How to Fix the Altitude Clutch Problem in the Meade DS Mount By John Zimmerman September 2005 Note: I claim no personal credit for the solution described here. Other DSX owners, whose real names I do not know, have posted messages on Yahoo and Cloudy Nights discussing this problem. Even the pictures are borrowed from those individuals. The Meade DS mount has a known problem with the altitude clutch assembly. When the clutch is tightened, it places a great deal of torque on a small slip ring that fits into a groove that holds everything together. Eventually, the slip ring slips out of the groove, and the scope will no longer move in altitude, even thought the motors are running. The solution presented here is to replace the small slip ring with something much larger. 1. Begin by disassembling the fork arm assembly: 2. Remove the tube from the L shaped support. 3. Remove the L shaped support by removing the 4 screws holding it. Note that the lower right screw is slightly longer than the other 3. Remember this when you go to reattach it. 4. Looking at where the L shaped bracket connected to the arm, you'll see a hole, and there should be a nut visible. Hold the nut with a pair of pliers, and unscrew the altitude lock. Behind the nut is a triangular shaped piece of aluminum that is also threaded onto the same shaft as the nut - it should come off also. This piece of aluminum, with its 3 prongs, is what provides the locking mechanism by pressing against the side of a large nylon gear you'll see later. 5. Now, facing the fork arm from the altitude lock side, pull the altitude lock out - the threaded shaft the nut and aluminum clutch were threaded on is attached to the lock. Note that there is a small nylon sleeve that fits over the shaft at the knob end - don't lose it. 6. There is a flat nut behind the altitude lock with two flattened sides that is threaded onto a shaft - the nut holds the declination circle in place. Unscrew the nut - a large crescent wrench is good for this. 7. Carefully pry the declination circle off of the shaft.7. Behind the declination circle is another, larger nylon sleeve. Carefully remove this by pulling it straight out. -1-
8. You should see two small screws that hold the large plastic fork decorative cover to the metal arm. Remove these two screws, and carefully remove the cover. Note that the cover is a bit tricky to put back on - you have to carefully seat it on the lower part of the fork arm before screwing it back to the upper part. 9. Now, back to the side of the fork where you removed the L bracket. Pull straight back on the large plastic ring that was part of the assembly the L support attached to. The disassembled components are shown in the picture below: From left to right the altitude lock knob, nut with flattened sides, declination circle, nylon sleeve, nut with flattened sides, large nylon gear/plastic ring assembly, 3 pronged triangular aluminum piece, lock nut, and tube cradle. A close up of the shaft with the slip ring is shown in the picture on the next page: -2-
If you look closely at the picture, the slip ring fits into a small groove just outside of the metal washer. If your scope has stopped moving in altitude in spite of the sound of running motors and a tight clutch, chances are this ring slipped out of the groove and has moved toward the right hand end of the shaft. What this does is because the large gear to move along the shaft and lose contact with the worm drive that turns it. The reason this ring slips out is because of the tremendous amount of pressure exerted against it when you tightened the altitude lock. The quick fix is to simply move the slip ring back into the groove. Unfortunately, it will likely slip over and over. To fix the problem, replace the small slip ring with something more substantial, as shown in the photos on the next page. The first photo shows the original slip ring, and one style that can replace it. The second photo shows a more substantial ring. These can be obtained at most hardware stores that have a good selection of fasteners and other small items. -3-
Removing the existing slip ring isn t too difficult, especially if it has already slipped out of its groove. Installing a new ring can be challenging. The second ring shown may require a special tool. I installed the first ring, which was possible with a large pair of pliers. -4-
Putting it all back together is pretty much the reverse of how you took it apart. Pay attention to the two plastic rings to the left of the large gear. They fit a certain way to provide the altitude stops, and they also slide back into the fork in a specific orientation. It's a good idea to have the altitude orientation pointing all the way down so you'll have a point of reference for reattaching the declination circle and the L shaped bracket. An additional thing I did as to cut and glue small pieces of #60 sandpaper to the end of each of the 3 prongs in the triangular aluminum piece that engages the nylon gear. The idea is these will provide for more of a friction fit. Finally, I keep the altitude axis locked all of the time, moving the tube only with the hand controller. This minimizes the chance for things to work their way loose. -5-