriculum has to be ME 315 Engineering Materials. Now, I’ve never cared much for chemistry, but this course ignited interest in a possible career of goggles, lab coats, and studying microstructures. The “material” in this course answers a question that I’ve always had: “Why did they use that material?” It seems like a very easy question to answer but there is so much that goes into answering it that it is, in fact, a science. The course covers dislocations to alloying techniques to fatigue of polymers and everything in between. This is the course that made me say, “Wow, chemistry is cool!” And yes that is a very nerdy statement, but I stand by it. The course covers the properties of certain types of pure metals, alloys, polymers, composites and how these properties can be used to select the correct material for the application. Not only this but how to change these properties to have a more effective material or a completely different material after processing. And if that wasn’t enough, even goes over how to perform a myriad of tests to have experimental evidence of predicted properties. It really is the basis of how we live our lives and how everything is made. Very profound stuff. I was very fortunate to have had a professor who was very passionate about the subject and inspired students to pursue a career in materials.
With all this said, taking the course did not make me an expert of material science, but this course did inspire me to take more materials related courses such as composites and corrosion science, both of which I highly recommend. I was not planning on it but if all goes well, I will be getting my materials minor this spring along with my mechanical engineering bachelor of science. So in conclusion, ME 315. Best. Class. Ever.
As with many things in life, you must learn to crawl before you can walk. Learning how to actually use an Arduino board is no different therefore we will continue our Arduino Journey by completing a simple project. The first thing a novice should learn is how to control an LED. Light-emitting diodes (LEDs) are small, powerful lights that are used in many different applications such as notification lights in our phones, displays, and in sensors. Designers most often times don’t want their LEDs to always be on or at their full brightness so controlling an LED’s state will be the focus of this project.
The first thing an inventor needs to do is gather all necessary components to build the project. This includes the following:
1 x LED (any color)
1 x 330 ohm resistor
Various jumper wires
Arduino Uno (or similar board)
Protoboard (to place your components)
Arduino Code (I’ll cover this after hooking everything up!)
Most beginner kits will have these basic components already but if you are missing anything your local electronics store should carry it. The setup of the circuit is very straight forward as shown below. NOTE: Be smart with your decisions! We are not responsible for misuse of electronics and injury! Before connecting anything together, it’s safe practice to disconnect the Arduino board from your computer or power source. This essentially cuts power to the board allowing the user to move things around without the risk of shock. Place a jumper wire from the 5V output on the Arduino to the red positive vertical strip on the protoboard. Do the same for ground; running a jumper from GND to the negative strip on the protoboard. The two vertical columns on the side of the protoboard are all connected to together. Anything placed on the vertical positive column will be charged to 5V. Anything placed along the negative ground column will be grounded. Conversely, the middle rows of the protoboard are connected horizontally. Anything placed along the same row will be connected together.
Courtesy of Vilros Starter Kit Guide by Sparkfun
Place a jumper wire from any pin (such as pin 13) to any location in the middle of the protoboard. Now we place our LED. The two legs of our LED are of different lengths. The longer leg should be connected to positive (+) and the shorter leg should be connected to negative (ground). LED’s are diodes which mean that the current is meant to flow from positive to negative, so knowing which leg is which is important. The positive leg of the LED is connected in the same row at the jumper from pin 13. Now that we have placed our LED we can place our resistor. Resistors are components that reduce current flow and act to lower voltage in circuits. It is used in this project to protect our LED by reducing the current flowing through it. One leg is placed in the same row as the negative LED leg and the other is connected to ground completing our circuit. You most likely have to bend the legs of your resistor by 90o to fit into the protoboard. If you are lost, just take a look above at the layout diagram to clear things up!
