OSH and the 400,000Volt Van de Graaf Generator & More Instructions/HOW TO MAKE A VDG 2012.pdf · a coil using two of the largest NST’s and cap banks you can find. In the long run

OSH and the 400,000Volt Van de Graaf Generator

& More

By Frederick W. Graff

Copyright@ Frederick Graff 2012

2 Frederick W. Graff©2008 | Graff Generators

~~~~TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS~~~~

Parts of a VDG and How it Works…………………….. 3

Choosing the VDG size……………………………............. 5

Tower Construction…………………………………………… 7

Roller & Belt Construction…………………………………. 12

Tower Base ………………………………………………………. 7

Base Design & Motor………………………………………... 17

Discharge Sphere……..……………………………………….. 20

Support System…………………………………………………. 22

Spraying a Charge…………..…………………………………. 24

Videos & Extra Resources……………….…………………. 28

400kv & 700kv Operation Instruction………………… 29

How a VDG Works:

The VDG simply works by taking

electrons from a bottom grounded comb and

transferring them to a top comb, where they

are then distributed to a smooth blemish free

metallic dome, that in turn produces a high

voltage electric field. The heart of this

charging process is dictated by two physical

principles. First being that opposite charges

attract and like charges repel just as in

magnets where north and south attract and

north and north repel. The second physical

principle is that most objects develop either a

positive or negative charge when rubbed

because of electrons being bushed off or onto.

Passing electrons by rubbing surfaces is often

done on a daily basis such as when you rub

your feet on the carpet so that you may shock

a friend or when you rub a balloon on your

head then stick it against the wall. According

to the triboelectric series, which will be

discussed in more depth later in this

document, some materials develop a stronger

+ or – charge than others.

With these physical principles in mind,

let’s now look more closely at how the VDG

dome receives the charge that process the

popular hair standing feeling. When the latex

belt runs across the bottom nylon roller it

develops positive charge which then produces

a positive electric field. The free roaming

electrons on the bottom metal grounded

comb begin to feel the attraction from the

positive electric field, causing them to fling

toward the positively charged roller.

However, since insulating latex belt is between

the comb and the roller, the electrons attach

themselves to the latex belt surface, where

they are then carried to the top to be flung

right back off.

The top acrylic roller during this

process develops a negative charge that emits a

negative electric field. As the electrons on the

latex belt begin to approach the top roller,

they start to feel the repulsion forces from the

nearing negative electric field. Upon reaching

the top roller, the electrons are now immersed

overwhelming repulsive negative electric field

where they are excessively flung to the closest

conductor they can find, which so happens to

be the top comb. They are then pushed

through the metal support system, to the

metallic discharge dome. As the belt system

finally rounds the top roller, now approaching

the bottom, it could possibly have a positive

charge if too many electrons were ejected. If


this is the case, as in the VDG you are about

to build, its just going to run all the stronger!

To cover one last aspect of the VDG,

the dome accounts for at least 80% the

generator’s final output voltage. So that a

maximum voltage can be achieved, it is

essential to understand conceptually how the

electrons interact with the metal sphere.

Once the electrons make it to the dome, they

are now roaming around and cramming

against each other due to their individual

electric fields. Essentially they are looking for

a way out, which consist of any edge or point

on the surface that offers a path of least

resistance. By referring to the illustration,

there is a high concentration of electrons

located at the discharge spheres bottom edge

because this is a region where the electrons

feel the least resistant and will try to

prematurely leak off (leakage), hence creating

a lower voltage. To prevent this from

occurring, the dome has an insulation that

lines the bottom edging. Not only will the

electrons try to leak off from this bottom

location, but from any protruding scratch or

even dust/dirt particles. Because insulators

become conductors at high voltages, mostly

any material on the dome could create

leakage.

Parts of a VDG:

Discharge Sphere

Top roller

Bottom Roller

Static Belt Tower

Latex Belt

Motor

Top and Bottom Combs

Discharge Sphere Support System

AC Motor

Ground Wire

Base

Drive Belt

Choosing the VDG

Size and Initiating the

Building Process

When designing a VDG there are a

variety of routes that one may take relative to

the VDG’s size, dive system, static materials,

dome capacitance, aesthetics and so on. To

many experimenter’s surprise, the final output

voltage of a VDG is dictated not by the RPMs

or even static material (though these are very

crucial aspects), but through size of the dome

or better yet, the dome capacitance. Using

the break down voltage of air and general

capacitance equations for a dome, it may be

analytically found that for every 1 inch the

dome’s radius increases, the output voltage

increases by 70,000 volts. One the other side,

if the belt and rollers do not operate

efficiently enough, this maximum potential

cannot be achieved.

