Finally building a big van de graaff

[moody07747]

ive been meaning to build one for some time now but never got to it....built a tint one but im goin for a big, 5 foot tall one

top roller: nylon from old bed frame wheels
bottom roller: silicon tape on a motors drive roll
motor: blower from an over the stove microwave....knew that would be useful some day lol

this photo link will update when i add pics so ill only post it once

**broken link removed**

 

[Someone Electro]

The hard to get part is the metal ball for the top.

Hearing the word van de graaff alwys reminds me of the mithubusters messing whith it (at that static canon mith).

 

[moody07747]

i was watching mythbusters on tivo and thats where i got this into my head again

best show ever

that thing made some nice sparks

as for the metal ball i will get 2 bowls...aluminum and cut off the rims....i will then tig weld them togeather

 

[Someone Electro]

If you want nice sparks make an tesla coil.

They make arcs in to mid air.

 

[moody07747]

i find those hard to build and expensive

are those dangerous sparks?.....i dont know much about them

 

[Someone Electro]

Dont think so.
But it probobly dosent feal good to get zaped by one.

And yea they are prety complicated.They can light neon and flurectent bulbs from a distance.

Also teslas output high freq. AC like an TV flyback.Thats why they can make arcs in to nothing but air.

The van de graaff outputs DC.So it can staticly charge stuff.

 

[Dr.EM]

Cool, this looks like a great fun project. I have a big 12vdc motor from a battery powered lawnmower around (yes there is/was such a thing), its very powerful, but so many RPM.

 

[moody07747]

is there a way to find the rpm of a motor w/o any spec plate?

what would be the limit on the rpm got a van de graaff

everyone says to keep the speed up for faster charging...

 

[akg]

is there a way to find the rpm of a motor w/o any spec plate?

photointerrupter??

 

[Someone Electro]

There is an xheap method. Stick an pice of paper to the shaft and then put somting close to the paper hits it.Then you an microchopne close and meshure the freq. of that sound the freq should be the RPM.

 

[akg]

There is an xheap method. Stick an pice of paper to the shaft and then put somting close to the paper hits it.Then you an microchopne close and meshure the freq. of that sound the freq should be the RPM.

will that work for high rpm :?: :roll:

 

[moody07747]

not sure....this motors really fast.....i saw an rps light thing on mythbusters....got to be expensive

 

[moody07747]

isnt there a calulation to find RPM?

i can get amperage, voltage, and wattage from a meter i have and as soon as i figure out my new electrician calculator ill have HP

 

[Nigel Goodwin]

isnt there a calulation to find RPM?

Not really, and any calculation wouldn't be accurate anyway, the speed will vary with a lot of external factors.

I presume that there's probably an optimum speed for a 'van de graaf'?, if you go faster than that efficiency will probably drop?.

Anyway, what are you using for a belt?.

 

[audioguru]

Look at this project that makes one million volts DC:
**broken link removed**

The sparks are four feet long!

He had to use four flyback transformers in parallel to provide the voltage multipliers with enough power. :lol:

 

[Someone Electro]

But first you need lots and lots of HV caps.

 

[Someone Electro]

Heres some sparks

 

[Someone Electro]

Some more

 

[moody07747]

isnt there a calulation to find RPM?

Not really, and any calculation wouldn't be accurate anyway, the speed will vary with a lot of external factors.

I presume that there's probably an optimum speed for a 'van de graaf'?, if you go faster than that efficiency will probably drop?.

Anyway, what are you using for a belt?.

im trying to get some latex strips to make a belt...wonder if a rubber band would work, never seen one 5' long before

i was going to cut up latex gloves but i would have to cut up like 30 of them to use and that wont work

so im still working on a belt

maby some latex surgical tubing 1/2" OD split down the middle would work

 

[moody07747]

those look like dangerous sparks