DIY

Vibration Unthreading

Get inexpensive small motors and accesories for DIY projects here:
From Amazon: BUY NOW DC Motors Kit

A DIY project to see if just shaking a bolt at the right frequency could make a standard nut rotate and fall off. Similar physics to the phase locking propeller toy featured in my last post. Motivated by videos seen on Instagram where a brass bolt is placed in magnetic putty and the nut mysteriously rotates up and off- now convinced that vibration is how that effect is produced. Here a small DC motor spins an offset mass to produce the vibrations.

3D Print Planetary Gearset

Similar 3D prints available as fidget toys here:

From Etsy: BUY NOW: Gear Spinner Fidget Toy

Or print it yourself! (.stl files are available here):
From Thingverse:
Emmett Lalish Download: Gear Bearing 
Refined version featured here by Don Stewart Download: Honeycomb Gear Bearing 

3D Print Planetary Gearset: amazingly this gear set is printed assembled, with interlocking herringbone teeth. The gears will not come apart, in fact this design can only be accomplished by 3D printing the gears interlocked with each other. Designed and first printed by Emmett Lalish in 2013, and this version with refined precision and honeycomb by Don Stewart. 

Floating Rings Illusion: Dr. Manhattan Booth

Created in my shop with these parts:

From Amazon: plastic rings, plastic sphere, blue paint

Inspired by the Phone Booths in the new Watchmen series.

Calling Dr. Manhattan: floating rings illusion device inspired by the recent Watchmen series. Two attached rings appear to roll in an impossible way around an orb, featured in a number of scenes on top of blue interplanetary phone booths in the new Watchmen series. Created in my shop with plastic rings and some blue spray paint. 


Wringing Guage Blocks

Guage block sets can be a bit pricy, but some fairly inexpensive pieces and small sets can be found for demonstrations and such:

From Amazon: BUY NOW: Gauge Blocks

Wikipedia has a nice description of Gauge Blocks and the Phenomenon of Wringing

Wringing Gauge Blocks: two blocks of metal (not magnets!) will stick together by a process called wringing if their surfaces are flat to high precision- such as these gauge blocks found in most machine shops. Here two blocks are forced apart with a snap, and then wrung back together with the characteristic sliding motion technique. Gauge blocks are flat to less that one millionth of a meter and are used by machinists for precision length measurements and calibration. The science of the wring force remains somewhat a mystery and no one has yet found a fully excepted physics description- but we do know that blocks will wring in a vacuum and that the force can be up to 30 times that of weight of the blocks. Fun physics from the shop!

Single Strand Tensegrity

Get the 3D print files here:

From Thingverse: Make Now: Single String Tensegrity

Click here for more tengerity in my collection.

Single Strand Tensegrity: a vertical chain- when held under tension a single length of thin chain can become a rigid support structure. In this design four 3D-printed struts each act like an archer’s bow to stretch the chain under tension. Beads placed on the chain interlock with the ends of the struts. Design and .stl files by Ernie Condone and printed by Roger Key (thanks!)

Disappearing Spoon

Gallimum metal and a silicone mold to produce the spoon- available here:

From Amazon: BUY NOW: Gallium Mold Spoon Kit 

Disappearing Spoon: the metal gallium has a melting point of 30°C (86°F) and will melt quickly when exposed to tea temperature hot water- or melt in one’s hand if handled too long. This spoon was made with a silicone mold (swipe to see process), and feels and sounds just like a regular spoon, except solid gallium is brittle and the spoon can shatter like glass if dropped. An amazing parlor trick as well as a classic and historical class demonstration.


Gravity Defying Nail and Magnet

Neodymium magnets will produce the largest gap when suspending a nail.
Please use exterme caution when handling these magnets. 

From Amazon: BUY NOW: Neodymium Super Magnet

Magnetic Defiance of Gravity: a nail suspended between a chain and a powerful neodymium magnet. Ferromagnetic attraction over a distance of many millimeters, and a reminder of the presence of the typically invisible electromagnetic forces all around us. Make your own with a paperclip, string, and a refrigerator magnet- or get a neodymium magnet and see how massive an object you can suspend in air. 

