How Provably Loaded Dice Lead To Unprovable Cheating

December 18, 2017 by Donald Papp 16 Comments

Here’s a really interesting writeup by [Mike] that has two parts. He shows that not only is it possible to load wooden dice by placing them in a dish of water, but that when using these dice to get an unfair advantage in Settlers of Catan, observation of dice rolls within the game is insufficient to prove that the cheating is taking place.

[Mike] first proves that his pair of loaded dice do indeed result in a higher chance of totals above seven being rolled. He then shows how this knowledge can be exploited by a Settlers of Catan player to gain an average 5-15 additional resource cards in a typical game by taking actions that target the skewed distribution of the loaded dice.

The second part highlights shortcomings and common misunderstandings in current statistical analysis. While it’s possible to prove that the loaded dice do have a skewed distribution by rolling them an arbitrary number of times, as [Mike] and his wife do, it is not possible to detect this cheating in a game. How’s that? There are simply not enough die rolls in a game of Settlers to provide enough significant data to prove that dice distribution is skewed.

Our staff of statistics Ph.D.s would claim that [Mike] overstates his claims about shorcomings in the classical hypothesis testing framework, but the point remains that it’s possible to pass through any given statistical testing process by making the effect just small enough. And we still think it’s neat that he can cheat at Settlers by soaking wooden dice in water overnight.

This isn’t the first time we’ve seen Settlers of Catan at the center of some creative work. There’s this deluxe, hand-crafted reboot, and don’t forget the electroshock-enabled version.

[via Reddit; images from official Catan site]

Books You Should Read: The 3D Printing Handbook

December 18, 2017 by Brian Benchoff 12 Comments

3D printing was invented in the 80s, twenty years passed, patents expired, and then several diverse uses for 3D printing technology were found. As such, the tips and techniques for 3D printing — especially filament-based printing — have been discussed and documented almost entirely on the Internet, mostly in chat rooms, forums, and YouTube videos. Everything you could ever want to know about 3D printing is available on the Internet, but that doesn’t mean you’ll be able to find it.

There have been dozens of books published as a guidebook to 3D printing over the years, and some of those are even in their second edition. Yes, despite the disappearance of 3D printers from the headlines of TechCrunch, and despite the massive public disillusionment of computer-controlled hot glue guns, there are still people that want to learn about 3D printers. There’s actually a market for 3D printing guidebooks, and people are buying them.

The latest such guidebook for 3D printing is The 3D Printing Handbook from 3D Hubs. 3D Hubs has been around for a while, and can best be described as, ‘3D Printing as a Service’. The usual use case for 3D Hubs is that someone would upload a 3D model to 3D Hubs, and get a quote from someone with a 3D printer. This quote could come from a professional 3D printing outfit with machines that cost more than a house to someone with a LulzBot or Prusa in their garage. 3D Hubs is going to be fantastic when people realize you can do CNC milling on the service as well.

This book was written by Ben Redwood, Filemon Schöffer, and Brian Garret, all employees of 3D Hubs. In one way or another, 3D Hubs has a hand in every conceivable type of 3D printing technology, and this book aims to be an introduction to the uses of these technologies, and a guidebook on how to use 3D printing technology the right way. There’s a question with this book: does it live up to expectations, and for that matter, can any book live up to the expectation of being a ‘guide to 3D printing?’

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A Dynamometer For Measuring Motor Power

December 18, 2017 by Jenny List 26 Comments

If you have ever ventured into the world of motor vehicles you may be familiar with a dynamometer, possibly as a machine to which your vehicle is taken for that all-important printout that gives you bragging rights (or not) when it comes to its ability to lay down rubber. A dynamometer is essentially a variable load for a rotating shaft, something that converts the kinetic energy from the shaft into heat while measuring the power being transferred.

Most of us will never have the chance to peer inside our local dyno, so a term project from a group of Cornell students might be something of interest. They’ve built a dynamometer for characterising small electric motors, and since their work is part of their degree courses, their documentation of it goes into great detail.

Their dynamometer takes the form of a shaft driving a stainless steel disc brake upon which sit a pair of calibers mounted on a fixed shaft that forms a torsion bar. The whole is mounted in a sturdy stainless steel chassis, and is studded with sensors, a brace of strain gauges and a slotted disc rotation sensor. It’s not the largest of dynamometers, but you can learn about these devices from their work just as they have.

This is a project sent to us by [Bruce Land], one of many from his students that have found their way to these pages. His lectures on microcontrollers are very much worth a look.

3D Printing The Final Frontier

December 18, 2017 by Tom Nardi 29 Comments

While down here there’s room for debate about the suitability of 3D printing for anything more serious than rapid prototyping, few would say the same once you’ve slipped the surly bonds of Earth. With 3D printing, astronauts would have the ability to produce objects and tools on-demand from a supply of inert raw building materials. Instead of trying to pack every conceivable spare part for a mission to Mars, replacements (assuming a little forward thinking on the part of the spacecraft designers) can be made to order out of the stock of raw plastic or metal kept on-board. The implications of such technology for deep space travel or off-world settlement simply cannot be overstated.

