Date: Fri Feb 16 10:07:00 2007

Author: Santos Ramirez

Subject: Re: Van de Graaffs

I wonder if teflon tape (used for the threads of pipes) would
work if it was glued on to the roller?

This would solve the problem for us that do not
have a machine shop handy to make the teflon rollers.


> I think you have to just try samples of the different materials and see
> what
> works best. You can't go wrong with teflon on the negative side.
> I found an opinion on the plastic sheet, the claim was that it is a
> dielectric material used to make a capacitor for a bloomline for a
> nitrogen
> laser. We have about 50 lbs of the stuff and its been sitting on a shelf
> in
> the stock room for ~20 years. I was told if I did a search on nitrogen
> laser
> in the amateur scientist I would be able to find out what the material is
> made of.
> Also, the teflon cloth idea is brilliant! No more problems getting as
> much
> positive charge on the acrylic rod as negative charge on the teflon rod.
> Mike
> On Thursday 15 February 2007 18:38, John Welch wrote:
>> When I look at the triboelectric series at this website:
>> it says that
>> pvc
>> and acrylic aren't that far apart. Am I missing something? The Winsco
>> comes
>> with aluminum (or maybe wool covered aluminum?) and amber, which should
>> be
>> farther apart than pvc and acrylic. The best combo according to that
>> chart
>> would be something like nylon and PVC (or teflon better yet). But this
>> is
>> all theoretical- I want to temper it with people's direct experience.
>> -John
>> Sam Sampere wrote:
>> Funny how these VdG comments and questions come up at this time every
>> year.
>> Which end of the tribo series is Teflon on? I don't remember and I'm too
>> lazy right now to look it up. I spent 2 hours shoveling last night, my
>> back hurts and I'm tired.
>> Anyway, make sure that Teflon is towards the negative end of that
>> series. It would be silly to make rollers out of materials very close to
>> each other.
>> Aluminum is right in the middle, or neutral, so that's a safe bet. I
>> don't really like Al because it sputters easily. I can envision the
>> inside of the column of the VdG coated with an Al film. That's a short
>> right back to ground.
>> Sam
>> -----Original Message-----
>> From: [] On
>> Behalf Of Michael Timmins
>> Sent: Thursday, February 15, 2007 4:41 PM
>> To:
>> Subject: Re: [tap-l] Van de Graaffs
>> I'm about to replace mine with a teflon roller, I'll let you know how it
>> goes.
>> I covered the upper roller with a plastic sheet material that charges
>> positive against the rubber belt. Just doing that made the dome charge
>> positively. The bottom roller is aluminum . I'm hoping the teflon will
>> improve performance.
>> Mike
>> On Thursday 15 February 2007 16:12, John Welch wrote:
>> Since my earlier post ended up without a subject, I'll try asking this
>> again-
>> Has anyone tried replacing the cloth covered metal roller in the base
>> of
>> a Winsco VDG and/or reversed the rollers to get a positive charged
>> ball? I'd like to try but it doesn't look trivial, so any tips would
>> be
>> appreciated.
>> -John
> --
> Mike Timmins
> University of Virginia
> email:
> phone: (434) 924-6800
> mail address:
> 382 McCormick Rd
> Charlottesville, VA 22904