Cartesian Diver

Glass divers available here: 
From Amazon: BUY NOW Glass Divers or this complete set Cartesian Diver Kit

Inexpensive and fun diver kits to make in a bottle available here: 
From Educational Innovations: BUY NOW Cartesian Diver Kits 
 

Cartesian Divers: increasing pressure on the water compresses the air bubbles in the small glass vials filling them further with water making them sink. Pascal's principle states that any change in pressure on an enclosed fluid (such as pushing on the rubber cover) is transmitted evenly to every part of the fluid- the physics of hydraulic brakes! Named after the physicist and philosopher Rene Descartes.

In Defiance of Gravity

Neodymium magnets will produce the largest gap when suspending a nail or other iron rich objects.
Please use exterme caution when handling these magnets. 

From Amazon: BUY NOW: Neodymium Super Magnet

In Defiance of Gravity: a 3 oz plumb bob in suspension between a chain and a powerful neodymium magnet. Ferromagnetic attraction over a distance of many millimeters, and a reminder of the presence of the typically invisible electromagnetic forces all around us. Sculpture: oak, stainless steel chain and hardware, neodymium super magnet, standard plumb bob tool. Iron filings in oil align and chain together to reveal the magnetic field lines of the equilibrium configuration.


In-Feed Google 2

Self Propelled Homopolar Motor

Here are disk magnets I used for the "wheels": 
From eBay: BUY NOW Neodymium Disk Magnets 
From eBay: BUY NOW Neodymium Disk Magnet 

Wire that looks and works well is just 10 gauge ground wire. Inexpensive and available at any local hardware store-- or order a small quantity here: 
From eBay: BUY NOW 10 gauge Copper Wire 

Wikipedia has some good details on the physics of homopolar motors 

Self Propelled Homopolar Motor: cylindrical neodymium magnets supply the static magnetic field for this motor and become the wheels of a very simple vehicle with an AA battery as the energy source. As soon as both ends of the copper wire make contact, an electric current will flow which in turn induces a magnetic field around the wire. This induced field around the copper wire will then interact with the neodymium magnets on each end causing them to spin- a wonderful example of a motor with minimal components.

The FluoroSphere

The kit includes the UV LED base, elegant glass sphere, and enough fluorescent gel for many repeat lights shows. 

From PyroFarms: BUY NOW: FluoroSphere

From Amazon: BUY NOW: FluoroSphere

The FluoroSphere: intricate and dynamic lights shows are produced within an elegant glass sphere as fluorescent dyes in mineral oil slowly mix into room temperature water. Ultraviolet LEDs (in the base on which the sphere rests) make the dyes glow brightly and reveal the initial nondiffusive mixing structure which includes the phenomena of drops, plumes, and other features of Rayleigh-Taylor instabilities. Shown here, slightly sped up, is the first 8 minutes or so of the process which takes up to half an hour to mix evenly. The green light is characteristic of the famous fluorescein dye.

 


Polarizing Filter Black Wall Illusion

Amazon lists acrylic tubing at a reasonable price: get a 2 foot long tube with an inner diameter of 1.5 inches for about $17 US. This will accommodate a large marble for the demonstration. 
From Amazon: BUY NOW Acrylic Tubing 

For a 1.5 inch inner diameter (3.8 cm) tube you will need a 10 inch (25.4 cm) wide sheet to complete a cylinder inside the tube. 
From Educational Innovations: BUY NOW Polarizing Film

Polarizing Filter Black Wall Illusion: two sheets of polarizing film (with polarization axes oriented at 90 degrees to each other) create this illusion inside an acrylic tube. Physics magic!

