I've had an opportunity to work with many models of Wimshurst Machines during my years at Sci-Supply. While demonstrating them at trade shows and conventions, they can sometimes act up. This has led me to become somewhat of an expert on Wimshurst Machine repair. I'm frequently asked about how to get an older Wimshurst machine working again, and I've compiled some simple tips and tricks below. I hope you find the information helpful, and remember, if a Wimshurst Machine worked in the past and there are no mechanical problems, it will most certainly work again. For those of you building a Wimshurst machine, these tips may also help you in troubleshooting. Good Luck!
Begin with a thorough cleaning. Dust accumulations on the Wimshurst Machine can inhibit electrostatic charging. Clean the disk surfaces with a paper towel and water. Avoid chemical solvents, as they can damage modern acrylic plastic discs. You can use rubbing alcohol if there are any oils/grease present on the discs which may have come from the spindles. Grease the spindle on the Wimshurst Machine to ensure that the discs move fluidly. Do not get carried away. A small amount of grease is plenty to lubricate the spindles! When you are finished with the discs, move to the leyden jars. For those of you not familiar with a Wimshurst Machine, the leyden jars are the cylinders that collect and store the electrostatic charges developed by the movement of the brushes over the disc surface. The leyden jars should be disassembled, cleaned and dried thoroughly. If your leyden jars are plastic with foil linings, you can simply wipe them off inside and out. If you have a more expensive model of Wimshurst Machine, your leyden jars will have inner and outer linings made of acrylic, metal, glass, etc. You will need to disassemble the jars completely and clean all surfaces of dust.
After you have cleaned the device, make sure that all 4 brushes are in solid contact with the disc surfaces and that the brushes are in proper alignment. If the brushes are out of alignment, the Wimshurst Machine will never work. When you look at either side, the upper brush should be at the 11 O'clock position and the lower brush should be in the 5 O'clock position. If your discs are transparent, the brushes should make an X when you look at them from one side. Some models of Wimshurst Machine have the brushes mounted on a circular disc that wraps around the spindle. During use, the brushes can move out of position if they are not fixed. Check the drive belts to ensure that they are not worn out, and that the discs rotate in opposite directions and roughly the same speed when the Wimshurst Machine is used.
At this point, the Wimshurst Machine should be clean and ready for use. You may be saying to yourself that you've already tried the steps above to no avail. I've read (and smiled to myself while doing so) where people on other websites have suggested drying the discs with a hair dryer to "dry the plastic disks" because they will absorb water. Never do this! You can damage the discs if they are made of plastic. I can only assume that the author was extremely frustrated at this point and grasping at straws. My theory as to why Wimshurst Machines stop working from time to time is this: When placed in storage for a while, they may be subject to minute amounts of charge. The leyden jars could in theory collect these stray charges while in storage. If a small amount of charge were present in a Leyden jar after storage or disuse, it would repel like charges when in use. So if both jars "absorbed" a small amount of positive charge while in storage for example, one jar may not allow charging because the incoming charges are being repelled by the small amount of like charges already present in the leyden jars.
Ok, enough BS, lets get this Wimshurst Machine working again! Its time to find some yourself some scrap Styrofoam from around the lab or house. Find the largest piece you can. Yes, I'm talking about the cheap nasty white Styrofoam that so many products out there are packaged in. If you can't locate a piece of Styrofoam (this works best), you can also use a balloon. Charge the Styrofoam by rubbing it over material like clothing or carpet. When finished, you should be able to feel the electrostatic charges when you hold it close to your face. Place the discharge spheres (small metal electrodes where the high voltage emanates) about 1/2" apart. Hold the charged Styrofoam over top of the discharge spheres and SLOWLY turn the handle on the Wimshurst Machine. I've never encountered a Wimshurst Machine where this method did not work (assuming that at one time it was working in the past).