Loading ...
Sorry, an error occurred while loading the content.

Re: [ETXASTRO] Re: ETX125AT ALT/AZ percent numbers

Expand Messages
  • sdwest
    Hi, Andrew, ... I assume you mean that everything that is supposed to move, moves freely, and things that aren t supposed to move are rigidly immovable? I
    Message 1 of 23 , Jan 1, 2011
    • 0 Attachment
      Hi, Andrew,

      > As you note, it's pretty simple, but i found it very sensitive to how much
      > preload is used in each step of the reassy.

      I assume you mean that everything that is supposed to move, moves freely,
      and things that aren't supposed to move are rigidly immovable? I discovered
      that a couple of the fork arm ball bearings were stiff, and so freed them up
      with some very light RC oil. Probably should order some new ones.

      > There also one extra caveat if you do fully disasemble the base like you
      > did.
      > When reassembling, you must make sure the small pin that stops the
      > hardstop slip ring spinning is not between the fingers of the floating
      > hardstop ring. If the pin gets set between the fingers, you will not get
      > the 700 deg of RA rotation.

      I discovered this the hard way (no pun intended). What are the odds of
      randomly assembling the floating hard stop ring such that it is captured by
      that pin? Well, I did that, and when I checked the rotation, found that I
      had a little less than 360°. It did cause me to discover just how that hard
      stop works, however.

      > If you run patched firmware, i have added a special drive train function
      > to my PEC Editor that will allow you to do repetitive drive trains in both
      > directions and at different speeds and for different times. This allows a
      > fairly subjective test of the train repeatability.

      Although I've never done much astrophotography other than planets with my
      webcam, I've been reading about PEC and your patches, and I'll look into it,
      more for my GEM than these ETX scopes. I do run patched firmware, I have a
      couple of RoboScope mounts that have custom gear ratios, etc., in them. Of
      course, my old CG-5/Autostar with DS motors (which now uses LXD75 motors and
      custom gears) uses Dicks patches. I really don't enjoy drive training much,
      although it certainly isn't difficult, but generally want to get it done and
      get back to something more interesting. I usually do three passes, make
      notes of the training numbers, and make sure they are all consistent.

      > I just put some masking tape on one i played with.

      Why masking tape? Increased friction?

      > The problem isnt those clutch faces, its if the top clutch face slips.

      Actually, there is a tiny bit of slop in the RA axis with the clutch tight,
      it may be because the worm/worm gear mesh is not as tight as before. You'll
      recall that the fit on my RA clutch outer disk "key" was sloppy. I don't
      know if it's worth trying to find a fix for that, or not.

      > You need to make/get a bearing puller.
      > I made a custom puller up to remove the gear in situ.

      Did you pull against the gear itself with the puller? I'd be afraid to try
      that, since there are NO replacement parts of any kind available for these
      things. I think I'll leave that for now, until I am able to determine if
      it's still a problem.

      Thanks for your patience with all my "challenges", and questions.

      Wade
      Port Byron, IL


      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
    • sdwest61275
      Hi, all, Drive Training accomplished this morning. Average Alt number = 200, AZ number 580, plenty good enough for me. Alt ratio percent = 5%, Az ratio
      Message 2 of 23 , Jan 1, 2011
      • 0 Attachment
        Hi, all,

        Drive Training accomplished this morning. Average Alt number = 200, AZ number 580, plenty good enough for me. Alt ratio percent = 5%, Az ratio percent = 25%. Both axes begin to move in about 2 seconds after button push, and there is no overshoot. Gone are the retrograde movements in the gears when slewing is stopped. The motors run smoothly, and now it's time to check the goto accuracy under the stars. This ETX125 acts very much like my ETX105 at this point, and I'm confident that goto accuracy will also be much improved.

        One thing to note. My first drive training result was 1200, the second was 1500 after tightening the worm/worm gear mesh even more. So, tighter gear mesh was, indeed, the wrong way. When I loosened it all up again, (including the motor mounting screws with "O" rings), and used finger pressure to hold it while I tightened all the screws, it dropped back to 580. And, there is almost no play in the RA clutch now, either.

        You're probably all tired of hearing about this rebuild by now, I apologize for taking up so much of the ETXASTRO Group bandwidth, but it certainly was an interesting and worthwhile endeavor. Thanks to all who offered their assistance, and if I can be of any help to anyone, don't hesitate to ask.