Now that we have hooked up all of our components, we can move onto the code. For the Arduino code to successfully operate two “functions” are necessary to define. The first is setup() which essentially sets up all the pins we need to work with. We can make our pins operate as inputs or outputs depending on what our project needs. For this specific task all we need to do is set pin 13 (or the pin you’re using) as an output. This is done by saying: pinmode(13,OUTPUT);
The next function is called loop() which runs indefinitely until we unplug our Arduino board. Here we place our desired actions, calculations, and operations. For this project we need to make the LED turn on and then turn off. This is done by saying: digitalWrite(13, HIGH) and digitalWrite(13,LOW). Setting our pin HIGH means supplying the pin with 5V, which turns our LED on. LOW supplies the pin with 0V which turns the LED off. Adding the delay, as shown in the code below, pauses the loop for a given amount of time (measured in milliseconds). Adjusting the delay value will change how long the LED stays on versus the time it stays off. You can simply copy the code below into your code window and it should work. All that’s left to do is connect your Arduino board to the computer, click verify, click upload, and your project will be up and running!
CODE
void setup() { pinMode(13,OUTPUT); }
//this is setting up pin number 13 on the arduino board as the output pin. //the first value in the parenthesis is a pin and the second value is the function.
//now we move onto the loop which will run forever until the board is unplugged or reset.
void loop() { digitalWrite(13, HIGH); // LED on.
//digitalWrite is a function used to make an ouput HIGH or LOW, 5V or 0V.
delay(1000); //this pauses the loop for a given amount of time measured in milliseconds
digitalWrite(13, LOW); //LED off.
delay(1000); }
As I said before, adjusting your delay values will result in different blinking rates so go ahead and try it out! Keep a look out for my next tutorial on controlling multiple LED’s.
We appreciate all of your support! Please check out our GoFundMe site to help us complete our senior project. Thanks!
Welcome back to TeamUV.org and let me just start off by saying that we are going to have a busy next couple of days. We (of course) have this Well Read post today, will have a special Veterans day post at 1300 hours (1 p.m./in 3 hours), a post announcing the start of our fundraising campaign tomorrow (Wednesday 1000 hours/10 a.m.), and then we will be back to our regular schedule with a Presentation post by Andrew on Thursday. Whew!
Today, we are going to continue off of my last Well Read post with a discussion of the science behind fireworks. More specifically, today we are going to take a brief look at what determine the actual shape of the burst, whereas last time we took a look at the thrust created during the initial firing of the fireworks. Without getting too much into the chemistry of this subject, we can basically see the compounds within the firework’s shell as consisting of a mixture of liquids and solids (fuel, oxidizer, color-producing compounds, a binder, and possibly other additives) that are used for both the bursting charge and the aesthetic effects. When an aerial firework is initially fired, the reactants combust to produce thrust (as discussed last time), launching the actual firework shell into the air. At the same time as the shell is rocketing up into the air, a fuse (which was lit by the combustion) is burning. Eventually, that fuse will burn down to the firework’s charge, igniting the charge and thus producing the explosion, and triggering the reaction of all the other compounds within the shell. Upon explosion of the entire shell, a bunch of particulate jets are formed and are shot out in many directions. Generally speaking, these jets are what determine the form of the burst that we see when we watch fireworks. These jets are shown below; it is also interesting to note the Karman Vortex Streets visible in the turbulent wakes of the projected particulate, as caused by flow separation (and subsequent recirculation) along the blunt body of the projectiles.
Screenshot from the video in the last fireworks post showing particulate jets after explosion of the firework’s shell. Photo Credit: Discovery Channel
So what governs the size, shape, and behavior of these jets? While a lot is unknown about the exact cause of the instabilities associated with the jets, the main factors that are commonly seen as governing the jet structure are: nature of the particles (composition; liquid, solid, etc.), geometry (shape) of the charge, and mass ratio of explosives to particles (amount of explosive vs. other compounds). These assumptions are reflected in the research video below (Video Credit: D. Frost, Y. Gregoire, S. Goroshin, F. Zhang) which shows different combinations of particle nature, charge geometry, and explosive-particle mass ratio and their effects on jet structure. A cool note is that you will be able to see the shock wave (a pressure discontinuity, or large change in pressure in a very small distance – across the shock wave) created by each blast in the video. The main conclusions of the video (and some possible reasons for these observations) are:
1. Wet mixtures produce more jets (possibly due to smaller molecule size), which disperse sooner (maybe due to liquid surface tension effects).
