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.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Demo Fusor Progress Update

Post by Richard Hull »

The simple 100 meg system sounds nice for 50kv but that resistor would need to be a 25 watt resistor! 50,000/100e6= 500ua.... 500e-6 X 50 e3 = 25 watts demanded and wasted from your 50kv supply just to measure the voltage with a single simple resistor! Not many 25 watt 100meg resistors on the market. To limit heating and drift you might look for a 75 watt 100 million ohm resistor! Good luck!

Gotchas all over the place here. What sounds so simple, the math and the availability crush to dust.

5X10E4/10E9 ohms = 50ua.....50X10E-6 X 5X10E4 = 2.5 watts. With 5 200meg resistors in series 0.5 watt resistors demanded. With 10 100meg resistors in series only 0.25 watt resistors demanded. The thermal drift in high ohm resistors being heated by dissipation is terrible and thus the measurement accuracy suffers. In this paragraph, 2 watt resistors would be ideal.

Smart money does the math and matches it against the resistors you can actually buy and the amount of power you are willing to lose from you 50kv supply just to measure the voltage output.
High voltage measurement demands a bit of consideration.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Demo Fusor Progress Update

Post by Dennis P Brown »

The difference between an engineer's solution and a physicist's; so, the cow being assumed spherical does not work in reality! ;)
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Demo Fusor Progress Update

Post by Richard Hull »

I'll never forget my fellow engineer, Tom Ligon, Doc' Bussard's lab rat, telling me he was Bussard's set of "gravity boots".
physicists feel if it can be imagined, surely, there is kit to make it happen. An engineer needs to be there to say, "they haven't invented that yet or they don't make something that is that big or that capable." Material science has stopped many a project or idea from getting out of the starting gate.

In this case it just crushed the idea of a single resistor 50kv metering effort. But there are always clever methods and workarounds that can make it happen. You just gotta' make some extra space and use what is readily at hand.

I have 2 electrostatic volt meters... Rather giant contrivances with infinite resistive loading that go to 40kv in the largest reading. It has U.S. Atomic Energy Commission marked on its case. (Hamfest buy)
They work on the needle moving across the scale as two chorme-plated plates are being electrostatically moved into various physical alignment based on coulombic action. Most all GM service manuals prior to 1980 stipulate the use of an electrostatic voltmeter to set the high voltage. (effective zero loading)

I attach an image of such a meter. They contain zero electronic parts being 100% capacitively based electro-mechanical action in nature. These leviathans weigh about 20 - 30 pounds. One of mine has three ranges changed by pulling a knob out of the case at three detents which vary the static plate to three precisely determined positions. I own both of these style meters

Richard Hull
Attachments
electrostatic-voltmeter.big.jpg
electrostatic-voltmeter.big.jpg (44.07 KiB) Viewed 4005 times
ESV meter range.jpg
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Demo Fusor Progress Update

Post by Dennis P Brown »

Impressive instruments. Yes, being practical is both a necessity and part of training for engineer's. But spherical cows could have some advantages ... wonder if biologist have considered that issue?

Understand the effect of a high voltage electric field all too well; my 100+ kV voltage multiplier created a field (while under oil) that really impressed me (in a bad way.) Even my high voltage probe responded without contact. I gained a powerful respect for voltages in those ranges.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Demo Fusor Progress Update

Post by Richard Hull »

Electrostatic fields of intense magnitude within a high dielectric constant fluid insulator can actually mechanically stir and move that media. Intense Amperian currents within a highly conductive molten metallic media can likewise stir and move it as is seen in molten aluminum reduction operations where tens of thousands of ampere currents are common. Such studies and rarely seen events are far outside the gaze of virtually all living beings. It is enough to know that they occur in singular high field events. Electrostatic fields where the currents are in the picoamp range with potential differences of many thousands of volts with almost no magnetic field present create motion within a medium. We also observe motion within intense surrounding magnetic fields in suitable conductive media where the potential difference is almost non-existent within the medium.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
Posts: 505
Joined: Thu Sep 23, 2021 10:36 am
Real name: Matt Gibson

Re: Demo Fusor Progress Update

Post by Matt_Gibson »

Dennis,

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

-Matt
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Demo Fusor Progress Update

Post by Dennis P Brown »

Uh, the spherical cow?
Jim Enright
Posts: 46
Joined: Sun Aug 04, 2019 7:12 pm
Real name: Jim Enright

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
Posts: 46
Joined: Sun Aug 04, 2019 7:12 pm
Real name: Jim Enright

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
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

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
Posts: 46
Joined: Sun Aug 04, 2019 7:12 pm
Real name: Jim Enright

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
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

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
Posts: 46
Joined: Sun Aug 04, 2019 7:12 pm
Real name: Jim Enright

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
Post Reply

Return to “Images du Jour”