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Dismantling EQ6

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Grant Privett's picture
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Dismantling EQ6

In a momentary lapse of reason, I have started dismantling a 2008 vintage NEQ6 to apply a Rowan belt upgrade.

As part of that activity, I need to get the large circular bolt off the RA axis (seems to hold the taper bearing in place).

Has anyone else trod this path?

The problem is, its jammed. I undid the 4 grub screws round the edge of the 58mm wide circular bolt, but the surface is smooth and I cannot get a decent grip on it with my hand even with rubber fabric in place.

I tried lightly tapping it with a hammer and heating the bolt with a very hot coverless waterbottle.

I even tried putting two allen/hex keys in two of the grub holes and trying to use those to rotate the thing off, but its not budging. I've now poured WD40 down the grub screw holes in the hope that might free it up but, so far, no go.

I've ordered a oil filter plastic/rubber wrench, but am not confident.

I noticed one of the clutch bolts was Loctited and am hoping SkyWatcher didn't use it on this bolt too.

Thoughts anyone? Loosely translated as "Help!". :)

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Can you post a picture of the

Can you post a picture of the bit which is stuck?

Have you used this site to help you:

http://www.astro-baby.com/EQ6%20rebuild%20guide/EQ6%20RA%20strip%20down.htm

James

Grant Privett's picture
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Pics

Was taking them a few minutes ago. :)

Astrobaby suggests a bolt/strap based oil filter wrench, but most of those don't go down to 58mm diameter. Might try one of the 60mm ones with a few layers of rubber after I try the strap based one arriving tomorrow.

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Can't help you with the NEQ6

Can't help you with the NEQ6 (I have one of the belt-modded ones but the mod was done before I bought it) but I'm sure Mrs. Beeton won't be too happy to see her cookbook used in this way.

Grant Privett's picture
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Cookbook

It had the essential ingredient of being just the right thickness! 

Have noticed though that the hot water bottle doesn't really warm it. Perhaps a blow torch would do better!

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Yes, I think a hot water

Yes, I think a hot water bottle is a bit pathetic really. What kind of engineer are you? A propane blowtorch would be better, particularly if the thread is loctited. When I was doing some work on my mount in the summer I bought one of the cheap cookery ones from Amazon. It worked for me. If it doesn't work to free your thread you can always make a creme brulee.

Grant Privett's picture
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Engineer!

I'm no engineer, me.

The flame thrower option is now my third resort - and I can console my self with pudding if it fails. Whats not to like?

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Reverse thread?

Are you sure you are turning it the correct way?

Robin Leadbeater's picture
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conventional right hand thread

This video suggests a conventional right hand thread. (Though it also shows it to be deceptively simple to remove !)

https://www.youtube.com/watch?v=SrvkKjgjbRY

(16 min 30 sec)

Grant Privett's picture
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Youtube

Apologies. I never think of youtube. I associate it with music mainly. Thanks for the steer.

Yes, the video did make it look easy. Sufficiently so that I now have a second oil filter tool on order - for the price of a pint of beer in London, why not!

Will let you know what transpires.

Grant Privett's picture
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Widdershins

I'm trying counter clockwise. Open to offers though!

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Dismantling EQ6 - desperate measures

Have you tried a little 'impact engineering' (thumping it with a rubber-headed hammer)?

It may not work but it could make you feel better.

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tapered roller bearing preload

Does this ring preload the taper bearing?  If so it should not really be that tight (Just enough to preload the taper bearing by the right amount, hence the use of the grub screws to lock it in place.)  Has it been stripped down before and retightened?  (These internet strip downs never seem to talk about torque settings which I would have though are pretty critical for precision engineered parts like these)

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Dismantling EQ6

Rother Valley Optics do a lot of EQ6 belt mods, so it might be worth giving them a ring for advice. Their shop is closed, but still manned, I think, and I have always found them very helpful.

Can’t help further with the mount, but it’s snowing heavily here in Sheffield so I’m prepared to make a good offer for your hot-water bottle...

Good luck!

Bill 

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Rother Valley Optics

Thanks for the thought. Rother Valley were who I bought the upgrade kit from and have always been helpful with me too.

Grant Privett's picture
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Success

The nut came off! .......  Eventually.

It required the metal band oil filter wrench. Because its only meant for 60mm diameter or greater nuts I had to introduce a 4mm deep strip of rubber and it took me leaning very heavily on it to make it move - even then it was reluctant. Doesn't, look especially corroded or glued. A poor thread originally perhaps. The surface of the nut is slightly damaged, but I use my scopes rather than worship them, so I'm really not fussed.

Anyway, I strongly recommend an oil filter wrench to anyone trying this sort of thing - and also the bearing removal tool thingy (technical engineering term) that Rowan sell.

Mine is an old EQ6, which probably also explains the bad thread on the gear wheel attached to the RA worm - . Even after 24hrs doused in WD40 it was still hard enough on that I thought the Allen key would snap...

That said, I'm happy to say I have not seen any of the swarf recorded on some accounts of servicing an EQ6.

So, the mount now is at max entropy. Now to try and put it back together with the Rowan upgrade.

There may be a whining and the gnashing of teeth heard throughout the land.

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All the pain is definitely

All the pain is definitely worth it. I have a belt-modded NEQ6 and it tracks very well with remarkably small and smooth PE for such small gears.

Presumably, as Haynes manuals used to say: "reassembly is the reverse of disassembly" although I've generally found that springs make disassembly a one-way process.

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Oops

Losing one of  the externally threaded nuts/slotted insert that holds the RA worm and bearing in place has a similar impact. :)

3 hours into the search for it, floor, table, hall, rest of kitchen and will be searching conservatory tomorrow (in case it got stuck to soles of shoes). Even checked the rubbish bin in case it got caught up with a greasy tissue. I'm really not enjoying this activity very much so far... :)

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Assuming you can find the

Assuming you can find the lost widget this is what to expect from the NEQ6 once you've modded it. This is the unguided performance. In this case the exposures are 60s so the graph covers around an hour. The Dec drift is due to polar misalignment (this is a "portable" mount) but the 8 minute periodic error in RA is clear and it has a peak-to-peak amplitude of around 15 arcsec (the scale is pixels which are 2.1"). It is very smooth too and guides out easily if you can be bothered. I don't bother and just rely on relatively short exposures (60s) and stacking. That is a pretty good approach for CMOS sensors anyway and makes for a very easy imaging setup. This plot corresponds to the performance obtaining this image.

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Performance

That looks very hopeful. The EQ6 I have was pretty usable with a quite good PE, but was becoming more prone to nights where there were large spikes superimposed on the PE waveform - dirt in the RA worm I assume.

Interesting what you say about  CMOS. Is it that you need to take fresh darks every night and can't rely on using a bias frame and long exposure dark to generate darks for arbitrary exposure lengths? CMOS certainly are having an impact these days and with CCD foundries closing round the world, we may not have any choice soon.

I must admit that, CMOS sensors like the QHY600 have nice looking specs - interesting to see how the spec and actuality compare. 

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Not to do with darks. I'm

Not to do with darks. I'm using the same darks for my camera that I've been using since the beginning of last year. I have a library of darks for each exposure that I use and I never scale them. CMOS cameras generally have much lower read noise than CCD cameras so stacking loads of short exposures works well. This has benefits in the stacking process since outliers (satellite trails, the odd badly guided image etc. can get rejected in the stacking process. You are right that CCD sensors are becoming specialist items now limited to a very few applications. Even cameras on spacecraft are gradually making the transition.