In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.
Subject: Re: Cheap Vaccuum Gear
Date: Jan 12, 3:17 pm
Poster: Richard Hull
On Jan 12, 3:17 pm, Richard Hull wrote:
>Can Richard or some of the other people here who have built fusors give some pointers on how and where to obtain inexpensive vacuum gear and what substitutions can be made using ordinary parts instead of their vacuum rated counterparts?
I am not rich......I am not even well off....... Hell, I am not even comfortable with my income, but I am happy, get to come home at 5PM every single day and I have a vacuum system which improves with time.
Stay with only Lesker and Duniway. Duniway is expensive, but usually not so much as Lesker, although, I have found times when Lesker was cheaper (rare).
First get a good used mechanical pump. One of my favorites, and the current in use on the fusor, is a precision 6CFM belt drive unit. I found it and a nice 4CFM Alcatel direct drive unit in a single add in our local "trading post" newspaper rag sold at convience stores here in Richmond. I picked both up for $300.00 total, cash in hand. Both, after new oil and a bit of TLC pulled to 10u or so in a minute or two at the head. (excellent)
I have two perfect welch 1402's- 5.6cfm and one 1397- 17cfm. I also have an Alcatel 8 cfm direct drive and a super sweet Edwards direct drive- 18cfm. All are held in reserve. Not one of them cost me over $350.00, all were deals found at hamfests, or from people who knew people who knew me.
Next, look at what your plans and needs are. If only for a fusor, then you are a bit better off. However, if you wish to use the vacuum system for a wide range of experiments, you will have to be a bit more genralized in your process of assembling the system.
Start small and set up for general useage. That means you need a good solid pump of 3CFM minimum size. (mechanical) Get a good Thermocouple gauge. Most of you will use a 3/4" ID hose (absolute minimum size!!) A few with pumps over 6CFM should consider 1".
This will determine your fitting size. Yes, you might as well bite the bullet and leap into KF (kwik fitting) system connections. My suggestion is whether you are using 3/4" or 1" lines, use only the KF25 fittings. I started off using the KF16 with is ideal for 3/4" hose, but by going to KF 25, you can still use the 3/4" hose and upgrade to the 1" hose and lines later should you snag a nice large pump. As I moved up, I had to buy new larger KF25 fittings for my new stuff and also purchase or make rather costly KF16 to KF25 adapters to not make a total loss of what I already had. Heed this well! Ignore it at your own peril.
Start off with enough KF25 fittings to make a minimum of three complete dual fitting connections. Duniway is where I buy all my fittings. Try and avoid brass, but for those who have no TIG welding or silver solder abilities, the brass fittings can easily be machined and soft soldered into a medium vacuum systems. Make sure to get a minimum of two of the aluminum KF25 hose barbs.
I prefer pure gum rubber hose for my pump connections. Keep such lines very, very short!
You will need a minimum of one good KF25 bellows vacuum valve. New, the cheapest units are brass and KF16 only (~$165.00). The best are KF25 SS rebuilt units from Duniway and an incredible buy for $175.00 each. I knuckled under and bought three (ouch).
New, all this stuff would be about $2500.00. With good scrounger skills and lucky buys, it can all be had for under $500.00.
Try hamfests, local thrift shopper magazines, vacuum websites, E-bay, etc. There are a lot of deals out there.
Never try to make a complete ultra high vacuum system from scratch. Learn to use a medium vacuum system first.........Learn the basics of vacuum and gauging with the low end system. Expand as you go and as your needs and knowledge advance.
Serious neutron producing fusors whould be served well by the extra cleanliness and deeper vacuums obtained with the Lesker micromaze added inline with the mechanical pump. WARNING...... This demands TWO KF25 SS valves. Without them, you will really make more of a mess than you had without the micromaze. The three items are an immediate $500.00 addition with no way to bypass these purchases.
Yes, you could add a diffusion pump, but that really increases the complexity of the system. In the beginning, you don't need complexity........
Beyond glass lines, there is little the amateur can handcraft as the materials neede in vacuum service are rather critical.