I’m performing an experiment where I have to build a ~1 meter length of PVC pipe that a large steel ball bearing can fall through. There are three catches, though:
The interior of the pipe has to have a low-grade vacuum.
I need to be able to vary the length of the pipe(don’t need to have much fine control over the height, being able to change it in 10cm increments is okay).
I need to be able to gain access to the interior of the pipe easily.
Now, one is mostly covered; I have a vacuum pump and hosing for it. Number two is what’s stumping me. I figured that I would do is buy a bunch of small attachments that I can screw together, then seal with window sealant. Unfortunately, I know next to nothing about piping and fitting, and the jargon is ridiculous. What is the name for this kind of thing, and is there a better way to do it?
I don’t know if it would work, but I suppose you could use two different diameters of PVC pipe to make something like a trombone slide. Then take a large inner tube and make a sleeve around the sliding joint, sealing it with rubber cement (e.g. Plumbers Goop). Use an endcap on the top of the PVC pipe to allow access.
Or…you could just buy X different lengths of PVC pipe if you’re doing a science experiment. Line them up side by side and do them one at a time.
Going of Finagle’s idea, you can set up whatever you need to set up on the end, and have a male (or female) joint on that end. Then, cut 10 sections of pipe, of 10cm, 20cm, etc. lengths, up to 1m. If you buy two 10ft sections of pipe, you should be able to do this with two pipes (the first would have a 100cm, 90cm, 80cm, and 20cm section cut out of it. The second would have a 70cm, 60cm, 50cm, 40cm, 30cm, and 10cm.) Put a female (or male) joint at the end of that section. You can do the same for the opposite end if you need connections at both sides.
You may be able to get away with using an O-ring instead of window sealer, which would greatly improve the modularity.
Going off **Finagle’s ** idea to just cut a bunch of lengths - PVC pipe is dirt cheap - at the bottom end where the vacuum is to be attached, you could use a “compression repair coupler” to go between the various-sized pipes and the vacuum pump.
There are some pictures of the construction of a PVC syringe type water gun in this thread that you may find useful.
O-rings and grease will hold water under pressure, so they’ll also hold some vacuum.
Nope, research under a professor. His suggestion was to get a bunch of male-female connector/adaptor/i don’t know the word and just screw them on one by one to vary the height.
This may not be solving the right problem, but could you just draw the steel ball up the tube from the outside with a magnet to different levels, then remove the magnet to release? Then you just need one long tube, with perhaps a more permanent seal. If you need more accuracy on release time, you could use an electromagnet.
