[UPDATE: The mic boom build using this telescoping section is now posted here.]
What if you wanted to make the main post of the PVC light stand (as described by The Frugal Filmmaker) to be telescoping? Here’s one option for adding telescoping sections to just about any PVC project. It’s quick, easy, and very inexpensive.
This first photo show the business end of a telescoping section of thin walled 1″ and 3/4″ PVC. It is important that the outer section be thin walled because 3/4″ PVC will not fit inside the normal schedule 40 or schedule 80 1″ PVC. The inner section can be whatever class of 3/4″ pipe that is handy.
This particular telescoping section has not yet been built into anything yet. It is about 30 inches long in total, with the inner pipe being about 3 inches longer than the outer. This next photo shows the inner pipe extended to indicator marks about 4-5 inches from the bottom end of the inner pipe.
Here, the inner section is pulled farther out to show the friction producing element that keeps the whole shebang extended and in place where it is left. The purple rope is 3/16″ diameter rope from Home Depot.
The astute observer will notice in the photos above and below that the purple rope is frayed some on the right hand side. This would be due to the sharp edges on the holes through which the rope is threaded. (Note that this particular section was an early prototype of the telescoping PVC section.) The edges of the holes should have been rounded to prevent/minimize the fraying of the rope.
The rope is threaded through two sets of holes drilled through the 3/4″ section as show in the photo below. The rope exposed on the outside of pipe is about 2.5-3″ long. The pair of holes at the open end of the pipe should have been drilled closer to the end, about 3/4″ from the end.
Drilling those holes closer to the end side allows tying a tighter knot in the inside of the pipe to keep the rope loop as taught as possible. The photo below shows the square knot that was tied inside the pipe between the two holes at the end of the pipe.
Here’s another photo showing how deep inside the pipe the knot was. The rope is threaded straight through the holes farther back. The ends of the rope were inserted into the holes at the end of the pipe. Once the two ends are inside, the square knot is tied as tightly as possible. The rope should be cut a little long to allow for the length that gets taken up in the knot; longer ends will help in tying a tighter knot..
And that’s pretty much it. Rub the rope that’s exposed with wax from a sacrificial candle to give some lubrication. Then stuff the rope end of the 3/4″ pipe into the end of the 1″ thin walled pipe. If desired, mark the inner pipe so you know how far you can pull without yanking it out all the way out.
I used a different telescoping section like this to build a mic boom meant to keep interviewees farther away than the 3′ minimum focus distance of my Kodak Zi8 camera. I wanted it to telescope because I was filming interviews on the street and wanted the boom to be comparable in length to my tripod. It doesn’t make an ideal mic boom because if the inner pipe is not fully extended, it can rattle in the end of the outer pipe.
Here are some planned but as yet unimplemented improvements on this telescoping assembly (hence no photographs):
One way to keep from pulling the inner section out too far would be to not cut the rope off the spool when tying the rope onto the inner section. After tying, leave a length of rope somewhat longer than the 1″ outer section. The rope end can then be tied such that it keeps the inner section from pulling all the way out. Using rope to constrain the inner section allows later disassembly, if ever necessary.
Another way to keep the inner section from pulling all the way out would be to drill out a 1″ PVC end cap to the outer diameter of the 3/4″ pipe. This would be carefully glued to the end of the 1″ pipe after the inner section has been inserted. The disadvantage of using an end cap in this way would be that it is permanent.
The amount of friction can be controlled by the length of exposed rope on the inner section. I.e., more rope will give more friction. Salt and adjust to taste…