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David S
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Posted on Saturday, March 12, 2005 - 5:09 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

im making the mini Van de Graaff generator

im trying to find out what to use for a bottom pully that mounts on the motor

im useing a small hair dryer motor on a light dimmer circuit and am useing 1" PVC



the problem is that i dont know what plastic item to use for the bottom pulley

i want it to be solid so i can drill a hole in the center for the motors' shaft and i also want to cut a notch in the plastic pulley to keet the rubber band in place

any ideas on what to get for a plastic pulley
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David S
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Posted on Monday, March 14, 2005 - 8:38 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

well i jused a piece of wood and covered it with scotch tape

the thing worked for about 2 minutes then
no more shocks

ive been messing with the brushes but still nothing


i think ill just upgrade to a really big Van de Graaff

i saw a small tabletop one in action and was not happy with the results so im making a 4 foot one



any ides on where to get parts?
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David S
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Posted on Tuesday, March 15, 2005 - 10:34 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

here is a mod for the small van de graaff

i made a plastic pulley and covered it with scotch tape

the top pulley is the fuse as in the orgignal plan

bugger pipe was used but the pulley was too bug so i had to cut up some 90 bends to make the new motor mount


so far i am getting 1 1/2" sparks and the generator charges fast
(fast = a shock every 1/2 second)

here is a pic of it



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Simon Quellen Field (sfield)
Senior Member
Username: sfield

Post Number: 278
Registered: 12-2004
Posted on Friday, April 15, 2005 - 9:20 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Nice!
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Anonymous
 
Posted on Friday, May 6, 2005 - 9:23 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

i am interested in making a small table top van de graaff generator, but have no plans, so if you have any please post them here and i will check back, lots of detail if possible.
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Simon Quellen Field (sfield)
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Username: sfield

Post Number: 381
Registered: 12-2004
Posted on Friday, May 6, 2005 - 11:36 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

The plans are in the "Fun with High Voltage" section.
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Kevin H
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Posted on Tuesday, May 10, 2005 - 7:47 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Ok...here's the deal...i haven't yet assembled my van de graaff, but i was having trouble when I temporarily assembled it to test it...the rubber band kept moving around so I used hot glue to make little rails on the edges of the glass fuse tube...when I upgraded to a wider but smaller rubber band, I found that it rides up on the little rails and wants to stay there...since these are at the edge and not the center, I'm going to melt the original rails and replace them with a central one...but here's the dilemma: I don't know what effect the hot glue will have on the generation of static...will it still generate static even if the rubber band does not touch the glass but rides on the rail? I really want this to work and have already had one disappointment: after I had finally soldered the wires to the motor, I tested it and it didn't work (it had worked the day before)!!!GRRR I took it apart but im just going to replace it with a remote control car motor (i think probably 6 volts [it had a 6 volt battery])which was used for the steering of the front wheels. Its definitly not flimsy as the motor that died on me (which came from a 2 AA battery powered fan), but I want to know whether a 9 volt battery will kill the battery (and approx. how long) b/c the 2 AA's definitly aren't cutting it... Please help!!!
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Kevin H
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Posted on Tuesday, May 10, 2005 - 7:58 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Oh, one more thing... If i place a grounded object near the can (or just the wire that should go to the can) will it make a constant lightning/spark discharge like tesla coils? What about putting the bottom brush near the can instead of grounding it...won't there be sparks jumping from the can to the wire?

I just want to be able to see a CONSTANT spark (or lightning-ish thing) b/c I want this to be as visually appealing as possible and being able to see the static power without getting shocked (by touching it)...I know that it will make sparks to a grounded object every so often, but is it possible from a generator this size to achieve the voltage necessary to generate a constant spark?
Please respond ASAP...I'm backlogged in work and would like to know exactly what to do come the weekend (or any free time)...
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Kevin H
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Posted on Tuesday, May 10, 2005 - 8:00 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Sorry aobut all these multiple posts...but...Thanks.
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Jonathan Grova (Jonathan8388)
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Username: Jonathan8388

