Dec worm movement after Belt mod

[LightBucket]

Hi,

I have an EQ6, and did the belt mod a while back, and have not used the scope much since. I have been getting some power issues sorted, which I have now done, and also been learning some new software, ready for the new season..

Anyway I noticed a very slight bit of play in the DEC assembly, and I new when I did the mod that both axis were nice and tight with no noticebable backlash, and no binding, more about binding later.... so I though that it must be side to side play of the worm gear, so took the black cap off, and yes the locking ring was only just hand tight, and moved with a screwdriver quite easily, so nipped it up about 1/8th of a turn and play now gone.

But first of all, how has that come loose..?

and secondly after reading the Astro baby guide, which says, “to tighten up the locking ring so it’s tight but not too tight as to cause binding”..well how tight is that..? And how do I tell if I have binding, what are the symptoms, I have tightened it up pretty tight (it would go a bit tighter) and all seems fine, the motor turns the mount no problem, I did a full 360 degree turn on the DEC axis.

As the worm is a shaft which is in a fixed position, how can that locking ring be too tight, as the shaft can’t move anywhere...! Can it, so what can bind...? And what damage can be caused if it is too tight..?

thanks in advance

[1parsec]

Hi L B.  
The adjustment ring touches on the outer race of bearings which presses the outer race against the ball bearings and then on to the inner race. This takes out the natural clearances manufactured in to the bearings.
If you over tighten the ring the pressure on the bearing can be such that it doesn't turn smoothly. It can get really 'lumpy' if you really over do it and could be damaged to the point the may not run smoothly ever again  
Just 'finger tight' is all that's needed on the ring adjustment.
The shaft isn't in a fixed position, rather supported between 2 bearings which 'position' can be adjusted.
 

[LightBucket]

2 minutes ago, 1parsec said:

Hi L B.  
The adjustment ring touches on the outer race of bearings which presses the outer race against the ball bearings and then on to the inner race. This takes out the natural clearances manufactured in to the bearings.
If you over tighten the ring the pressure on the bearing can be such that it doesn't turn smoothly. It can get really 'lumpy' if you really over do it and could be damaged to the point the may not run smoothly ever again  
Just 'finger tight' is all that's needed on the ring adjustment.
The shaft isn't in a fixed position, rather supported between 2 bearings which 'position' can be adjusted.
 

Hi, and thanks for that

If I have them just finger tight, I still have a little play on the DEC worm, whereas if I go a bit tighter I can remove that...so which is best, a little tighter and no play or backlash, or a tiny bit of backlash..?

[spillage]

As I have just completed the same mod I can add to this. I have found that whilst backlash or the removal always seems to point to adjusting the worm screws on the worm housing this is no always the case. I found that the worm gear and bearing  (bearing on the axis) also need adjusting and its a balancing act with these three parts to have the mount working as best you can.

I also tighten up the worm gear ALLOT and it still would not bind. This was done whilst it was running. I did back it off as I did not want to leave it too tight.

My thoughts are that if you really do tighten it too much then the gear wheel may rub against the mount or you may strip the threads.

[spillage]

1 minute ago, LightBucket said:

Hi, and thanks for that

If I have them just finger tight, I still have a little play on the DEC worm, whereas if I go a bit tighter I can remove that...so which is best, a little tighter and no play or backlash, or a tiny bit of backlash..?

If you get the chance check this whilst guiding and see if it makes any difference. I have not had clear enough skies but tonight may give me the chance of some fine tuning.

[LightBucket]

1 hour ago, spillage said:

If you get the chance check this whilst guiding and see if it makes any difference. I have not had clear enough skies but tonight may give me the chance of some fine tuning.

Well I have just been out to the garage and redone them, loosened and then slowly tightened until all the play out of each axis had gone...they are just about hand tight, but with the correct tool would go about another 1/4 to 1/2 turn..

Any idea where I can get the special tool from to remove these nuts, I know there is one..?

Ok found the tool on Rowan site, knew I had seen one somewhere...

[astromerlin]

Hi, I'm just in the process of doing a belt mod on my Black EQ6. I have noticed whilst stripping it down that the worm spindle end cap that covers the worm bearing adjustment ring is locked with a grubscrew. I suspect that originally there were shims between the adjustment ring and the endcap so you could snug the adjustment ring, add shims and then fit endcap and lock endcap in place with the grub.

