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Old 7th Jul 2020, 9:01 pm   #41
Ed_Dinning
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Default Re: DIY X-Ray & Auto Jigger transmitter

Hi Sing, try a plasma globe next; quite simple to make and nothing too dangerous in their construction and use

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Old 7th Jul 2020, 9:43 pm   #42
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Ed I have not messed around with high voltage (e.g. 20KV-500KV) for a long time. These days i focus my attention to amplification of micro volts of RF signal and the ever confusing antenna and transmission line theory. I did fancy building a Lord Kevin's water droplet electrostatic generator, Geiger counter and a Wilson cloud chamber...
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Old 8th Jul 2020, 6:52 pm   #43
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I still have a working 1920 Wimhurst electrostatic machine. It wont have enough juice to produce X-ray for sure. You can create very weak x-ray using 20KV TV flyback transformer with certain type of valve tubes for sure.
Does your 1920 Wimshurst machine have leyden jars fitted? They may increase the current capacity somewhat. I my electro freak period ( mid teens 1954 1956 ) Lash up leyden jars increased the discharge diameter about tenfold I estimate
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Old 8th Jul 2020, 7:46 pm   #44
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Yes, it has a pair of original Leyden jars using metal chains as conductors. I wish i can take a photo of it but I boxed it up in my storage locker along side mountain of junks. I purchased it from an antique shop in Convent Garden,London paying 250 back in 1990. The machine was made in the UK. It can produce up to about 5 inches of spark under dry weather condition.

I also have a working motorised, Van der Graaf generator made by Griffins in the UK. It can produce about 4 foot of spark. I dont understand why I liked high voltage and electrostatic so much, maybe i got the excitement from the sparks. I was fascinated by lightning in my childhood as I witnessed some bad ass lightning storms.
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Old 9th Jul 2020, 12:27 am   #45
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Yes, it has a pair of original Leyden jars using metal chains as conductors.

I also have a working motorised, Van daar Graaf generator made by Griffins in the UK. It can produce about 4 foot of spark.
I have a number of large Leyden jars with my machine - they can be quite dangerous if left around when fully charged! And surely you mean 4 inches of spark and not 4 foot
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Old 9th Jul 2020, 9:01 am   #46
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On a good day my home built wimshurst would produce 4" of spark. A Van der Graaf generator would greatly increase the voltage.

I also made a Van der Graaf generator with a square sided perspex tower ca 3 ft high with a modified ball cock copper float as the dome. Meccano motor and mechanicals carrying a silk belt ( modern plastics for belt not available to me at that date.

Used the wimshurst as the priming source of charge. ( pointed brass pins for collectors on both machines were made from old acoustic gramophone needles )

Problem was leakage all over the place. Run in the dark, cloudy discharges all the way up the corners of the tower. Very long 18" or so feathery sparks from the equatorial seam of the copper float.

The longer sparks could be felt as a very mild tingle about 2 ft away.
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Old 9th Jul 2020, 9:02 am   #47
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I have a number of large Leyden jars with my machine - they can be quite dangerous if left around when fully charged! And surely you mean 4 inches of spark and not 4 foot
Would love to see your machine if you manage to dig it out.

You are right. it is 4". My Van der Graaf produces very weak spark. It prefers a "blow dry" with a hair drier after storage.

I used to be a high voltage junkie that now leaves my living quarter like a mad scientist lab. In the photo below, it is my small collection of DIY tesla coils: the big Tesla coil can produces 1.45 m spark. The small ones include a musical DRSST using IGBT and a half bridge solid state tesla coil with mosfets.
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Old 9th Jul 2020, 11:25 am   #48
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At school we had a Van der Graff generator. One evening in the after school radio club one of the lab technicians gave us a demonstration. First he showed us the "normal" 4" sparks which impressed us but then he connected a Leyden Jar across the output and moved the balls apart to about a foot. We were told to stand back as he turned the handle for what seemed like an age then suddenly an almighty crack as a spark jumped the 12". That left a lasting impression on us all. Of course that would not have been allowed in the class but he did show us the best way to draw a spark from it with your finger. Point the tip of your finger towards the dome and you'll feel it but if you point one of the joints in your finger at the dome you'll still draw a spark but you won't feel the shock as much. Something to do with the fact that there are more nerves in the tip of your finger that in the joints.

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Old 9th Jul 2020, 12:32 pm   #49
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I only remember ours being used to impress parents at open evenings.
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Old 9th Jul 2020, 12:50 pm   #50
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I once built a Marx generator demonstrator for an open day at the lab. There was a large rotary handle on the front which, via a couple of pairs of chain-driven step-up cogs, turned a Mini Metro alternator. This powered a solid-state HV invertor which delivered +/-10kV to 5 pairs of 220nF capacitors. So the stored energy at full charge was 110J. The bottom spark-gap in the column self-broke at around this point and the Marx 'erected' (yup, that really is the technical term) delivering 100kV out of the top into a 120mm air arc. The bang wasn't loud enough to be harmful, but we did encourage the audience to put their hands over their ears. They went away impressed too.

