Jump to content


Photo

Backlash Adjustment - G11

  • Please log in to reply
6 replies to this topic

#1 dawziecat

dawziecat

    Vanguard

  • *****
  • Posts: 2425
  • Joined: 20 Oct 2010
  • Loc: Rural Nova Scotia

Posted 06 October 2012 - 08:03 AM

I just finished reading through the old thread G-11 Blues.

My G11 exhibits 1.1mm of play in the RA worm/gear mesh as measured at the end of the standard Losmandy 15 inch CW bar which is 21" from the center of the PA.
In "doing the math" to convert this to an angular measure. I come up with, more or less, 6.5 arcminutes.

Should I be aiming at bettering this? It seems tricky to get it less without the gears binding.

#2 Charlie B

Charlie B

    Viking 1

  • -----
  • Posts: 967
  • Joined: 22 Mar 2008
  • Loc: Sterling, Virginia

Posted 06 October 2012 - 08:20 AM

Do you have the OPW-11 (one-piece worm block - see here )? If so, it may not be too difficult to improve without binding. If not, I recommend that you upgrade.

Charlie B

#3 TxStars

TxStars

    Apollo

  • *****
  • Posts: 1382
  • Joined: 01 Oct 2005
  • Loc: Lost In Space

Posted 06 October 2012 - 08:31 AM

"Backlash in the R.A or DEC gear is caused by two things.
First, the meshing of the worm to worm gear and second if there is play of the worm between the two worm bearings"
Play of the worm between the bearings can be seen by watching the worm as you move the Dec by hand with the clutch tight.

#4 dawziecat

dawziecat

    Vanguard

  • *****
  • Posts: 2425
  • Joined: 20 Oct 2010
  • Loc: Rural Nova Scotia

Posted 06 October 2012 - 09:02 AM

An update:

I have continued to fiddle and have eliminated the backlash . . . seemingly entirely! No binding . . . worm turns easily with fingers rotating the Oldham coupler.

Sounds too good to be true. I suppose there IS still backlash but it has diminished to the point that I can not reliably even estimate it.There is still noticeable chatter when rotating the worm with the mount unbalanced in the wrong direction so, I guess that means there MUST still be some play in there.

So, I feel this is good.

Stock G11 worm and block, not Ovision and not OPWB.

#5 Charlie B

Charlie B

    Viking 1

  • -----
  • Posts: 967
  • Joined: 22 Mar 2008
  • Loc: Sterling, Virginia

Posted 06 October 2012 - 09:42 AM

Good for you.

Charlie B

#6 Dan Finnerty

Dan Finnerty

    Messenger

  • -----
  • Posts: 437
  • Joined: 11 Sep 2011
  • Loc: Pasadena, CA

Posted 06 October 2012 - 05:49 PM

"Backlash in the R.A or DEC gear is caused by two things.
First, the meshing of the worm to worm gear and second if there is play of the worm between the two worm bearings"
Play of the worm between the bearings can be seen by watching the worm as you move the Dec by hand with the clutch tight.


I upgraded to the Losmandy OPWB on my G11 and ended up with a lot of play at the end of CW shaft, maybe 5 to 7mm. An unacceptable amount. I could not eliminate it by cranking down on the worm without RA stalling. I came across a post on the Losmandy yahoo forum that suggested the problem could be end play in the worm between the blocks and provided a link to some shims. I ordered several thicknesses (.002 and .006 inches as I recall). It took about 4 shims of varying thicknesses to tighten things up, but it did solve the problem. I left things at about 2mm end play on the CW shaft and it all seems to work just fine.

#7 JoseBorrero

JoseBorrero

    Gemini

  • *****
  • Posts: 3170
  • Joined: 04 Sep 2009
  • Loc: Puerto Rico Island

Posted 06 October 2012 - 10:05 PM

theres a great info in losmandy user groups, it start some where in astromart website http://www.astromart...?article_id=861


but the true info is in yahoogroups :waytogo: goodluck






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics