The other factor is that typically you'll get early breakdown / brush discharge from a pointed wand or a hand with hairs, whilst with a toroid the topload will get to a much higher voltage (so higher energy) before breakdown.
You can see this clearly if you replace a wire ended wand with one with a 6" sphere on the end. The latter gives much meatier but less frequent "cracks" whilst the former will tend to give softer crackles.
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Bert Hickman
Sent: 25 August 2015 21:55
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Toroid & VDG
Hi Doug,
By putting the grounded toroid in close proximity to the VDG sphere, you effectively increased the capacitance of your VDG topload versus its surroundings. A simple capacitor is nothing more than two conductors (i.e., the sphere and toroid) separated by an insulating medium (air).
Depending on the geometry and orientation of the sphere and toroid, it's quite possible that you increased the effective capacitance of the sphere by a factor of 2-4, and perhaps more. Assuming that the VDG charged the sphere to the same potential, you had 2-4X the stored energy as when you just had the isolated VDG sphere. Since this energy is mainly concentrated in the electrical field between the toroid and sphere, you'll see significantly higher energy "capacitor discharges"
when you short-circuit the system.
Best wishes,
Bert
--
Bert Hickman
Stoneridge Engineering, LLC
http://www.capturedlightning.com
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World's source for "Captured Lightning" Lichtenberg Figure sculptures, magnetically "shrunken" coins, and scarce/out of print technical books
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Doug wrote:
> I have been experimenting with my 14" VanDeGraaff and found something
> interesting. I made a Toroid from 4" semi ridged vent pipe it is 20"
> dia. and has no center plate, it is just a ring. With the VDG running
> full bore the spark to the regular discharge wand or my hand is
> tolerable and not to fat, but when I pick up the toroid ,[which is not
> connected to the VDG] and get it within about 4" from the VDG sphere I
> receive a substantial jolt and a very fat loud spark between the
> sphere and toroid, quite uncomfortable to hold! It would seem that the
> toroid is acting as a capacitor just being somewhere near the sphere.
>
> On 8/25/2015 11:30 AM, David Boyle wrote:
>> I made a large vdg for the Calgary Science Center in the early 80's.
>> You can see some pictures on my website:
>>
>> http://h2g.ca/miscellaneous.html
>>
>> We found that the problem with most rubber belts is that they are
>> doped with carbon black to make them less of an insulator and to
>> reduce sparking. It wasn't until we were given a true belt made by
>> the Van de Graph corporation that we got really good sparks.
>>
>> We charged the belt with a 10kv dc supply from a photocopier. The
>> re-entrant edge at the bottom of the sphere is very important. We
>> found a metal spinning shop that made our large sphere for $400. We
>> needed a crazy strong motor - 1 hp - because driving a 10kv belt into
>> a 600kv sphere is hard work.
>>
>> Calgary is very dry so it worked well most of the year. High humidity
>> and smoke filled rooms would really cut down on the output.
>>
>>
>> On 15-08-25 10:21 AM, John Nelson wrote:
>>> Thanks for sending those. You have given me some ideas that I can
>>> work on. Instead of bowls for the sphere I use garden gazing balls.
>>> They come in many sizes and look great, but the same old problem of
>>> the opening is there. I can see that you have tried to cut down on
>>> the corona like I have using rings. I tried rings made out of
>>> copper tubing and plate aluminum and still get corona discharge. I
>>> have tried to turn the opening upward like the ones you can buy, but
>>> have not been successful. The main problem is that the gazing balls
>>> are made out of stainless and the professional ones are aluminum.
>>> Aluminum is much more malleable and is easy to shape. There is a
>>> company that will form any size ball up to 36 inches and will also
>>> form the opening that is turned upward. I contacted them and they
>>> only want $4000 to make one. Might as well be 4 million to me. I
>>> would make a nice display though. I keep on entering the lottery,
>>> but so far I have only won one dollar. 3999
>> to go. A
>> s far as the belts, I have been using vinyl strips that is used in
>> upholstery. Vinyl does not work on rounded rollers as I will not
>> conform to the round shape. It is too stiff. I got some exercise
>> latex straps, cut them to length, fastened the ends together and
>> tried to run them, but I think the material is too thin as it did not work.
