My First Instructable

I just posted my first Instructable on It has already been featured in the technology section. You will find it here:



Pendulum Wave Preliminary Design

I have been working on a design for a pendulum design on and off for the past couple of weeks (instead of turning in overdue projects). Here are a few digital pictures demonstrating my very own design for a complicated wave and release mechanism:

Pendulum wave at rest:


Release mechanism grabbing pendulums:


Pendulums about to be released into a glorious wave:


Why the extravagant release mechanism? Because this wave, unlike most, is intended to be viewed from above rather than the side. Since the amplitudes of each pendulum should be equal, they must be released at a constant distance from the center of the frame. Of course, this results in each release having a different length and each pendulum having a different release angle. Admittedly, I could have used a choppily “curved” board to release the pendulums, but that would not have been nearly as beautiful.

Pendulum Wave Demonstration With Matlab


I’ve decided to build a pendulum wave and write an Instructable to document the process.

In the meantime, here’s a matlab demonstration showing how I hope it will behave. Matlab function is posted after the video.

%Created by Eric Cox - - 5/17/2012

function [] = PWT(n,f,df,t)

%This function plots pendulum wave motion as seen from the top view.
% n is the number of pendulums, f is the frequency of the first pendulum
% in the wave, df is the incremental change in frequency between pendulums
% (added), t is the time to display the animation

%set initial time to zero.

%preallocate lengths of matrices.

while (t>t_n)

%for each value in x,y matrices, populate with value at current t.
for j=1:n

%Plot pendulum wave

%Define axis
axis([0 n+1 -1.5 1.5]);

%Increment loop time

%Animation delay


Lenovo X220t Hackintosh


Update: Apparently, this post has been attracting a little traffic from people who want to do something like this. For my x220t (the tablet version) hackintosh, I followed the guide posted here by user “peroxide”:
Note that the built-in wireless is not supported. I suggest a Mac-compatible USB dongle. 


Everything seems to be working quite well except for wireless (intel cards are not supported) and battery indicator.

Spherical Gear Configuration

7/27/12 – Update: I have posted the process and calculations for creating a spherical gear configuration here.

For a while now, I’ve thought about how awesome it would be to have a spherical configuration of bevel gears with a surface radius of curvature equal to that of the sphere composed. I have made great progress in figuring out the math. If I find time, I might post the calculations in the next month or so. I haven’t added the teeth yet, but that will come sometime after finals.

I spoke to the dean of mechanical engineering at my school, and he gave me permission to build a solid model using the department’s rapid prototyping facilities. So, solid model coming summer 2012! 🙂

Here is the rendering I have so far: