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Dolly Track System

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This track system can handle an extreme amount of weight and so is very heavy-duty. While my original PVC dolly was inspired by Ron Dexter's tutorial, the track system is completely my invention. (Unfortunately, there's nothing patentable about it though, as it really is just common handrail laying on the ground.) I spent a lot of time trying to devise a good track system, and now that I have, I'll explain it in as much details as possible.

I bought 1-1/2" Schedule 40 Aluminum Pipe. If you want to save money, you can use steel. Aluminum is about 3 times the cost of steel, but is also 3 times less heavy. Additionally, steel is a lot harder, making this whole process a real pain. Have fun drilling through steel without a drill press! Although I recommend a drill press in any case, if you don't have one but are very careful, you can still line up the holes just right. (I didn't have one and am very impressed with the quality of my track.)

The best price on raw aluminum pipe is from a metal supply company. In Los Angeles, the best choice is Industrial Metal Supply (IMS). Whoever you go to, they sell it by the 20-foot pipe. (If they sell smaller pieces, they're probably also charging more.) As of March 2003, IMS in Irvine, CA, was charging $3.49 per foot as long as you bought whole 20-foot pipes. They had an additional charge to cut the pipes. I bought two 20-foot pipes and had them cut into 5-foot long sections (and so ended up with a total of 8 5-foot long Aluminum pipes). You definitely don't want to cut these pipes yourself unless you have the capability to cut very clean and straight (that is, have access to an industrial metal saw)--descent precision is important on these cuts. The total cost for this raw material was about $165 after tax.

So now I had 40 feet of Aluminum pipe, cut into 8 pieces of equal length. The reason to get them cut, if you haven't figured it out, is to simplify transporting them. After all, the primary use for something like this is to take it on location filming.

So the next step is how to rejoin the sections into long track. I picked 1-1/2" Schedule 40 Pipe for a reason: this is the standard size pipe used for handrails and the like. A company called Hollaender makes a ton of different joints for 1-1/2" pipes and some of their components go by the brand-name SpeedRail®. By the way, I'm not the first person to think about using SpeedRail® for entertainment. The particular piece of interest from Hollaender is their 1-1/2" No. 70ES Internal Locking Splice (Note: on internal fittings, the 1-1/2" is the outer diameter, which corresponds to the inner diameter of the pipe it will fit in.) Hollaender is a manufacturing company without a store-front and doesn't sell a few pieces at a time to consumers. While Industrial Metal Supply can order them for a fee, the best place I found that had them in stock (or would order them at no extra fee) is Budget Fence. So, with 8 sections of pipe, 4 sections to make up a 20-foot run of track on one side of the dolly, and 4 sections to make up the other side of the track, I order the required 6 internal locking splices. With shipping, the total cost was about $45. You may need to supply your own Allen wrench, but here's what you get:

The No. 70ES Internal Locking Splice works by forcing the set screws into the opposite wall. As you tighten the screws, they push against the opposite wall, forcing open the splice further, thereby growing tighter against the wall of the pipe you set it in:

The next step is to start making careful measurements on your aluminum pipe and tapping where you'll drill to make the hole that allows access to the set screw. Note there is just one hole for each end of your aluminum pipe that you will drill. Make the measurements such that the pipe will join the next piece of pipe perfectly in the center of the length of the locking splice. A smooth interface without any gap is critical to insure the dolly won't sense a bump when it travels over sections when you perform a tracking shot. The hole size is a 3/8" hole that allows the access to where you put the set screws in the internal locking splice. Drill the holes and install the splices. (Note you cannot put the splice into the pipe with the set screws on. Take the set screws out then slide the splice in.)

Also, be sure to have all the holes for your pipes on the same side. That is, with your pipe you'll have a total of two holes in it, one at each end of the pipe. Make sure both of these holes are on the same side of the pipe and as close to lined up as possible, though if they are not there is no impact on the stability of the camera.

The impact that it would have is if you decide to create crossbeams for the sections of the track, since such crossbeams will most likely bolt through the pipe and into the locking splice. I chose not to make crossbeams, and instead feel that for my use I can just duck-tape the ends of my connected 20-foot length of track into position. Crossbeams only add structural support. They don't dictate the smoothness or stability of a tracking shot. As long as you have both sides of track reasonably parallel, the act of tracking with your dolly will force the two sides of the unconnected track into a true parallel position. In fact, practicing a track before filming is advisable to insure the track is aligned, then consider duck-taping the ends before recording.

So, with all of the 3/8" holes drilled and the splices installed, begin tightening the set screws as tight as possible using a 3/16" Allen wrench:

The final product of the joint:

  

If you do all of this right, you'll end up with an extremely smooth track and dolly system.

Also, make sure to bring your allen wrench with you on location!!!



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