2. Dry mixtures produce less jets (possibly due to larger particulate), which disperse slower (possibly due to higher momentum due to larger particulate mass and more friction effects due to the generally larger particulate vs. the wetted particulate mixture).
So there you have it: a relatively brief look at what governs the shape of the burst of fireworks! Please remember to check back later today for our salute to the brave men and women who have served this great nation! I’ll leave you with another image of fireworks and the Statue of Liberty as today is a great day for patriotism!
The Statue of Liberty surrounded by fireworks. Photo Credit: crazywebsite.com
Cal Poly Pomona Engineering. Photo Credit: Engineering.CSUPomona.edu
The Cal Poly Pomona (CPP) school year has just begun but, for some of us on Team UV, the end of our undergraduate career is quickly approaching. I recently enrolled in my last quarter and it feels amazing to almost be done after such a long journey. I also want to note that no one is more excited about this than my parents and girlfriend! For this week’s Open Mind, we were given a reflective prompt regarding which class we would say is the most vital in an undergraduate Mechanical Engineering career and which class we personally enjoyed the most.
Mechanical Engineering word cloud. Photo Credit: Oregon State University
In case you didn’t know, Mechanical Engineering curriculum covers many different sciences and engineering fields. In a very short and summarized fashion, CPP mechanical engineering students receive education in mechanical/machine design, electrical engineering, thermal fluids, material and structural analysis, coding, and the control of all these subjects when used together. The real list of classes is a mile long but I’m sure you get the picture: CPP Mechanicals are versatile!
Choosing one class out of more than 198 units and deeming it THE MOST IMPORTANT CLASS YOU WILL EVER TAKE is difficult because, for me, it has to be all encompassing. The first class that satisfies this condition would have to be ME 325/L Machine Design/Lab. The goal of this class is to instill students with the ability to design sound mechanical components. Topics covered in this class include the design and analysis of: brakes, clutches, gears, belt systems, and power-transmitting shafts, to name just a few subjects. In order to safely and effectively perform such designs, one would need background knowledge of, at the absolute least, stress analysis, material selection, classical mechanics, and something very unique. That special something is engineering intuition or in other words, the ability to make decisions without the help of a book or equation. Sometimes engineers don’t have all the information necessary to make a design happen but they can make an educated assumption and check on that assumption later on. ME 325 is one of the only classes that gives students the opportunity to build their intuition and see how it effects the outcome of their design. The ability to make solid design decisions and think creatively is invaluable to their education and is very desirable in industry. An added bonus of this class is at least one design, build, and run project. Here students can utilize other fields of engineering such as electrical and electronics engineering and thermal fluids to complete a given task. For example, Team UV used our knowledge of fluid mechanics, electronics, classical mechanics, and materials engineering to develop a propulsion system (SHEILA-D!) as our final project.
Since I only have one ME class left I can safely name my favorite undergraduate class: ME 439 Control of Mechanical Systems. I am currently taking this class but it has quickly turned into the most exciting part of my week. I have really taken an interest in robotics and micro-controlling as shown in my Learning Arduino posts and my preparation this summer has really helped me out. Students in this class utilize their knowledge of system modeling and response to help control mechanical systems. Our in-class projects heavily rely on Arduino usage and the use of really cool electronics such as ultrasonic sensors (to determine distance) and motors (for actuation). Keep an eye out for these new projects as they are completed in my Learning Arduino series!
