Mount tuning question.. Losmandy GM8.

[AlexN]

Hi everyone..

Just wondering if anyone here has pulled a Losmandy GM8 to bits for a re-grease etc?

I got my hands on a GM8 yesterday that has not been used in quite a few years, both axis of the mount were stiff and upon a close inspection of the worms, the grease has dried up into a glue... This is no concern, being that the mount hasn't been used in quite a while, it was to be expected..

Now, I've stripped the mount down to bare bones, cleaned everything with de-greaser.. There are two large roller bearing inside the RA shaft housing, and inside the DEC shaft housing that I can't get out... the ones in the RA housing look clean and the motion seems smooth, the ones in the DEC housing are stiff... I can't get to them try and clean them or if need be, replace them. Any ideas?

Other than those bearings, I must say Losmandy mounts are a dream for the home tinkerer.... If you have a set of imperial allen keys, the mount simply falls apart piece by piece until it is a shadow of itself...

Another part that needs to be lubed and or replaced is the bearings holding the worm into the worm blocks... the worms spin freely, but there is a slight grindy feeling to the bearings. These, I could not figure out how to remove...

Now that its all sitting here, ready to be lubed and put back together.. I am confronted with a question that I really should have asked before starting the job... What grease should I use? Anyone have the name of a product and where to buy it on the top of their heads?

Cheers..

Alex.

[multiweb]

I do my G11 every year. I assume the GM8 is the same. First get a bucket, a nylon tooth brush and a bottle of mineral turpentine. Undo everything that can be removed, turp it up, brush it and let it dry.

Get a bowl fill it in with WD40 and dump in all the bearings. Let them soak overnight. Rinse the ones in RA and DEC (the one you don't remove) with WD40 also. For the gears, get a wooden tooth pick and clean every single notch (... only 359 to go :lol:). Get some thick white lube and apply it in all the clean gear notches. Don't put any thick grease in any of the bearings. When water gets in it gets sticky and glues the whole mount.

If you have time, get some real fine sanding paper and sand the axis shafts to remove bearing/ringing marks.

Don't lube anything you don't have to.


For the worm tightness, it's a compromise. I run the whole DEC/RA gears by hand until I got a hard spot then relax a bit then do it again until it's good all around. Takes time but it's a one off so spend a bit of time on it. The worm cover (angle) can be used as traverse to align the end blocks so they're square when you tighten up the bolts.

That's pretty much it.

Here's the Lube (http://www.mektronics.com.au/index.php?option=com_virtuemart&page=shop.browse&manufacturer_id=22&Itemid=57) - SUP31040 for bearings and SUP92003 for the gears.

[AlexN]

Awesome, Thanks Marc! :)

Do you know where to buy said white lube??

I have already done the RA and DEC gears with toothpicks.. took quite some time to do both gears and the worms, but they look brand spankin new now, so i guess it was worth it.. Luckily for me the RA/DEC gears are only 180 tooth in the GM8, not 360 like in your G-11 :)

Just reassembled the mount with everything cleaned but no grease in the gears and the motion is already silky smooth in comparison to before... I'll strip it down again, give everything a once over with WD40, get some lube and then get it up and running! :)

This time when its in 1000 bits I'll get some photos.. This is the first time I've pulled a mount apart, I must say I was pretty proud of myself to man up and do it, and after seeing the grease (read: glue) on the gears, I'm very happy I did do it before trying the mount out..

PS - Clutches.. What a dream... Dinky RA/DEC axis locks on the HEQ5 are an annoyance... this clutch idea is one right out of the box isn't it! :) Lovely!

[JohnG]

One thing that I will add, make sure that you do not get any oil or grease onto the white nylon clutch pads or the surfaces they bear on, these need to be totally dry. With your greasing, you only need to apply a little grease, work it into the bearings with your finger.

Remember that in time any excess oil and grease will wick onto the white nylon clutch disks and get onto their respective bearing surfaces, as Mark say's, this should be a once a year service to clean them.

