10 Terrific Trebuchets


Hurling objects at long distances with a catapult or trebuchet isn’t anything new (they were being used in their modern form since the 4th century BC) but it sure is fun and certainly satisfying when they actually hit a target. Most of the catapults today were designed for educational (historical recreations) or recreation purposes using everything from pumpkins (the annual Pumpkin Chunking contest) to vehicles as projectiles.

Actually, believe it or not, they are still being used in modern warfare today with Syrian rebels using a makeshift catapult to launch explosives at government troops in the Battle of Aleppo (in 2013) and rioters in the Ukraine used them to launch Molotov cocktails during the Hrushevskoho street riots of this year.

No matter what they’re being utilized for one thing is certain- catapults and trebuchets are making a comeback, especially with the homemade DIY maker community. Collected here are a few of the more unique and interesting takes on the age-old hurling contraption designed by the maker community

If you want to build your own, there does just happen to be a Trebuchet kit available in the Maker Shed.

Talkin’ Tinkering with the Masters of Automata

Keith Newstead's pieces "In the Garden with Charlie" and "Sing Cats Heads"

Keith Newstead’s pieces “In the Garden with Charlie” and “Sing Cats Heads”

The Exploratorium Tinkering Studio invites all of you to join a Hangout this Friday, November 21st from 9am to 10:30am (Pacific time) to talk about one of their true specialties—Automata!—with some of their favorite masters of this art/technology.


Joining the Tinkering Studio team will be a star-studded group:

  • artist Keith Newstead (whose pieces are at the top of this post)
  • Gautham and Vanya from Srishti School of Art, Design and Technology
  • Monika and Allan from Lawrence Hall of Science
  • Brooke from Oakland’s International High School

While this will be tailored mostly for those who are teaching others to make automata, anyone and everyone is welcome. Karen from the Tinkering Studio writes:

We’re huge fans of automata here in the Tinkering Studio and think we could dedicate several hangouts to this topic alone, since it’s such rich territory for exploration. It’s one of those activities we think holds tremendous potential for making and tinkering, but isn’t the easiest one to facilitate in an open and “tinkerable” way — that’s why we think it’s worth thinking more about.

You’ll hear from an interesting mix of people, who will share their experiences working with automata in different contexts and thinking about the educational implications. We have a rough outline of what we’ll cover below, but it’s likely to change based on where collective interest takes us.

This hangout will be useful to both education and exhibit folks and those with an interest in arts education in general (think STEAM).

On the agenda:

  • Material possibilities / wire, cardboard, trash, flotsam, food
  • The importance of examples – figuring out what the right selection is
  • Automata Workbench: An interactive exhibit prototype
  • Trying to move it away from being step-by-step
  • Mini-revelations related to construction
  • Transition from intensive workshop to doing it on the floor
  • Automata artists
  • Training someone else to facilitate the activity
  • The tradeoffs in terms of creativity
  • Automata as part of arts education
  • Incorporating circuitry and linkages


This promises to be a visual delight. Join live or if you have to miss it, watch the recorded archive.

To be able to ask questions live, use the Google+ event page. You’ll need a Google+ account to participate.

Or view the hangout via YouTube, but viewers won’t be able to ask questions of the presenters.

How to Rebuild Society (with the Survivor Library)

Source: Wikipedia

Source: NASA via Wikipedia

Ever since reading Bill Bryson’s A Short History of Nearly Everything a decade ago, I’ve had some background worry about large-scale global catastrophes. A couple of chapters in the middle I couldn’t bear to finish reading. I’ll sheepishly admit here that even the remote possibility of a super-volcano or a comet collision making life very unpleasant for a long time, also perhaps thrusting us a millennium or two into the past technologically, scares me a little bit. (Not a lot, just a bit!) And then I wonder what we are doing to prepare for these society-disrupting terrors in all their horrifying non-zero possibilities. Earlier this year, I was glad to hear that Lewis Dartnell had written a book called The Knowledge: How to Rebuild Our World from Scratch, but as the book weighs in at just over 300 pages, I wagered many details would necessarily be left out.

Screen Shot 2014-11-16 at 3.40.36 PMI’m happy to report there is someone on the case. Rocky Rawlins comes to us with a hero’s name and an idea for rebuilding society: his Survivor Library intends to preserve for the remaining 0.000001% to 10% or so of humanity details on “how to survive when technology doesn’t.” You can hear an interview with Rocky on NPR’s On The Media or if you’re up for a dystopian read, the library’s about page lays out the grim future we could face, and how we can dig ourselves out of our knowledge-free hole:

As the library has grown over time we’ve tried to cover both the simplest, more basic self-sufficiency skills, such as growing food and raising livestock through the most advanced and sophisticated technology of the time such as aeroplanes and communications systems like telephone and telegraph.

