help with roller! need help asap

i built a vdg and it works. but since the top roller is AL all it does is produce static electricity until it sparks to the AL on the roller. instead of going to the dome. i have to present it at science fair so i need another roller. i was thinking nylon. so i bought a bed frame roller wheel. but i dont know if it is nylon. so does anyone know if there is any thing i could use that would be at hardware stores or any stores?

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it's not molded it's actually an 1/5 inch drill bit epoxed at right angles to the bolt.
The roller is friction fit to the motor, the other end is slip fit on a piece of hardened steel epoxied to the end of the bolt, the bolt is mounted with nuts to the bucket and by adjusting the nuts I could align the roller.
I assume you mean the belt is coming off the roller. It's necessary tohave the two rollers perfectly aligned, so you'll need to make them adjustable until the belt tracks straight. Alternately I've read that making the roller spindle shaped will solve minor alignment problems.
Yes you still have the wire, length doesn't matter, and it leads to the inside of the dome.
It shouldn't still spark, and yes it will make bigger sparks.
The entirety of the roller brush mech should be contained within the dome, but i doesn't need to be centered. When the brush/roller is outside the dome you create a weak capacitor where the dome/brush is one plate and the roller/belt is the other plate. When the brush/roller is inside the dome you create a spherical capacitor where the dome is one plate and the edge of the universe is the other (an over simplification but essentially true).
Oh,the roller/brush assembly absolutely must be inside the dome, there is no way to avoid that. Otherwise, what's happening will happen.
Then I'm at a loss to explain what's happening, if the brush and roller are inside the dome and the brush is wired to the dome, then, in theory, all the charge must migrate to the surface of the sphere.
At these voltages you want smooth edges of you lose voltage to sparking and coronal discharge, so that could be a problem.
No it didn't, can you post a picture? do a search for triboelectric series, it will give you idead for the best rollers.
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