Random chance can set all kinds of activities into motion.  Remember Abed’s discussion of the dice role and its impact in Community?  Do you recall the potential impending doom as a kid shaking the Magic 8 Ball, one of the toys in the National Toy Hall of Fame?  Sure, you could settle with a coin toss or dice roll, but why?  How about mixing up your next Dungeons & Dragons event with something different?  Today we’re building a study model of a device that generates random numbers and provides different random results based on probability theory, including a 360 degree rotating octahedron that acts like an orrery, triggered by a button, with a rack-and-gear drive, overrunning clutch, and a driven wheel.  It’s the UGEARS Random Generator (available direct from UGEARS here), the third model we’re testing after the 2-in-1 Arithmetic Kit (reviewed here) and the Gearbox (reviewed here).  The Random Generator is part of the model maker’s STEM Lab series, educational tools and fun models that aren’t just for kids.  This kit is full of surprises, and as it comes together you’ll see how science puts the “magic” in the Magic 8 Ball.

The four laser-cut sheets of plywood, punch-out tool, wax, wooden hook, rubber bands, and steel ball are all you need to build this gearbox.

The box includes everything you need two make the 3D, working, plywood gearbox: 4 sheets of pre-cut plywood, a piece of wax crayon to reduce friction, a steel ball, rubber bands, a press-out tool to ease removal from the sheets of smaller pieces, and a wooden hook for rubber band replacement.

A look at the box and what’s inside.

As with the other builds, it requires many parts to be rubbed with the wax stick, and if you don’t align the gears exactly right you will have problems later.  The recommended age for building this model is 8 and up.

This kit has a lot of repetition in its 160 wooden components.  It’s designed to replicate the Magic 8 Ball questions, but the final project includes a drawer for circles that can be cut from the instruction booklet where you can design anything you want for the six sides, and a set of dice dots to replicate standard game dice.  As with the earlier builds, the instructions were clear (written, with color visuals), and available in 9 languages, and an augmented reality option (QR code links provided) is included for further learning via a UGEARS app.  Note: One complaint on the instructions–if a part is shown with two numbers, that means use two parts to complete the assembly.  Twice we noticed the instructions seemed to show one part but two were intended, usually to make small pegs.

The design of the cube is nothing short of genius as engineering goes.  It’s built from the inside out, and resembles the innards of a Rubik’s cube:

Cube build Step 1.

Cube build Step 2.

And the completed cube.

No sanding was needed, but there is some coordination required to get some of the pieces to fit precisely.  Patience is a must, and you don’t want to force any parts.

Some of that magic includes two axles that allow the spinning of the cube, formed with four reverse-fitting assembly pieces.

A fully spinning cube. At this point you may think you’re done, but there is much left to do.

The base and button assembly, with clever rubber-band powered movement, is the final build component.

Instructions and examples are provided to demonstrate how and why each component works.  The main element of the design is a cube with an octahedron inside it that contains a metal ball to provide weight.  This construction is powered by a rack-and-gear drive initiated manually and providing energy through a driven gear that rotates a three-axle gear.  This is how the cube begins to move.  The vertices of the octahedron coincide with the sides of the cube.  As the energy of the system expires and it stops moving, gravity suspends the metal ball in the lowest part of the octahedron and due to the inclination of the walls it rolls within, it ends up in one of the octahedron’s vertices pulling it down.  Whichever of the vertices turns up in the bottom, the side of the cube it is attached to will be right under it and parallel to the floor, so the side of the cube with the answer will be the one facing up on the opposite side.

The probability to get any of the vertices facing down is virtually the same due to symmetry of the octahedron that rotates freely around the axis of its mass.  This leads us to the conclusion that the probability to receive one of six answers is 1/6 or 0.167.  And that also depends on the efficiency of the build, use of wax to reduce friction, etc.  You can run your own tests to confirm the effectiveness of your build.

Here is the Random Generator in action:

The model as we built it worked exactly as designed.

The UGEARS Random Generator project is estimated as a four-hour project, and we did it in one sitting in less than three hours.  The satisfaction of the button release and the immediate 360-degree smooth movement made this the most fun UGEARS project we’ve tried so far.

Another great tool for young learners and part of a great science and technology desk set for engineers–and it’s affordable, as of the date of this review it’s listed at about $20.  The Random Generator is available here at Amazon.  In the next few weeks look for builds of a UGEARS Variator and Tachometer, plus one of the advanced build sets.  Take a look at all the available UGEARS models here at Amazon, and check out the UGEARS website for more information and to order direct, which makes it easier if you need replacement parts.

C.J. Bunce / Editor / borg