Basic Rebuilding Part Ill: Replacing Slip Rings COLUMN BY RICHARD R. VENSEL Rotor slip ring replacing is an often- missed cost saving and quality assuring operation. It can save you up to 70 percent and you may not have |) . to spend a dime. These processes are simple with very little special purpose tooling required. Basic Process To Remove Slip Rings: 1. Inspect and test— Visually inspect the treads, bearing, surfaces and fans. Repair as necessary. First test the rotor for current draw, if it is open at the slip rings. Make sure you retest where the rotor coil leads come out of the pole piece’s slip ring. Next, while there is DC current going through the rotor, read the magnetic strength. Do not forget that a good ground test will really pay off in saving regulators. 2.Determine the slip ring ww location—Measure and record the location of the existing slip rings. We suggest measuring from the pole piece to the center of the slip ring groove between the two slip rings. . Cut leads—cCut slip ring leads from the rotor bobbin leads. It is best for this cut to be right behind any stand off or support toward the slip ring. Leave a good surface area to reconnect the new slip ring leads. 4. Remove the old slip ring—Pry up the slip ring leads that should have been held in place with sup- ports, varnish or epoxy. Removing the slip rings can be as easy as using two screwdrivers and prying up on both sides, or using a bear- ing splitter with a puller adapter set into the slip ring groove and pulling the slip rings. Basic Process for Slip Ring Installation: 1. Preparation of surfaces: A. Holding the coil lead and/or support, clean the surface where the new slip ring connec- tions will be attached. If these are going to be soldered, this is a good time to tin both surfaces. If you are using solder we sug- gest using one consisting of 97 percent tin and 3 percent copper with a melting point over 400 degrees F. If you are going to silver solder using 85 percent copper, 15 percent silver with a melting point over 1200 degrees F, just clean the surface. B. Clean the surface of the pole piece where the slip ring leads will be attached after installa- tion. You need to get down to bare metal to provide a good bonding surface. 2. Slip ring installation: It is better to prepare the slip ring leads before they are installed on the shaft, this will allow less strain on the connecting points on the rotor coil leads. Cut to length and tin as in step A. 3. Install the slip ring to the correct location: A. Place the slip ring on the end of the shaft and locate the slip ring leads in the matching position with the rotor bobbin leads. Beveling the leading edge may help. B. Press the slip rings down the shaft to the same location deter- mined in disassembly, step 2 of slip ring removal. C. Make sure the slip ring leads are flat and tight against the pole piece. 4. Connecting the slip ring leads to the rotor bobbin leads: A. If soldering with the leads already tinned, simply press them together and apply heat where you want the solder to flow. Only add solder if necessary. B.Some slip rings have steel leads. We recommend these leads be only silver soldered. Apply solder past both the slip ring lead and the rotor bobbin leads where the weld joint will be located. Sandwich the slip ring lead, silver solder and the rotor bobbin lead and heat these in place. C. For silver soldering copper to copper, follow step 4B for installation. . Make sure the slip ring leads are tight against the pole pieces, and then epoxy the leads to the pole piece. Use just enough epoxy to cover the wire lead. 6. Retest and we suggest varnishing with a good high dielectric electri- cal varnish, not spray paint. 7. Cut and polish the new slip rings, keeping in mind that the finish should be 320 or higher. Note: Keep in mind that rotors were dual plane balanced when new, most to 1/10 of an ounce inch. These simple processes can be one of your biggest cost savings. All goes to your bottom line. Richard Vensel is owner of Vensel Enterprises, Crystal Lake, Ill. Nn ray) ae