Some builders may say the bigger the

better and right so, but before making such

costly leaps, lets first consider a few things.

For starters, this is a low current high voltage

devise that is meant to be tangible to the

operator. This is not a Tesla Coil. If you the

designer are looking for large arcs, then build

a coil using two of the largest NST’s and cap

banks you can find. In the long run though, I

promise you will find a VDG more intriguing

considering that you can physically handle

and manipulate a piercing 400,000KV electric

field.

To help us consider the VDG size to

build, larger VDGs are obviously more

exhilarating then the smaller ones and of

course do have draw backs. First as stated

above, you do want to be able to touch these.

I have found that anything over about 1.2MV

is almost too painful to handle not to

mention unsafe, so I would limit any design

to a 30 inch (1.05MV) dome but no less than

12 inches (320,000V).

Smaller VDG’s have not shown to have

any type of true design constraints unlike the

larger and more powerful units. Larger units

do need to operate at greater electrical

currents because of the larger dome that is

constantly being replenished with electrons.

The design constraint on the larger units

appears in the static belts system because as

the belt goes up with a negative charge the

other side of the belt comes down with a

positive which causes the two belts to flex into

each other and furthermore potentially

invokes harmonics in the system. Therefore,

larger systems will need much tighter belts to


avoid these deflections, which means more

costly bearings and possibly using neoprene as

the static belt, which does not deliver the

same amount of charge as a latex belt nor

have it’ tensile strength. There are few way to

combat this issue which is to design a duel

roller system and (or) choose a more pricey

Teflon belt that can carry the charge as seen in

the illustration bellow.

For the sake of introducing few more

ideas, I have built a dual tower VDG where

both roller sets produced a negatively charged

sphere. Because this system had two 15 inch

domes, the overall voltage was much greater

than a single dome due to the increase in

capacitance plus the output current was

doubled and reached currents as high as 70

micro amps. Considering the 8000 dollar

units produce 100 micro amps. Not bad!

Another design that I have been

building requires an external top roller system

where the top rollers are surrounded by 4

large domes. Because the domes are located

around the rollers, there will theoretically be a

be a zero electric field in the center, which

then allows the charge to propagate to the

outer domes. This design is theoretically

advantageous because there are no points to

create leakage on the dome and will yield voltages over 800 KV.

Tower Construction:

Before introducing the machining

techniques for building the VDG tower, I

wanted to first introduce a few illustrations

that will help the builder gain a visual for the

tower design that will be spoken of through

the next few pages. These illustrations show a

design that I have been using over the past few

years and have yet to make any major

modifications other than how the top rollers

fasten in and bearing grade. These towers

operate using a pulley drive system which has

a plethora of perks over other designs because

you can gear the system to suite maximum

speeds of your choice and the system allows

for a quick release of the static belt system.

Other designs have motors connected directly

to the bottom roller by a shaft which can be

financially advantageous because you do not

have to include the pulleys that cost roughly

25 dollars after shipping. Please access the

video links at the end of this manual to find

VDG’s with this design.

Beginning the Tower Construction:


Regardless if you are pursuing the

exclusively acrylic or plastic of your choice, the

initial steps to machining the tower are

identical. Through the course of this manual,

you will find additional instruction regarding

machining techniques for the acrylic design.

Furthermore, if you choose to deviate from

the design, I highly encourage everybody to

first thoroughly read through this guidebook

because there are crucial subtleties that must

be incorporated to insure an efficiently

operating VDG.

For my 400KV unit, I use a 4 inch OD

tube that is 2 feet long which seem to be in

good proportion. If you are using a 20 or 22

inch dome I would go with at least a 5 inch

OD tube that is a minimum of 3 feet long. A

30 inch dome will need about a 6-7 inch tube

and should be 4 to 6 feet long. Now that we

have a proper tube size, let’s start prepping the

material and making our first measurements.

Step 1: Squaring the Tower Ends

Despite the base that you choose, either

a PVC insert or an acrylic sheet, the ends of

the tubing must be square so that the top

rollers run perfectly horizontal and the base

sit perfectly perpendicular on the base. To

square the edges you will need either a 10” or

12” chop saw that contains a blade used for

cutting plywood. To square the ends, simply

trim a fraction of an inch off of each end.

When finished, place the tower on a flat

surface so insure that the tower stands

perfectly perpendicular. Repeat this process

for both ends and then sand the ends using

80 grit sand paper.

Step 2: Finding roller Locations The first step in constructing the tower,

now that it is prepped and ready to go, is to

mark the locations of the top and bottom

roller notches and the locations where the

aluminum support system will anchor in. As

seen in the illustration to the below, I have

marked four locations each equal in distance.