So there you have it! I’m sure that the other members of Team UV have different opinions on which classes are the most important so check back for their posts! Till next time…
Artist’s depiction of the Star Tours motion simulation theme park attraction. Photo Credit: a.dilcdn.com
Prompt: Entertainment engineering brings to light some of the more light-hearted aspects of engineering. Entertainment in itself is one of America’s most popular pass times and encompasses subjects such as film, television, music, games, reading, comedy, theater, circuses, magic, street performance, parades, fireworks, animal shows, and the list just goes on and on. Entertainment holds a very special place in the world and always has; whether in the form of the plays of Ancient Greece, the jesters of the medieval times, the shooting exhibitions from the days of the wild west, the black & white films that the soldiers of early wars watched to forget about their harsh reality, or the 3D special effects that seem to captivate us all on the building-sized screens of today, entertainment has always been there to help relieve the stress of those who indulge in it. Today this is especially important for the citizens of this great country as we work longer hours, spend more time stressed, and find the well-appreciated release provided through entertainment to be more and more refreshing. For all these reasons and many more, the entertainment industry is here to stay and will constantly require great engineers to keep it afloat and help it to progress. Pick 3 forms of entertainment and describe how a mechanical engineer could contribute to them, or 1 form and 3 considerations.
Recently I went to the Halloween Horror Nights at Universal Studios and I was pretty surprised at some of their choices to enhance the entertainment experience on some of their latest attractions. We are all familiar with roller coasters and their exhilarating speed, drops, and turns, but modern attractions at theme parks are going beyond simply high speeds and elevation to immerse guests into their worlds. As an engineer hired to further study and implement some subjects of my curriculum into new attractions, I would take kinematics/relative motion, machine design, and optics into consideration.
Kinematics/Relative Motion At many theme parks there is an influx of attractions that heavily rely on the principles of kinematics and relative motion to simulate movement in a small enclosed area. This is opposed to large physical roller coasters that take up tremendous amounts of space, cost incredible amounts of money to build, and raise many safety concerns and standards that have to be met especially for faster moving attractions. Disneyland in California has Star Tours in which the passengers are taken from planet to planet by only rotating from their seats. Universal Studios in Hollywood has the Transformers Ride 3D which does both real translating of the passengers cart as well as simulated motion. I much prefer the Transformers ride because if you are only simulating motion, you eventually realize that you are not actually moving but a combination of both confuses the mind and makes it wonder whether you are actually moving or not.
Machine Design Still I believe the E-Ticket attractions are still the bigger roller coasters where you zip though loops upside down and through the air at face melting speeds. Machine design takes into account all the loads on all the components of the ride and ensuring with a factor of safety that those loads will not cause a failure. A corrosion study can also be done to mitigate the effects of corrosion to not only prevent certain kinds of corrosion that are likely to happen, but also avoid an unexpected failure due to fatigue or stress. Taking a statistical approach to the possible loads that the ride will introduce on components will make the design the safest and most enjoyable that it could be.
Optics As a mechanical engineer there is not a course in my curriculum that approaches this study directly but it would be an area I would like to further study. 3-Dimensional movies and attractions make the audience believe that the action is really happening inches from their faces. Further developing this technology to make it more realistic would definitely improve the experience of the audience. Optics could also improve the experience by making images seem unrealistic like in the Clowns 3D maze at Horror Nights. The 3D glasses made certain images appear closer than they were but there were sections of the maze that blurred the line between real actors and projected imagery. I was stunned when I thought a menacing clown was only a screen projection but then came out of the screen was smiling right in front of my face. I was impressed but more scared by this effect.
It’s been some time since I posted Part 1 of this series. In my first post, I covered the idea behind Arduino and the many applications of their boards. I have taken the past month to gain experience in micro-controlling and, as promised, I will share more of my educational journey.
Photo Credit: Future Electronics
Layout
Since an Arduino board interprets inputs and controls outputs, it only makes sense that you mostly see inputs and outputs on the front face. For the sake of keeping this guide as concise as possible without technical overload, I will only highlight the most critical parts of the board. As shown in the orientation above, the UNO R3 (a popular starter Arduino board) has digital pins up top that can be used as an input and/or output. Working around the board clockwise, we have a reset button that can be used to disrupt the current task and start from the beginning again. Next, we have the ATmega328 micro-controller which acts as the brain of the board. Below the brain, we have another strip of inputs and outputs. Starting from the far left, the user has freedom to use 6 analog inputs which can be used for sensors or other components. The next 3 pins are unregulated voltage (Vin) and two ground pins. The last 3 pins are a regulated source of 5V, 3.3V, and a reset pin. Lastly, we find the external power supply and the USB plug for power and communication purposes.
