Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6405
Loc: 26.06.08N, +80.23.08W
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As some of you may know I've recently had some troubles with my Atlas. Specifically, I lost a tooth on the high resolution transfer gear that caused the mount to lock up out at our dark site last month. Stock Atlas owners need not worry - the high resolution gear was a custom job. The stock Atlas transfer gears could never have this problem. However, losing the gear meant I had to open up the mount to remove the gear set and (at least for now) replace it with the stock set. I figured that once I open up the mount I should go ahead and do a complete cleaning and re lube of the RA axis. I've been having trouble getting the RA worm gear mesh set properly for a long time now. It always was either too stiff for my taste or had too much backlash when it ran smooth enough. The DEC feels absolutely perfect so I'm not going to touch it.
So - I've disassembled my RA axis and had a look at the worm wheel - and I'm starting to panic. Aside from being difficult to find the mesh, the mount has run fine. However you certainly couldn't believe it looking at the worm wheel.
(let me say that I'm willing to admit that I'm overreacting here - when you see the picture you be the judge)
It is evident that the worm gear has not been running in the center of the wheel and to me the wheel shows evidence of gross over tightening. Although it's certainly possible, it's hard for me to believe that I had tightened the wom against the wheel as hard as this appears. In fact I don't know how it was working at all with the wheel tightened up that hard to the worm, or why the worm itself isn't bent due to the force that must have been needed to do this.
Anyway, there's my horror story, and I'm sticking to it. Time to move forward from here.
The big question looms - can this wheel be saved? If so, what needs to happen? If not, where can I get a replacement wheel?
Bummer!
Charlie
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Weston CSC:
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AlanT
sage
Reged: 08/20/07
Posts: 257
Loc: 122º36' W, 47º37' N, WA USA
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Now I dont have an EQ-6 but, Wow... that looks very odd to me. To remove that much material it seems the pinion would have had to be adjusted for tighter mesh several times.... and it would seem quite a bit of debris would have accumlated. Makes me think the worm wheel was machined that way (I'm just guessing maybe to allow a deeper mesh that would give less backlash for a bidirectional system). Does the pinion show corresponding contact at the root of tooth? It also looks like the tip of the worm tooth has had some contact with the wheel.
It will be interesting what other EQ-G owners say, but I agree, you just couldn't have adjusted it so tight to have caused this.
al
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Meade 80mm APO
Celestron C6
CGE, CG-5 GT
DSI Pro, DSI Pro II, ST-2000xcm
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scope dog
Pooh-Bah
Reged: 07/26/04
Posts: 1165
Loc: USA, NJ
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Hi Charlie,
To me the worm is worn by a too tight backlash setting. The worm shaft may appear not worn but it is. And this appears constant backlash adjustment was done and that increased the depth of the damage. Of cource the worm shaft was not align or a thicker washer was used.
If you purchased a new collar worm this damage would occur because of the shaft. Making a new worm.
This can happen. Check your local machine shops. I also
found this place worms
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Jim Fusco
Astreya 152mm F/7 SAPO
Santel MK91
Astreya-SAPO
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AlanT
sage
Reged: 08/20/07
Posts: 257
Loc: 122º36' W, 47º37' N, WA USA
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Hmmm, Looking at the pic on a better monitor it does look like wear from rubbing. It's hard for me to believe it ever could have been adjusted that tight (apparently over and over). Wow.
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Meade 80mm APO
Celestron C6
CGE, CG-5 GT
DSI Pro, DSI Pro II, ST-2000xcm
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John Carruthers
Skiprat
Reged: 02/02/07
Posts: 1596
Loc: Kent, UK
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I've seen this on ally wheels where a misguided owner has 'lapped' the mesh using Tcut or similar. A spring loaded worm can help, see AWr's site for more info.
http://www.awrtech.co.uk/oddtopic.htm#TORQUE
and scroll down to "Maximum Spring Force"
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Jc
ATM 10" F6.1, 1/25th wave spec (max wavefront error +/- 1/12.6 in zone 4 of 6, sodium light )
6" F7 spec
127mm F9.4 Refractor
10 x 50 bin
ETX80 (finder)
Canon 20D
and a curious mind
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Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6405
Loc: 26.06.08N, +80.23.08W
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Yep. It's a mess all right. What I'm looking to find out is if this wheel can be repaired or if I have to buy another worm wheel somehow.
John - I don't think that the design of the mount lends itself to spring loading the worm against the wheel but that would surely be an ideal solution for avoiding the possibility of over tightening if it could.
Jim - in fact I had a new worm gear made a couple of years ago for the RA axis.
As I mentioned it's been running okay from a PE standpoint (I've been using it for imaging at some long exposure times - autoguided of course - with good results) but I've never been pleased with the worm mesh ever since it came back. It was either too sloppy when it ran as smooth as the DEC or much stiffer than the DEC when the backlash was taken up. Looking at this wheel it's not hard to see why.
I'm sure that I could just put it back together and use it as is - but at best I would be stuck with the same difficulty getting a good balance between smooth running and workable mesh forever. Knowing that it's not right will bug me forever, too. I'd really like to cure this for good and all when I put the mount back together.