This is best done using a tailors measuring

tape.

You will find that a 4 inch OD tube

will have marks are exactly 8 cm apart. To

find the location of the bottom roller holes,

place the tower on a perfectly level surface and

then drop a plum bob from one of the top

roller locations and mark the bottom of the

tube with a Sharpy that aligns to the top

notch. Next using the tailors measuring tape,

find the location on the other side of the

bottom of the tube that aligns with the top

roller location. To finish finding the bottom

roller locations, measure up 4 inch from the

bottom alignment mark and then place a dot


for each side. To find the top roller holes,

just measure down a half inch from each

roller location and place a dot.

The aluminum dome support system

holes locations are found from the other two

notches. These holes are 1 inch apart and the

top hole a ½ inch down from the top of the

tower. For those who are pursuing the larger

VDG, these locations should be between 1.5

to 2.5 inches apart.

All holes should first be drilling with a

small pilot bit. After the pilot holes are

drilled, finish the roller holes location using a

3/8 bit only if you are using the flanged

sintered bearings. The aluminum holes

should be drilled with an 11/64 bit or larger.

To drill acrylic with the larger bits, run the drill on reverse and allow it to melt through otherwise you will crack the acrylic.

The top roller notch, as seen in the

illustration to the left, was machined by first

drilling the hole and then grinding out the

remaining material using a Dremel. This may

also be done using a file or smaller drill.

Step 3: Machining the Bottom Roller

Entrance Hole The illustration on the next page

shows the bottom roller entrance locations. I

have enjoyed this design because of how

efficient it both braces the bottom roller and

allows for a very quick belt adjustment or

maintenance. Other designs have the bottom

rollers fastened into the base which can be

time consuming when any type of

maintenance is at hand, especially since VDG

belts should be cleaned about every two hours

of use.

To machine the bottom entrance hole,

first do not be shy to design the entrance hole

to extend upwards a significant distance as

seen in the photo. Even with the much larger

units I have made, this design had worked

perfectly. Secondly, be sure to allow the

opening to extend enough circumferentially

such that you can fit your hand inside because

you will need to be able to reach you hand up

inside to grab the belt.


The best way to initiate the machining

once you have finalized your roller opening

dimensions, it to trace the opening using a

straight edge and dry erase Sharpy. Next,

carve the tracing with a Dremel Rotozip and

then smooth the surface with 80 grit sand

paper. When carving, make sure to cut the

bottom hole entrance notch so that it is

curving downwards otherwise the roller will

not hold.

The final step in preparing the tower is

to fasten it to the base. The photos on the

next page show two different strategies to

attaching the tower to the base. If you choose

to fasten an acrylic tower to an acrylic base

you will need Weld On Acrylic Cement and

the applicator that is sold through Tap Plastic

or various Ebay sources. If you choose not to

use the acrylic cement, super glue works

almost as well plus you do not have to deal

with the extremely caustic odors produced by

the Weld On cement. The other illustrations

use a PVC flange that may be purchased at

OSH or Home Depot for about 7 dollars.

The PVC flange will need a different diameter

for acrylic tubing for those who are trying to

go with the all acrylic design.

If you choose the all acrylic design,

there is a very simple way to center the tower

to the acrylic tower base. First, trace a line

through the center of the acrylic base as seen

in the illustration bellow. Next, place the

tower on the acrylic base and align the bottom


marks (from Step 2: Finding Roller Locations)

with the traced center line. Apply the Weld

On or super glue and you are good to go.

Weld On take about 24 hours to dry however

it does about 95% of its drying in the first

minute so you will be safe to continue with

the build only minutes after the application.

Acrylic Welding Supplies http://www.tapplastics.com/shop/product.php?pid=130& (glue) http://www.tapplastics.com/shop/product.php?pid=170& (applicator)


Roller and Belt Construction: Low RPM Rollers High RPM Rollers

Plain and simple, next to the dome size,

the rollers are a crucial component of the

VDG because if you cannot produce current

the then you will not be able to charge the

dome. The rollers, as stated in the

introduction, charge the system by one roller

producing a positive charge and the other

producing a negative charge. In short, one

roller (the positive) sucks electrons on to the

belt and the other roller (negative) flings them

back off to the dome. So essentially, you want

a set of roller that can produce a whapping

positive and negative electric field. So how is

this done? The answer lies in the triboelectric

series as seen bellow.