Where there are books on industrial processes, methods, formulas, techniques, we included those as well. Even the more advanced technologies of the periods are within the reach of people starting from scratch. Steam engines may seem primitive to most modern people but they powered the industrial revolution in much of the world well into the 1900s.

Basic knowledge of chemical formulas and processes are recorded in books from these periods ranging from the most basic industrial chemical needs through household materials in common use.

The Library in its entirety is a compendium of the Technological and Industrial Knowledge of the 1800 through early 1900s.

It is the knowledge needed to rebuild a technological and industrial infrastructure from scratch when the modern infrastructure ceases to function.

I’m not sure we need to know how to play whist or grow tobacco after the end of society befalls us, but books on the topics of medicine, sanitation, shelter, and many of the other 100+ categories would serve our survivors well.

You may note that this is an online resource, which depends on the Internet and the power grid to be accessed. Rocky and company expect you to plan ahead. All the books they’ve scanned are available as PDFs which he asks you to at least download and store locally, and preferably to print out on paper.

Interjection: Somehow I’m reminded of the Twilight Zone episode “Time Enough at Last“. Be sure you’ll be able to access this knowledge!


Scene from the Twilight Zone episode “Time Enough at Last” (1959) in which an avid reader is left with all the books he’d like to read, but… well, I’m not going to wreck the ending for you.

Keep in mind this important caveat: the books were written “before we understood such things as disease vectors and the toxicity of substances such as mercury. …. they do contain formulas, recipes and knowledge that we now know to be dangerous and harmful. Before considering using any of these techniques or applying the skills and knowledge in them, apply common sense and modern knowledge.”

That said, I am looking forward to the library that tells us how to rebuild the world without recreating all of the technologies of the 19th and 20th centuries—some of which were environmentally disastrous. We could rebuild society with the wisdom of learning from our mistakes, right? I’d like to know who is working on that library.

Whether or not you share my Bryson-inspired Chicken-Little fear of the end of life-as-we-know-it, the books contain a lot of lost and common knowledge any Maker would appreciate.

What would your ideal Survivors’ Library contain? Tell us in the comments below, and add them to the Survivors’ Library’s suggestion page.

[Note: I sent this writeup to Alexander Rose of The Long Now Foundation, and he pointed me to his piece on The Manual for Civilization. That post includes a running catalog of similar projects. He also reminds me that Lewis Dartnell will give a talk at The Interval at Long Now this spring.]

Crazy Cat Home Improvements


What does one do who loves cats? You can always become a “crazy cat person” that has 20 or so felines running around the house. On the other hand, if you have a serious amount of skill and dedication to home-improvement projects, you can modify your house to accommodate their climbing needs with a series of platforms, miniature stairs, and holes to climb through.

Greg Krueger is decidedly in the second category. He seems to have a manageable number of cats, and given how well he was able to “catize” his house, the felines living there seem to live like royalty. Living in Minnesota, it must be especially nice for them not to have to go outdoors to find an interesting place to climb.


In the video below, Greg says “I almost don’t wanna finish what I’m doing,” a sentiment that many people who make things as a hobby can relate to. I suppose most of us would also realize that you never actually finish something like this; it just gets to a good “temporary” stopping point.

If you’re looking for something for your cats to play in without permanently modifying your house, why not build a minuature AT-ST walker for him? Sure, you won’t get credit for being quite as dedicated, but if you live with other humans, they may have a greater tolerance for the project.

Making Tiny Cannons That Actually Work

It may look like a toy but make no mistake, this cannon fires steel ball bearings using real gunpowder.

It may look like a toy but make no mistake, this cannon fires steel ball bearings using real gunpowder.


Back in the day (the Civil War) naval vessels were outfitted with state of the art Dahlgren guns (nicknamed Soda Bottles from their distinctive shape), which could lob a shell close to 2 miles in distance. The North used to heat those shells until they were red hot and fired them into the sides of Confederate ships, which would set them ablaze.

Scope it out- Sighting in the cannon is done using a custom-made scope that attaches to the barrel.

Scope it out- Sighting in the cannon is done using a custom-made scope that attaches to the barrel. Is the scope that useful?


