3D printable mecanum wheel rollers using two materials

For version two of my mecanum robotics platform I’ll be providing a 3D printable version of the rollers for dual extruders. The outer shell of the roller can then be printed with a flexible rubbery filament to aid in increasing the friction between the roller and the ground. Otherwise you’ll have to spray or coat the roller in a material like plastidip.

Hopefully this will speed up the process of getting rollers ready, a total of 56 individual rollers.

However printing a full bed of radial items doesn’t go as quickly as one would hope.


Unlocking a password protected PDF file on Mac OSX/Linux

Recently had to edit a few protected PDF documents where the sender didn’t have access to the passwords, most likely due to using an automated PDF generating service.

Being a nerd I wanted to find a command line too that wasn’t seeping with spyware to fix this oversight. Which led me to this article on unlocking a pdf with a tool called MuPDF.

As the article was written 4 years ago I thought I would write an (easier) update to the process.

OSX instructions

Install homebrew

If you haven’t already.

homebrew is a nice package manager for OSX that allows you to install/compile generic unix utilities ported over to OSX.


Then on the command line:

Install MuPDF

$ brew install mupdf

Then clean your file

$ cd /directory/your/pdf/is/in
$ mutool clean protected.pdf clean.pdf

Here we run the mutool binary with the command subset ‘clean’ and pass it in the protected file’s name, then as the last argument we supply the name of the new file mutool will save the password protection stripped pdf to.

Easy peasy.

Linux Instructions

Cmon, you guys don’t need any instructions.

And in-case you do, you probably can just use whatever built in package manager your distro uses to install mupdf.

Happy non-DRMd PDF to you!

How to Fix Disqus comment width on the WordPress 2014 theme

As there is no html element wrapping the comments area with padding or margin the Disqus WordPress plugin when used out of the box does not display correctly in the latest  WordPress theme, 2014.

The Fix

In the sidebar menu go to Appearance Edit CSS  and then paste in the CSS below. If you have existing CSS make sure you don’t overwrite it.


As the theme uses media queries to adjust the padding around the content area so must we for the commends container. It would be easier to just add the Disqus comments css selector to the existing CSS file, however modifying the theme’s base css file would leave us vulnerable to updates. Which would clear out any changes we’ve made. So instead we’ll use a spiffy new feature of WordPress to just add our own custom CSS to the page.

cad image of mecanum education platform

Robotic platform progress

cad image of mecanum education platform


Here is the current Solidworks CAD mockup of the platform. I’ll be receiving some test hardware soon to hopefully help prototype the first working version on the mk2 of the design.

Details of the build will be posted on the blog and instructionalized on the MEPmk2 wiki page when the design becomes more solidified.

I’ll be organizing and posting the source files for the design ( STL, and solidworks files ) on github soon So people can track progress there and potentially print/laser out their own (probably not finalized version)