My NEQ6 Pro DEC axis froze, literally...

[kbrown]

Hi,

I've just returned from a partially successful holiday trip with my telescope. Had all sorts of tech trouble but one of them was something new to me. I had my tripod and NEQ6 Pro outside for 6 days to avoid having to level it up and do polar alignment over and over again. I had to take the telescope off a couple of times as there were some wet days and my cover is not big enough to cover everything.

Anyway, on the last night clear enough to do any imaging I encountered an issue that I haven't had before. The moisture in the air probably had condensed inside my NEQ6 and eventually froze when the temperature reached 0-1C and rendered the DEC axis unusable. It sounded "crunchy", skipped steps and was generally pretty nasty so I called it quits and took the whole thing back inside.

Next day when it had warmed and dried up I tried it again and it worked just fine. I don't think there's any permanent damage to the drive mechanism but what I would like to know if you have encountered anything similar and how are you preventing it from happening again? Is it just generally not a good idea to leave the mount outside like this?

[kbrown]

I should add that I have done the Rowan Astronomy belt modification to this mount and used TF2 lithium grease (rated from -30C to +130C I believe) to lubricate everything...

[LightBucket]

When you did the belt mod, did you do all the worm adjustments in working conditions, by that i mean in the cold outside, as they should be, if not and done in the warm, then when it gets very cold the metal parts can alter in size very slightly which in a precision bit of kit, can cause binding or other issues.. Just a thought  

[kbrown]

Good thought. Thank you! I did all the adjustments inside in room temperature. I haven't had any issues with binding before but I do recall the DEC axis being a bit fiddly when I did the adjustments. It did bind once or twice when I was adjusting it but didn't sound "crunchy" like it did on the cold night out couple of days ago.

I'll see if I can re-adjust both of the axis outside when it gets cold enough.

[LightBucket]

The only part that could crunch as you put it would be the worm itself as there is no other metal on metal, but don’t quite know how you would get damp in there to be honest... strange one that

[kbrown]

Strange indeed. I'm just guessing it was the moisture in the air that got in there and when it cooled down enough it condensed as dew and then eventually froze. It happened on the outside parts of of the OTA (steel tube) itself too on the same night.

[1parsec]

I think Lightbuckets suggestion is right.  The mesh is just a bit too close and on a cold night things have contracted a fraction causing the axis to bind.
I'd be very surprised if the mount was to freeze. The motors do generate some heat even when stationary and that would probably enough background heat to keep the mount from freezing.

[Ceph]

This thread started a while ago but I have something to add here.
I also have a NEQ6 mount and been having  some different issues with it, (see my webpage for more on that)
Mine is also belt modified, last thing I did was replacing 5 bearings with better quality bearings, the 4 worm
bearing and the large taper thrust bearing as it was infested with metall chips. Tested all inside and it sounded and worked fine.
When the first clear sky was on its way (14 days ago) I carried the mount outside in daylight as I needed to reset the balance and so on, it was around 0 C when I started. 3-4 hours later it was time to startup the night session
now in around -5C and when it was time to do the star ailgment the motors in the mount stalled sounding like they missed every cog, crounchy, the mount could not be moved either on RA or DEC. Nothing to do but to carry all inside again. Next day I went over all again meaning picking all parts down again and gently back together again.
Next occasion given I did same procedure again, out with the mount in daylight and after 3-4 hours started all up
again. Same result, both motors stalled and that night was ruined.
I have now been analyzing it for a while and come to this conclusion. 
I had never carried the mount out in cold weather before so early and letting it stand without any power just cooling down.
What happened was that the mount is reacting to the cold and the metalls is shrinking and even more problematic is that the housing is made of aluminium while the shaft is made of steel so they seperately reacts different to temperatures.
My normal procedure was to carry the scope out one hour before starting to let it cool down and when it was time
I carried out the mount and started the setup at once. Doing so and starting at once the small motors gave enough
heat to keep the mount not to shrink so much that the motors would stall.
To avoid this I have now ordered a dew heater tape that I will put around the RA and DEC heads and when I have carried the mount outside I will give power to this heater at once.
I think this is one of the reasons that this mount is so unpredictable.

[LightBucket]

Hmm, if this was the case the mounts would not have a very good following, as loads of people would have issues, these mounts are meant to be used in the cold weather, that’s the point, it seems that more people have issues after a belt mod or for any reason the mount has been stripped down, so it’s my conclusion, that it’s all about perfect adjustment after the mod, and people don’t seem to get it right first time, hence the issues.