Theoretically, it is best to make rollers

out of materials that are as far apart as

possible on the tribolelectric series, however

these systems charge by contact (friction)

when the belt runs past the rollers, just like

when you take a balloon and rub it against


your head. Therefore, the ideal materials are

the one that have both high friction surfaces

and lie very far apart on the triobo chart. For

example, I have made a high RPM roller set

out of nylon wrap in wool (positive) to give it

a rough surface and acrylic painted with a

high friction silicon coating called Pliobond

(negative). The low RPM set, as seen the

upper illustration to the left, is also made

from nylon wrap in wool and the other with

nylon wrapped in packing tape. Other

combinations that I would recommend are

Nylon and Teflon, Nylon and PVC, and

Nylon and Delrin.

High RPM and XL VDG Rollers :

Before we dive into the roller

construction for the low budget driven VDG,

let’s first answer a few questions for those who

are building the larger and higher RPM

systems. First, when constructing higher rpm

systems, you have to either use cast materials

or have a machinist turn the material which is

very costly. I would purchase 1.5 – 2 inch OD

cast materials from any one of the on-line

resources and then have a local machinist

punch the center holes, unless that is, you

have a lathe of your own. For those who

don’t, I would purchase a six pack of the

machinist favorite beverage and kindly ask

him if he would be willing to take a few

minutes out to punch a few center holes for

you. Otherwise, he will say I charge 60 dollars

per hour with the first hour to set up and plus

time to machine. The honest truth is that it

takes 1 minutes to place the quarter inch bit

in the machine and about 4 minutes to finish

the job with a small coffee break buried in the

middle. Go for the six pack! To further help

reduce machining cost, you do not have to

crown the rollers. If you notice on my higher

rpm rollers, the wool is centered on the roller.

This placement gives the belt a lip to ride on.

If you would like to create lip on the top

acrylic roller, wrap packing tape around the

very center as seen in the illustration bellow.

This is a bonus because packing tape has

incredible electrostatic properties that will

produce the hair standing charge that you are

designing for.

Relative to the bigger and better VDG

enthusiast, if you are using a tower that is 4

feet or taller you will need rollers at least 2

inch in diameter to alleviate the attraction

between the belts. This will also allow you to

run a greater belts speeds plus help eliminate

unwanted harmonics that develop at higher

RPMs. Another very common design flaw

that will create harmonics in the belt would

be rollers that have been over crowned.

When crowning the rollers never use more

than a 10 degree crown otherwise the belts

will pass through too much of a deflection


upon leaving the roller which will create

harmonics. In short, it

Material Resources:

Cast Nylon and Acrylic Material: Best prices!!! http://www.indplastic.com/index.cfm?id=1086026&fuseaction=browse&pageid=1

Flanged Bearings: Refer to ebay listings

www.ebay.com

¼ inch Dowel Rod: Osh, Lowes, Home Depot


Low RPM Roller Construction:

As described, the top and bottom roller

may be easily constructed out of 1.5 to 2” OD

stock rod along with proper machining. This

technique is sufficient for RPM’s greater than

2500. If you choose to run less than 2500, a

much more simple design may be pursued by

using nylon caster wheels which may be

purchase at any hardware store or Wal-Mart

being the cheapest at 1.99 each. The Nylon

caster wheels come in a wide variety of

different sizes and materials, therefore make

sure you choose the white larger caster wheels

that are about 2 inches in diameter. To

prepare these rollers you will have to first

remove the brass dowel pins that pass through

them by drilling out the riveted ends.

With the brass pins removed, you may

now place in the axles. I have used the

lengths of 4.5 inches for the top axle and 5.25

inches for the bottom. The bottom axle is

one inch larger because of the drive pulley

that is placed on it. Because the ID of the

caster wheel is slightly larger than the ¼ stock

rod, you will need to wrap the axle with metal

tape at the location the roller sits on. The

illustration bellow shows a picture of the

bottom roller axle (5.25 inches). The roller

may be fastened to the axle few ways, the first

of which is to use 2000lb two part epoxy. The

second way, being more efficient is to drill

holes through the ends of the roller and then

run set pins through them the press against

the axle.

The last step before inserting the bearings,

flat belt pulley, and shaft collar, is to coat the

bottom roller with your color of choice100%

wool felt. To adhere the felt, first cut the

cloth to shape and then super glue it to the

nylon roller using a brush on applicator.

When doing so, use the superglue sparing as

the glue itself will yield a negative charge

when rubbed. You will know you there has

been applied too much if the wool develop a

white milky stain on the outside. Next, wrap

the wool using nylon fishing string to further

secure the felt.


