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Registered Member #187
Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140
I have to say, 59µA is rather impressive for a generator that size. It's actually the first time I've seen anyone get above 20 with a small-ish VDG. Mine has almost a 4" belt diameter, a doubler, and the roller is 3450RPM, and the most I can get right now is around 30-35µA. I know it's working good too because there is corona and leakage everywhere, and in the dark I can see faint discharges inside the column between the up/down belt halves.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
After a days work, the top terminal now looks like this:
The joint btwn IKEA bowl and FREU toroid became less than ideal, so to avoid corona at that point, I had to apply an anti corrosive paint with a content of zinc. This paint managed to solve the problem.
I had hoped that the better shape of the terminal would boost the output with the missing 5 uA, and that this would reflect less leakage from the decending belt to the terminal, but this did not happen.
The maximum voltage was raised from 280kV to 320kV (measured by the 36cm Ø ball gap), but it is now limited by flashover to the base.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
DrZoidberg wrote ...
Looks really neat.
Did you also improve the shape of the base? If there is still a rim at the base that could explain the flashovers.
BTW What materials did you use for the belt and the column?
teravolt wrote ...
hi Finn what is the belt material and where did you get it
First the belt: This is a conveyor belt from the food industry. Most of these belts are anti static, but this one is not. The company that produces them is HABASIT and the factory code for this particular one is F-2EQWT The nice thing is that I specify length and width, then they weld it together, with a really nice, long finger joint. It costs 40USD which I think is more than fair. It is washable, doesn`t stretch and is capable of running at high speeds. I don`t know how it stands up to corona, ozone and all that. The column is made from HDPE. This is a piece from the local water supply.Therefore the nice blue.
I did not make the base like the top electrode, although I should, and this does contribute to the tendency to flashover. However, the column is only 500mm or 20" and this is also a major reason.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
Sulaiman wrote ...
Looks really great -certainly display quality. Lovely job.
Thanks!
Sulaiman wrote ...
Out of curiosity, you say the column is 500mm and it flashes over at about 320kV that's 640V/mm, quite low I thought, is it surface tracking?
I can`t say for sure. But when the spark length btwn. 360mm balls exceeds 135mm, the flashovers start. These flashes run on the surface of the column, but they don`t leave any marks. I frankly don`t know if this qualifies as tracking.
Registered Member #187
Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140
Sorry, the way I started describing the dimensions of my VDG parts was quite vague.
My roller diameter is 2.25in, or 57.15mm Belt width is actually 3.5in, or 89mm
Upper roller is solid aluminum, soon to be made of nylon Lower roller is solid acrylic, no forced charging. My goal is to get maximum results WITHOUT a HVDC sprayer.
Belt is made of nylon reinforced neoprene, ends are hand sewn together, and it is 1/16" (0.0625in or 1.6mm) thickness, which is pretty heavy. I am in the process of making a new belt out of 0.022in, or 0.56mm neoprene coated nylon so I can double the belt speed.
Present speed: 34 ft/sec or 23mph.
I should be able to get it up to 60mph maximum (this is typical for a good VDG), which would be about 2.5 times my present speed.
Registered Member #205
Joined: Sat Feb 18 2006, 11:59AM
Location: Skørping, Denmark
Posts: 741
cbfull wrote ...
Sorry, the way I started describing the dimensions of my VDG parts was quite vague.
My roller diameter is 2.25in, or 57.15mm Belt width is actually 3.5in, or 89mm
With a roller speed of 3400 RPM, the max you can get is 38uA with a doubler, so I`d say you are doing very well indeed. I have to thank Da. Antonio for the nice litle program Elcal, which calculates this in a jiffy.
cbfull wrote ...
Upper roller is solid aluminum, soon to be made of nylon Lower roller is solid acrylic, no forced charging. My goal is to get maximum results WITHOUT a HVDC sprayer.
Yeah well, to each his own. I like the sprayer, because it reduces the need for low humidity to get output. Have you had problems with alluminium contamination on the belt?
How long is your column and how is your terminal made, how big is it?
cbfull wrote ...
Belt is made of nylon reinforced neoprene, ends are hand sewn together, and it is 1/16" (0.0625in or 1.6mm) thickness, which is pretty heavy. I am in the process of making a new belt out of 0.022in, or 0.56mm neoprene coated nylon so I can double the belt speed.
Present speed: 34 ft/sec or 23mph.
Mine is 34 MPH at the present. The belt could go *a lot* faster, so I think it is time to introduce a belt and pulley btwn. motor and the lower roller, so that the speed can get higher. This is for the next generation.
cbfull wrote ...
I should be able to get it up to 60mph maximum (this is typical for a good VDG), which would be about 2.5 times my present speed.
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Inside the Van de Graaff
