A simple dolly from PVC pipe
I started my dolly project with analyzing existing designs. I wanted a small contraption to hold my tiny camera mounted on a tripod. I did not feel like building a heavy platform, I was looking for a portable and lightweight solution.
One of the best compact dolly designs that I've come across is the MicroDolly. Very compact yet sturdy, durable, and hi-tech looking, the MicroDolly is a perfect travel dolly... if you can afford it. The base package costs about $2500. If all video equipment you've got is a $300 camcorder, you have to get inventive.
I decided to build my dolly from a PVC pipe. It provides three mounting points for a standard camera tripod, it is simple and cheap to build, it can be easily assembled and disassembled, and it is small enough to be carried in a bag.
Bits and Pieces
The dolly frame is made of a 1-1/4" PVC pipe and two matching tee sleeves. You can find these materials in a home improvement store. The pipe is sold in 10 ft sticks, so you will need to cut it. You can do it at home or you can ask a store associate to cut the pipe for you. Make sure that you have correct measurements for the pieces. I cannot tell you exact numbers because the dolly size depends on size of your tripod.
Basically, just extend the legs of the tripod, measure the distance between two legs, divide in half, this would roughly be the length of each of two larger wheel carriers. Add an inch or two just to be safe. For precise dimensions, you must take into account the outer size of the sleeves and the size of their inner fittings.
To calculate the length of the connecting piece you will have to solve a simple square equation. Or you can just put the tripod on the floor, draw a line representing a crosslink, and measure it. You will also need two shorter wheel carriers about 8 inches each, to mount wheels on another side of the dolly. After you got the pieces, you can assemble the frame to verify that all pieces come together nicely.
Axle Holes and Tripod Mounts
Most tripods are outfitted with handy spikes that are used for shooting outdoors. We are going to drill the holes in the dolly frame for these spikes to secure the tripod. Just put the tripod beside the frame and mark the spots for the spikes.
Drill the mounting holes, then file off some plastic to make a sort of angled foot rest. Assemble the dolly frame and try the tripod on. You may need to rotate the wheel carriers in the tees to provide the best position for the holes.
Next step is to drill the holes for wheel axles. We will be using 1" PVC pipe for the track, so the wheels should be at angle to hug the track nicely. If you are going to mount the wheels close to the dolly frame as I did than the angle between axles should be about 120 degrees. If you are going to mount wheels farther from the frame to provide more clearance between the dolly and the rail, then you may prefer the smaller angle.
Let It Roll
Bad wheels killed the dolly... sounds like a proverb. But really, do not even think about buying wheels in a hardware store, they are not smooth enough for this job. The common practice for a home-made dolly is to use wheels from inline skates. These wheels are durable and have high-quality ball bearings. You will need eight wheels for this project.
Eight wheels? What a coincidence. The same number as on a pair of skates. Ask around for used skates, maybe your friends have an old pair sitting in the darkness of their garage. You can buy used skates too, for like $25 or less. A good deal considering that a set of new wheels and bearings costs about $80.
If you cannot get a pair of used skates for free, then look for used wheels in a used sports equipment store. In my area, used wheels cost $1 per wheel or $5 for a set of 8. You will also need bearings, and it is unlikely that you'll find used bearings for sale. The bearings will be your most expensive item. A set of 8 bearings costs about $10. Keep in mind, that you need two bearings for each wheel.
It is very disirable that you also got spacers to go between the bearings. These spacers distribute the load between outer and innter bearings more evenly. If you don't have the spacers, this is ok. They are not essential for our project, after all the CentiDolly is not going to carry more than 20 pounds.
You will also need a few bolts and nuts. The standard inline skate axle is 9mm in diameter, but a simple 1/4" bolt will work just fine. You will need eight 1/4" bolts 3-1/2" long. It does not really matter whether these are hex bolts or carriage bolts. Hex bolts are easier to tighten, but carriage bolts look better and don't stick out. You will also need 8 1/4" washers, 16 1/4" fender washers and 16 1/4" nuts.
Assembling the Dolly
First assemble the wheel carriers. Put the bolt through the wheel, put on one 1/4-inch washer, then a fender washer, insert the bolt in the pipe, another fenter washer, a nut, tighten by hand, not too tight, make sure that wheel rotates smoothly. Put on another nut and tighten thoroughly. Use two wrenches to tighten two nuts together.
Insert wheel carriers into the sleeves, two long carriers for one rail, two short carriers for another rail. Connect the sleeves with the trasversal piece. Looking good!
Improving the rigidity
You may have noted that the tripod is not mounted on the dolly very reliably. After all, the frame is tubular, not the best shape for our task. We will improve this situation right now with a rubber band.
The point is to tie the tripod to the dolly. First, make a hole in a connecting piece and put an eye bolt into it. You will connect one or several rubber bands to the bolt, the other ends of the bands should be connected to the tripod. The specifics depend on your tripod. For example, you can use a dowel with a hook in it, inserted into the central column of the tripod. But for now I decided to utilize the tripod's cross links.
I simply tie a rubber band between the cross links and an eye bolt... voila! Look at this, quite rigid and much safer for your camera.
Just like many others, I use 1" PVC pipes for the track. There are quite a few other tutorials that explain how to connect the pieces together, so I will not bore you with details. One thing that I want to mention is that the CentiDolly has staggered wheels, that is two wheels on each carrier are not directly opposite. When dolly is moved the wheels hit the joint one at a time, which improves overall smoothness.
This quick and dirty video is the result of two different takes. Looks pretty sad, but I hope that it will be interesting nevertheless until a shoot a proper one.