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LOOSE FASTENERS ON ORION BIG GOTO DOBS

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  • Chuck
    ATTENTION ORION BIG GOTO DOB OWNERS! DISCLAMER --- IF YOU OPEN YOUR SCOPE S GEAR COVERS UP, YOU ARE RESPONSIBLE FOR YOUR OWN ACTIONS. I CAN NOT BE HELD
    Message 1 of 1 , Jan 3, 2013
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      ATTENTION ORION BIG GOTO DOB OWNERS!

      DISCLAMER --- IF YOU OPEN YOUR SCOPE'S GEAR COVERS UP, YOU ARE RESPONSIBLE FOR YOUR OWN ACTIONS. I CAN NOT BE HELD RESPONSIBLE FOR ANYTHING THAT MIGHT GO WRONG. IF YOU ARE NOT MECHANICALLY INCLINED, DELETE THIS EMAIL.

      Now that I have scared half of the group away...

      HOW I KNEW I NEEDED SOMETHING DONE.

      I found that there was some "slop" in my scope. I would tighten my clutches so they would hold the axis tight, and then if you apply just a bit of pressure you feel it "give" just a little bit. Also when adjusting the FOV after it has been tracking a bit, I would poke a move button on the handset and would hear the motor come on and it would hesitate a very short bit before actually moving the OTA. I was CERTAIN something was afoul and I would have to contact Orion, who I am sure would want me to mail both HEAVY motor assemblies back to them for checkout. I figured I would take the covers off and have a "look-see" and ended up fixing it rather easily.

      FIRST! If you have not applied Loctite to the screws that hold your bearings to the lower OTA, and anything else that looks like a screw you should.

      =====

      Last night I just found eight more fasteners on my XX14G that have worked their way loose and had NEGATIVELY affected my tracking and goto performance. They are a little harder to get to though.

      There are four hex head Allen screws UNDER the worm gear friction disc on each of the axis. I had three screws on the RA axis and all four on the DEC axis finger loose.

      To get to them you must remove the black plastic cover after unscrewing and removing the clutch knob. The cover is connected to the motor assembly by a some small cables, I just let mine dangle carefully while I worked. If you remove the little connector plugs, take care to remember which one goes where AND their orientation.

      Next there is a big nut on the shaft which must be removed, be sure to loosen the 2mm hex head set screws (2) one on each side. Also remember how much tension is on the nut, as you don't want to crank it down upon reassembly it will make the axis difficult to adjust if it is too snug.

      After the nut is a bearing surface disk and under it is a bearing race which is about 3" in diameter that slips off of the shaft. Put them down on a clean piece of wax paper in the order you are taking them off.

      Next comes the worm gear disc, you may have to gently pull on the worm gear block to slide the disc off of the shaft.

      After the worm gear disk there should be a fiberboard washer almost the diameter of the gear disc. Take care NOT to get grease on any of the fiber washer's surfaces.

      Under all of that you should see the inside friction disc which is held on with four hex head Allen fasteners. These are the ones that were loose. Remove the four fasteners and remove that disc.

      What you have left is the encoder gearbox and gear which is held on with four Phillips head screws, I just checked them for tightness, all of mine were tight so I DID NOT remove them or the encoder gear.

      I cleaned the four Allen head fasteners and then reinstalled the friction disc and fasteners with a dab of Loctite on their threads. I also cleaned the surfaces of the friction discs with alcohol (not the fiber one) as I reassembled things so the surfaces would be grease free.

      Reassemble everything in the reverse order you took it apart and it should work much better.

      I did both axis (RA & DEC) in about 35 minutes.

      The procedure is much SIMPLER in actual practice than what it reads. Just take your time and remember the order things come off and to keep flat surfaces grease free.

      Just thought I would share.

      v/r
      Chuck Jagow
      Rott'n Paws Observatory
      36:46:23N / 76:13:31W
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