After the ¼ inch OD brass dowel rods

have been inserted as axles, it is now time to

include the bearings, shaft collar, and flat belt

pulley and so here is where things may go

wrong. If you use unsealed flanged ball

bearings or low quality sealed flanged

bearings, the VDG’s electric fields will suck

every ounce of oil from them which will both

destroy the bearings and turn off the VDG,

plus crack all of the acrylic bearing holes due

to a reaction with the oil. Oil and VDG’s do

not mix!

Materials Resources:

1) Caster Wheel – Lowe’s, OSH, Home Depot, Walmart (4 to 8 dollars for 2 large caster)

http://www.idealtruevalue.com/servlet/the-63955/Detail

2) 2500lb two part epoxy – Lowe’s, OSH, HomeDepot (4 dollars) 3) ¼ Flanged Bearings: OSH http://www.sdp-si.com/index.asp (1 dollar at web site)

4) ¼ inch ID Shaft Collar: OSH or http://www.sdp-si.com/index.asp

5) Set pins for rollers: OSH 6) ¼ inch dowel rod: OSH

7) 100% wool felt: http://www.twiningthread.com/Wool-Felt01.html


Additional Roller Designs:


Base Design Ideas & Choosing the Right Motor:

A huge misconception about Van de

Graaf Generators is that you do not need a lot

of horse power to drive a VDG system. Even

my largest generators only use fractional horse

powered motors. If I chose to, I could have

even ran my 1 MV system off of a Dayton

1/15Hp motor, the same that I use for my

mid size 700KV system. A second item that is

often flawed is that if your generator has an

efficient roller set, then the VDG will not

need to run over 2500 RPM. Of the motors I

have come across, I would highly advise the

1/15hp 5000 RPM Dayton (part number

2m066) because it can operated with an

external router

speed control and

it has more than

enough power to

run most size

systems.

The base design that I have chosen over

the past 5 years uses a drive belt as seen in the

illustrations. This route may be more

advantageous than directly connecting a drive

shaft from the motor to the roller because it

allows for gearing the drive system and allows

for easy belt changes. For those who own a

commercial VDG know the frustration of belt

changes considering how often belts need

replaced and cleaned. To allow flexibility in

the design, I have used Narco rubber bands

for the drive belt as appose to a neoprene

timing belt which require immense precision

when anchoring the motor unless an

adjustable motor mount is to be used. In

addition, I have also used dirt devil 12

sweeper belts for my larger 700KV VDG

model. Please use the following illustrations

to help ferment a creative drive system for

your VDG. These illustrations show a variety

of models that I have built over the past few

years.



Advised Motor and Drive Component Resources:

1) http://www.sciplus.com/

(Variety of motors and great prices)

2) http://www.electricmotorwarehouse.com/Dayton_AC_DC_Motors.htm

(Dayton motor as seen in illustrations\

3) http://www.surpluscenter.com/electric.asp

(Variety of motors and great prices)

4) http://search.harborfreight.com/cpisearch/web/search.do?keyword=speed+control

(Speed control for 1/15Hp 5000 rpm Dayton AD/DC motor)

5) http://sdp-si.com/

(Timing Belts, flat belt pulleys, Gears, Etc…)


CONSTRUCTING A DISCHARGE SPHERE:

When making a discharge sphere, your main goal is to prevent leakage which is the

premature discharge of electrons from the sphere. Leakage is primarily caused by pointy

conductive edges, therefore your job is to construct a dome that has a very smooth surface. To

construct the dome, one may go about two different ways, the frugal route or the expensive route.

I prefer the more expensive route because it is more efficient

The Frugal Route:

The least expensive way of making a discharge

dome is to buy a cardboard globe at Target and then

paint it silver. Silver paint works well because it has a

high concentration of metal in it, making it conductive.

When you are finished painting, cut a hole in the

bottom of the dome so that it may be placed over the top

of the VDG tower. When you cut the hole, make sure

that it is not to large because you want a snug fit. The

last thing you must do is place insulation around the

edge of the cut hole so that there will be no leakage.

The other option, which yields much higher voltages, would be to purchase two very large

bowls and tape them together and grind out the bottom tower entrance hole and insulate with

electrical tape. The best bowls to use do not have a lipped rim because the lip will create a point of

leakage. The dome seen in the illustration above produced 22 inch arcs!!!

The Classy Route:

To buy a metal sphere with a lipped bottom from

a manufacture may cost from 500 to 5000 dollars,

therefore the best route for making a VDG sphere is to

buy a stainless metal sphere in the form of a gazing ball

or garden globe. These are the

same metal spheres that your

grandma keeps in her back

yard. The price of the globe

is dependent upon the size

you seek with a 30 inch dome

being the largest on the

market.


