I wanted to take a minute to share with you guys something that I have been using and working on all spring. I will call it the Dual-Use Skater Dolly.
First, I will say that this is not the least expensive option for a slider/dolly available, especially for a DIY project. I settled on this design for the dolly based on the materials that I had laying around, and at panic about a job that I won with 24 hours notice, that called for bunch of smooth camera moves. I would estimate the total cost for the project to be around $100, not including the head, and assuming you have all of the tools necessary for construction. The rails and end blocks cost about another $50. You may be able to lower the cost a bit by using zinc plated hardware and using stacks of washers instead of spacers.
If you are not the DIY type, there is a guy who will build you something similar to this (without the head) and ship it to you as a kit for less than $100. I can't seem to find the site, but google "cinemover" and you will eventually find it. His design is a bit less robust, but is flexible in a way that mine is not. I will explain this further down the page.
I already had few sets of skate wheels from a previously constructed tripod dolly, enough that I originally build two of these, one for myself and one for a friend. The construction of the wheels and axles is pretty simple, a wheel, a pair of press fit bearings, a 5/16" bolt and a couple of washers and spacers.
The axles each mount to a set of square nickle plated tubes, I used some pre-drilled tubing from an old wire rack, but you could use aluminum tubing and drill the holes yourself if you have the tools. I would highly recommend a drill press for this, as it would be difficult to drill holes precisely enough with a hand drill. Drill pilot holes first or the bit will wander. I had some little plastic end caps that I used to protect fingers and other gear from the sharp metal edges of the tubes. They also help give a finished look to the unit.
The two wheel assemblies are held to the proper spacing with some lengths of threaded rod. In theory, you could adjust the spacing to accommodate different sizes of track (this is what they did with the Cinemover dolly). I chose to lock everything down once I had it adjusted for the track I was using.
For the deck of the unit, I used a sheet of 1/2" PVC. Again, I had it left over from a previous project and I felt like it would help dampen any vibration from the wheels before it reached the camera. PVC is plenty rigid in this thickness and can be easily machined with wood cutting bits and blades.
Two words of caution (actually three). Wear safety glasses when cutting the stuff, it will heat up pretty quickly and is very painful to get in the eye. You are at risk for burns and abrasions from the sharp chips. I would also recommend a respirator, PVC does off-gas. The health risks are debatable, but at the very least it smells bad when you cut it. Lastly, use compressed air to cool the workpiece while you cut if possible, PVC like to reweld and will leave an ugly edge if it heats up to much.
You could use acrylic, or any number of other plastics if you can't get PVC. In fact, I would recommend either HDPE (cut up a plastic cutting board) or nylon (order on line) both are a bit more "waxy" than PCV and probably easier to work with.
I cut a suitable piece and drilled and inserted a variety of helicoids for 3/8"-16, 1/4"-20, and #10-24 as well as pass-throughs for those sizes. I know I went a bit overboard on the mounting points, but it adds a bit of flexibility to the unit. I added the helicoids so I could attach an articulating arm directly to the base to hold a monitor or other accessory. All you really need is a single 3/8" or 1/4" hole in the center to mount the head of your choice.
Speaking of heads, I am using a Manfrotto 502HD head on mine. It is probably a bit of overkill, but it is very solid and allows for smooth pan and tilt moves along with the standard dolly movements.
I also built a set of custom track blocks to mount my track (1" tubing) to a set of tripods to allow for use on uneven ground. Although I primarily use this dolly with the track, one of the great features is that you can remove the vertical guide wheels and use the dolly for tabletop moves, it is limited to linear moves, but still very useful.
I used the dolly to shoot the Spring Sale TVC for Outdoor Outlet last month and I am very pleased with how smooth it tracks. I am planning to change a few more things on it to make it more user friendly, after I finish it I will post some more detailed pictures.
More to come. -J.H.