I'm tempted to set the wheel up to the worm correctly and see what happens but I'm afraid that the damage is too great and at best the results would be worse than just leaving it alone.
I don't know of a machine shop in my area that can do this kind of work. Moreover, even if I find one I'm wondering if resurfacing this wheel would alter the tracking.
The best solution may be to find someone who has maybe installed a new worm and wheel in their Atlas/EQ6. A guy in Germany made some nice ones and someone may have an old wheel lying around that I can talk them out of.
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Weston CSC:
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Kaizu
sage
Reged: 08/17/07
Posts: 236
Loc: Finland
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How the worm gear looks?
If you are a perfectionist, the only allowed solution was the new gear.
I might try to align the worm gear correctly and then lap little more with fine grinding paste so that the gear turns against a light load. Only couple big wheel turns, othervise the worm gear may disappear. Then I assembled it allowing a small running clearance. I have got the best results with my G-11 so that I have accepted a small backslash an d I have unbalanced the mount so that it works against a light load.
This I would do in both cases, with new gear and with a worn one.
Kaizu
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There is nothing as wise as German engineer
http://www.kaiforssen.fi
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Mert
scholastic sledgehammer
Reged: 08/31/05
Posts: 935
Loc: Spain, Pamplona
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Ouch Charlie, that doesn't look very nice!
Likely the fastest way is mounting it again and
use as is.
But if you would like to get rid of this, maybe
your best bet is Jim Egger from Aeroquest.
He made some worm/wormwheels I believe and also
new gear-sets for the transfer etc.
You also have the Gierlinger site, he used to make
worm/wormwheels for the EQ6.
Don't know if he continues nowadays!
I hope they can do something for you!
Regards,
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Mert
42º49"N 1º38"W
3" Unitron refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD 
Webcam with 1.25" nosepiece
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Telescopeman54
Vendor - Trapezium Telescopes & Services, LLC.
Reged: 08/17/07
Posts: 1021
Loc: New Hampshire
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Charlie:
I am of the opinion that you can pretty much kiss that gear good bye! If you try to re-center the worm on the wheel you will get even faster and uneven wear. Look carefully at the gear and you will see why.
I have exactly the opposite problem. I have a Gemini GI-1 and some meat head who had it before me tried to lap the gears. He totally trashed both worms. Luckily, the worm wheels are OK. The worms are trashed, though.
Here is a picture of the results of someone who has no idea what they were doing! I have just finished turning a new worm for the RA axle and will make another one for the DEC axle. A picture of the new one will follow.
CS
Steve
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Steve Forbes
6.25" f/15 Mogey/NASA refractor on GOTO GEM
6" f/15 Jaegers refractor on GOTO GEM
5.1" f/8 Burgess on CG-5 w/GOTONOVA
4" f/15 Jaegers on ORION ATLAS GOTO
2x 6" f/6 Edmund Palomar reflectors on GEMs w/ RA and DEC drives
2x 4-1/4" Edmund Palomar Jr. reflectors on GEMS w/ RA drives, (all circa 1965 - 69)
3" Edmund reflector on "EQ" mount from @1963
4" Criterion reflector with "EQ" mount from @1956.
150mm f/12 MAK w/iOptron Mini Tower
Lots of other stuff, too!
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Telescopeman54
Vendor - Trapezium Telescopes & Services, LLC.
Reged: 08/17/07
Posts: 1021
Loc: New Hampshire
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Here is the new one ready to be removed from the lathe.
sbf
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Steve Forbes
6.25" f/15 Mogey/NASA refractor on GOTO GEM
6" f/15 Jaegers refractor on GOTO GEM
5.1" f/8 Burgess on CG-5 w/GOTONOVA
4" f/15 Jaegers on ORION ATLAS GOTO
2x 6" f/6 Edmund Palomar reflectors on GEMs w/ RA and DEC drives
2x 4-1/4" Edmund Palomar Jr. reflectors on GEMS w/ RA drives, (all circa 1965 - 69)
3" Edmund reflector on "EQ" mount from @1963
4" Criterion reflector with "EQ" mount from @1956.
150mm f/12 MAK w/iOptron Mini Tower
Lots of other stuff, too!
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Mert
scholastic sledgehammer
Reged: 08/31/05
Posts: 935
Loc: Spain, Pamplona
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I really love this image Steve!!!!!!!!!!!!!!!!!!
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Mert
42º49"N 1º38"W
3" Unitron refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD
Webcam with 1.25" nosepiece
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Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6405
Loc: 26.06.08N, +80.23.08W
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Nice work Steve. I'll check the worm with a straight edge just to be certain but I think it's okay.
Charlie
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Weston CSC:
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scope dog
Pooh-Bah
Reged: 07/26/04
Posts: 1165
Loc: USA, NJ
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Charlie,
This type of mount that uses a collar worm and like the GP's
GP-DX, CG5's and such. When things are made a gap is require to move, any bearing surface.
An example, when tightening the "taper bearings on a drum brake system" too tight the wheel will not move, so it needs to be losen,for movement.
