MadSci Network: Engineering

Subject: Questions about wimhurst machine

Date: Tue Jan 9 11:35:44 2001
Posted by grahame jeffery
Grade level: No grade entered. School: No school entered.
City: No city entered. State/Province: No state entered. Country: No country entered.
Area of science: Engineering
ID: 979058144.Eg

Hi knowlegeable ones,
I wonder if you can help? About 1year ago I built a wimshurst machine using
400mmD X 2mm thick acrylic disks. Aluminium foil segments, earthing brushes 
2 leyden jars all according to accepted construction methods. At the start 
worked unbelieveably well.It would throw good 125mm sparks and hold its 
for 24 or more hours in times of low humidity weather. If it did discharge I
would rub briskly a thin sheet of polyprop, put it between the two disks 
the handle and it would start every time. Now comes the problem. After some 
months it became slugish starting, would not throw sparks more than 15mm, 
discharged after about 10 mins. I notice that the insides of the disks are 
due to the rubbing action of my starter sheet. It may be that this has 
the disks to become slightly conductive. I have taken the precaution of 
down the disks with detergent and copious quantities of water to make them
immaculately clean in case they have acquired a film of grime and all to no
avail. Has someone out there got any ideas?
 My web site contains a page describing this machine.
                        Cheers and thanks         Not so knowlegeable one
Grahame Jeffery.

Re: Questions about wimhurst machine

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