>> I could use some heavier latex, but I don't know where to get it.
>>> As far as Tesla coils are concerned, I have made several, the first
>>> one in high school back in the 50's. I got a kit from Tesla works,
>>> (Alan) and it works OK, but I wanted bigger. I then got a solid
>>> state one from Dan McCauley (Eastern Voltage Research), but it does
>>> not work and they can't fix it. $2100.00 down the tubes. It now
>>> just collects dust in my garage. I contacted the man in Oklahoma
>>> that built the very large one he runs outdoors, but he won't release
>>> any information on how it is built. You can see it run if you
>>> search "very large Tesla coil".
>>> I have a larger VDG in partial assembly, but am waiting on how to
>>> solve the belt walk issue and the corona issue as well. A search
>>> for thicker latex is next, I guess. I can machine any parts I need
>>> as I have a machine shop.
>>>
>>> Thanks
>>>
>>> John
>>>> -----Original Message-----
>>>> From: msweeney23@xxxxxxxxx
>>>> Sent: Mon, 24 Aug 2015 20:54:02 -0500
>>>> To: tesla@xxxxxxxxxx
>>>> Subject: Re: [TCML] Seaching for Mike Delosier
>>>>
>>>> Here are some videos from my older models. I did build a six foot
>>>> model with a 14inch sphere running at 10x power delivery. It was a
>>>> beast but caused me much trouble due to extremely high electrical
>>>> field potentials around the sphere opening. I used steel Ikea bowls
>>>> and they just wanted to buckle when I radius them. I have made a
>>>> few corona rings that help, but I'm not so good at joining the two
>>>> ends and soldering a nice smooth joint =(
>>>>
>>>> All my devices are completely home built including PVC form (well I
>>>> purchased the PVC), belts, rollers, corona tubes, comb assemblies
>>>> and various discharge rods. Of course the motor and hemispherical
>>>> bowls were items I could not make myself. Note all devices are
>>>> extremely quiet- I used high quality bearings everywhere and drill
>>>> press for accuracy.
>>>>
>>>> My 6 foot high-power version was insane throwing off continuous
>>>> charges up to 40 inches in length which seems way more than
>>>> possible using a 14inch sphere.
>>>>
>>>> I have cannibalized my large generator and am building two 3 foot
>>>> dual-pole positive/negative generators in an attempt to 'double'
>>>> the voltage gradient. We shall see!
>>>>
>>>> Next project is a new Thunderstorm built very high quality and full
>>>> self-contained re-pumping. After that it's either a giant Van De
>>>> Graaff or a tesla coil. I can build belts up to 6inches wide and
>>>> many 10's of feet long, but I cant yet built large spheres over
>>>> 14inches =(
>>>>
>>>> https://www.youtube.com/watch?v=Fb-tWeJ3Z0U
>>>>
>>>> https://www.youtube.com/watch?v=ABKCGXuJDlw
>>>>
>>>> https://www.youtube.com/watch?v=eRsl6rs2cEo
>>>>
>>>> https://www.youtube.com/watch?v=Hs3K0C1CeVk
>>>>
>>>> https://www.youtube.com/watch?v=O3CSO9fIQu0
>>>>
>>>> https://www.youtube.com/watch?v=o8ZHrSiVEXs
>>>>
>>>> https://www.youtube.com/watch?v=v6KdIKDr4Tc
>>>>
>>>> https://www.youtube.com/watch?v=em67iXD5-ms (voltage specified is
>>>> likely
>>>> incorrect)
>>>>
>>>> https://www.youtube.com/watch?v=I37C5qWRi3A (voltage specified is
>>>> likely
>>>> incorrect)
>>>>
>>>> https://www.youtube.com/watch?v=cQTRKiYsCEc (just for fun).
>>>>
>>>> Any questions please let me know, I'm certainly no expert but have
>>>> learned a few tricks to provide excellent charge rates, smooth
>>>> operation, and huge reduction in expensive (my 6ft long 2ft wide
>>>> belts are only $3 each and work better than any other I have
>>>> tried).