To begin construction, mark the size of the hole you wish to make. Next, using a Dremel

with a metal grinding cut off wheel, slowly cut out the hole and then grid off any burs. Lastly,

insulate the edge with your choice of insulation of which I prefer to use edge trim that may be

purchased at Tap Plastic or Michael’s.

Another technique of insulating the

bottom of the sphere would be to use a door edge

trim however, in order to do so, the sphere must

have a tight fit around the VDG tower. In this

process, as seen in the illustration to the right, I

made a tight fit with the dome and then the edge

trim is wrapped directly around the tower so that

the tube rest against the edging with a slight

amount of pressure. Lastly, to secure the edging,

I wrapped black electrical tape around it. Of the

two techniques listed, I have found both to work

just the same.

If you wish to significantly increase the

charging capacity of the dome, further wrap the

bottom with electrical tape to prevent leakage.

Proceed with absolute caution when testing!!!


Material Resources:

Frugal Route:

Cardboard Globe: Target (10 dollars)

Silver Paint: Your choice (3 dollars)

Bowls: Target

Classy Route:

Gazing Globe or Ball: 16 to 22 inch globe

http://www.krupps.com or research gazing globes on ebay

www.physicsplayground.com (please contact me at [email protected] for best price)

Edge Trim: Michael’s

http://www.tapplastics.com/


CONSTRUCTING A DISCHARGE SPHERE

SUPPORT SYSTEM:

The support system’s main purpose it

to hold the discharge sphere and combs in an

insulated environment. One of the biggest

mistakes that I made on my first VDG was

setting the support system on the inside of the

tower. The reason why this hindered the

design was that the charge was leaking back to

the belt. As seen in the illustrations bellow,

the aluminum bar stock is placed on the

outside of the tower with nylon hardware use

for bracing to help further insulate the system.

A wide variety of materials may be used for

the support system, with the most pragmatic

being aluminum due to its malleability. I

have yet to change my design for the support

system because of its functionality. The top of

the support system may be tapped for the bolt

used to stabilize the dome and the swinging

comb arm makes the static belt very accessible.

For the Combs, I highly recommend

wire form over any type of rigid material

because it allows for many points for coronal

discharge, in addition if the belt is to jump at

high RPM’s the wire form will not cause

tearing.

Materials and Resource:

Plumbing Tape or Aluminum Flat Bar: Home Depot or OSH (2 – 10 dollars)

Copper Comb: (Use Wire Form) Michael’s (7 dollars)

Metal Foil: OSH (5 dollars)



Spraying a Charge:

Some of the diehard VDG

enthusiast will take the extra steps as to install

a charged spray system that will in turn allow

the system to produce more current. This

charging process is done by placing a positive

charge on the bottom roller and negative

charge on the bottom comb to force feed the

electrons onto the belt. This may be carried

out using an 8000V Neon Sign Transformer

(NST) along with a rectifier to straighten out

the 60hz AC current to a pulsing DC current.

On this page is a schematic diagram for the

spray charge system.

From my years of experience, I

would only recommend a spray charge system

if you do not have a sufficiently operating set

of rollers, otherwise, you will be able to

produce more charge in a field induced by

friction than an artificially induced

environment. I have found that with a nylon

Teflon roller combo, I can produce at least

twice as much charge than a sprayed system.

On the other hand, if it is a humid day, the

VDG roller will not be able to naturally

produce the charge therefore a sprayed system

is crucial. A sprayed system may also be

advantageous because the current sprayed to

the belt may be controlled using a variac

giving that operates a full range from zero to

the maximum operating current. The current

may also be controlled by adjusting the speed

of the drive system as in a traditional static

charged system.


There are a variety of ways to design a

sprayed system depending upon how much

charge you would like to produce. The

current output is dependent upon how the

rollers are set up. Below is a list of roller

combinations for a sprayed system ranked

according to current output:

Top Roller Bottom

Roller

Output

Performance

(☺)

Teflon Nylon Wool

Coated in

Magnetic

Wire

☺☺☺☺☺

Teflon Aluminum ☺☺☺

Aluminum Aluminum ☺

The most current roller configuration

that I have used for my 1MV model was the

hybrid nylon wool coated (wrapped in

magnetic wire). This technique is appealing

because it creates the best of both worlds

because it invokes both the static properties of

the materials and the induced charge. Of the

two, the static charge takes the upper hand.

In the photos, though it is not

apparent, the wires are epoxied at various

locations and soldered to the axle. The

positively charged source was directed to the

bottom roller support system that was coated

in aluminum foil so that contact could be

made. When pursuing this technique, I

would first run the rollers with the belt

connected, minus the magnetic wire, in order

to press down the wool.