        Wade
        Port Byron, IL



        --- In ETXASTRO@yahoogroups.com, "sdwest" <sdwest@...> wrote:
        >
        > Hi, Andrew,
        >
        > > As you note, it's pretty simple, but i found it very sensitive to how much
        > > preload is used in each step of the reassy.
        >
        > I assume you mean that everything that is supposed to move, moves freely,
        > and things that aren't supposed to move are rigidly immovable? I discovered
        > that a couple of the fork arm ball bearings were stiff, and so freed them up
        > with some very light RC oil. Probably should order some new ones.
        >
        > > There also one extra caveat if you do fully disasemble the base like you
        > > did.
        > > When reassembling, you must make sure the small pin that stops the
        > > hardstop slip ring spinning is not between the fingers of the floating
        > > hardstop ring. If the pin gets set between the fingers, you will not get
        > > the 700 deg of RA rotation.
        >
        > I discovered this the hard way (no pun intended). What are the odds of
        > randomly assembling the floating hard stop ring such that it is captured by
        > that pin? Well, I did that, and when I checked the rotation, found that I
        > had a little less than 360°. It did cause me to discover just how that hard
        > stop works, however.
        >
        > > If you run patched firmware, i have added a special drive train function
        > > to my PEC Editor that will allow you to do repetitive drive trains in both
        > > directions and at different speeds and for different times. This allows a
        > > fairly subjective test of the train repeatability.
        >
        > Although I've never done much astrophotography other than planets with my
        > webcam, I've been reading about PEC and your patches, and I'll look into it,
        > more for my GEM than these ETX scopes. I do run patched firmware, I have a
        > couple of RoboScope mounts that have custom gear ratios, etc., in them. Of
        > course, my old CG-5/Autostar with DS motors (which now uses LXD75 motors and
        > custom gears) uses Dicks patches. I really don't enjoy drive training much,
        > although it certainly isn't difficult, but generally want to get it done and
        > get back to something more interesting. I usually do three passes, make
        > notes of the training numbers, and make sure they are all consistent.
        >
        > > I just put some masking tape on one i played with.
        >
        > Why masking tape? Increased friction?
        >
        > > The problem isnt those clutch faces, its if the top clutch face slips.
        >
        > Actually, there is a tiny bit of slop in the RA axis with the clutch tight,
        > it may be because the worm/worm gear mesh is not as tight as before. You'll
        > recall that the fit on my RA clutch outer disk "key" was sloppy. I don't
        > know if it's worth trying to find a fix for that, or not.
        >
        > > You need to make/get a bearing puller.
        > > I made a custom puller up to remove the gear in situ.
        >
        > Did you pull against the gear itself with the puller? I'd be afraid to try
        > that, since there are NO replacement parts of any kind available for these
        > things. I think I'll leave that for now, until I am able to determine if
        > it's still a problem.
        >
        > Thanks for your patience with all my "challenges", and questions.
        >
        > Wade
        > Port Byron, IL
        >
        >
        > > ------------------------------------
        > >
        > > Yahoo! Groups Links
        > >
        > >
        > >
        >
      • johansea
        Gday Wade ... Sort of. When i first reassembled my base, i left the main preload nut loose so the RA could spin very freely . On doing Az moves, i could see i
        Message 3 of 23 , Jan 1, 2011
        • 0 Attachment
          Gday Wade

          --- In ETXASTRO@yahoogroups.com, "sdwest" <sdwest@...> wrote:

          > > As you note, it's pretty simple, but i found it very
          > > sensitive to how much preload is used in each step
          > > of the reassy.
          >
          > I assume you mean that everything that is supposed to move,
          > moves freely,

          Sort of.
          When i first reassembled my base, i left the main preload nut loose so the RA could spin "very freely".
          On doing Az moves, i could see i was getting Alt moves as well
          ( i had a webcam set up )
          When you look at the force diag i drew in my writeup, you will see that the design of the bearings ( with the wormwheel effectively on the end of a cantilevered shaft ) means that the looser the bearings, the more "flexible" the axle alignment becomes.
          Hence the note re maybe removing the teflon bearing and using a roller bearing instead.
          The tighter you make the base bearings ( to prevent the axle moving laterally ) the harder the worm has to work to turn it etc etc.
          I set mine so i could free spin it about 1/4 of a turn before it stopped.

          > What are the odds of randomly assembling the floating hard
          > stop ring such that it is captured by that pin?

          About 1 in 30 based on size of the fingers :-)

          > Although I've never done much astrophotography other than
          > planets with my webcam, I've been reading about PEC
          > and your patches, and I'll look into it,

          My editor doesnt only do PEC, it allows you to read/write data to your scope as well as a whole pile of diagnostic functions.
          One of which is drive training.

          > I really don't enjoy drive training much,

          You will love this.
          Just set a webcam on your scope.
          Start the app.
          It will ask you to centre a target then slew out back
          and log the data, then keep going out and back and recoding data on eack pass. You can do 10 trains in the time it takes to do one using the std means, and you cain see what results you get in both directions. Very usefull when doing stuff like you are doing now.

          > Why masking tape? Increased friction?

          Sort of. It held better even when it had a bit of oil/grease on it.

          > Actually, there is a tiny bit of slop in the RA axis with the clutch tight,
          > it may be because the worm/worm gear mesh is not as tight as before.

          Probably correct, but reread my notes on how the lower clutch plate works. If the "upper" clutch face gets greasy ( very easy ), then all the clutch torque is taken by that little slotted connection in the bottom of the RA axle. If that has any slop in its fit, it can also appear as "lash", but its inconsistent.
          Its not easy to fix this

          > > You need to make/get a bearing puller.
          > > I made a custom puller up to remove the gear in situ.
          >
          > Did you pull against the gear itself with the puller?

          Yep, but i did it in situ.
          If you remove the worm from its carrier, you can also use a hammer to gently punch out the worm
          Ie Unscrew the socket head capscrew a few turns and use it as the punch for the hammer.

          Andrew Johansen Melbourne Australia
        Your message has been successfully submitted and would be delivered to recipients shortly.