Frabjous Geometric Sculpture Puzzle

Get one here- five colors to choose from:

From MoMath: BUY NOW: Frabjous Sculpture Puzzle

Frabjous Geometric Sculpture Puzzle: 30 identical laser cut acrylic pieces interlock into 12 interconnected five point stars (each with a spiral vortex center) in this puzzle based of the Frabjous sculpture by artist and professor of mathematics George Hart (Prof. Hart is now on Instagram, follow him at @george.hart.sculptor to see more of his amazing work.) Note that if one connects the tips of the stars one gets the outline of a dodecahedron, with its 30 edges and 12 sides, and if one considers the face planes of the linked pentagrams the underlying shape is a polyhedron called the “great rhombic triacontahedron”. A year or so ago I got to visit the National Museum of Mathematics in NYC where I bought this puzzle in the @momath1 museum shop. This puzzle was great fun to assemble- buy one to support this inspirational museum, and make a great sculpture for your bookshelf! 

"Impossible" Domino

Get the 3D print files here:

From Cults3D.com: Download Now: Impossible Domino

This video from The Action Lab has a good decription of rhe physics. 

“Impossible” Domino: a pair of specially engineered domino type objects where the right domino knocks over the left one, but then stands back up! When seen in slow motion the process becomes more clear. The main factor here is that the center of mass of the left domino is higher than that of the right one, giving it much more potential energy so when the left one topples over it can transfer some energy back to the right one. Created by the folks at viralvideolab and 3D printed by my friend Roger Key (thanks!)


Harbottle Air Pressure Demonstration 

This item came to me in my Spring 2022 Curiosity Box subsciption:
Get (or give!) a Curiosity Box subscription here: JOIN NOW: The Curiosity Box

A nice glass version is available from this trusted seller:
From Educational Innovations: BUY NOW Harbottle Demonstration 

Harbottle Balloon Demo: a regular untied balloon remains inflated- one can even look down the neck of the balloon and see inside! Just blow up the balloon inside the bottle and then cork the hole in the opposite end- in so doing the inside of the balloon is experiencing the full force of air pressure, but the exterior of the balloon is protected from the crush of air pressure by the rigid wall of the bottle. Air pressure at sea level is 10.1 Newtons of force per each square centimeter of area (14.6 pounds per square inch). The bottle allows a pressure differential, pressure on the inside but much less on the outside of the balloon. The inside air pressure would lead to 12.5 pounds of force pushing outward on a 2 inch diameter balloon- more that enough to balance the elasticity of the rubber balloon material. Take the cork out and now both sides experience the same air pressure and the elastic force is no longer balanced. A fun demonstration reminding us that we live at the bottom of a deep sea of atmosphere! 

Salt Fractionation

All the ingredients are available from your local market/drugstore. The trick is to find a dye that works for acetone, but will not color water- believe it on not blue glitter will color the acetone nicely and not change the salt water. Follow this link for details: 
ChemEd X: Blog of Prof. Tom Kuntzleman 

Of course Amazon has what you will need:

From Amazon: BUY NOW 
acetoneblue glitterfood coloring, cool bottle 

Salt Fractionation: two liquids that won’t stay mixed! Acetone (dyed blue) floats on top of the higher density salt water (dyed orange). Acetone usually dissolves in water through hydrogen bonding interactions, but solubility can be altered. In a process called “salting out” a sufficient amount of salt is dissolved such that the water molecules, which are much more attracted to the resulting Na+ and Cl- ions (through ion-dipole bonds), will then ignore the weaker acetone hydrogen bonds. This results in the spontaneous separation (shown here in real time) of the liquids no matter how well shaken up. 

Compliant Mechanical Elephant

Get the .stl files for this 3D print here:
From Thingiverse: Download NOW: CM Elephant

Learn more: mechanical engineering of compliant mechanisms

Compliant Mechanical Elephant: a demonstration of engineering using flexible elements instead of pivot joints when creating linkages. In this whimsical and clever linkage design a sideways translation of the elephant creates only rotation at the tip of the pachyderm’s trunk. Note that the hole at the end of the trunk remains eerily stationary as the body translates horizontally back and forth. This demonstration model comes from the Compliant Mechanisms Research group at Brigham Young University. Thanks once again to Roger Key for producing this 3D print.