DIY

Bottle, Hoop, and Nail Trick

The hoop used is just the inner circle of an embroidery hoop. Get one for a couple dollars here: 
From Amazon: BUY NOW Wooden Hoop 

The science writer Martin Gardner has published many books of physics tricks and simple but amazing science experiments like the one in this video. Highly recommended. 
From Amazon: BUY NOW Martin Gardner's Science Magic: Tricks and Puzzles 

Bottle, Hoop, and Nail Trick: with some practice, a snap of the wrist removes the hoop and the nail falls straight into the bottle. Newton's 1st Law as seen in slow motion- a mass at rest tends to stay at rest. (Best to watch with sound/audio) Balancing the nail on the hoop ensures the nail is directly over the top of the bottle. The hoop is removed so quickly that it does not interact significantly with the sufficiently massive nail, and thus the nail remains over the mouth of the bottle so that gravity pulls it in. G4G Week repost- a favorite from Martin Gardner’s collections of physics tricks. 

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Ring Catch Chain Trick

Get a set here: 
From eBay:(best selecton) BUY NOW Ring Chain Catch 
From Amazon: BUY NOW Ring and Chain Set 

The physics of this trick in great detail with more slow motion: Ring Falling into a Chain: No Magic — Just Physics 

Ring Catch Chain Trick: a solid ring will be caught by a loop of chain if it tumbles during its fall. By Newton's Third law, when the ring twists into and hits the chain, the impact transfers momentum to the end of the chain, which rises up and over the ring- seen here in 480 fps slow motion. 


Tumble Rings

I made this set of tumble rings from reading Martin Gardner's description in his famous mathematical recreations books- highly recommended: 
From Amazon: BUY NOW Knots and Borromean Rings by Martin GardnerDescribes the Tumble Rings 

From Amazon: BUY NOW Books on recreational math and puzzles by Martin Gardner Lots of physics and math toys in these pages! 

Tumble Rings: the links in this chain are connected in a special way such that the top ring appears to tumble to the bottom- a compelling illusion! 

Mobius Zipper

If you like this kind of math exploration I highly recommend this book by Matt Parker: 
From Amazon: BUY NOW 
Things to Make and Do in the Fourth Dimension 


... and any of the books by Martin Gardner 
 
From Amazon: BUY NOW 
Recreational Math Books 

Möbius Zipper: exploring topology with a bisecting strip (a zipper with velcro ends). 0 twists creates a cylinder which simply gives two cylinders when split, ½ twist creates a Möbius strip- splitting down the center produces one long loop with with two full twists, 1 twist in a loop-splitting in half produces two interlocked Möbius loops! Just some of the curious properties concerning the Möbius strip, an unorientable, one sided surface, with only one boundary. 

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Spinner Fidget Trick

Click this link for a gyroscope that will perform the same trick! 

Spinner Fidget Trick: defy gravity!- a trick to try with a fidget spinner you might have in a drawer somewhere. For the trick to work the spinner needs to have most of its mass far from the center (not all spinners will work)- and you may need to drill a hole down its center to attach an axle. This Spinpal spinner has three heavy steel spheres placed to maximize rotational inertia, that along with precision bearings, gives this fidget toy properties of a quality gyroscope. Give the spinner significant RPMs and it will suspend from, and precess around, a string! Thanks to @spinpal for sending me this a while back. 

Faraday Train

Here's the parts to make your own: 
From eBay: BUY NOW Neodymium Spheres 15mm 
From Amazon: BUY NOW Bare Copper Wire 10 gauge 

The wire used for the Faraday Train has to be bare- so make sure it does not have any kind of clear coating on it. The solid grounding wire sold at hardware stores works great. 

Here is a nice description of the Faraday Train and the physics of its propulsion

Faraday Train: two magnets, one battery, and a coil of bare copper wire are the simple essence of this self propelled craft. The magnets conduct electricity, thus when put in contact with the coil current will flow creating a solenoidal magnetic field in the vicinity of the battery, which in turn pushes on the magnets at each end of the battery moving the craft along. The spherical neodymium magnets used allows the craft to slide along the coil with minimal friction. 