Perhaps the most alternative route of producing a VDG is to make a pelletron which is a device

that does not depend upon a static charging system but mini capacitors that are charged at the base

and then transport the charge to the dome. This form of charging in the presence of sulfur

hexafluoride is used for generators that produce 5 MV and more. Such equipment is obviously not

meant for the amateur science hobbyist, however that does not mean that you cannot dabble just a

little. Below are a few links pertaining to how the pelletron functions and simple homemade

pelletrons. Hope you enjoy!

Pelletron Resources

http://www.geocities.com/marktecson/pelletron.htm (Build your own)

http://www.youtube.com/watch?v=fNz5trXBZIg (Video of Homemade Pelletron)

http://www.pelletron.com/(Operation and Manufature)

Below is a schematic diagram for a chain belt VDG

Material Resouces:

Variac: Search on ebay for the best prices

High Voltage Diodes: Search on ebay for best

prices

Larger Bearings and Shaft Collars: Search on

ebay for best prices


Extra Resources:

~ Van De Graaf Generator Videos~ http://www.youtube.com/watch?v=vMpNXIZK5u8&feature=related ……………(Very Rustic Design)

http://www.youtube.com/watch?v=OyS5bZx1fns&feature=related ………………(Rustic Design)

http://www.youtube.com/watch?v=ecXmq71A5Xc&feature=related …………….(Miniture VDG)

http://www.youtube.com/watch?v=4szKjLsa5lY&feature=related …………………(Very Nice Design)

http://www.youtube.com/watch?v=lgCo8WqOQS8&feature=related …………..(Very Rustic Design)

http://www.youtube.com/watch?v=7qgM1A3pgkQ&feature=related ……………(Mythbuster’s

Generator)

http://www.youtube.com/watch?v=U2NmIVSX9OM&feature=related …………(Very Nice Design)

http://www.youtube.com/watch?v=I2G0IdTWGQU ……………………………………(How a VDG

Works)

http://www.youtube.com/watch?v=1qX6eUXpW5c&feature=related ……(Very Nice Design)

~Van de Graaf Generator Documents and Websites~ http://www.instructables.com/id/Be-a-Scientist%3a-Build-an-Electrostatic-Motor . Build

electrostatic Motors

http://www.sciencefirst.com/artcls/9.pdf#search='build%20graaf%20generator' ..(Building a Toy

VDG)

http://freespace.virgin.net/paul.z/VDG/vp1.htm#Van%20De%20Graaff.... (Beautiful Design)

http://www.physics.ucla.edu/demoweb/demomanual/electricity_and_magnetism/electrostatics/va

n_der_graaff_experiments.html .....(Experiments)

http://web001.greece.k12.ny.us/files/883/Van%20de%20Graff%20generator%20demonstrations

.pdf …….(Demonstrations)

http://www.metacafe.com/watch/2478358/van_de_graaff_demonstrations ...(Demonstrations)

http://www.waynesthisandthat.com/vandegraaff.htm ...(Types of VDGs and Arcs)

http://www.goldmine-elec-products.com/prodinfo.asp?number=C6917 …(The 90 dollar kit)

http://www.scribd.com/doc/2602893/Midget-Van-De-Graaff-Generator ....(Midget VDG)


VDG Operation Instructions for the

400KV & 700KV VDG: 1) When bolting in the aluminum dome

support system and tower, only slightly

snug the bolt otherwise you will crack the

acrylic.

2) Before placing on the belt and rollers,

rewash the belt and both rollers using

dish soap. Try to avoid getting water on

the bearings. When finished, dry a paper

towel.

3) To assemble the belt and rollers, it is

easiest to first place the belt on the top

roller and then proceed to attach the

bottom roller. Allow for about .5 to 2

cm of spacing between the rollers and

combs.

A VDG with a black bottom wool roller

will cause a negative charged dome and a

clear acrylic bottom roller will cause a positive

charge dome.

4) Turn the generator on without the dome

attached and feel the top support system

for sparks. If there are no sparks, blow a

hair dryer through the bottom opening

until it develops a charge. This may take

up to 10 minutes. Under optimal

conditions, there should be a continuous

stream of sparks consisting of 2 inch arcs

coming from the support system when

touched. If the VDG is still lagging,

allow is to run for about 30 minutes.

You will find the more you use the VDG,

the stronger it will operate.

5) Gently place the dome on top of the

support system and insert the nylon bolt

through the dome. This nylon bolt only

hold the dome in place.

6) The sparks should average about 12

inches, with max sparks at 24 inches. If

you are not getting 12 inch arcs, it could

be due to a variety of reasons such as

high humidity levels or sharp pointed

grounded objects in the vicinity that

create ion jets and pull the electrons

from the dome, hindering the VDG

from building a charge. Please refer to

trouble shooting. 7) If vibrations occur within the system you

may need to tighten the tension between

the roller bearing and tower by either

slightly prying out the axles or adjusting

the shaft collars.