Cheers

[AlexN]

Thanks for that John, While I have it apart I'll be sure to clean the nylon clutch pads and respective surfaces. I'll do my best to keep it as clean and dry as possible, and I'm more than happy to do this yearly, the mount is such a joy to break down... not like some of the nightmare guides I've seen for breaking down other mounts!

[multiweb]

Here's the Lube (http://www.mektronics.com.au/index.php?option=com_virtuemart&page=shop.browse&manufacturer_id=22&Itemid=57) - SUP31040 for bearings and SUP92003 for the gears. As John pointed out no grease on clutches that's why I said only grease what you have too. Drain the bearings before putting them back and make sure the shafts are dry. The bearings just need to be "moist". Most clutch slippage is from oil from the bearing on to the shaft that transfers to the disk. The slightest drop will contaminate the whole surface because there's no big gap when they're tight and it will spread in minutes. I have actually glued mine on the bearing side both in RA and DEC with Selley's Rubber Gel Grip. So It only slides on one face. I get more break away force this way. I ran into problems when starting using the C11/Hyperstar with clutch slippage and inertia. Now it's rock solid.

[Gerald Sargent]

Gummed up G8's I know. Take the whole thing apart and soak in
woolworths shelltox, actually "N-hexane" a smokeless kerosine
for lamps. One can use Mineral turps. What ever totally remove
any previous grease, Losmandy used to grease the pin bearings
during assembly, this grease reacted with the grease in the already
greased bearing and resulted in a waxing, which you have
encountered. What ever you do do not mix greases. A good grease
to use is a high quality "front wheel bearing grease" for motor
cars. This is a high temperature grease and very good and easy to
get. As to worm adjustment, well prepare youself for some tedious
work, You must ensure that the two blocks are squeezed together
so there is no end play along the worm shaft, I made a small hand
tool from a piece of 1/4" dowel with a cut in it to fit over the end of
the worm sghaft then rotate the pinion a full 360 degrees and look
fir tight spots, and adjust so that they dissapear. On of the problems
is that the hole in the pinion is a loose fit over the respective shaft,
resulting in what is known as "run out" So adjustment of the worm can
be a task that need to be repeated as the pinion is moved once the
clutch is loosened and re positioned. I eventuall sold my G8 as it
"consumred" gemini motors at a great rate, the steppers I much prefer,
or the German FS2 which is far more rhobust than the Gemini.

[AlexN]

Thanks again Marc, You're a champ.

Gerald - Thanks for the extra info - My GM8 is a stepper driven model, not a Gemini.. Hopefully it wont consume motors! :D I'm going at it now with turps cleaning all the components as best as possible. the mount will be rebuilt and greased tomorrow using automotive wheel bearing grease as per Geralds instructions..

I'll take a series of photos along the way for anyone who's interested..

Thanks again guys.. As always, Ice in space proves it is invaluable! :)

[[1ponders]]

Well you've got me motivated Alex. I've been putting it off and putting it off. Now I'm sitting out in the shed rubbing my hands together. The G11 will be next. ;)

[AlexN]

Good going Paul! :) I was thinking about you earlier today actually... I was looking over this mount thinking to myself "Now I see why Paul loves these things..." It is, as you say, SEXY! Its beefy, it anodized black, its pure functionality.... It means business and I'm in love with it.. :)

[[1ponders]]

Check your GM8 plate on the side of the mount head. I'll post what I found under mine





Here it is. There was a GM8 plate stuck over the top with what looked lik a smear of thin white silicon as adhesive

[AlexN]

lol!

Yours is newer than mine.. Mine does not have the altitude locking nuts.. just the center hole.. Appart from needing a trip to Supercheap Auto for grease tomorrow, mines all done... bearing are still soaking in WD40, everything has been polished with turps, gears and worms have been cleaned with turps/tooth picks... Its looking the goods!!

Paul - Here's a question for you... Power.. Do you know the specific plug that the Digital Drive 492 box uses? I have plenty of 12v power supplies.. I have a 12v 10A unit, a 12v 80AH battery, and a 13.8v 15A lab power supply.. Which would you recommend for the GM8, and what plug do I need.. Also - Is it center positive?

Thanks.

