This is a quick post, i'll get more photos and information up soon:
This was something I designed a long time ago, but haven't shared it with the DIY community. It was still a work in progress and has been through many different phases. I've tried different types of materials, but feel if you want best results, you'll need to go with solid aluminum. The base plate is cut from 1/4" solid aluminum. The axles are also solid aluminum rods which were carefully set on a drill press to get exactly centered. If you're slightly off on this part it will ruin the whole tracking motion. The ends of the rods are tapped with threads, so it's a nice clean mount for the wheels and bearings. I've tried different types of wheels, but the cheap ones you find aren't cast true. They might look fine, but really they are warped plastic that wobbles as you roll. In the end I just bit the bullet and purchased an awesome set of Urethane wheels and high end Bones Red Skate Bearings..
A group of friends helped through the entire process and through their kindness is offering to manufacture the parts for anyone who can't DIY one for themselves. We realize there are many of us who live in apartments and don't have time or access to such tools for cutting, grinding, precision drilling, tapping, or powder coating aluminum. You can get in contact with them about the DIY Skater Dolly at http://www.spidertraxdolly.com.
I hope you enjoy the DIY projects I create, leave some feedback and please link back to my website.