As cool as cannons are, owning one is incredibly expensive and ammo is tough to find, however making one at 1/9th the scale is a lot cheaper provided you have the tools. Imgur user [Jefenry] designed his Dahlgren cannon using 4130 seamless alloy stainless steel with a 1-inch bore. The barrel fits snugly into his steel carriage with brass wheels, which was laser cut for an exact fit. Elevation is adjusted using a simple screw and sighting in is accomplished with a detachable scope.

The scaled down Dahlgren cannon complete with ball bearings and black powder.

The scaled down Dahlgren cannon complete with ball bearings and black powder.


Jefenry made his own shells using steel ball bearings, which are fired using 100-grains of black powder wrapped tightly in tin foil so there’s no accidental discharge when lighting the fuse. To test out his cannon, Jefenry took to the firing range where he systematically obliterated a watermelon. Yep, his cannon is no toy, can injure a person in the same fashion as a firearm and should be treated as such.

To see the complete build process head over to Jefenry’s imgur page.

Can Teachers Build a Physics-Go-Round?

The Joy Wheel, at the now mostly defunct / relocated Playland at the Beach. Read on for a vivid, gorey memory of physics experiments by a San Francisco teen employee there decades ago. Photo courtesy of Mike Winslow's  Playland at the Beach

The Joy Wheel, at the now mostly defunct / relocated Playland at the Beach. Read on for a vivid, gorey memory from decades ago by a San Francisco then-teenaged employee. Flashback photo courtesy of Mike Winslow’s Playland at the Beach site.

How would you build a giant turntable or merry-go-round for the physics classroom? I was recently sent a discussion among teachers from the Exploratorium’s Teacher Institute on this very subject. It reminded me of the summer before my senior year of high school, when I took a physics class at Caltech with a juggling grad student who looked a lot like Jesus. Our best lesson of the summer? He took volunteers to a nearby park to see him and his pal juggle on a roundabout, and a few of us got to join him on the rotating platform. He gave us a playful metaphor to understand the alphabet soup of the calculus-rich vector exercises we did in the classroom.

Back to this teacher’s query. Ben posed the original challenge:

Our physics teacher and I have been fantasizing about having a large turntable on which students could explore a variety of concepts. Ideally we would like a surface around 3 or 4 meters in diameter that will stay flat, turn smoothly, support three or four high school students, and be sturdy enough to survive the wear and tear of years. Have any of you built a large turntable for class demonstrations? I would appreciate any plans, suggestions, or cautionary tales. It’s a long-term goal. We’ve been going round and round (so to speak) about size, materials, safety, bearing setups, used vs. new, placement etc.

Mandy suggested our oversized spin-art machine, but Ben needed something a bit slower. He defined it more clearly:


Courtesy of gyroscopes.org

We want the students to study motion on a rotating surface, from various perspectives. I’d like to use it to demonstrate the Coriolis effect, for example.

We would like students to be able to sit on it, throw and roll balls between them, and film the ball’s motion from on, above, and beside the surface, both moving with the surface and not moving with it.

It needs to be strong enough to support them, and large enough to be able to observe the motion of objects moving above the surface for some distance.

Ellen Koivisto of Asawa School of the Arts in San Francisco chimed in with a clever, STEAMy suggestion:

Talk to your theatre teacher/s and tech people. Turntables have become common set items again in recent decades (after Les Miserables). They were often built for Victorian melodramas, then fell out of favor with the rise of movies and kitchen sink naturalism.

I’m doing a show right now that uses a relatively small turntable — 11′-6″ in diameter. There are three concentric rings of casters that take the weight. I believe it’s two layers of 1/2″ ply, laid perpendicular to each other and glued together. One person can push it with their foot, or there are pole holes so a person can stick a metal pole into the hole and pull the turntable around. It moves smoothly and easily.

I did a show once with an 18′-diameter turntable. That required more people to move and bigger casters, but it was lovely to work on. I haven’t done a motorized turntable yet, but there’s tons of info on making and using them in technical theatre magazines and websites and books.

Caren Kershner similarly suggested checking in with the old Creede Repertoire Theatre in Creede, Colorado about how their three stages mounted on a turntable function.

While looking for images for this post, I found this detailed how-to on how Texas A&M’s Scene Shop built this rotating stage turntable for its production of Th3 B3ggar’s Op3ra.

Texas A&M's Scene Shop built this rotating stage turntable for its production of Th3 B3ggar’s Op3ra." Read more about how they built it here.