Inputs and Outputs
The 14 digital pins located up top can be used as inputs or outputs to fit various needs. They operate at 5V and can stand up to 40mA of current. Some pins have special functions but I will cover that when the times comes to use them.
The 6 analog inputs on the UNO have the same 5V operations level and provide 10 bits of resolution. Working with analog and digital signals at the same time can be a bit tricky but, like stated above, I will get to that when the project calls for it.
Power
The UNO R3 can be powered via an external power supply such as a wall adapter or by USB connection. The board can be supplied with 6 to 20V but anything above 12V is NOT recommended. The board can become very hot at higher voltages! Connecting a USB cable supplies the board with 5V but more potential can be supplied using an external power supply. This is important for driving components that may need more power than the regulated 5V supplied by USB.
Software
Standing by the idea of making coding and micro-controlling easy to learn, the software supplied by Arduino allows the user to jump right in without any headaches. The IDE (Integrated Development Environment) is easy to setup and looks very clean. A sample screenshot is included below to help highlight some important areas.
Arduino IDE Screenshot. Photo Credit: Majd Srour
The 5 buttons at the top left starting from the right are: verify, upload, new, open, and save. Verify is used to compile your code and approve it for use. Upload sends your code to the Arduino board. New opens up a new “sketch”, or code. Open allows the user to open an existing sketch and Save is self-explanatory. The magnifying glass to the top right is a serial monitor that shows what the Arduino is transmitting and is useful for debugging. The large white field is open space to write your code and the black field below is a message area where the IDE tells you of any errors.
What a post! I hope Part 2 doesn’t confuse you and if you have any questions, please feel free to comment. I will get back to you as best as I can but just know that I’m learning this environment for the first time too! My next post will get into our first project dealing with LED’s and code debugging. I will also include a video to help you visualize what all is going on. Until next time!
Fireworks seemingly have the capability to fascinate people everywhere, while trouncing any language, cultural, or religious differences. But the universality associated with the magnificence of these pyrotechnic displays is not the only aspect of their prominence that makes them so vastly interesting; they are scientifically remarkable!
While one could talk for hours (if not days) on end in the aim of exposing all scientific aspects of something as seemingly ephemeral as a firework display, we are going to look at just one consideration as it relates to the world of engineering: the baseline fluid mechanics that describe the interaction of fireworks with the atmosphere around them. We will begin this by watching a quick video (below) produced by The Discovery Slowdown, as was found through an article on FYFD (you can find the original article that inspired this one through the link; pardon the blog title, the content is excellent). For the record, I have no idea what the deal is with the baby sloth in the beginning of the video, haha.
From 0:14 to 0:30 in the video, you can see the uncontrolled combustion of the reactants used in the fireworks. This gives you a basic understanding of how this combustion takes place in the absence of any kind of container or packaging. When the reactants “burn” on the table out in the open atmosphere, the gaseous exhaust products (“smoke”) billow(s) upwards in a turbulent manner, with no real direction.
From about 0:31 to 0:58 in the video, the combustion of the reactants is repeated; however, this time the reaction take place in a cylinder with the top end open. Now you have controlled combustion (with regards to direction) and the result is effectively a jet of exhaust products (and some still-combusting reactants) that fires out the end of the cylinder in a way analogous to the exhaust kicking out the back end of a rocket, providing it with its thrust.
At 0:41, the video shows a closeup of the top of the tube, where the gases leave the confines of the tube and exit out to the air. As Nicole Sharp over on FYFD notes, this provides an excellent example of what we term an “under-expanded” nozzle.