The grubscrew and shims were missing and the previous owner had put a dab of thread lock after adjusting. This had worked well as there was no perceptable play in the shaft and the adjustment ring unscrewed after a small force.

If you do use threadlock, make sure it is the blue one and only use a pinhead size dab after you have snugged the ring down. This will be enough to stop it moving of it's own accord, put too much and it will be a pain in the elbow to remove.

 

[LightBucket]

1 hour ago, astromerlin said:

Hi, I'm just in the process of doing a belt mod on my Black EQ6. I have noticed whilst stripping it down that the worm spindle end cap that covers the worm bearing adjustment ring is locked with a grubscrew. I suspect that originally there were shims between the adjustment ring and the endcap so you could snug the adjustment ring, add shims and then fit endcap and lock endcap in place with the grub.

The grubscrew and shims were missing and the previous owner had put a dab of thread lock after adjusting. This had worked well as there was no perceptable play in the shaft and the adjustment ring unscrewed after a small force.

If you do use threadlock, make sure it is the blue one and only use a pinhead size dab after you have snugged the ring down. This will be enough to stop it moving of it's own accord, put too much and it will be a pain in the elbow to remove.

 

Yes, mine has the holes for grubscrews but none fitted, I don’t think they are fitted as standard anymore...they are not needed to be honest, I am going to fir a rubber O ring in mine between the black cap and the lock ring, to stop any vibration loosening the lock ring, as that is the only reason I can think of why it came slightly loose...

Dont think I will use any form of locktight..

[LightBucket]

On 21/09/2017 at 16:44, spillage said:

I also tighten up the worm gear ALLOT and it still would not bind. This was done whilst it was running. I did back it off as I did not want to leave it too tight.

My thoughts are that if you really do tighten it too much then the gear wheel may rub against the mount or you may strip the threads.

I don’t think this is possible, as the worm shaft is up against the black cap on the far side of the mount, which gives it its position, so as long as that cap is in place, it can’t really move any further that way.. unless you do distort the bearing in some way to achieve this...

Which was the point of my initial question, how tight should the lock ring be... I cant seem to find the info anywhere, and the Astro Baby Guide is not very good when describing this bit, as it just states to “tighten till it binds then back off a little”, well I’m sorry but if you tighten till is binds, couldn't you damage the bearings at this point..?? So it’s not very helpful really..

I have mine set so just removed all the side to side worm play, and then another 1/8th of a turn, but to be honest, it’s still a tad “loose” (loose not really the right word here) in my opinion, hence needing to know exactly how to do this...

I will keep searching..

[spillage]

yeah did not really think about the cap stopping the shaft moving that far. I guess I just did mine up till using the tool by hand and then used a screwdriver and gave it a twist. I can only describe it like when you change your car wheel and you tweek the bolts up before lowering the car . I would say if its loose do it up a bit and then run it and see how the graph is. If its that bad then you can adjust the worm on the fly.

[kens]

10 hours ago, LightBucket said:

I don’t think this is possible, as the worm shaft is up against the black cap on the far side of the mount, which gives it its position, so as long as that cap is in place, it can’t really move any further that way.. unless you do distort the bearing in some way to achieve this...

Which was the point of my initial question, how tight should the lock ring be... I cant seem to find the info anywhere, and the Astro Baby Guide is not very good when describing this bit, as it just states to “tighten till it binds then back off a little”, well I’m sorry but if you tighten till is binds, couldn't you damage the bearings at this point..?? So it’s not very helpful really..

I have mine set so just removed all the side to side worm play, and then another 1/8th of a turn, but to be honest, it’s still a tad “loose” (loose not really the right word here) in my opinion, hence needing to know exactly how to do this...

I will keep searching..

The only way to know is if the worm and ring gear bind. You test binding by slewing the axis through its full range or as close as possible (remove the OTA and weights!!!). If it binds it will make an unmistakable noisewhich I believe is the motor skipping.

[LightBucket]

Well an update, recieved the special tool today from Rowan engineering for removing the locking ring, really does make the job much easier...it also come with two removable pins to undo the black caps too, excellent design.

So I removed the locking rings and refitted with the tool just tightening to the the point where the lock ring starts to turn the outer race of the bearring as it tightens against it, then stopping, it works out about 1/8th of a turn past the point that all the side to side worm play is removed, I had some advice by email via a company that does mount tuning....

May be useful for others..

 

[spillage]

Thanks for the update and the info. If I get chance tonight I may risk rechecking mine depending on how brave I am feeling.