Texas A&M’s Scene Shop and its rotating stage turntable in progress.

Raleigh McLemore had lots of ideas:


Photo: wikipedia

My first thought was that you could build off of a platform like a playground merry-go-round. Some simple welding or carpentry might be all that it takes to either remove the uprights or add structure to them to build a platform that a student could safely stand on. You are working with bigger kids and some of the cheap (about $750) small structures may not have enough carrying capacity. Larger built spinning structures are heavy and expensive (around $2K). Outside chance your local parks department might have a broken one, or one that is in storage after a playground change up.

Another idea might be to start with a junkyard car wheel and wheel bearing. A front wheel kingpin might be pretty cheap and could be located vertically in a strong base with the wheel and bearing slipping over the kingpin to become a center to the car wheel spinning on it horizontally. Not sure how it would happen, but I’m sure the car wheel would be a very strong point to begin to weld or assemble a wooden structure upon. I haven’t thought it through very far but I would start with buying a wheel with a wheel bearing(s) and a kingpin if they were reasonably priced.

If a kingpin doesn’t seem right then I would look for an appropriately sized shaft to support the wheel and bearings. Perhaps even a hardwood axle could be fashioned although first thoughts seem to me that it wouldn’t be strong enough. Any upright axle that could be located into a solid plywood base would get you started. The junker car wheel bearing would fit upon the upright axle, the wheel would then be the spinning base of the structure. Done correctly you should have a stable spinning base. The platform couldn’t be too heavy or unbalanced, or it would wiggle and wobble. Putting additional support wheels around the outside of the large spinning platform might make the platform more level and add to stability.

Seems a bit elaborate, but I suppose you could use a dryer motor and belt to spin the wheel by mounting it on the plywood base at a distance to put tension on the horizontal spinning wheel using the dryer belt. You need guards and a speed control for this. What with the variable loads this could be a mess and deserves a lot of thought unless you can get the junk for free. Done poorly you could have a fire or a short.

Last, I wonder if you could hang something from a rafter/joist support (use rope? wire rope?) and put some good wheels around the outside of the platform so that the center is supported from a high point and the outside edges are held up by the wheels? This might be reasonably cheap if the overhead support is equal to the load. This might not be very smooth or stable for the experiments you have planned. Not sure how you would have a smooth controlled motion without a rail to guide the wheels. You wouldn’t have a clear center with this, the support rope popping out of the center of the platform.

Detail of a mural hanging at Playland Not at the Beach. Photo by Jef Poskanzer.

Detail of a mural hanging at Playland Not at the Beach. Photo by Jef Poskanzer.

Raleigh wrote again a little later to reminisce about his time working the Funhouse “Joy Wheel” at San Francisco’s old Playland at the Beach.

This thing was a very large flat, slick, spinning disk with about 20–25 folks climbing on, sitting as close to the center as they could squoosh. My job was to control the speed and spin the disk as fast as it needed to go to spin the folks off and have them slide hopefully to the padded wall and away from the spinning wooden platform. It was lots of fun until folks frantically grasped others and took off a large clump of people who slid off together. The resulting crush of humanity wouldn’t fly off of the disk completely and over and over again somebody would get jammed into the edge of the wheel, unable to move away due to the others being pushed against the wall. I had a “panic stop” button but it really didn’t stop the device very quickly when I hit it. Very gruesome injuries would sometimes occur, never life-threatening, but bloody. My job was to clean that up too.

When the midway had no customers, and I was free to move about the site freely, I used to roll stuff across the slick Joy Wheel surface, pour water at different places and occasionally even be able to anticipate where my experiments might exit the wheel. I remember thinking that somehow if I threw a dart in the air over the spinning disk the dart would begin to rotate with the spinning wheel before it hit…it is still surprising how much I want the disk to alter the trajectory of the dart, although I know it can’t.

From Raleigh’s description and the photo at the top of this post, I’m finding myself wishing there were a giant rotating disk in every city. It sounds like such fun! Except the bloody part. If you can’t quite make out the sign in the top of that picture, it reads “The best cure for blues is joy. Get cured here” (Also, who else thinks that might be Raleigh in the picture?)

We now turn to the Maker-verse. Have you built a large rotating disk? Can you share plans and tips for building it?

Incredible Aviation-Themed Desk


If you need a desk you can, of course, always buy one. Or you can make an excellent “normal” desk with right angles and the occasional rounded edge. On the other hand, you could make a truly exotic aluminum covered aviation-themed desk like the one pictured above.