In the more immediate future, 3D printing can be used to rapidly develop and deploy unmanned spacecraft. Tiny satellites (referred to as CubeSats) could be printed, assembled, and deployed by astronauts already in orbit. Innovations such as these could allow science missions to be planned and executed in months instead of years, and at a vastly reduced cost.

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Small Jet Engine Model From Students Who Think Big

December 18, 2017 by Roger Cheng 21 Comments

We love to highlight great engineering student projects at Hackaday. We also love environment-sensing microcontrollers, 3D printing, and jet engines. The X-Plorer 1 by JetX Engineering checks all the boxes.

This engineering student exercise took its members through the development process of a jet engine. Starting from a set of requirements to meet, they designed their engine and analyzed it in software before embarking on physical model assembly. An engine monitoring system was developed in parallel and integrated into the model. These embedded sensors gave performance feedback, and armed with data the team iterated though ideas to improve their design. It’s a shame the X-Plorer 1 model had to stop short of actual combustion. The realities of 3D printed plastic meant airflow for the model came from external compressed air and not from burning fuel.

Also worth noting are the people behind this project. JetX Engineering describe themselves as an University of Glasgow student club for jet engine enthusiasts, but they act less like a casual gathering of friends and more like an aerospace engineering firm. The ability of this group to organize and execute on this project, including finding sponsors to fund it, are skills difficult to teach in a classroom and even more difficult to test with an exam.

After X-Plorer 1, the group has launched two new project teams X-Plorer 2 and Kronos. They are also working to expand to other universities with the ambition of launching competitions between student teams. That would be exciting and we wish them success.

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Machined Lightsaber Pen For A More Civilized Age

December 18, 2017 by Tom Nardi 13 Comments

In an increasingly paperless society, writing implements are becoming an obsolete technology for many of us. Certainly not the kind of thing the average person would think to spend more than a couple bucks on, to say nothing of machining one out of a solid piece of aluminum bar stock. But clearly [Bob] is not most people. He recently dropped us a line about a video he uploaded to his aptly-named YouTube channel “Making Stuff”, where he goes through the steps required to turn raw materials into a writing instrument worthy of a Jedi.

Starting with a piece of aluminum chucked up in the lathe, [Bob] cuts out the iconic ribbed profile of Luke’s saber and fills in the gaps with nothing more exotic than a black Sharpie. He then moves on to the more complex shape of the emitter, and then flips the handle over in the lathe and hollows it out so a brass tube can be inserted.

Somewhat surprisingly, it seems more effort ends up being put into the acrylic “blade” than the aluminum handle itself. A chunk of acrylic is drilled and tapped so that it can be mounted in the chuck, and then turned down into a long cylinder. A tip is then cut in the end, the length of the blade is hollowed out, and finally it gets polished up to a nice shine.

The build is completed by inserting a standard ink pen cartridge down the center of the now completed saber. Surely the pen aficionados will lament that he didn’t attempt to build his own ink cartridge as well, but we think he gets a pass considering the rest of it was made from scratch.

If even a glorious writing instrument such as this isn’t enough to get you to re-learn how to write your name, fear not. Whether you’re making music or capturing flags, we’ve played home to numerous other saber projects; eye-safe or otherwise.

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The Miracle Of Injection Molding: How Does It Work?

December 17, 2017 by Bryan Cockfield 18 Comments

Pretty much any household item nowadays has an involved, extremely well-thought-out manufacturing method to it, whether it’s a sheet of paper, an electrical outlet, a can of tuna, or even the house itself. Some of the stories of how these objects came to be are compelling, though, as one of the recent videos from [This Old Tony] shows as he takes a deep dive into a $5 ball valve, and uses it to talk about all of the cool things you can do with injection molding.

Injection molding is the process of casting molten plastic into more useful pieces of plastic. In this case it’s a plumbing valve which might seem simple on the surface, but turns out to be much more involved. These ball valves are extremely reliable but have a very small price tag, meaning that a lot of engineering must have gone into their design. What is unearthed in the video is that injection molding allows parts to be cast into the molds of other parts, and the means by which those parts don’t all melt together, and how seals can be created within the part itself. All of this happens with a minimal number of parts and zero interaction from a human, or from any robot that isn’t the injection mold itself.

The video goes into exceptional detail on these valves specifically but also expounds on various techniques in injection molding. Similar to the recognition the seemingly modest aluminum can deserves, the injection molded ball valve deserves a similar amount of respect. While [This Old Tony] usually focuses on metalworking, he often tackles other interesting topics like this and this video is definitely worth checking out.

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