These are precise instruments and so need to be adjusted accordingly, there is not much room for error as you are finding out, my guess is your problem is worm gear adjustment, also bearing tolerance, you replaced the bearings and if they are a fraction out in there size you will also have issues.

People who have not had a reason to strip the mount down, don’t seem have issues like these, ...  

[Ceph]

Why the belt modification would affect anything I cant get myself around as rubber is more elastic then steel and very much nicer with temperature changes
Of course if you done the operation bad it would give issues, I as many others have been using belt mod for a while now and I had no more issues than before
it improved the mount slightly.

The thread starter had the same issues without changing any bearings.

And yes the adjustments on the worm RA and DEC is done most accurate in my case. And of course SKF bearings cant be out of fraction of size as the orignal is.

I had several reasons to strip my NEQ6 down as you will see on my webpage.

 

[Jkulin]

The crunchy noise sounds like a lack of voltage output, usually when the voltage is low, was your LED flashing, if so they would bet that you have a problem with the voltage.

When mine had problems it sounds like a bag of bolts, you really need more that 12.5V

[Ceph]

No the LED was/is not flashing and yes it sounds like a bag of bolts, it is the motors that cant perform their work, they are tiny motors and if you by force tries to stop any of RA or DEC axis you will hear it.

Starting to play with the volatage output I will leave to the manufacturer. It works above 0 C. I have owned mine NEQ6 for 2 years now, as I said the last two times I did a different procedure by

putting it outside 3-4 hours before starting it up and it, which was my mistake.

[SteveA]

I have definitely had issues after tuning out backlash in the DEC axis on my EQ6. I got my DEC axis as close to binding as possible to eliminate as much backlash as possible and whilst the temperature was around 10 C I had no problem at all on the axis, I could slew in in either direction with no binding. However as the temperature dropped to around freezing, the worm started binding and I ended up having to back it off a bit. I've had no problems since despite unfortunately having to put up with more backlash than I wanted.

Needless to say..when you do get binding it is quite a distressing noise!

Steve

[LightBucket]

20 minutes ago, SteveA said:

I have definitely had issues after tuning out backlash in the DEC axis on my EQ6. I got my DEC axis as close to binding as possible to eliminate as much backlash as possible and whilst the temperature was around 10 C I had no problem at all on the axis, I could slew in in either direction with no binding. However as the temperature dropped to around freezing, the worm started binding and I ended up having to back it off a bit. I've had no problems since despite unfortunately having to put up with more backlash than I wanted.

Needless to say..when you do get binding it is quite a distressing noise!

Steve

Yes totally agree, it’s all about finding the middle ground with adjustment, I don’t think that you can ever remove all backlash and still have a working mount in all conditions, but it does defy science a bit, as when it gets cold the mounts seem to bind more, which is odd as metal shrinks when cold, so you would think the gaps would open up and not bind..!, but hey ho such is life in this hobby

[newbie alert]

2 hours ago, Ceph said:

No the LED was/is not flashing and yes it sounds like a bag of bolts, it is the motors that cant perform their work, they are tiny motors and if you by force tries to stop any of RA or DEC axis you will hear it.

Starting to play with the volatage output I will leave to the manufacturer. It works above 0 C. I have owned mine NEQ6 for 2 years now, as I said the last two times I did a different procedure by

putting it outside 3-4 hours before starting it up and it, which was my mistake.

So if you started at say 8 in the evening and it was at 2 degrees and by the end of the session it' at -5  would you have a problem?

And saying you lived in Canada or Norway  where temps of -20 are fairly common..would you have a problem there also?

[Ceph]

1 hour ago, newbie alert said:

So if you started at say 8 in the evening and it was at 2 degrees and by the end of the session it' at -5  would you have a problem?

And saying you lived in Canada or Norway  where temps of -20 are fairly common..would you have a problem there also?

If I started my session at once I never had any problem as the motors gives away some heat.
Can't say about -20 but it has been out in -12 and worked fine (Starting at once)

From now on I will have a dew heating tape around the mounts worm heads, maybe this will in fact help to minimize the backlash as I now can tighten this up, time will show

[SteveA]

2 hours ago, LightBucket said:

Yes totally agree, it’s all about finding the middle ground with adjustment, I don’t think that you can ever remove all backlash and still have a working mount in all conditions, but it does defy science a bit, as when it gets cold the mounts seem to bind more, which is odd as metal shrinks when cold, so you would think the gaps would open up and not bind..!, but hey ho such is life in this hobby

That's a good point actually.....though if you think about it its not just the worm & gear that would shrink, but the whole worm carrier its self. Its a big block of metal and it certainly gets cold, so I guess as Ceph mentioned above.....heating the worm carrier/ axis housingcould work.