[[1ponders]]

I just use any 12 - 13,5 V regulated source that can provide more than 500mA. Yep its center positive. Its the same size as the Argo Navis plug. 3.5mm I think but dont quote me on that.


Just reading the manual :P and all it says is 12V 500mA and nothing about the pin size

[[1ponders]]

Ok I'm a lucky fella. All cleaned up already. Thanks to either Robby Beck or Gary Beal (the previous two owners) it had already been stripped down and cleaned and re-greased with white lithium so it was easy as. I probably didnt need to go all the way but I dismantled it fully anyway to give it a good clean up. Although it has been about 5 years since I got it :lol:

Tomorrow night the regrease and reassemble. ;)

[AlexN]

Mines all cleaned up... looking super shiny!

Will get some white lithium grease tomorrow morning and hopefully have it all up and running tomorrow...

Its funny.. I never had it in me to open up an EQ6 or HEQ5, but being a metal worker, the GM-8 just seemed... Easy.. Felt right at home pulling it down and cleaning it up... Its just so industrial..

[gbeal]

Oii. Didn't pay for that did you? LOL.
Shipping was cost effective too.
Gary

[[1ponders]]

Nope, got one up one the Kiwis there. :D

It might have been cost effective when you include the deer crap embedded int he soles of my shoes but I'd think about it twice next time after the hernia the courier got carting it around Brisbane in his suitcase. :lol:

[ghsmith45]

Losmandy are bringing out a new one piece worm block in the next month or so.
Geoff

[[1ponders]]

About time. How long has that taken. Its definitely a down side having the worm blocks able to move independently of each other.

[adman]

Alex

I had to mail order the SuperLube for when I did my mount - but I still have most of a tube left if you would like it. PM me if you want to come pick it up and I'll let you know where I am.

Adam

[multiweb]

That's exactly what I think everytime I pull my G11 apart. It's such a simple well designed mount. It's like lego blocks. A monkey could do it.... and every year he does :P

[JohnG]

:rofl: would love a quid for everyone I have shown how to dismantle either a GM-8 or G-11.

Cheers

[AlexN]

John... Being paid to show people how to pull these mounts apart would be like taking candy from a baby in many respects....

Step 1, find an exposed allen head bolt.
Step 2, Get correct size allen key and turn bolt anti clockwise
Step 3, Repeat the process until mount is dismantled. :)

Gary & Paul - Now that does sound cost effective! Gary, next time Im buying something big from you, (Yes... We both know there will be a next time) I might have to jet over and pick it up :D )

Adam - See, this is why I need to check the forums before I leave the house. I just got home from the shop buying lubricant.. Thanks for the offer mate!

[adman]

what did you end up buying?

I remember now what happened when I did mine - I looked through all sorts of forums at other peoples experience of regreasing their mounts and the most used greases were white lithium grease, and SuperLube, with people mostly raving about SuperLube. So I ordered some online, but then I would look at my poor mount just sitting there in bits, so I went and bought some white lithium, and did it with that. The SuperLube turned up a couple of days later. Sometimes you just can't wait.

Adam

[AlexN]

I got Valvoline Valplex EP..

For : wheel bearings, chassis, suspension and uni joints, construction & farm equipment.
Operating temps : -20c to 195c
Lithium based.

$10 for 500g @ Supercheap Auto

[adman]

Doesn't say anything about Losmandy GM8's on there anywhere does it??:)

[AlexN]

No it doesn't.. And whilst that has me concerned, I think it will be ok :)
hahha.. I figure, if it can handle being in wheel bearings on a car thats cruising at 100kmph down the highway, it can handle being in a mount that rotates 15 degrees per hour or there abouts..

[[1ponders]]

Any suggestions on what to use on the Needle Bearing Washers? A light oil or just a very thin smear of SL? When I pulled the bearings off there didn't seem to be any noticeable grease on them at all (though they didn't seem dry).

