Demo Fusor Progress Update

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
Matt_Gibson
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Re: Demo Fusor Progress Update

Post by Matt_Gibson »

Dennis,

Got to hook that bad boy up to an ion engine :-)

-Matt
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Dennis P Brown
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Re: Demo Fusor Progress Update

Post by Dennis P Brown »

Uh, the spherical cow?
Jim Enright
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Re: Demo Fusor Progress Update

Post by Jim Enright »

Thanks Richard and Dennis for the additional information! I have been trying to figure out the best solution to this dilemma, and am considering using two 500 Meg ohm resistors in oil. My preference is to have the resistors in oil rather than in the air. If it turns out that the math works better with five 200 Meg ohm resistors, and that the availability of products is better suited to the 200 Meg ohm resistors, then I will go that route. I am only using a 30kV power supply but have the 50uA gauge that I'm using to keep the math and variance easier. Now, I'm just combing eBay looking for the right resistors...unless of course someone has the right ones available for sale?
“Whether you think you can, or you think you can't — you're right." Henry Ford
Jim Enright
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Re: Demo Fusor Progress Update

Post by Jim Enright »

Richard, you had inquired about the vacuum pump I was using for my set up as to whether it was a Yellow Jacket 5 CFM pump. It was actually a Yellow Jacket 8 CFM but it has been giving me problems to the point where it will not pump down even below 10k microns when I have my digital gauge attached. I suspect that that is causing many of our problems. You mentioned that you have a Yellow Jacket 5 CFM pump that works fantastic, pumps down to 10 microns, and you highly recommended it. Can you share with me the model as I am looking to purchase a new pump. I do have a Welch 1405 that we are going to rebuild in a few months, but I would like something that will be well-suited for our demo fusor for right now. Thank you!
“Whether you think you can, or you think you can't — you're right." Henry Ford
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Richard Hull
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Re: Demo Fusor Progress Update

Post by Richard Hull »

10k microns ???? Ten thousand microns!!! that is ~10 torr. Did you buy the pump new or used? Real used refrigeration pumps can be worn to death. Have you changed the oil? Used pumps can store gunk and even after an oil change, the new oil can foul, especially if it is run long and hard to get good and hot. Have you measured the vacuum at the head of the pump with a well sealed joint?

I hope you did not assemble your entire system without checking the pump's pressure directly at the pump inlet!! ( a gross newbie mistake and demanded in all the FAQs.) Those long hoses have to go! A very long vacuum system hose is one foot long!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
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Dennis P Brown
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Re: Demo Fusor Progress Update

Post by Dennis P Brown »

Don't know if that yellow jacket pump is dead, just seriously dirty, or if the system you've constructed is the issue (massive leaking or a questionable gauge?) Yet you have that belt driven Welch vacuum pump - those are easy to open and inspect (if needed.) Rather easy to clean, too. Those are excellent vacuum pumps so I'd think putting efforts into getting that Welch vacuum pump up and running might pay better dividends. Focusing on vacuum is priority #1 since all else doesn't matter until one has a decent pump.
Jim Enright
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Re: Demo Fusor Progress Update

Post by Jim Enright »

Hi Richard and Dennis, thanks for the replies! Richard, I am not sure what is happening with the Yellow Jacket pump, and it may just be a matter of a faulty gasket or other leak in the system. We of course drained the oil and added new oil (the oil specifically noted for Yellow Jacket pumps), and tested it with a digital vacuum gauge connected to the pump. We started off with the ballast open, and then closed it. We very well may be making a silly mistake, and will try it again. This is the same pump that my son and I used in July 2020 when we reached plasma in our borosilicate chamber, so it would seem like it should be fine. We changed the oil at that time, but will change it again to see if that makes a difference.

Dennis, I agree that the Welch should be a viable pump. We purchased a rebuild kit from Duniway and are waiting for it to be delivered. The kit includes all gaskets, seals, valves, o-rings, springs, vanes and mechanical shaft seal. We had not intended to rebuild the pump, but it got to about 1000 microns and wouldn't get any lower. We bought the Welch for $100 last Winter and knew that it might possibly need some work. Unfortunately, we have no experience rebuilding vacuum pumps or motors, but we are going to give it a shot.

In the meantime, we are gathering parts for the voltage and mA metering. We are hoping to do some more work on our system this weekend.
“Whether you think you can, or you think you can't — you're right." Henry Ford
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Dennis P Brown
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Re: Demo Fusor Progress Update

Post by Dennis P Brown »

I've open a similar Welch pump and they are much simpler and easier to rebuild than most current two stage vacuum pumps. I think you will have no major issues.
Jim Enright
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Re: Demo Fusor Progress Update

Post by Jim Enright »

Thanks Dennis! We are eager to receive the rebuild kit and get started. It seems to be taking a bit for Duniway to ship their products (I ordered viton gaskets on 12/22 and they still haven't shipped from Duniway yet). But once we get started, I will post pictures.
“Whether you think you can, or you think you can't — you're right." Henry Ford
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