>>>>
>>>> Thanks!
>>>>
>>>>
>>>> Matt Sweeney
>>>>
>>>> On Sat, Aug 22, 2015 at 9:54 PM, wt5y <wt5y@xxxxxxxxx> wrote:
>>>>
>>>>>
>>>>>
>>>>> Cornel dubilier 942c20p15k-f .15uf 2000v caps can be had $4.99 ea
>>>>> from
>>>>> easternvoltageresearch.com
>>>>>
>>>>> Sorry don't know mike. Someone else may.
>>>>> If you don't mind can I see some of the van DE Graaf you've made
>>>>> ie website,youtube? And what are Kelvin thunderstorm project,
>>>>> will Google it but never heard of it.
>>>>>
>>>>> John cooper WT5YWt5y@xxxxxxxxx
>>>>> Sent from my Samsung GALAXY S5™, a Cricket 4G LTE smartpho
>>>>>
>>>>> -------- Original message --------
>>>>> From: Matthew Sweeney <msweeney23@xxxxxxxxx>
>>>>> Date: 08/22/2015 16:10 (GMT-06:00)
>>>>> To: tesla@xxxxxxxxxx
>>>>> Subject: [TCML] Seaching for Mike Delosier
>>>>>
>>>>> Hello, I recently joined this mailing because I didn't know it
>>>>> existed.
>>>>> I
>>>>> don't make tesla coils any more but I produce large Van De Graff
>>>>> generators and simple kelvin thunderstorm projects to amuse myself
>>>>> and keep my nephews amazed.
>>>>>
>>>>> Anyway I visited my local Axe-MAn today and learned that they have
>>>>> a customer named Mike Delosier who lives in minnesota and has
>>>>> some impressive coils.
>>>>>
>>>>> I am hoping very much to contact Mike but I have not been able to
>>>>> find his e-mail address. I don't see any recent posts with his
>>>>> name so maybe he is not a member anymore?
>>>>>
>>>>> So, if anyone knows him, I would be delighted to send him an email.
>>>>> Alternatively he can send ME an e-mail as to be less intrusive:
>>>>> msweeney23@xxxxxxxxx
>>>>>
>>>>> I did build several decent coils over 20 years ago with home made
>>>>> plate class capacitors and a horribly inefficient stationary spark
>>>>> gap. I didn't have any protection circuitry in place but somehow
>>>>> my HV transformers survived, however my capacitor eventually
>>>>> exploded.
>>>>>
>>>>> Now I have three perfect 15,000v 250ma NST's just sitting waiting
>>>>> for a purpose - so I think it's time to start planning a new
>>>>> build. I have never built a proper solid state coil and am
>>>>> considering this option. But a traditional rotary spark-cap coil
>>>>> with high-voltage capacitors would be much less effort. The
>>>>> secondary will be 5 Feet and using enameled magnet wire.
>>>>>
>>>>> I'm looking for good sources of (cheap) high voltage capacitors
>>>>> and much info on recent developments in the field. I especially am
>>>>> interested in inductor usage to prevent spikes back to the NST.
>>>>> Also I need some advice on secondary wiring cable is there a
>>>>> preferred variety for recent coils?
>>>>> Ill use copper tubing for primary. I may also build my own rolled
>>>>> capacitors but I'm thinking obtaining newer HV caps in a bank may
>>>>> actually be cheaper.
>>>>>
>>>>> If there other members in the Minnesota/Wisconsin I would also
>>>>> like to connect. I'm desperate to find a powerful coil to blow my
>>>>> nephews minds
>>>>> =)
>>>>>
>>>>> Thank you for any help you can provide. I'll be reviewing the
>>>>> lists looking for new info also but direct contact for any
>>>>> suggestions would be welcomed.
>>>>>
>>>>> Regards,
>>>>>
>>>>> Matt Sweeney
>>>>> _______________________________________________
>>>>> Tesla mailing list
>>>>> Tesla@xxxxxxxxxx
>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>> _______________________________________________
>>>>> Tesla mailing list
>>>>> Tesla@xxxxxxxxxx
>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>
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