[AlexN]

WD40 it I reckon... at work 99% of bearings get no more than a monthly spray of WD40.... Mines all done and dusted.. just resizing some photos and eating lunch then i'll post up said photos.. :)

[AlexN]

I must have done a good job.. It just started raining.. :)

[[1ponders]]

Ok, I just used the thinnest smear of SL, basically a wipe with a greasy finger on both sides. Should be enough. I've adjusted the Dec Worm and now onto the RA. Feels nice, and its great to have the clutches tighten up with just finger adjustments now. Why did I wait so long :lol:

[AlexN]

Glad I could provide some much needed motivation Paul... I might need your assistance to get these worms lined up right....

I definitely already see how annoying the worm blocks are going to be. I think I will invest in an O-vision worm eventually...

[AlexN]

Heres some pics....

1 - Mount mostly stripped, still had to pull the base apart.
2 - Grease used.
3 - RA worm gear, cleaned with grease applied
4 - RA Worm cleaned and greased.. I know that only a small fraction of the middle of the worm will actually make contact with the worm wheel, but I greased it all anyway..
5 - Half way through re-assembly
6 - Rebuilt.
7 - The imaging rig.

[[1ponders]]

Yep I'm all dressed up with no place to go. :D I've done an adjustment on the worms but the proof of the pudding is in the eating so they say. I'll just have to wait for a clear night for dessert then. :)

btw if you haven't already, get a short piece of dowel and put a notch in it to turn the worm. Its much easier on the fingers. I use a fairly narrow piece of bamboo stake. That way I can only roll it with the tips of a couple of fingers. Thicker dowel give too good a grip and you might be tempted to 'ride' over those rough spots.

[AlexN]

The proof is probably in the sticky date pudding that I know you want to cook for me! :P

Good idea on the dowel.. I've been doing it by hand.. :eyepop:

[[1ponders]]

Ouch. A little over pencil thickness. ;)

Well if this rain keeps up and I can't get out to go to work on Mon Tues and Wed :prey:, I know what I'll be doing. The G11 :lol:

[JohnG]

Another way to bed in your worm is to take the Oldem Coupling off the motor, reverse a 3/16th drill bit, put the coupling on the shank of the drill, put it in a cordless drill and rotate the worm at slow speed in both directions, saves the fingers. :P

Cheers

[kinetic]

Great thread, will be watching it with interest.:thumbsup:
It's a pity it was so glugged up Alex because it would have been
great to measure it's PE before and after the tune up as you will
be messing with the worm mesh and clutch faces etc.

They certainly do look like a tinkerer's dream...good, sturdy and
functional.

Steve

[[1ponders]]

I wonder what torque setting on the drill would do to work out when the worm is getting too tight?

[JohnG]

At slow speed you will soon hear/feel a tight/high spot. :)

[multiweb]

By hand - motor removed. That's how you feel it best. If you can't turn it with your fingers, no good. It's not that hard. I run my index on the side of the oldham coupling. If it can't turn this way then I relax the worm.

[[1ponders]]

I agree Marc, for final adjustments, but just to be able to wind the gears through a couple of cycles to bed them in would be a definite advantage.

I'll let you know how I go. Its raining here and I've got little more interesting to do. :)

[multiweb]

:lol: You guys are lazy bums. You've got to put your backs into it. No pain - no gain. I want to see those blisters on those fingers :lol: ;) Nah... seriously it has to move pretty freely. Hard to judge with the drill even with very little torque. I tried it both ways.

[AlexN]

Lazy bums?? I've never pulled a mount apart in my life and between last night and today I've completely stripped and rebuilt this GM8 twice, I've cleaned god knows how many threads and gear teeth with toothpicks, I've polished every surface of the mount, I've been working on this worm alignment....

Lazy Bum... Tsk Tsk.. How dare thee!! :P

[[1ponders]]

Well I gave the drill a go and it was great. I set the worm where I felt it needed to be (either Dec or RA) and then ran it at a moderately slow speed with the torque set at the 4th lowest setting. I went back and forward a few times, loosening off the worm each time it bit. Once I got a free run I lowered the torque again and repeated. Each time I checked by hand that the area that was tight was free enough to turn by hand with just a little bit of pain. Now it only jams on torque 2 and I can move that quite easily by hand. Too easy. I'd better check that my mounting blocks are aligned before I jump too much for joy

[multiweb]

:lol: Got black fingers yet? :P ;)

[multiweb]

Use the angle cover as a traverse to keep them square in relation to the worm axis (i.e. traverse pushing the front of the blocks toward the gear while you squeeze the two blocks together with your fingers.)

