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Stretchless belts for Van de Graaff generators

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Lyonel Baum

Wed Jul 25 2007, 08:03AM

Registered Member #894 Joined: Thu Jul 12 2007, 02:38PM
Location: Macon , France
Posts: 12

Hi all,

There are many virtues to stretchless belts. Primarily, if the belt cannot stretch, the upgoing side will not be able to touch the downgoing side. This happens on stretchy belts because they have opposite charges and, of course, are attracting each other. If they should touch, a lot of the charge will never reach the top terminal.

I am using vinyl impregnated nylon. The splice is at a 45 degree angle to the direction of travel. Tracking and splice durability are enhanced with an angular splice. I chose the vinyl version because Plexiglas solvent cement will achieve a very strong splice. The belt must be made carefully and you must be able to fine tune the rollers attitudes to optimize the tracking. Also a new belt has to be run in for a bit so it will accommodate the slight crown of the rollers but in the end it is worth the trouble.

Vinyl impregnated nylon is practically non stretch so fine adjustment of the rollers is necessary to achieve reliable tracking. The crowning of the rollers is minimal since the material will not wrap around a typical crowned roller. A good flexible 45 degree splice can be obtained by overlapping about 3/16â€ and gluing with Weldon, a solvent cement used for acrylics. Also, the belt needed some run in time to contour to the roller surface. For rollers I am using Nylon on the bottom and Teflon or PVC at the top.

The vinyl-laminated nylon fabric at McMaster-Carr is their item number 8810K142. The cement to use on it is number 7515A11. It is for acrylics, but it works well on vinyl, too.

Lyonel Baum

Wed Jul 25 2007, 11:10AM

Registered Member #894 Joined: Thu Jul 12 2007, 02:38PM
Location: Macon , France
Posts: 12

I gave up on latex a long time ago. I tried assorted thicknesses and they all exhibited similar problems. After many failed experiments and lots of scrap in the rubbish barrel, I finally settled on vinyl impregnated nylon ( stuff is white and .015" thick). It has minimal elongation, angled lap splices using â€œWeldonâ€ acrylic cement are flexible and almost indestructible and electrostatically works well with nylon and PVC or teflon rollers. The major drawback is that the rollers must have a very slight crown and must be adjustable to tweak the tracking. But, once the belt has been run in a bit and rollers adjusted properly, tracking is very stable.

D.C Cox ( Dr Resonance ) uses a Teflon/Fluoroelastomer belt for his big VDG ( 32 " large belt - 75 ft/s ) -
48 " x 7 ' wide cylinder terminal . Sprayer : 7 kV @ 20 mA DC on the lower comb . Sparks : 5 ' - 2 / s.

Finn Hammer

Thu Jul 26 2007, 06:23AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Here is an edited post from the other VDG thread:

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.

I have later found that polyuethane stands up to ozone very well.

I have tested it up to 125FPS with no problems.

Cheers, Finn Hammer

cbfull

Thu Jul 26 2007, 02:30PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

Wow, long finger bond, sounds almost ideal. I wish I could do that to my belt. If anyone has trouble finding the stuff Lyonel mentions, it's actually called Vinyl Laminated Nylon Fabric in the catalog. It's nice because it is very thin and has a pretty good dielectric strength, which we know is essential to maintaining charges on the rollers.

They also list neoprene coated nylon (which I just bought a big roll of) and polyurethane /nylon, which I have heard works great as well.

Lyonel Baum

Sat Jul 28 2007, 06:16PM

Registered Member #894 Joined: Thu Jul 12 2007, 02:38PM
Location: Macon , France
Posts: 12

Vivitron ( in memoriam )

Initially designed to operate at voltages up to 35 MV, 10 years of studies and observations have shown that the upper limit was closer to 25 MV than the initial value. Apart from its size, (tank length 50 m, tank diameter in the middle 8.5 m, 60 t of SF6 dielectric gas) the Vivitron differed mainly on the following points: The inner mechanical structure was made of large dimension longitudinal girders and radial insulators posts. The materials used were fibre glass epoxy in the former case and aluminium oxide charged araldite in the latter.
Seven porticoes holding 7 discrete electrodes (intershields) equally spaced by insulators, ensured a quasi-uniform field distribution everywhere inside the tank.
The charging system was made of a belt running between both ends of the tank.

Closed in 2003.

The belt ( 100 m long ) of the super VDG Tandem Vivitron was made by CIGO ( Italy)

Steve Conner

Sat Jul 28 2007, 07:14PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Awesome. Thanks for posting this information!

Lyonel Baum

Wed Aug 08 2007, 07:50PM

Registered Member #894 Joined: Thu Jul 12 2007, 02:38PM
Location: Macon , France
Posts: 12

Hi all ,

HVEE made Van de Graaff , Singletron , Tandetron .They wrote on their web site :
Van de Graaff accelerator charging belts
For Van de Graaff accelerator charging belts, we have established Passaic Rubber Co. as a qualified supplier to completely take over the production, service and sale of these belts effective June 1, 2002. All technical drawings, know-how, production equipment and test equipment has been transferred to Passaic Rubber Company.
For further information and support, please contact:
Mr. Jeffrey Leach
Passaic Rubber Co.
45 Demarest Drive
PO Box 505
Wayne, NJ 07474-0505, USA
Tel: +1 973 696 9500
Fax: +1 973 696 0686
E-mail: **link**

]1186602617_894_FT28969_singletron_broch.pdf[/ file]
]1186602617_894_FT28969_tandetron_broch.pdf[/file]

Lyonel Baum

Wed Aug 08 2007, 07:59PM

Registered Member #894 Joined: Thu Jul 12 2007, 02:38PM
Location: Macon , France
Posts: 12

Van de Graaff accelerator charging belts
For Van de Graaff accelerator charging belts, we have established Passaic Rubber Co. as a qualified supplier to completely take over the production, service and sale of these belts effective June 1, 2002. All technical drawings, know-how, production equipment and test equipment has been transferred to Passaic Rubber Company.
For further information and support, please contact:
Mr. Jeffrey Leach
Passaic Rubber Co.
45 Demarest Drive
PO Box 505
Wayne, NJ 07474-0505, USA
Tel: +1 973 696 9500
Fax: +1 973 696 0686
E-mail: **link**

Steve Conner

Thu Aug 09 2007, 10:15AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Thanks for the details. I wonder if they will be bothered selling smaller belts to amateurs, though.

Also, if you want to add information, can you please edit your existing post with the Edit

button instead of starting a new one. We have a rule against double posting within 48 hours.

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob