Telescope Reviews: ETX 80 RA Clutch info

INNER WORKINGS OF THE RA/AZ AXIS OF AN ETX-80

The body of the ETX80 is two 'halves' that I'll call the UPPER and LOWER halves. There is a central axle through which passes a screw which threads
into a locking nut. The nut and other hardware can be seen by removing the cover plate on the bottom of the scope. The screw, which I'll call the
ACTUATION SCREW, helps hold the two halves together, along with a nylon bushing or RETAINING NUT which threads into the axle. This RETAINING NUT is
originally glued into the mating threads, these threads are very shallow and are unavoidably stripped during disassembly, you can't seperate the two
halves without removing it though. I suppose that Meade would use a new part when re-assmbling, but who knows! This nut really does most of the work
holding the two halves together (along with the ACTUATION SCREW assembly) and it fits back in rather snugly after reassembly, it could be glued back
in, but I haven't seen the need as of yet. The end of the nut has 4 protrusions which fit into mating holes on the THREADED LOCK WASHER to keep the
washer from backing off from clamping/unclamping using the ACTUATION SCREW. Beneath the lock washer is a plain washer which sandwiches a needle bearing
between itself and what I will call the CLUTCH PRESSURE PLATE. Moving on to the actual interior, we have a nylon washer I call the LOWER CLUTCH DISC,
which has three tabs that fit into slots to keep it from rotating. The RA/AZ GEAR is next; it rotates freely around the axle and can also slide up and
down. This freedom of movement allows rotation when the RA axis is unclamped. Beyond that the UPPER CLUTCH PLATE, which is unable to rotate, being
pretty solidly attached to the lower half. Before I got inside here, I had a tough time understanding how this thing worked or didn't work as the case
may be. Here is how it works:

The WORM GEAR is always engaged into the RA GEAR, held against by a clip spring. The RA GEAR floats, it's not attatched to anything, this is what
allows rotation when the RA clamp is loosened. Tightening the ACTUATION SCREW causes the CLUTCH PRESSURE PLATE to force the LOWER CLUTCH DISC into the
bottom of the RA GEAR which forces the gear into the UPPER CLUTCH PLATE. The UPPER CLUTCH PLATE is attached by three screws to the lower half of the
body and can't turn. The worm gear is attached to the UPPER half, where the scope is and the RA GEAR is now 'fixed' between the two halves, at least to
some degree and the scope will now rotate when the motor turns the worm gear. Of course, this sometimes doesn't work too well. I have read that
sometimes grease gets between the clutch surfaces, thereby reducing friction, which is what we don't want to happen! So, if we want friction, why don't
we just clamp the daylights out of it? Well, too much of a good thing is not a good thing I always say, and I guess you run the risk of deforming the
CLUTCH PRESSURE PLATE causing it to have a reduced footprint where it pushes the LOWER CLUTCH DISC and possibly even stripping the threads on the
screws which hold the UPPER CLUTCH PLATE. The general consensus is to increase the friction between the gear and clutch plates by roughening the
surfaces slightly, so that they grab more easily with not too much pressure.

The only part that I haven't discussed is what I call the AXLE BEARINGS. These split nylon sleeves fit betweeen the axle, which is on the upper half
and the axle housing on the lower half. They did appear to have some lubricant on them. Enough or not enough, I don't know. I added some white lithium
grease to mine.

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