[[1ponders]]

Yep they look pretty good. I've just completed a couple of revolutions in Dec using the stick method (still get sore fingers) and a few rounds of RA+ &RA- with the stick as well. Feels great. Now all we need are some clear skies.

[AlexN]

haha.. yes.. :)

Hey - I've hit a snag here guys... one of the bolts on my dec motor has something jammed in the hex head, I can't pull it off... hence, I can't adjust the dec worm and then re-attach the motor? Any thoughts?

The RA one is done, I can rotate the RA axis with my fingers, no tight spots... smooth as silk. the dec worm I got smooth, but then in order to reattach the motor, I needed to undo the worm blocks.. :(

Is it possible for me to use the Dec motor in order to adjust it, start with it really loose and slowly tighten it until its tight enough?

HEEELLLLPP MEEEE!!

[multiweb]

Just losen the oldham coupling and remove the central plastic link. As long as the motor is not coupled you can turn the worm.

[[1ponders]]

how did you get the motor off to clean the worm and gear, in the first place? Or did you leave the motor attached to the worm?

[AlexN]

I'll give that a go Marc..

Paul.. If I loosen off both of the worm bolts, I can remove the worm by sliding it out of the plastic coupler between the motor and the worm shaft.RA is all sorted now.. Just need to do the Dec..

[DavidU]

Guitars have glugged up hex socket bolts all the time. Just clean it out with a needle, and soak in WD40.

[AlexN]

Dave - The hex socket is glugged up with something metallic that will not come out... My guitar does get glugged up hex bolts too.. I know what you're talking about ;)

On the bright side, I was able to remove one bolt from the RA motor, and rotate the motor around on the other bolt, allowing the plastic coupler joining the motor and the worm to come free, and I was able to adjust the RA worm... It is now silky smooth in both RA and DEC, feels to be very little backlash.... I am really happy I was able to get this all sorted myself.. I was going to pay to send it to NSW and get Mr. Ward to service it for me, as I feared pulling it apart... Seems my metal working background and the wealth of information on IIS has seen this job done for a grand total of $10 worth of grease (which I may have used 0.05c worth on this service)

Bargain! And satisfying too...

Can't wait to get this out under the sky!!!

Thanks everyone for your help and contributions to the thread... Very helpful bunch!

[[1ponders]]

For those thinking of doing this themselves. Here it is all layed out. It may look a mess but there is actually meaning in this madness. :)

[multiweb]

:eyepop: :lol: That looks like a garage sale! What are you doing with SWMBO table cloth? You're walking on thin ice mate... ;)

[[1ponders]]

pfft.... do what ever I damn like, the dog doesn't care. :lol: :) And it was an old sheet (from somewhen in the late 70's early 80's by the look of it :) ), not a table cloth. Long been relegated to the roll of paint drop sheet.

[AlexN]

Paul - I am lucky like that too... My dog, lizards and snakes rarely complain about what I decide to do with sheets/towels etc... Nobody even complained when the degreaser got onto the floor yesterday... I cleaned it at my leisure and the world did indeed go on.

[[1ponders]]

To the beat of a different drum :D

[Phoenix]

Hi Folks

Really interesting thread Alex - thanks. I too just serviced my GM-8 with advice from JohnG and Bird (many thanks) and help from Mischa's links of course:
http://www.astro.uni-bonn.de/~mischa/mounts/g11_disassembly.html
and
http://www.astro.uni-bonn.de/~mischa/mounts/g11_tuning.html

I picked up my mount second hand recently, which was purchased new in 2005 from another IIS member - I didn't know the service history of the mount so though I would pull it apart. I'm not usually hesitant in pulling things apart but I read so many posts about worm block adjustment difficulties that I decided to clean the worm shaft and gear insitu.