Steve

[KemalOz]

On 24.03.2018 at 11:22, SteveA said:

I have definitely had issues after tuning out backlash in the DEC axis on my EQ6. I got my DEC axis as close to binding as possible to eliminate as much backlash as possible and whilst the temperature was around 10 C I had no problem at all on the axis, I could slew in in either direction with no binding. However as the temperature dropped to around freezing, the worm started binding and I ended up having to back it off a bit. I've had no problems since despite unfortunately having to put up with more backlash than I wanted.

Needless to say..when you do get binding it is quite a distressing noise!

Steve

All gears should have some backlash in order to work, it is impossible to get it all out without them binding. Furthermore, these mass-produced mounts have more backlash then needed in most cases because of imperfect manufacturing of all the other parts. They have to produce the gears with higher tolerances so that worm wouldn't bind in one part of the worm gear while working fine on another part. I have heard of stories of people lapping their gears outside of the mount and when they put them back in it was worse than before because they just bind up due to having very low tolerances after lapping.

So, the best-case scenario is to learn to live with the backlash. Adjust it of course to an acceptable level and then try to guide in one direction only or imbalance the scope to one side.

[lux eterna]

+1 on the "accept the backlash" thoughts.

I have pretty much backlash in both dec and ra on my HEQ5 Pro, but never had any issues with it even when imaging with 1600 or 2000 mm FL. Adjust ra for "east heavy" and also a little unbalance (front or back) on dec (just beware that the imbalance gets zero:ed out in certain ota positions). Or you could skip the dec imbalance and make yourself a dec backlash killer. I have used it for years now and it is just perfect, independent of the ota position.

That is a piece of 90 degree aluminum profile, attached with double-sided tape. In the beginning, I always forgot to loosen the thumb screw when slewing so I had to replace the coil spring a few times .

Ragnar

[LightBucket]

44 minutes ago, lux eterna said:

+1 on the "accept the backlash" thoughts.

I have pretty much backlash in both dec and ra on my HEQ5 Pro, but never had any issues with it even when imaging with 1600 or 2000 mm FL. Adjust ra for "east heavy" and also a little unbalance (front or back) on dec (just beware that the imbalance gets zero:ed out in certain ota positions). Or you could skip the dec imbalance and make yourself a dec backlash killer. I have used it for years now and it is just perfect, independent of the ota position.

That is a piece of 90 degree aluminum profile, attached with double-sided tape. In the beginning, I always forgot to loosen the thumb screw when slewing so I had to replace the coil spring a few times .

Ragnar

When you say East heavy, I assume you mean slightly more weight on counterweights...but doesn’t that swap to West after the Meridian flip..??

[spillage]

Might it of been that when you fixed the ota back on the mount is was not balanced as well as it was before? Also if the gears shrink then the crunching would be where the gap increases and the gears can then slip rather than bind.

[KemalOz]

7 hours ago, lux eterna said:

+1 on the "accept the backlash" thoughts.

I have pretty much backlash in both dec and ra on my HEQ5 Pro, but never had any issues with it even when imaging with 1600 or 2000 mm FL. Adjust ra for "east heavy" and also a little unbalance (front or back) on dec (just beware that the imbalance gets zero:ed out in certain ota positions). Or you could skip the dec imbalance and make yourself a dec backlash killer. I have used it for years now and it is just perfect, independent of the ota position.

That is a piece of 90 degree aluminum profile, attached with double-sided tape. In the beginning, I always forgot to loosen the thumb screw when slewing so I had to replace the coil spring a few times .

Ragnar

nice design. what is the tension of the spring? Is it properly pulling or more like a slight imbalance?

[lux eterna]

8 hours ago, LightBucket said:

When you say East heavy, I assume you mean slightly more weight on counterweights...but doesn’t that swap to West after the Meridian flip..??

If the scope is on the east side of the mount, the scope side should be heavy; if the counterweights are on the east side, the counterweight side should be heavy. You need to adjust as the CW:s pass north.

[lux eterna]

59 minutes ago, KemalOz said:

nice design. what is the tension of the spring? Is it properly pulling or more like a slight imbalance?

The spring tension - hard to tell but maybe I pull the string/thumbscrew, before I lock it, almost as much as you would need to lift 1 kg (= 10 N). That equals a very small force on the top of my OTA.