If you get HP worms made there could be still issues as machining alignment may be out.
Worms need to be align with shafts. This design mount will throw alignment out every time when the clutch is enguaged. Because alignment is dependent to "gap between worm collar and shaft" "gap between bearing and race". When this type of mount has the clutch engage the "worm collar" will *BLEEP*.
Vixen design a "floating worm shaft" this did 2 things, 1 adjust to misalignment, 2 antibacklash.
As we seen people install bearing instead of o-rings this wear will occur. This mount you have cannot have a tight back-lash. The worm shaft is fixed with the atlas so a gap "backlash" is require.
In order for this design to work well, machining needs to be done rather well, along with good bearings. Almost everything is dependent on each other. The backlash can be adjusted, but for proper operation and running tight, the whole system needs to be accurate. I believe takahashi uses this system too. Regardless, though if one this is out, everything will be out.
I think you can reassemble this mount and use it for basically visual use.
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Jim Fusco
Astreya 152mm F/7 SAPO
Santel MK91
Astreya-SAPO
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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Quote:
...I have exactly the opposite problem. I have a Gemini GI-1 and some meat head who had it before me tried to lap the gears. He totally trashed both worms. Luckily, the worm wheels are OK. The worms are trashed, though.
Steve
Well, that's ONE way to create a double-throated worm wheel set. Not the way I would have used... 
Charlie:
I agree with Steve. IMHO your wheel probably cannot be repaired for any reasonable amount of money. It would have to be taken to a machinist to be rehobbed, with a new worm; probably cost as much if not more than a new worm wheel.
Check your worm carefully. Is it tool steel, S/S, or bronze? If the first two, it's probably fine. If the latter, it may be damaged.
If you're getting good imaging results, I'd put everything back together and continue using it until a replacement worm wheel can be found. Back off on worm pressure slightly, and use the "east-heavy" balance trick to take up any RA backlash. Don't back off too much on the worm gap, though - with the damage your pic shows, I'd start worrying about slippage.
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In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
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blueman
professor emeritus
Reged: 07/20/07
Posts: 574
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I have often wondered about the outcome of someone trying to lap in a worm. This was a disaster for sure. I know that it can be done correctly, but I think this guy used valve grinding compound or something like that! 
I have the bronze worm and the PE is pretty good, so I think I will pass on the lapping.
Blueman
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WO 80mm f/6 APO
DSI III Pro Televue .8 focal reducer
Atik filter wheel Astronomik filters
Losmandy G-11 Gemini Auto-guided
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Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6405
Loc: 26.06.08N, +80.23.08W
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Quote:
Check your worm carefully. Is it tool steel, S/S, or bronze? If the first two, it's probably fine. If the latter, it may be damaged.
Looks like the worm is stainless, and doesn't appear to be worse for the wear. I'm going to give it a closer look tonight.
The smart money would be to buy a new custom worm/wheel set but I don't think that's something I can swing just now. I'm hoping to find somebody who actually has put a new worm/wheel set in their Atlas/EQ6, still has the old wheel or set and wouldn't mind helping me out in some way.
(hint, hint - if any of you out there fit that bill please PM me!)
I'm thinking that it would pretty much be a waste of effort (not to mention a perfectly good tube of hard-won Super Lube) to put this one back in my mount as it is. I'm saving that option as a last resort though - I'd almost prefer to wait until I can afford a new unit if I cannot find one used in good shape.
Charlie
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Weston CSC:
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Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6405
Loc: 26.06.08N, +80.23.08W
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Quote:
I have the bronze worm and the PE is pretty good, so I think I will pass on the lapping.
If that run is typical I wouldn't touch a thing!
Charlie
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Weston CSC:
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Mert
scholastic sledgehammer
Reged: 08/31/05
Posts: 935
Loc: Spain, Pamplona
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You might check the link of Gierlinger who made even better worm/wormwheels.
Maybe he still has some on stock!
There is also a brief description on how
this results for the EQ6, it's german but I think pritty
self explanatory.
Hope this helps.
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Mert
42º49"N 1º38"W
3" Unitron refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD
Webcam with 1.25" nosepiece
Edited by Mert (06/23/08 05:04 PM)
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Ed Kessler
professor emeritus
Reged: 05/17/06
Posts: 724
Loc: Millersburg, PA
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Quote:
Here is the new one ready to be removed from the lathe.
sbf
Now, that's nice!!!! 
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Ed Kessler
sic itur ad astra (Just to look profound!)
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blueman
professor emeritus
Reged: 07/20/07
Posts: 574
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Hi Charlie,
Yes, this is a typical run for my setup. I have been very lucky I guess in my purchase.
The whole recording was for 24 minutes or 6 revolutions of the worm and it was just like that for the entire time. This shot shows 1000 seconds of the run.
I did adjust the worms a while back, but other than that it is just a stock G-11.
Blueman
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WO 80mm f/6 APO
DSI III Pro Televue .8 focal reducer
Atik filter wheel Astronomik filters
Losmandy G-11 Gemini Auto-guided
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