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Old 14th Jul 2020, 12:15 pm   #51
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Details of Home Mechanics book
Thanks Dennis. My copy arrived this Ack Emma.

Splendid book!
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Old 16th Jul 2020, 12:39 pm   #52
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Would love to see your machine if you manage to dig it out.
I haven't located it yet, but I have managed to dig out some of the Leyden jars, as I used to have them displayed around the house as ornaments. After cleaning them up a bit from all the dust and spiders, I've taken some pictures of them.

I used to have 'charge' (pun!) of a couple of VdG generators, and the trick was to dry the belts well before use. I used to have a couple of belts for one of them so that one would run on the machine until it picked up too much moisture from the atmosphere and stop working and would then be swapped for the other one which I'd have stuffed in the grill of a fan heater drying and ready for use. I'd then stuff the damp belt in the heater grill to dry and be ready to swap back to replace the one in use that would eventually pick up more moisture and stop working once again - and so on. I expect both of those machines eventually ended up in a skip - shame I didn't save one!
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Old 16th Jul 2020, 1:41 pm   #53
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L

I am in awe. Wire them in parallel to create loud pops, bring the Frankenstein back alive and keep your fingers away from them.

The rubber belts tend to disintegrate over time, cracking and flaking.
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Old 16th Jul 2020, 2:29 pm   #54
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Default Re: DIY X-Ray & Auto Jigger transmitter

I co-built a Wimshurst machine with a school friend circa 1966.
It was a design from a book, and used a pair of 12 inch 78's.
The design included a home made condenser using paper and tinfoil cut to a template, and

I remember "dope thinners" was required.

I'd quite like to find a copy of that book, or article.
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Old 16th Jul 2020, 4:53 pm   #55
regenfreak
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I remember "dope thinners" was required.
in the US, they use "Corona Dope" for TV flyback transformer. I think they will need to rename their product from now on.
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Old 16th Jul 2020, 6:49 pm   #56
rontech
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Originally Posted by rambo1152 View Post
I co-built a Wimshurst machine with a school friend circa 1966.
It was a design from a book, and used a pair of 12 inch 78's.
The design included a home made condenser using paper and tinfoil cut to a template, and

I remember "dope thinners" was required.

I'd quite like to find a copy of that book, or article.
My first attempt at a wimshurst machine used 12" 78's The machine would simply not work. I mentioned this to my physics lecturer at Tech He replied "Of course it wouldn't, the carbon filler in the 78's would be sufficient to be conductive at electrostatic voltages!"

My second attempt a year later using perspex discs worked fine.
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Old 16th Jul 2020, 7:25 pm   #57
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Quote:
Originally Posted by rambo1152 View Post
I co-built a Wimshurst machine with a school friend circa 1966.
It was a design from a book, and used a pair of 12 inch 78's.
The design included a home made condenser using paper and tinfoil cut to a template, and

I remember "dope thinners" was required.

I'd quite like to find a copy of that book, or article.
There is a chapter of 'The Boy Electrician' covering this. It may have been what you remember. It requires you to cut two 18" glass disks, glue them to wooden mandrels, and stick tinfoil sectors on. Good luck to doing that without injuring yourself and maintaining good balance.

The book is available here

https://worldradiohistory.com/BOOKSH...n-2-Morgan.pdf

Chris K
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Old 16th Jul 2020, 7:26 pm   #58
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I have just done a couple of experiments.

The 78's I used were very old acoustic recordings.They would be from about 1920 I imagine.

So I tried rubbing a 12" 78 with a soft cloth and it charged up and would attract scraps of paper. This was a 1946 recording.

I have a 10" 78 from 1909 and no amount of rubbing would produce a charge.

I guess there was a change in the composition of 78's at some date.
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Old 16th Jul 2020, 8:07 pm   #59
regenfreak
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So I tried rubbing a 12" 78 with a soft cloth and it charged up and would attract scraps of paper. This was a 1946 recording.

I have a 10" 78 from 1909 and no amount of rubbing would produce a charge.
Two years ago I bought a special transparent rod from ebay, it grows purple in the dark after rubbing it with a cloth. It grows very bright purple near a Tesla coil. I can't remember what material it is made of.

When I was a kid, I used to have a ginger cat, i got good output of electrostatic charge from her furs from rubbing a plastic ruler under dry weather conditions.
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Old 17th Jul 2020, 12:04 am   #60
rambo1152
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Default Re: DIY X-Ray & Auto Jigger transmitter

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Quote:
I remember "dope thinners" was required.
in the US, they use "Corona Dope" for TV flyback transformer. I think they will need to rename their product from now on.
That word has a habit of causing problems.

The early US spy satellites dropped canisters of 70mm film that were recovered by the USAF.
The project was called "Corona" (The public knew it as Discoverer and were not told of it's real purpose).

One problem they had to solve was fogging of the film caused by...

...you've guessed it, electrostatic corona discharge in the camera.
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