NexStar 8SE azimuth broken
Posted 21 July 2013 - 09:45 AM
The azimuth now rotates freely by hand. When activated by the hand controller, the motor can be heard running, but the mount does not rotate.
Am I likely to be able to fix this myself. Where are parts available if necessary? Or if necessary where can it be shipped for repair?
Posted 21 July 2013 - 10:45 AM
If you are so inclined to repair yourself,disassemble it taking images of each procedure so as to remember where everything goes and see if you can find the broken part. Contact Celestron to see if you can get the part and if so, good,if not, you should be able to locate a used mount on here or on Astro Mart. Sorry to hear about your misfortune.
Posted 21 July 2013 - 11:50 AM
Hard to tell what might be wrong without opening it up. It sounds likely that a gear tooth was broken or something similar, but it could also be that a drive gear was moved on its shaft and can simply be repositioned and the set screw retightened. If you're handy with tools, I'd suggest opening it up.
If anything is broken, you won't find too many parts available for replacement. Like Tim says, you're probably better off getting a used one. Then you can keep your old one for spare parts for the next time the scope gets blown over.
Posted 21 July 2013 - 01:57 PM
So sorry to hear of your misfortune.
As others have already stated, it's impossible to say at this stage what may or may not be damaged.
However, you do say that the azimuth axis now rotates freely by hand, which, clearly before this misfortune, it was not designed to do.
This therefore might indicate that the motor (drive pinion) has become dislodged, (or disengaged) from the main, large, static (cog) wheel: hence the motor turns, as evidenced by the sound you hear when the HC is operated, but, without the engagement of the two sets of intermeshing teeth, does not rotate the azimuth axis.
I'm afraid you will have no alternative but to open up the azimuth axis drive if you wish to investigate this (any) possibility yourself, but perhaps, the attached archived text might help. (?)
Just a thought.
Posted 21 July 2013 - 02:42 PM
As far as the OTA, it seems to have survived quite well. No visible damage, and an out of focus star was quite even and circular. Looked at the (filtered) sun today with it, and it performed quite well.
Posted 21 July 2013 - 07:37 PM
Posted 21 July 2013 - 08:37 PM
Looks like I need a new gear, unless I can put it back in and the damaged tooth is out of the way.
Posted 22 July 2013 - 01:41 AM
There are, (according to the above link), two set screws which hold the gear (pinion) to the motor shaft.
It might be possible to reshape that bent tooth and retighten depending on your overall assessment of the damage, otherwise it does sounds like a new gear is required.
Is though the motor shaft and gear still in line with the toothed disc, (i.e. the az. motor/shaft/gear have not been bent or otherwise damaged as a result of the impact) ?
Posted 22 July 2013 - 07:19 AM
Posted 22 July 2013 - 08:26 AM
Bore diameter = 5mm
Number of teeth = 18
Body length = 11mm
Body material = brass
Body diameter = 10.45mm
Pitch diameter = ??? but slightly less and likely 9.5mm ( 10.45 * 0.91 )
Pitch = 48 ( Number of teeth divided by pitch diameter in inches )
I did not find the right gear at the above link but there are literally hundreds on that site just in brass.
Posted 22 July 2013 - 09:27 AM
Posted 22 July 2013 - 10:42 AM
If your gear is long like mine then you can slide it on the shaft, or reverse it, and use an undamaged area. The shaft has only one flat so one of the setscrew holes will be empty.
I was thinking of this. Does the big azimuth gear mesh at the bottom or top of the brass gear?
Posted 22 July 2013 - 11:50 AM
You should also note the AZ position of the damaged portion of the large gear and avoid using it in that region. Even though the small gear has been replaced, there will still be a tracking error in that region as the bent teeth will cause a lead or lag when engaged. It will be a small angle, a few degrees.
Posted 22 July 2013 - 08:41 PM
I think. I put the gear back on, with the set screw on the other side, where the hole was undamaged. Put the gear as far on the end of the shaft as I could, so the damaged tooth would be out of the way. It seems to be working, at least mechanically. Will have to wait until the next clear night to field test it.
Thanks for all your help.
Posted 23 July 2013 - 01:45 PM
Posted 23 July 2013 - 03:20 PM
Posted 24 July 2013 - 04:23 PM
Just in case, I ordered a spare drive gear.
Cloudy Nights folk are the best!
Posted 24 July 2013 - 05:01 PM
Posted 24 July 2013 - 06:37 PM
Posted 26 July 2013 - 09:09 AM
*With the wife out of the house....
Posted 30 July 2013 - 11:11 AM