Wimshurst Capacitor Jigs

Mork

Mork

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This is a Wimshurst Machine which generates high voltage. The capacitors on this machine are made of acrylic and the glue lines need to be perfect or they will fail. The link are videos that show a jig I made for my lathe for cutting the disks and finishing the ends of the acrylic tubes (necessary to get a good glue joint).

http://1drv.ms/1Pfut6m

spark2.jpg
spark2.jpg WP_20160124_001.jpg
 
For some reason, I thought that Wimshurst machines need conductive pads mounted on the inside faces of the spinning disks.
What is inside of the copper ? capacitors to store the charge? It looks like a solid cylinder without much surface area to hold the charge?
I've built VanDeGraaff generators in my youth which is purely electrostatic. Fun to hold onto the dome and see your hair stand on end.

Very well done, fine workmanship. Congratulations, you might just be able to influence some young person to pursue a career in the sciences
with this kind of demonstration.
 
The disks are spinning in the picture so you can't see the foil pads (segments) however the segments are on the outside of the disks. There is a neutralizer brush (in this case a conductive thread) touching opposing segments on both disks and collectors that do not touch the disk. Yes the capacitors are simply an acrylic tube (1/8" thick) with a layer of foil on the inside and outside. The electrodes are connected to the inner conductor of the capacitor via a rod and thin strip of shim stock bend to make contact. The problem I had about with about 50% of the capacitors was the glue joint at the bottom. When moving the electrodes apart to achieve a maximum spark the spark would jump between the two conductors of the capacitor through the glue joint. Originally I cut the tubes on my table saw. It was a fairly smooth cut but still had some saw marks. After doing a little research I found out that to achieve a really good glue joint the end of the tube has to be cut very smooth. Additionally I chucked the disks (bottom and top of the caps) in the chuck and cut a shallow groove to match the tube diameter. This allowed me to flood the groove with a solvent glue and then set the tube into the groove. All air bubbles are now gone and I have achieved a perfect glue joint. It was fun but cutting a 3" bar down to 2-1/4 was a lot of turning and a big mess. If I had it to do over I would have started 2-1/2 of smaller.

This machine packs a lot more punch than the VanDeGraaf. I've been zapped many times so it isn't fatal but if you make a good connection while the disks are turning it really hurts. The machine is charged even when idle if you don't take steps to discharge it. Thats when it get you... when you forget to do this.
 
A really beautiful build.
I built one as a kid using two 78 records for the disks, cigarette foil for the segments and if I remember correctly a couple of leyden jars for the capacitors made from small jam jars.
It worked but looked like it came from a dumpster.
Where is the video link?
 
It's above the pictures but here is it again. This is a link to my OneDrive and I'm curious if people will have problems accessing it.

http://1drv.ms/1Pfut6m
 
It played for me with no problems, thanks.
 
savarin said:
A really beautiful build.
I built one as a kid using two 78 records for the disks, cigarette foil for the segments and if I remember correctly a couple of leyden jars for the capacitors made from small jam jars.
It worked but looked like it came from a dumpster.
Where is the video link?
Click to expand...


Thanks for the compliment! I've heard of people making them out of LPs and CDs. These machines can be finicky. Oddly enough glass makes a terrible capacitor while acrylic is excellent. I've built 4 machines and the spark lengths average between 2 and 4 inch and I never did get one of the machines to work at all. Of course I'm perfecting and learning as I go... and a lot of effort went into building the lathe jigs to make them even better. The larger the disks the more you have to have your ducks in a row. For instance, the glue line failures on the capacitors happened at a 2 inch spark length so if I want the machine to do better i have to have a perfect glue line. I'm hoping to build one with 18" disks soon. The one in the post is 12 inch. Hopefully I'll get a 10 inch spark! :eek:)
 
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