The film groups I work with have a need for dolly shots, so I built my own. It works in a straight line, or you can pivot one or both axles for a circular shot. I also added an old mount off of a broken tripod so I can lower the dolly on an inclined surface for a boom shot effect. I seem to find inline skates being thrown out a bunch. I hate seeing good stuff go to waste and I often will pick them up just for the nice sealed bearings and soft rubber compound wheels. Start by stripping the inline skates of their wheels and axle screws.
Step 1: Build the Deck and Wheel Mounts
I made the deck 15"long x 3" wide out of 3/8" thick red oak. The axles are 1"x1"x 6.5" I found center with a finder. I drilled my holes a little smaller than the screws and screwed them in place with CA glue to keep them from slipping out I needed to use it that night or else I would done something nicer. I have been surprised at how much abuse they have held up to. To do this I cut the deck down to 3" width and then ran it through my thickness planer and then cut to length. You could leave the thickness, I wanted mine to be light weight. The axles needed squaring and chopping to length as well.
I added a slot down the middle since the different small film crews I work with have different cameras and it gives the rig more flexibility. I was going to just drill holes where I needed them as needed but our main camera man suggested the long slot and it works swimmingly. I used a pin router to cut the slot. I found a bolt with the right thread to accept the tripod head or a camera. I attached it with a large washer held in place with an e clip.
I added some craft foam mat material between the axles and the deck. This gives it some grip and helps it stay in position when in use.
Lastly I disassembled the rig and coated all surfaces with shellac to keep it from warping. you can use paint or poly, just anything to seal the wood so it doesn't absorb water and deform
Step 5: Options for Use
After it's dry and assembled there are a bunch of things you can do with this sort of rig. You can set up a table for a nice sideways dolly shot. Turn the axles for a radial dolly shot. Add some rope or cord to one side and you can let it slide down a surface at a gentle angle or a near 90 degree drop for what looks like a boom shot. If you do the boom shot, make sure to be at a slight angle so the wheels keep contact with the surface of the slope.
Here's a nice way to lower the rig, take a length of paracord and tie a long loop on it with a square knot (?) That way its easy to slip over the axle. When not in use tie it around the rig. Enjoy! I hope this helps.