The results look very good and well polished. Naturally, results like this don’t come about easily. According to the imgur part 1 documentation of this project, 60 hours had gone into the project by the end of the “part 1” documentation. I hope to see “part 2” soon. Hopefully this will explain the finishing process.

The part 1 documentation, of which an abbreviated version can be seen below, goes through what appears to be most of the woodworking process. Like a real plane, spars had to be constructed, as well as rib members that were rounded off to give it an “aerodynamicish” look. The frame was then covered with a thin layer of aluminum .5 millimeters thick. Not seen in the documentation, but hinted at in the text, the final version has plastic pipes running through it for efficient cable management.


View All

If you’d like even more information and comments on this project than the image set gives out, it was originally seen here on Reddit.

Rana: A Biologically Inspired Hexapod

Rana, which is Italian for “frog,” is really an interesting six-legged robot design. The locomotion, which according to their writeup, has never been used before and combines the walking methods of an ant and a frog.

This kind of locomotion, as opposed to three-servo based ‘bots that simply rock back and forth allowing the front and back legs to move, requires ten servos. Two servos are attached on both pairs of front and back legs, while the middle legs receive only one servo each.

View All

Although the robot’s motion is complex, the mechanical housing and legs are kept simple.  Pieces of wooden rod are used for all the legs, while a larger piece of balsa wood (presumably for weight savings) is used for the body. As no other linkages are used, this may be a surprisingly easy walker build for those wanting to build one.

Although it looks like there is a plan for the robot’s walking gait, the code is not released yet. As the write-up states that “programming is one of the hardest steps,” the code is apparently not done or not to a state that the author is ready to let others look at. Hopefully we’ll see some further development on this interesting project!


How-To:Quick & Easy Digitigrade Stilts For Halloweeen


Halloween is fast-approaching, and makers everywhere are gearing up. They’re strolling right past the aisles full of mass-produced costumes, heading instead to the hardware aisle, the fabric section, or the arts & crafts department, gathering materials for their own custom costume creations.

One item that can play a starring role in a variety of custom-made costumes is a good set of digitigrade stilts. These are stilts that imitate digitigrades, which are any creatures that walk on their toes (or digits). This includes animals like cats and dogs, as well as mythological creatures like werewolves, dragons, fauns, and minotaurs.

A custom set of these stilts can be pretty expensive, not to mention hard to find. But with a little elbow grease, a quick trip to the hardware store, and a Saturday afternoon, you can make a pair of your very own digitigrade stilts for a fraction of the cost.

I recently put together a pair of my own digitigrade stilts over the course of a few hours, and afterwards I made this quick video to show you how it’s done.

Here’s what you’ll need to make the stilts:

  • 2x)  1″x4″x2′ boards
  • 1x) 2″x6″x4′ board
  • 1x) Box of 1 3/4″ wood screws
  • 8x) 1″ machine bolts with matching nuts
  • 24x) Washers to fit machine bolts
  • 8x) lock washers to fit machine bolts
  • 4x) 2′ sections of shelving brackets
  • 4x) 3″ x 3″ T-Plate connectors
  • 2x) Adjustable velcro straps
  • 1x) 4″ PVC coupler
  • 1x) length of pipe insulation foam
  • 6x) zipties
  • 2x) 24″ bungee cords
  • 1x) Old pair of shoes

You’ll also need these tools:

  • Phillips screwdriver
  • Electric drill with drill & driver bits
  • Pliers (or socket set – used for tightening bolts)
  • Hacksaw
  • Miter saw (or handsaw with miter box)

For step-by-step instructions (and to see the finished product), check out the video below!



Jamie Locke: Beautiful Carved Mandalas



If you were at Maker Faire New York, you inevitably heard the news about the Dremel 3D printer. However, if you stopped by their booth you may have found yourself staring at something other than the printer. The beautiful and intricate artwork of the artists that Dremel brought in absolutely stole the show.

I stood for some time and watched Jamie Locke delicately carving mandalas into a ukelele. It was mesmerizing and inspiring.

View All

Jamie does fine dremeling of patterns into all kinds of things. From art pieces that hang on your wall, to instruments, straps, bracelets, or pretty much anything she can get her hands on. There are tons of great pictures and some videos on her site, but you may have better luck following her facebook page for more up-to-date art.

View All



I really have to congratulate Dremel on bringing in skilled artisans. So many of the nice tools are taken purely by their specs and the beautiful creations of the artists that use them take back stage. This was refreshing and wonderful!