Post Number: 1
Registered: 5-2005
Posted on Saturday, May 21, 2005 - 3:34 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

i have been using my van de graff generator for a while now and i must say that it is working well(except for the fuses breaking). i am able to get 3/4 inch sparks to my finger at the rate of about 1 spark per second. i was looking at the messageboards on your website yesterday and i came across someone who made a pulley for the motor of the van de graff generator and was able to get 1 1/2 inch sparks at the rade of a 1/2 a second each spark! i then tried to make my own pulley by wrapping multiple layers of scotch tape around the shaft of the motor, and this improved it a little bit and gave me 1 inch sparks at the rate of 1spark per 1/2 a second! my question is: why would making a pulley around the motor shaft improve the performance of my generator? would there be a different material instead of tape that i could use for the pulley to improve the generator more?
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Simon Quellen Field (Sfield)
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Username: Sfield

Post Number: 429
Registered: 12-2004
Posted on Saturday, May 21, 2005 - 3:49 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Looking at the triboelectric series in the VDG section,
I would say that glass pulleys and a silicone rubber band
might get the best performance. You could try making the
band by cutting a loop from a nylon stocking and then coating
it inside and out with a thick layer of silicone caulking
from the hardware store. Or wrap some waxed paper around
a jar, and then paint a band of silicone rubber around it,
and apply another layer of waxed paper over that, to make
both surfaces smooth. When it dries, you have a silicone
rubber band.

Once you have a silicone rubber or teflon band, you might
try nylon pulleys. Then you wont have fuses that break.

PVC pulleys and a nylon band might also do well. Or, if
you want the same level of performance but without breaking
fuses, try a rubber band and PVC pulleys.

The triboelectric series is your guide to optimizing the
performance.
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Jonathan Grova (Jonathan8388)
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Username: Jonathan8388

Post Number: 2
Registered: 5-2005
Posted on Saturday, May 21, 2005 - 4:02 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

i have been using my van de graff generator for a while now and i must say that it is working well(except for the fuses breaking). i am able to get 3/4 inch sparks to my finger at the rate of about 1 spark per second. i was looking at the messageboards on your website yesterday and i came across someone who made a pulley for the motor of the van de graff generator and was able to get 1 1/2 inch sparks at the rade of a 1/2 a second each spark! i then tried to make my own pulley by wrapping multiple layers of scotch tape around the shaft of the motor, and this improved the performance of the generator and gave me 1 inch sparks at the rate of 1spark per 1/2 a second! my question is: why would making a pulley around the motor shaft improve the performance of my generator? would there be a different material instead of tape that i could use for the pulley to improve the generator more?
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Jonathan Grova (Jonathan8388)
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Username: Jonathan8388

Post Number: 3
Registered: 5-2005
Posted on Saturday, May 21, 2005 - 4:04 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

oops, sorry for the double post. i tried to delete it, but it wont let me!
my question is would the pulley that i made around the motor be the cause in the better performance of my generator? also, how could i make a nylon pulley? would bigger pulleys give better performance? also what material would you choose as the BEST material for the pulley ON THE MOTOR?

sorry fotr all of the questions. answers would be greatly appreciated



(Message edited by jonathan8388 on May 21, 2005)
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Anonymous
 
Posted on Monday, June 27, 2005 - 8:28 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Does a Van de Graff generator have any useful purpose besides being a toy? I've heard that they produce high voltage at extremely low current, making the power generated very small (too small to do anything useful with). Is that true? I also read they are viewed as a constant current source if you were to connect them to a load. Is that also true?

On a side note, I was thinking... would it be possible to connect a wire with a spark gap to the metal top (in this case a can) and connect the other side of the spark gap to a capacitor. So that when the charge gets to a certain point it discharges into the capacitor and in effect charges the capacitor. Then you could use another spark gap to discharge the capacitor into a load when the capacitor reaches a certain value. This might make the generator more useful. Especially, if instead of using an electric motor, you used a small wind mill or water wheel... Does this seem possible?

Thanks
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Bill beaty
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Posted From: 128.95.172.173
Posted on Tuesday, August 23, 2005 - 1:31 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

> Does a Van de Graff generator have any useful purpose besides being a toy?

The first large VDG built by Robert VandeGraaf was used to power an
atom smasher at MIT. Here's a drawing:
http://www.mos.org/sln/toe/diagrams/rhcutaway.jpeg

Today VDGs are used in physics lab, go search on "Pelletron"
http://www.google.com/search?q=pelletron+voltage


> I've heard that they produce high voltage at extremely low
> current, making the power generated very small (too small to
> do anything useful with). Is that true?

A commercial VDG such as used in a classroom can put out 250,000
volts at a few millionths of an ampere. Wattage is volts times
amps, and 250KV times 10 uA gives 2.5 watts. Two and a half watts
would light a dim flashlight bulb, or light a whole bunch of LEDs,
or it could operate the electric motor in a toy car. But first
you'd have to figure out how to step the voltage down about fifty
thousand times!

