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Atlas/ EQ-6: can you help with disassembly?

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#1 macdonjh

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Posted 18 August 2019 - 10:43 AM

I am working on an Atlas/ EQ-6 and need help with the last bit of disassembly of the declination axis:

 

20190818_102634.jpg

 

That top casting looks like it's threaded on to the top end of the declination shaft, but it won't budge with the tools/ force I've used so far.  I don't want to go too hard with it until I know I'm going down the right path.

 

20190818_102641.jpg

 

So does anyone know how to get that casting off the shaft?



#2 sg6

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Posted 18 August 2019 - 11:04 AM

Maybe: Astro-Baby



#3 PirateMike

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Posted 18 August 2019 - 12:40 PM

I don't think there is any reason to take it apart. Just clean it.

 

I have a different mount, but I have "cleaned" it many times.

 

 

20170507_013137 small.jpg

 

 

 

Miguel   8-)

 

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Edited by PirateMike, 18 August 2019 - 12:41 PM.


#4 macdonjh

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Posted 18 August 2019 - 07:32 PM

I don't think there is any reason to take it apart. Just clean it.

 

I have a different mount, but I have "cleaned" it many times.

 

 

attachicon.gif 20170507_013137 small.jpg

 

 

 

Miguel   8-)

 

.

 

I think I need to take those two pieces apart to get that bearing off.  I need the bearing off to get rid of the rest of the old grease.



#5 macdonjh

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Posted 18 August 2019 - 07:35 PM

Maybe: Astro-Baby

 

Great resource, but unfortunately she didn't have the same trouble with the third declination axis bearing I am having.  She didn't take those two parts apart.



#6 EFT

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Posted 19 August 2019 - 12:58 AM

There is absolutely no reason to take the head off of the shaft.  DO NOT DO IT.  If the bearing is "stuck" on there then, while holding the shaft, hit the end of the shaft straight downward onto a flat, solid object (e.g., a vise anvil) until the bearing moves down past the contact surface.  The bearing may only move slowly down, but it will eventually fall down and you won't do any damage.  Judging by your photo, one good whack and the bearing will probably fall.

 

P.S. PirateMike's mount is an Atlas Pro AZ/EQ-G which is different than the Atlas and doesn't have this issue.



#7 macdonjh

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Posted 19 August 2019 - 11:41 AM

Thank you, EFT.

 

That bearing is stuck pretty well.  I was able to get it as far down the shaft as it is simply by setting the shaft "head" end up on a piece of wood on a concrete floor and then tapping the "head" with a hammer (another piece of wood on the "head" so the hammer didn't mar it).  However, it's now stuck.  I tried sliding a piece of wood between the bearing and the head and tapping the wood; no luck.  I tried heating the whole thing to 350F in my oven and then tapping; again, no luck.  I tried a bearing puller from the auto parts store- jaws weren't long enough.  So I'm a bit stymied.

 

I'm also having the same difficulty in reverse.  The bearings are not sliding back into the worm wheels easily (I did have to tap them to get them out, too).  Should they be a pres fit, or a slip fit?  Would a little light sanding with some sandpaper or emory cloth be in order to make reinstalling the bearings easier?  If they are supposed to be pressed in, I can borrow a suitable tool from the auto parts store I'm sure.

 

On a different topic: what about removing the shields from the radial bearings to remove the old grease and repack them?  The mount, I hear from my club, is close to thirty years old and the bearings, while smooth, are pretty stiff.  Some of the original grease I removed had turned into wax, so I will guess the same thing happened inside the bearings.  What is the likelihood of removing the shields and reinstalling them without damaging them?



#8 mikerepp

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Posted 22 August 2019 - 07:38 AM

Throw everything in the freezer for an hour or two and see if you can get it to budge then.

 

You will more than likely damage the bearings trying to remove the shields.  Just soak them in solvent, that will get rid of the old grease then repack by hand.



#9 macdonjh

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Posted 01 September 2019 - 01:31 PM

I didn't think of cold, my ideas stopped with heat.

 

Removing the bearing seals didn't hurt anything.  They are thin brass rings coated with rubber.  They pop out with a jeweler's screw driver easily and slip back on just as easily.  Made getting all the old grease out and repacking the bearings simple.  The bearings supporting the worms have metal shields, so I didn't try taking them apart.

 

I have everything back together.  The mount is really stiff, especially in RA, it takes quite a bit of force to rotate it.  The motors don't have any trouble slewing the mount and it's smooth and quiet, but I don't know if it can be effectively balanced.  So my question: is the brass worm wheel supposed to rotate freely within the mount's housing (unless the clutch is tightened, of course)?  My theory is there's a burr or out-of-round going on that has the worm wheel stuck- I had to tap the RA and declination axes to get the mount disassembled.



#10 Sleep Deprived

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Posted 01 September 2019 - 01:52 PM

I work in a machine shop and when we have to remove (or install) tight fitting details, we 'shrink' the inner piece with liquid nitrogen and expand the outer piece with heat.  It is easier when installing, since the different details can be heated/cooled separately.  Be careful that there is no water in anything when cooling (expanding ice can damage stuff) and be careful not to ignite anything when heating.  Spend lots of time heating/cooling so that the entire piece gets heat-soaked.  Other than that, lots of force.  If you have access to a dead-blow (heavy hammer or sledgehammer with the outer surface made of plastic), use it so you don't dent anything.  Next best is whack away with wood in between hammer and target, like you are doing.  Also, a heavier hammer (as opposed to faster hitting) seems to work better.  I think this is counter-intuitive (E=0.5MVsquared) since physics says energy goes up with the square of the velocity.  First hand experience has shown me that a larger hammer is much more effective than swinging a small one harder.

 

Good luck!




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