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Registered Member #4762
Joined: Sun May 06 2012, 05:59PM
Location: Russia
Posts: 93
So, having first met these wonderful machines about 6 month ago, I decided that I need a large one to have fun with. 2.5 meters overall height, 800mm sphere diameter, 250mm PVC tube. Washing machine brushed ac engine, aluminium lathed rollers, latex band (15 mm wide), external HV supply. Max sparks about 700-800 mm long, limited by sphere's edge curvature. I have no idea how to bend it smooth enough. Maybe I should try attaching an external toroid to it...
Registered Member #59110
Joined: Mon Apr 11 2016, 04:35PM
Location: Camarillo, California
Posts: 74
Nice.
I gave a friend with a small van de Graff a few small (12mm dia) glass plasma tubes (2mm wall) and he managed to punch a hole in one of them near the seal point.
So be careful with your lovely plasma glass near this vicious vacuum killers
Registered Member #61435
Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25
Sounds like you're using an HV "exciter". I had only read about it and have never seen anyone build one. What are the specs on the HV supply? I have heard of people using one end of a neon sign transformer.
Having tackled the Jacob's Ladder and now in progress on a smallish Tesla Coil, I think the Van De Graaf will be my next project. I have an old bandsaw motor that I may use - unless I find something with higher RPM (I think the one I have is 1350). Out of all the projects, it seems that VDG's are the most fussy.
You might be able to mitigate the streamers at the base of your electrode by employing a few different methods. If the cut is sharp, try taking some pliers and rolling the edges in a bit. You might even find some sheet metal tools designed for folding edges. Failing that, file any sharp edges. Seems like I have read about people using a rubber trim material to "finish" the edge. I believe that's what PhysicsPlayground does on his VDG's and they apparently perform well.
Registered Member #4762
Joined: Sun May 06 2012, 05:59PM
Location: Russia
Posts: 93
Sphere's edges are not sharp, as I managed to bend them inside a bit, but the curvature (not more than one inch, I think) is obviously not enough to expand this construction's possible efficiency and max voltage. Unfortunately, I have no idea of tools capable to do the job. That's how one of failed attempts (on another sphere) look like: Chinese are able to make custom toploads according to the drawing but the prices are a bit high to afford it.
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Large Van de Graaf
