Slightly Brown

Afternoon Happy-kat ... No I don't, but I've just taken some !!! Having made the adjustments I can say the GOTO is way more accurate, so I reckon the clutch/s were iffy to start with or "on the move" due to lack of grip on the locking grub screws. Having tried and tweaked a few times now, I've worked out that the bottom Az clutch should be just tight enough to alleviate any mechanical "slap" if you take hold of the mount's body and try to move it from side to side. Then, the top clutch needs to be tight enough to guarantee 100% slip free motion when doing a real life slew, complete with the tube. At some point I'll get a spring balance to measure the kind of forces that are working for me !!. With the top clutch reasonably tight, and the bottom clutch just doing enough to maintain the main shaft's stability, your mostly "feeling" resistance due to the top clutch, when moving the scope tube by hand, and, just the slightest "too much" on the bottom clutch makes manual movement "stiff & sticky". With almost no resistance from the bottom clutch, manual movement of Az axis, is incredibly smooth, with no initial "tight spot" to overcome - really nice ! I've now also done the same to the Alt clutch. Much easier, it's just under the hand wheel. Again, I found "not entirely tight" locking grub screws !!!. Tightened the clutch a little (rotating the adjuster plate clockwise) and now it's like it was when it was new - tighten the hand wheel and the tube position pretty well locks, useful if your not motor driven tracking / slewing or re positioning the tripod and don't want the tube flapping around !

I'm just adding to an earlier thread, instigated by Bezzi on September the 7th last year, on the the subject of the Star Discovery mount's clutches. Thought I'd start a new discussion, given the 4 months between then and now, and since I have some findings on the subject. Like Bezzi, I too noticed a "lack of ooomph" on the mechanical side of motor driven slewing (rather than voltage related issues, which was also mentioned) Unlike Bezzi's issue, which I seem to recall started after just a few days ! my issues came to light after nearly a year of use. To be fair, it was probably getting progressively worse for some time, but wasn't until the scope stopped mid slew to a 2nd star during an alignment procedure, I finally realised there was a real problem. To be clear we are talking about the Star discovery & 6" Newt package, which, should be absolutely fine, since it is sold as a package, and since the tube itself is a slightly lighter weight version of other 6" Newts. (No tube rings Etc.). Therefore we shouldn't need to consider exceeding the mount's carrying capacity with use "as the manufacturer intended". I use mine with a small CCD video camera, which is less weight than a chunky "expensive" eyepiece, although I do have an ali bracket attached to the base of the head, carrying the Synscan handset and a DVR. Even so, we're well under the mount's 5 kg "limit". Having had the scope actually stop mid slew (but with motors still running fine) it did make me think that perhaps, both axis were "looser than I remember" them being initially. Certainly manually moving the scope tube really did seem "freer and easier" that when I first acquired the beast. So I tried an Azimuth slew, with the handset at default slew rate, and physically tried to stop the tubes movement. It took no force at all to stop the tube - the torque/power to the head was truly pathetic. We're in "couldn't pull the skin off a rice pudding" territory here. Whipping the top cover off for a looksee I found two clutches on the Azimuth axis. Hadn't particularly expected that, but thinking about it, yes you do need two. I'm please to say they are nicely engineered, "dry" multi plate affairs - but how on earth do you adjust them !. Some one on the original post way back in September mentioned a "good manual" - of course I got a 404 page for my trouble clicking the link, and having Googled around I can't find anything that goes as deep as "under the bonnet" clutch adjustment. So if any one know of different - let us know !. Actually adjustment isn't really a problem but what would be useful is some guide to "output torque" as I can see, over tight clutches having a long term implication on the motor's plastic gear train. However, it turns out (on the Azimuth axis), the top clutch is effectively the "motor to head (Azimuth rotation) power [removed word] torque control". While the bottom clutch does effectively the same as the hand control does on the Altitude axis. Both clutches have an adjuster plate at the top of a chain of other "motion" plates, that slip n grip accordingly. The top adjuster plate rides on a thread on the main shaft, so that (viewed from the top of the main shaft) "screwing in" (clockwise) drives the adjuster closer to the little gaggle of motion plates, increasing friction, and therefore "output" power. You have to release 2 tiny Allen grub screws in the top adjuster plate boss (opposite the spanner flats) which lock the plate in it's final adjusted position. Interestingly on BOTH the top and bottom clutch, only one of these locking screws were remotely tight. That in itself could account for everything ! Then, after manufacturing a spanner the right size, and slim enough to get into the rather tight access, I gave the top clutch's adjuster a tiny (% of a turn) clockwise, and re tightened both lock screws. Powering up the Synscan I tried a handset driven slew, and was greeted by 2 notable things: 1) It took a whole load more effort to stop the tube and make the clutch "let go" - far more like I remember it being when it was new. 2) Since the slew motors start "instantly" and don't "ramp up" to speed (always thought it was a shame they didn't ramp up - far less stressy on the drive train) there was a visible shudder from the tube. Partly due of course to the lighter weight tube to mount connection having rather a lot of movement and "bounce", specially when suddenly being asked to quickly change state from stationary to moving. I'm not a great fan of things like that though, as, in my little brain, it always translates to mechanical stress somewhere else. Backing off the the clutch adjustment a tiny weeny bit rewarded me with, still plenty of force needed to stop the tube mid slew, but a far, far less aggressive start to the slewing motion. Clearly, there's a delicate balance between over stressing the drive train, while having sensible slewing forces. But the next time I'm delving in there (I'm sure there will be a next time !) I'll actually hook up a spring balance to the "open" end of the tube, and get a real measure of the force involved. By then it will have done some hours, so I can also see if theres any tell tale signs of premature wear and of course check that the adjuster plate locking grub screws are still tight !. It's not beyond the realms of possibility that they just work themselves "un tight" over time and motion. It's also "not beyond the realms" that after an initial run-in period they simply do need adjusting. We see this requirement in other mechanics day in and day out. It's also possible that the initial factory setting could be quite variable … depending on who does it, and whether there's an "R" in the month or not !. Of course all this might amount to nothing (apart from severe embarrassment on my part), if on the second night out I strip the motor worm gear !!!. But I really don't think that will happen !! …