Work has still been busy, it's been tough to get time in my garage lately. However I did manage to get an old de-humidifier taken apart, I'll be using the the compressor as a makeshift roughing pump. I got it all wired up, the pump starts and runs great. I used instructions from here: http://www.belljar.net/refrig.htm

Next I need to build a small chamber and see how low this free pump can go. I'm hoping for about 1 Torr. I have a small, decently thick aluminum plate, and I'll place a jar on top of that, upside down. Anyone have ideas for how to seal a glass jar to the aluminum? I'm thinking I'll polish the aluminum real good and start with a scrap of rubber from a bike tire. (this is just for the rough vacuum chamber, no high vac stuff needed here yet). Other thought is to use a bead of silicone caulk. Thoughts?

Also, I thought of another neat way to "measure" the vacuum inside. Partly, @DeepSOIC wisely pointed out that I'm likely overreaching with my "optical vacuum measurement" idea (see the last post). Partly, I've just always wanted to see if I could build one of these radiometers. I tried when I was 7 years old, but didn't realize you needed a vacuum to do it. Anyways, according to @Ben Krasnow these things start spinning in the millitorr range, about the right vacuum I think I need to make the discs work. My junk pile roughing pump will probably not get down low enough to make it spin well, but it's worth a shot. So, this would be a VERY crude but hopefully super accessible way of measuring the vacuum in both the rough and high vacuum chambers.

Put one radiometer in the rough vacuum, and if it spins then you've got a good starting vacuum. Put a second one in the high vacuum chamber. If it stops spinning (while the rough vac radiometer keeps spinning), then you've got better than 6x10^-4 torr. Not exactly a "high" vacuum, however for a proof of concept to see if this whole disc idea has any promise at all, it's a start. And I can build these with aluminum foil, a sewing needle, a magnet, and black spray paint. I think...