An under-expanded nozzle is simply one where the static pressure associated with the flowing fluid at the nozzle exit is greater than that associated with the atmosphere (P>Patm); in essence, the nozzle has not expanded enough to reduce the pressure in the flow to that of the atmospheric pressure, so when the exhaust gases exit the tube, they expand (or fan) outward rapidly in order to equalize their pressure to that of the atmosphere. There’s your first mini-lesson in rocket science!
It also interesting to note how (at about 0:35) the tube jumps upwards as the gases leave. This is more than likely due to the fact that as this combustion occurs and the exhaust gases blast out of the tube at high speeds, they form a near vacuum in the tube behind them (by taking the contents of the tube and forcing them upwards, thus leaving a region of relatively low pressure behind the escaping gases in the cylinder). This vacuum, however, is not representative of a natural state; in essence, the air in the cylinder wants to be at atmospheric pressure, but instead it is at a pressure far lower than the atmospheric pressure. Once the bulk of the exhaust gases have escaped, the low pressure region immediately begins to collapse upon itself (thus increasing the pressure in the tube), but since the contents of the tube are still moving upwards, the cylinder itself is tasked with collapsing the region and thus is pulled upwards to decrease the volume in the tube between the cylinder base and the escaping gases! And so the cylinder jumps upwards towards the sky before gravity goes to work pulling it back down.
So there you have it, there are some basic fundamentals of the way firework exhaust gases behave in different settings. During my next Well Read post, I will discuss how we can use science and engineering to analyze the behavior of the actual jets that shoot outwards from a firework and what charge parameters affect their behavior. Thank you for your support and please check back on Thursday for Andrew’s Presentation post!
Prompt: You are in an office and the annual Office War is about to begin. You have less than an hour, a desk (w/ pullout drawers), rolling chair, computer, keyboard, mouse (old roller-type), mouse pad, stapler, staples, three hole puncher, desk lamp (old fashion bulb), rubber bands, paper clips, pushpins, envelopes, printer, printer paper, clicker pens, No. 2 pencils, a white eraser, highlighters, 15 ft. Ethernet cable, scientific calculator, engineering pad, corded desk phone, a gallon water jug, a tin of Altoids, a hot cup of coffee (in a ceramic mug), and a frozen 4 lb. steak. It’s either you or them, and remember you are a mechanical engineer, not a tinkerer. Go!
NOTE: DO NOT try or create any of these ideas at home. This is purely for fun and we will not be held responsible for your actions! Enjoy!
Well, let me first of all state: I am a lover, not a fighter. I often help those around me to the best of my abilities and in the case of a real office war, I would probably lose as a result of my being too caring; I truly could not hurt a fly. With that being said, I have decided to explore a scary side of design to help me survive this Open Mind.
So with an hour to go before all chaos ensues, I would start with creating basic but effective weapons. The frozen steak found in the freezer would make a great blunt attachment to a handle of some sort; one leg of my rolling chair could be broken off to create a handle with good material properties. I figure a chair leg is designed to support relatively heavy loads and to resist bending under loading. Attaching the steak to the leg could prove difficult but rubber bands or the phone cord would have to do. With this combo, I have now obtained a caveman-style blunt weapon for close combat!
Another basic weapon I could fashion quickly is a slingshot or crossbow. I have a number of pencils, pens, and rubber bands to create the structure while the push pins, paper clips or other sharpened objects could act as ammunition. I would have to double up the pencils in areas of high stress especially since I will be pulling back on the attached rubber bands. Incorporating a channel to guide a fired projectile could help with control and repeatability. Overall, a slingshot or crossbow would be easy to make and allow for long range defense/attacks.
So far I have a means of defending myself and attacking if need be. My mind now goes to protecting my resources and securing my cubicle fort. An electric fence could be erected around the perimeter of my safe zone. The wires from the Ethernet cable, keyboard, mouse, and computer can be collected for the live wire. The drawer slides can be removed and used as the ground poles. The voltage can be supplied by the computer power supply/wall outlet providing about 120V. Without a person in contact with the fence, the circuit is grounded by the poles. With a person in contact with the fence, the circuit is completed…Bye-Bye intruder!
Would I stand a fighting chance in an office war? I think so!
