Fixing Warped Hemispheres for a DIY Van De Graaff Generator

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Discussion Overview

The discussion revolves around the construction of a Van De Graaff generator, specifically addressing the issue of connecting two warped hemispherical bowls to minimize coronal leakage. Participants explore various methods for securing the bowls and preventing electrical discharge, considering materials and techniques for optimal performance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses concern that the slight warping of the hemispheres may lead to coronal leakage if connected with aluminum tape.
  • Another suggests that connecting the bowls with a wire may not effectively prevent leakage, as the charge would still discharge prematurely due to exposed edges.
  • A proposal is made to use a layer of aluminum foil between the bowls to mitigate leakage, with emphasis on ensuring no protrusions are present.
  • Participants discuss the importance of maintaining a smooth surface to avoid discharge points, particularly around the area where the belt passes through.
  • One participant recommends using epoxy to secure the bowls if they are made of aluminum, suggesting a fixture to hold them in place during curing.
  • A participant shares their background in electricity and previous projects, indicating a level of experience that informs their approach to the generator construction.

Areas of Agreement / Disagreement

Participants express differing views on the best method to connect the hemispheres and prevent leakage, indicating that no consensus has been reached on the optimal solution. Various suggestions are made, but the effectiveness of each remains uncertain.

Contextual Notes

Participants highlight the importance of surface smoothness and the potential impact of pointed edges on electrical discharge. There are also considerations regarding the materials used for the hemispheres and the methods of securing them, which may depend on specific conditions and definitions.

Who May Find This Useful

This discussion may be useful for individuals interested in DIY electronics projects, particularly those involving high-voltage equipment like Van De Graaff generators, as well as students seeking practical insights into electrical engineering concepts.

655piano
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Ok, so I'm building a Van De Graaff generator from parts I've been collecting for some time now. I have 2 hemispherical bowls that were supposed to line up perfectly to make the ball at the top. shipping has warped them just the slightest bit. I'm wondering if this will produce coronal leakage if i just connect them how they are with aluminium tape. That's the other thing, these bowls have no brim to reduce leakage, so would you recommend that I connect them with aluminum tape or something different.
 
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this is an image of one of the bowls
 

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655piano said:
Ok, so I'm building a Van De Graaff generator from parts I've been collecting for some time now. I have 2 hemispherical bowls that were supposed to line up perfectly to make the ball at the top. shipping has warped them just the slightest bit. I'm wondering if this will produce coronal leakage if i just connect them how they are with aluminium tape. That's the other thing, these bowls have no brim to reduce leakage, so would you recommend that I connect them with aluminum tape or something different.
Doesn't have to be aluminium tape. It can be ordinary tape, but connect the domes inside with one wire/piece of a metal.
Of course, align the domes to make sphere as perfectly as you can.
 
zoki85, That still doesn't seem like it would solve the leakage problem. The voltage on both bowls will be the same even if they are touching the slightest bit so the wire doesn't seem like it would do much. The charge wants to move to the outside and collect until it needs to discharge. When there is an exposed edge, it will discharge into the air before it reaches its max storage potential. Do you think putting a layer of aluminum foil between the two bowls would work? Even if the layer is wrapped around the seem and then taped on.
 
Carefully made layer of Al foil would work if it makes no protrusions.
 
Ok thanks, Ill let you know how it works. Might have more questions pertaining to the rollers and belts.
 
655piano said:
Ok, so I'm building a Van De Graaff generator from parts I've been collecting for some time now. I have 2 hemispherical bowls that were supposed to line up perfectly to make the ball at the top. shipping has warped them just the slightest bit. I'm wondering if this will produce coronal leakage if i just connect them how they are with aluminium tape. That's the other thing, these bowls have no brim to reduce leakage, so would you recommend that I connect them with aluminum tape or something different.

It looks like you are a senior in high school. Do you have a mentor at your school or other experienced person who is helping you with this project? What is your background so far in electricity? What other projects have you built? :smile:
 
berkeman, yes I am a senior in high school. I have a few teachers that have inspired me and occasionally answer my questions. I've built bio generators, steam engines, distillation apparatus, a vortex cannon. Currently I'm working on this generator and also approaching my third month working on "The Miller-Urey Experiment". I have a descent background in electricity. Mostly self taught from textbooks new and old. AP Physics has helped a great deal as well.
 
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Try to avoid any pointed bits and keep the surface as smooth as you can. Although the surface will be at an equipotential the electric field strength will be greater at more pointed (smaller radii) places and discharge is most likely to occur at those places. I think by far your biggest problem is in fashioning the area around the hole through which the belt passes. If you look at demonstration Van de Graaff domes you will see that the edges of this area curve inwards.
 
  • #10
655piano said:
berkeman, yes I am a senior in high school. I have a few teachers that have inspired me and occasionally answer my questions. I've built bio generators, steam engines, distillation apparatus, a vortex cannon. Currently I'm working on this generator and also approaching my third month working on "The Miller-Urey Experiment". I have a descent background in electricity. Mostly self taught from textbooks new and old. AP Physics has helped a great deal as well.

Good stuff. Sounds like you are on a good path forward. :smile:

Safety is a big issue when working with high voltage. Be sure to keep safety in mind as you work your way through this project.
 
  • #11
655piano said:
... would you recommend that I connect them with aluminum tape or something different.
If the hemispheres are made of aluminum (not able to solder), make some sort of fixture to hold them in the correct position and use epoxy (use a procedure that would apply it to both parts, mostly on the inside, so it (epoxy) will run together when in fixture to cure).
 

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