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martin_h

Dec backlash

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Ever since I've had my mount, 6 years or so, it's suffered from chronic Dec backlash, so much so that PHD2 can't tell me how much there is! The main problem being that I cant(couldn't)  adjust the worm end float nut, it refuses to move in any direction, the shaft is so loose that I can move it with my fingers, over the years this has made imaging interesting!

Last night being cloudy I decided to sort it once and for all, a set of needle nosed pliers in the slots wouldn't shift it at all, so I resorted to the old engineers standby......big hammer and a screwdriver in the slot. After the persuasion I went back to the pliers and gripping them in mole grips managed to get a small amount of anti clockwise movement, and , after a bit more persuasion managed to get very tight movement in both directions sufficient to say that I can no longer feel any slop in the Dec axis but only time and a clear sky will tell!

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34 minutes ago, martin_h said:

Ever since I've had my mount, 6 years or so, it's suffered from chronic Dec backlash, so much so that PHD2 can't tell me how much there is! The main problem being that I cant(couldn't)  adjust the worm end float nut, it refuses to move in any direction, the shaft is so loose that I can move it with my fingers, over the years this has made imaging interesting!

Last night being cloudy I decided to sort it once and for all, a set of needle nosed pliers in the slots wouldn't shift it at all, so I resorted to the old engineers standby......big hammer and a screwdriver in the slot. After the persuasion I went back to the pliers and gripping them in mole grips managed to get a small amount of anti clockwise movement, and , after a bit more persuasion managed to get very tight movement in both directions sufficient to say that I can no longer feel any slop in the Dec axis but only time and a clear sky will tell!

Just a word of warning, that end float locking nut only needs to be tight enough to take out any slack, it does not need to be tightened right up as it can distort the bearing...when tightened just right a little dab of locktight on the thread will hold in place well enough.. :)

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Well, that made no difference to my guiding as far as I can tell, hey ho!

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5 hours ago, martin_h said:

Well, that made no difference to my guiding as far as I can tell, hey ho!

Hi Martin

Did you check/adjust the (DEC) motor gear meshing? It's likely to be the prime source of backlash.

Louise

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4 minutes ago, Thalestris24 said:

Hi Martin

Did you check/adjust the (DEC) motor gear meshing? It's likely to be the prime source of backlash.

Louise

Yes I did, still, its no worse so I can live with it.

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I've had my fair share of problems with my NEQ6 Dec axis. The number one source of play has been the worm meshing adjustment. It can be very fiddly and take several iterations to get right. Some times less than an 8th of a turn on the adjustment grub screws makes the difference.

But of course if your worm shaft has axial end play then that should be fixed first. The locking ring might be secured with loctite and might require a bit of local heat to get it moving freely. A small gas torch is good for this but you don't want to over do it. You don't want to burn the rubber seals on the bearings... Might not be a bad idea to replace the bearings with new ones, clean the threads etc. The bearing on the opposite side to the locking ring should be leaning against the black cap thingy and like stated before the locking ring needs to be tight enough to take out any slack but no more than that.

Another unexpected source for  backlash / play on my DEC axis has been the clutch lock. I guess mine is a little worn and the lever wanted to go further than 90 degrees to engage. This made it harder to lock the clutch properly so I just unscrewed the lever and turned it a couple of notches back to have more leverage.

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On 13/09/2018 at 12:17, kbrown said:

 

Another unexpected source for  backlash / play on my DEC axis has been the clutch lock. I guess mine is a little worn and the lever wanted to go further than 90 degrees to engage. This made it harder to lock the clutch properly so I just unscrewed the lever and turned it a couple of notches back to have more leverage.

That's exactly what I have done!

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