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colin heath

Sun May 21 2006, 02:30PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Hi All,
I am just finishing a VDG Generator for a friend of mine. I have attched a pic of it nearly done. I now have it running but only get 1/2" or so spark. Now at present it's triobolectric charged rather than sprayed but will be sprayed when finished. I have teflon top roller and steel bottom roller. I have the roller bolted striaght on the motor shaft which is grounded through the motor. Will this work? Also if i run like this should i have roller grounded and spray the belt further up?
Any help much appreciated
Cheers
Colin

teravolt

Sun May 21 2006, 07:55PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

when I built my VDG I used white neoprean for a belt and a soft polyethaline roler. I don't it maters what material is on the top or bottom accept output polerity. the belt type MUST not conduct in any amount or this will drain the charge away. What are you using for a belt. N.B.

colin heath

Sun May 21 2006, 08:05PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

hi there,
Thanks for the reply. I am using an excersise band for belt which is white rubber. I looked on the triboelectric series and the steel roller will be a peoblem as it has no charge.
I will make a nylon roller tomorrow which is opposite of teflon so should work well.
Cheers
Colin

Marko

Sun May 21 2006, 08:23PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I think heard that neoprene is best for a belt, the stretchy and foamy thing they make wetsuits of. (and has some other uses).
It's usually grey/black and smooth when raw (white one was probably colored)

Maybe some shops that tailor it would give some 'waste' to you if you ask nicely.

Nik

Mon May 22 2006, 12:02AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I think you will have to isolate the roller from the motor (ground) to get good results. My VDG has a grounded comb under the bottom roller (the roller is metal) and a PVC top roller. This set up has givin me 3-4inch sparks on a dry day but they are usualy 1 - 1.5 inches. A word of warning, once you get your VDG working really well be wary or objects that can act like a capacitor (mainly yourself). Good luck!

ReddyK

Mon May 22 2006, 04:47AM

Registered Member #92 Joined: Thu Feb 09 2006, 03:11PM
Location: Indian Trail, NC
Posts: 39

Colin,
I would suggest that you cover the lower roller with wool felt. It will help isolate the roller from the motor and has the right tribo effect with the belt. Do you have a lower comb? I don't see one in your picture. I have always done really well with a similar setup, 16" spark on a winter day was about tops.
Hope it helps,
Steve

colin heath

Mon May 22 2006, 10:49AM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Hi All,
Well i have been looking at the triboelectirc tables and it appears steel has zero charge so will be no use! I have today made an acetal roller (hoping similar postion on chart to nylon).
This will isolate the roller. I have made cockcroft today so will have 12KV to spray the belt with. Will this work though while raining outside or will even an excited VDG fail then?
Thanks for the help
Colin

Dr. Drone

Mon May 22 2006, 07:53PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

colin heath

Mon May 22 2006, 08:14PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Hi Chris,
I have built one of those but beefed up

It puts out 12KV at a good current(will have to be limited for VDG). I ran today but it arced to the grub screws in roller and caused major probs. Have now insulated these and will try tomorrow.
Cheers
Colin

cbfull

Tue May 23 2006, 12:28PM

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

Most of the people I have chatted with have been very pleased with the results of using a teflon/nylon roller arrangement. If you are using a HV belt charger, then the bottom roller needs to be metallic, and electrically insulated from the motorshaft.

In the photo it looks like your rollers are pretty long and narrow. This generally limits the belt speed to a relatively low value. The belt will tend to fly right off of narrow pulleys the faster it runs.

You will get a world of difference by using a belt that has fabric reinforcement, like neoprene conveyor belt material, thinner is generally better because it allows higher speeds. That's what mine is made of, and I can run it many times faster than my previous gum rubber belt. McMaster-Carr has some great choices of materials for making a belt.

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