> I also read they are viewed as a constant current source if
> you were to connect them to a load. Is that also true?

Yes, the current from the VDG is always about the same, but
the voltage changes drastically depending on the load. If you
put some sharp needles on the top of your VDG, the current will
be the same, but the voltage will decrease greatly.
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Justin (Commander_bob)
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Username: Commander_bob

Post Number: 3
Registered: 10-2006
Posted on Friday, October 20, 2006 - 8:23 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I just made my VDG and I did it as it said in the High Votage section but it did not work. I was wondering if it mattered it the inside of the can was a little wet or that the rubber band rides on the side of the motor?
Thanks
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Justin (Commander_bob)
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Username: Commander_bob

Post Number: 4
Registered: 10-2006
Posted on Friday, October 20, 2006 - 8:27 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Also for the bottom pully I used electical tape and a metal screw head so it would not fall off. If this is a problem than what else could I use?
Thank You
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Justin (Commander_bob)
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Username: Commander_bob

Post Number: 5
Registered: 10-2006
Posted on Monday, October 30, 2006 - 9:29 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I decided to upgrade to a larger VDG after making the desk top one. I get about 2" sparks about two every second. I used PVC 1" attached to the motor and a very large rubber band from office depo I think. For the top roller I used 3 nylon spacers. Two large ones are on each side of a smaller one so the rubber band stays in the middle. For the can I got a lagrge Foster's. The motor I got from a old fan from a gradge sale for 50 cents. Here is a picture.VDG
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mike (Mike11298)
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Username: Mike11298

Post Number: 1
Registered: 10-2006
Posted on Friday, December 15, 2006 - 6:48 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

hi all,
just looking for some ideas in finding or making a nylon pulley. Any help is greatly appreciated - Thank you!
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surendra murthy.c (Science_boy)
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Username: Science_boy

Post Number: 5
Registered: 6-2007
Posted on Thursday, August 9, 2007 - 9:26 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

my vdg was a success, but tell me whether the brushes should touch the rubber band or not.
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Simon Quellen Field (Sfield)
Senior Member
Username: Sfield

Post Number: 1760
Registered: 12-2004
Posted on Thursday, August 9, 2007 - 10:12 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Not.

Please don't post the same question in three places.
Once is enough. We see them all.
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surendra murthy.c (Science_boy)
Junior Member
Username: Science_boy

Post Number: 7
Registered: 6-2007
Posted on Friday, August 10, 2007 - 10:34 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

i am sorry, i needed a quick reply.anyway thanks my vdg works better today.i connected it to the franklin bell as mentioned in the plan but it did not work.what are the possible problems that may be taking place
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surendra murthy.c (Science_boy)
Junior Member
Username: Science_boy

Post Number: 9
Registered: 6-2007
Posted on Saturday, August 18, 2007 - 1:17 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

will the rotatory high voltage motor work on the vdg?
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Joshua Lim (Vdg)
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Username: Vdg

Post Number: 1
Registered: 4-2008
Posted on Wednesday, April 30, 2008 - 5:26 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Mr. Field,
How does a electron gun work?
I am thinking of making one at home to collect high voltage. If you concentrate the beam of electrons with some magnets, would you get a spark?
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Joshua Lim (Vdg)
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Username: Vdg

Post Number: 2
Registered: 4-2008
Posted on Wednesday, April 30, 2008 - 5:27 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Sorry for posting in the vdg section, should have posted somewhere else.
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Simon Quellen Field (Sfield)
Senior Member
Username: Sfield

Post Number: 1895
Registered: 12-2004
Posted on Wednesday, April 30, 2008 - 11:23 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

"http://www.google.com/search?q=electron+gun".
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Aaron (Sciencenerd)
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Username: Sciencenerd

Post Number: 1
Registered: 8-2010
Posted on Thursday, August 12, 2010 - 1:42 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

could i use pvc rubber as the belt? thanks
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Patrick (Firewire)
Senior Member
Username: Firewire

Post Number: 145
Registered: 12-2007
Posted on Friday, August 20, 2010 - 10:48 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I am using those thick rubber bands used in slingshots, is it has almost the same width of the glass fuse I have. also. Also, the issue about the rubberband moving left or right, or trying to stay at one side is due to a mis-aligned axel for the fuse.

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