Hyperbolic Holes

This inexpensive kit available here: From eBay: BUY NOW
Hyperbolic Holes Kit

Hyperbolic Holes: a straight rod, in this case a pencil, glides through a symmetrical pair of curved holes. The design is based on the hyperboloid, the 3D ruled surface traced by an offset rotating diagonal line. This device is sold as an inexpensive kit to assemble yourself, and includes a motor with geared drive and pre-cut pieces. The pencil is my addition- just the right size to clear the curved openings.


Magnetic Suspension Sculpture

The DIY version can be assemebled with these parts. Steel wire of guage 10 or 12 should work well. 

From Amazon: BUY NOW: Quilting Hoop, Neodyumium Magnet, Steel Wire

Magnetic Hoops Suspension Sculpture: Steel circles are suspended by a magnet (black sphere) and held down to the base by a thin thread. The tops of the steel hoops, being ferromagnetic, become a north pole in the presence of the south pole end of the black magnet, so they are attracted to the black magnet, but repel each other. Made by Rathcon Inc. in 1970. Swipe to see my DIY version made from a quilting hoop, neodymium magnets, and some bailing wire. 

Electric Motor

Get this easy to assemble kit here: 
From Educational Innovations: BUY NOW Simplest Motor Kit 

Electric Motor: in its simplest form!- coil, magnet, and battery. The wire of the coil has an insulating coating- and this coating is carefully scrapped off one side on each end. When current passes through the coil it becomes an electromagnet and the permanent magnet repels it making it spin- as it turns the currents goes on and off depending if the copper posts are in contact with the bare wire (current on) or the still insulated wire (current off). I have motors with fewer parts- but they operate on more complex principles.

Centripetal Spheres

Just thread a rubber band through two of these drilled steel balls and you are ready to go! 
From Amazon: BUY NOW 
Drilled Spheres 

Centripetal Spheres: two ball bearings connected by a rubber band orbit each other as energy oscillates between elastic potential energy and rotation kinetic energy. Just wind up the rubber band and let go. When the rubber band has unwound the rotational inertia of the bearings winds it back up until it changes direction. The process repeats until the initial energy is dissipated through friction.


3D Print Planetary Gearset

The .stl files are available here:

From Thingverse:

Origial desing by Emmett Lalish Download: Gear Bearing 

Refined version featured here by Don Stewart Download: Honeycomb Gear Bearing 

Similar prints available as fidget toys here:

From Etsy: BUY NOW: Gear Spinner Fidget Toy

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. 

Hoberman Actuator with Sphere

The Actuator mechanism is out of production but can still be found on eBay, comes with power supply, Expandagon kit, and connecotors that snap on to a Hoberman Spjere. 
From eBay: BUY NOW: Hoberman Actuator

The spheres are still in production and come in various sizes and colors: 
From Amazon: BUY NOW Hoberman Spheres 

Hoberman Actuator with Sphere: This actuator mechanism creates kinetic art out of a Hoberman sphere, designed to smoothly expand and contract the isokinentic structure. The Hoberman sphere itself is a special assembly of foldable linkages consisting of rigid bars and simple hinges is kinematically over constrained- motion can only occur along the radial direction and the movement of any hinge creates motion in all the joints. The engineering and physics behind deployable space structures!

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.


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 

Wikipedia has the details on the Cartesian diver (and reverse diver)

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.

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.

Homopolar Motor

Fairly simple to make- here are the inexpensive supplies needed to make a few of these motors. 
AA batteries have a diameter of 14.5 mm, so a bottom magnet with a diameter of 15 mm is just right: 
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 

Homopolar Motor: a minimalist electric motor- battery, wire, and magnet. This type of motor does not need a commutator- the polarity of the electromagnetic coil does not need to reverse. The challenge with this design is balancing the coil to center on the battery as it rotates. A favorite DIY physics toy!