Trouble Shooting: 1) Problem: Humid day. This will

decrease the voltage by half. That is why

they say we have good VDG weather

and bad VDG weather.

Solution: Blow a hair dryer through

the bottom of the VDG roller entrance

hole.

2) Problem: Dust particles on dome that

cause leakage.

Solution: Clean the dome after each

hour of use. Even small dust particles

will cause points of leakage. To see the

points of leakage, run the VDG with the

lights out and look for small blue ion

jets. Brush the ion jet away and the

VDG will produce rather large arcs. Be

very careful while trying this technique.

3) Problem: High mineral content in

water used to wash the belt. This will

completely shut the VDG off.

Solution: Try washing the system with

distilled water which may be purchased

at the grocery store.

4) Problem: Oil on belt and rollers. This

will shut the VDG off.

Solution: Wash the top and bottom

roller with soapy water.

5) Problem: Belt is not dry enough after

washing. This will shut the VDG off.

Solution: Blow hot air up through the

bottom of the tower while running.

6) Problem: Dusty belt. This will deter the

charge a little.

Solution: Clean the belt with soapy

water.

7) Problem: Pointed metal objects around

the VDG will cause it leak.

Solution: The VDG cannot be around

pointed objects because they will

prematurely pull charge from the dome

and not allow it to build to its

maximum potential. Keep the VDG

located in open space.

8) Problem: Belt begins to rub on the

combs at very high speeds.

Solution: Once the belt develops a large

amount of ware, it will loosen and

possibly brush the combs during

operation. This will indicate that it is

time to change the belt. These belts are

made from a latex material and will

break down in UV light, therefore when

finished using the VDG, take off the

belt and place it in a dark location.

These belts should last a very long time

if stored correctly.

VDG Maintenance: 1) Do not allow the belt to come in contact

with the combs during operation in order

to maximize the belts life

2) Latex will oxidize when in the presence of ozone or UV light. The ozone is inevitable

due to the voltage produced however the

UV will inflict a significant amount of

damage over time, therefore always store

the belt in a dark place when not in use.

3) Never clean with alcohol or acetone due to sever cracking of the acrylic.

4) The VDG belt and rollers may be cleaned with dish soap and water. Try to avoid

water contact with the bearings.

5) All parts of the VDG charging system (dome, belt and rollers, and tower should

be cleaned every 2hours of run time.

VDG Safety: 1) VDG’s should not be used around people

with heart condition or pacemakers.

2) Be careful not to make items that will act as high voltage capacitors. The current

from the VDG’s are fairly safe, however

when the current is allowed to store at

such high voltages they can become lethal.

3) Larger VDGs over 300KV will produce welts from prolong exposure to arcs.

4) Keep away from all electronics and outlets that are connected to them.

5) Operate in well ventilated areas due to the ozone produced.

6) Avoid making human chains.

Experimenter Ideas: 1) Insulate yourself and touch the VDG while

pointing at various objects in the room to

place a charge on. When done to a

chandelier it will cause arcs within the chain.

2) Insulate and charge yourself with

700,000V and then step off of the insulated

material and experience the feeling of your

body just electrically shut off from the field.

3) Wrap the bottom roller with a metallic

coating and force feed it with a

15,000V charge to induce higher currents.

These VDG are designed to do so. (Very

Dangerous)

4) Wrap a balloon in foil and then hang it

from a string attached to the ceiling so that it

can touch the dome. Turn on the VDG and

watch the outcome.

5) Take two pie pans and attach a positive

and negative lead from the VDG to each pan.

Next place small foil leaves between the pans

or string. Very cool to see!

6) Bring fluorescent tubes near the VDG.

This makes a great visual for examining

electric fields. The tube will begin to glow at

5 feet away.


7) Charging Lynden Jar and high voltage beer

cup capacitors (Dangerous!!!)

8) Place pie pans on the generator and watch

them fly.

9) Static electricity motors and ion jets.

10) Just insulate yourself to feel your entire

body light up from being immersed in the

700,000V electric field. ABSOLUTELY

AWESOME!!! However, if someone touches

you....ouch! This seems to be my students

favorite thing to do especially with the x-large

770KV VDG where they will develop 8 inch

arcs coming off of them when approached.

Yes, this is a crowd pleaser!!!

All of these demos are extremely fun and exciting to do, however as in every situation when

experimenting, please consider all dimensions of safety. Use at your own risk.