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?
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 ). 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 - SUP31040 for bearings and SUP92003 for the gears.
Last edited by multiweb; 26-02-2010 at 07:01 PM.
Reason: added 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!
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.
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!
Here's the Lube - 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.
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.
Gerald - Thanks for the extra info - My GM8 is a stepper driven model, not a Gemini.. Hopefully it wont consume motors! 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!
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.
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..
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?
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 and all it says is 12V 500mA and nothing about the pin size
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
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..
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.
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, .
Losmandy are bringing out a new one piece worm block in the next month or so.
Geoff
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.
). 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.
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.. ![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
and all it says is 12V 500mA and nothing about the pin size