The mount was actually in pretty good nick but I decided to service it anyway. Once removed I cleaned all of the clutch washers and their roller bearings using isopropyl alcohol (bunnings) as well as all shafts. The centre RA and DEC shaft needle bearings were a little difficult to get at and clean properly, but I found a thread on CN that recommended CRC Brakleen, which cleans grease, oil, etc and is supposedly non-corrosive and leaves no residue - "cleans without disassembly". Well, I purchased it but didn't use it in the end - thought it would be a little too aggressive - but I did use CRC CO Contact cleaner:
http://www.crcind.com.au/catalogue.nsf/web_brands/CO+Contact+Cleaner?openDocument

This stuff is excellent and is safe to use (low toxicity) and is used on electronic circuit boards to clean them with no harm. It comes in a spray can with nozzle so you can direct the spray accurately (areas where you don't want it to go protect with a rag). The old grease and oil just pored out of the mount. Turn the needle bearing using your finger, spary a little more, turn again, spray, etc. until it runs clear and there is no oil/grease residue when testing it with a rag.

The general consensus on the Losmandy user group is to use slick 50 (PTFE) grease for the shaft bearings but I found this a little difficult to get hold of so I used the 'similar' SuperLube multipurpose grease with PTFE (SUP21030) for both bearings and gears/worm. Apparently only a very small amount should be used on the shaft bearings (thanks JohnG) and after working a small smear of grease on the end of my finger into the bearings I found that the bearing was a little harder to turn. While this was concerning, once the shaft was replaced it turned buttery smooth. My only concern about using the CRC CO contact cleaner is that it completely cleans the needle bearings DRY! So I am concerned the superlube has not worked its way into the needle points - ie. the location within the bearing where there is likely to be ware. Now I see the logic in Marc's suggestion to use the aerosol version of this grease which is:

"temporarily thinned with a solvent that cleans and penetrates the components to be lubricated, carrying the grease to those components. After a short time, the solvent evaporates, leaving behind a thin film of grease that provides long term lubrication that does not evaporate, dry or wash out"

Very cool - provides a solution to my concerns about the tube version of the grease - should I clean out the grease I have just applied and re-do with the aerosol? Particularly because I have used the CRC CO contact cleaner?

Anyway, I also used the isopropyl alcohol and toothbrush to clean the worm gear in place as well as the worm shaft - I also use the CRC CO cleaner on the worm shaft, which blasts out any contaminants - make sure to protect the worm bearings from the CRC CO cleaner at the end of the worm shafts with rags. With the motors removed and a notched piece of wooden dowel to spin the worm shaft I went round with my toothbrush and cleaned all gears and worm - applied superlube grease and rotated the gears several times to work in the grease.

Re-assembled everything and she seems nice a smooth. I'm very keen on the rumored one-piece Losmandy worm block (about time) so I thought I would remove the gears properly once I get my hands on one of these to clean a re-grease the gears. Perhaps I will use the aerosol on the needle bearings when I take the mount apart then.

Thanks again Alex

nix

[AlexN]

Glad you've found the thread useful Steve! :)

Yes the idea of a single piece worm block sounds great doesn't it? O-vision from Italy make a high precision worm for the GM8/G-11 mounts. The kit for the upgrade is $499US. however it is reported to drop the PE of the mounts HEAPS! G-11's are apparently capable of 5" peak to peak...

http://www.ovision.com/Losmandy_PresentationNS_english.htm l <- This is the information page.

http://www.ovision.com/images/NSmonte.jpg <-- A picture of the block unit..

Looks the goods to me...

[Phoenix]

Hi Alex

Thanks for the info - yes I'm aware of the one-block Ovision worm (from France I believe - but very close to the Italian border). Yes, they do seem to be the goods as you say, but only half the improvement on the GM8 compared to the G11 as you point out. While much cheaper than changing the mount altogether, the $499US + shipping for the Ovision is a little too rich for me at the mo. The reported/rumoured $299US for the losmandy one piece block is doable but who knows whether this will include the worm shaft or whether it's only the block into which you install your existing worm.

We wait in hope.

Cheers

[AlexN]

Agreed, $299 for the Losmandy one piece is sounding like a better deal, even more so if that includes a high precision worm..