Saturday, April 26, 2014

Vacuum Fittings... Lab Work!!!

I had  lot of ups and downs in the lab yesterday.  The kids, (Jr. aged 3, and Sam aged 1), and I went out ot Bryan Hose and Gasket and picked up our new vacuum hose yesterday.  They had the hose ready and waiting for us and they had the free popcorn machine up and running, so the kids got popcorn.  So, that was cool.  The hose looked a bit small though.

After taking the kids out to visit Blinn College for lunch with their physics professor mom and then returning them to daycare after their mini-adventure, I made it back into the lab.  Sure enough, the hose was too small to fit over our vacuum fitting.  It had seemed like a good idea to cut the old hose behind the fitting to get a better measurement, but I hadn't really thought about the pipe that someone had jammed into one end to permanently expand it so it would fit over the fitting.  The 'jam a pipe in' expansion technique worded fine for red rubber vacuum hosing I'm replacing because its stretchy.  Unfortunately, it won't work at all for our new tubing.   There's a metal coil running through the center of the new tubing to keep it from expanding or collapsing, consequently, the hose is not at all stretchy.  So, that was a bummer.

The net result of all this was we needed new hose, which takes a week or so to get, or new vacuum fittings which I could build in a few hours.  That might sound like it could be a bummer, but it's not.  It means I got to play in the machine shop!!!  I like the theoretical aspects of physics, it's fun to play with the math and especially with the geometry, but I love getting to play around in the lab and the machine shop.  I guess at heart that makes me an experimentalist.  I'm not sure yet, and I'm definitely not ready to decide, but man I love playing with equipment.  To build new fittings, I had to start out with the two blank flanges shown below.  They had to be drilled through to provide a path for air to flow.  Next, a beveled bottom had to be added so the pipe would have something to sit rest on while it was being soldered into the flange.

Using the machine shop lathes, I bored out a hole in each flange, the same size as the inside of the brass tubing that would fit into the new vacuum hose.  Then, I using a boring bar I carved out the bezel that would fit the pipe.

The next step involved playing with the acetylene torch!  I cleaned the pipe and the flange using emery cloth in preparation for the application of soldering flux.  Wikipedia has the best most concise explanation of flux I've seen recently, so here goes:
"In high-temperature metal joining processes (welding, brazing and soldering), the primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead solder (e.g.) attaches very well to copper, but poorly to the various oxides of copper, which form quickly at soldering temperatures. Flux is a substance which is nearly inert at room temperature, but which becomes strongly reducing at elevated temperatures, preventing the formation of metal oxides. Additionally, flux allows solder to flow easily on the working piece rather than forming beads as it would otherwise."[1]
Here are the fluxed parts

The next step?  Get the torch to light.  This is a bit simpler than it seems...  You'll see:

The whistling towards the end is my nervous habit when I think things are about to explode.  All was well though.  The issue turned out to be that the gas nozzle was dirty.  After a little cleaning, the torch lit right up.

A few minutes later, (ok, more like half an hour), I had two new fittings.

1 comment:

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