TAL-2 EQ mount servicing

[Andy McK]

Hi all,

Shot in the dark, anyone pulled a TAL-2 EQ mount apart?

I need to change the RA bearings

anyone done this, have diags, etc.

Cheers,

Andy

[jamespels]

Oh yes

Just done exaclty the same thing, except I want on to take the dec apart too

PM on its way.

Edited November 8, 2011 by jamespels

[AndyH]

Hi.

Like others on sgl, I''ve done this a few times.

THE FIRMAMENT - Solar System and Deep Sky webcam images

Scroll down the left hand sub-menu and look for 'Tal 2M'. Once in there, click on 'periodic error' and there is information in there that's useful.

We Tal-ites should really do a nice 'pic-heavy' guide to to the strip down and rebuild.

Andy.

[AndyH]

Woops, double post.

Edited November 8, 2011 by AndyH

[jamespels]

AndyH, can you check this over please?

Will sort out something a bit better with pics later on. For now, start by taking the motor drive out. The motor is held in place with three large screws you will see on the underside of the mount body. It is soldered into the switch, red light and power socket which can all be easily removed using the obvious screws around them - be careful to keep all the nuts, bolts and spacers - I reassembled them once the bits were removed from the mount head. The switch is held in place with a collar nut - I used a pair of pliers to undo this, with a bit of cloth to protect the nut. You will now be able to remove the motor and gearbox and all the electronics. Having done that, remove the three bolts that hold the RA clutch plate in place and take off the clutch plate itself (leave the large brass drive gear for now).

Next, you will need to remove the worm drive. The plastic knobs that you can use to manually drive the RA axis can bre removed by holding them while you undo the central bolts with a large screwdriver. Pop the knobs off afterwards by prising them off the axle with a screwdriver against the mount head if they don't come off easily. You will now see four small bolts around the worm drive on each side of the mount. Undo these to release the round securing plates on each side. Note which is which - the full circle goes on the right as you look in; the "C" shaped on goes on the left, on the same side as the motor. You should be able to "jiggle" the axle out now; if not, release the large gear on the motor (left as you look in) side - there are two grub screws locking it in place, 90 degrees apart. Whatever you do, take great care not to damage the worm drive or the large brass gear around the RA axis.

Once the worm drive is out, carefully remove the brass drive gear. Probably worth giving all this lot a good soak in de-greaser, then re-greasing it before reassembly.

Now you will need to take the dec arm off. From here on, all the screws may be sealed in palce (like loctite, you will see a hard red film left on the bolts). To remove the dec arm, locate the two grub screws (about 6 mm) in the body, on the RA axis near the RA indicator wheel. These are simply covers and can be removed. If you look through the resulting holes, you will see two more grub screws. Undo both of these by about three turns (much more than that and you risk losing them inside the dec axis body).

To remove the dec axis body, insert a large screwdriver into one of the three holes you can see in the RA drive plate back in the mount head. Rotate the dec axis counterclockwise until the screwdriver catches against the body. Now force the dec arm counterclockwise (as you look at it from the front of the mount, so that the head is behind the dec axis body). I had to belt mine several times with a rubber mallet to get it to move (be careful the screwdiver in the back doesn't let go!).

With the dec axis body removed, you will see what appears to be a large washer with two holes in it around the RA axis: this is a locknut. Carefully knock it loose - I used a small screwdriver in the hole and tapped in with a small hammer- but be gentle as it is quite delicate. Now remove the remaining washers, etc. (get the order right when you put them back). One of the plates is held on with three screws, when you have removed this you will be able to remove the RA setting wheel if you want to.

At this stage, you should have exposed the smaller front bearing. All that remains is to knock the RA axis back into the mount - again, a rubber mallet or a metal hammer with a bit of wood between it and the threaded end of the axis.

You will now be able to pop both the bearings out.

To put it back together, to the above backwards!

Hope this helps, if you need a pic from any stage, drop me a line.

J.

[jamespels]

meant to say, the bearings are as follows. One of these is the lower dec axis bearing - I think it is the smallest one but am not sure - it will be obvious when you look at them. I got the cheap ones from Simply Bearings Ltd ~ Oil Seals SKF FAG TIMKEN KOYO NTN NKE TRULOC Needle Rollers Taper Rollers Rod Ends Oilite Bushes Loose Balls O Rings Grease Plain Thrust and had great service.

1 x 60052RS Budget Rubber Sealed Deep Groove Ball Bearing 25x47x12mm (6005.2RS.EU) = £2.99

1 x 69042RS Budget Rubber Sealed Thin Section Deep Groove Ball Bearing 20x37x9mm (6904.2RS.EU) = £5.84

1 x 6006 Budget Open Type Deep Groove Ball Bearing 30x55x13mm (6006.EU) = £2.83

I also replaced the dreadful slotted machine screws holding the mount head together:

M3 x 12 Black Countersunk Allen Key Screws x 20PK

M3 x 12 Black Countersun

£1.90

1

£1.90

M3 x 6 Black Countersunk Allen Key Screws x 20PK

M3 x 6 Black Countersunk

£1.90

1

£1.90

These came from needabolt (High Tensile Socket Cap Screws, Allen Key Screws, Machine Screws, Nylon Nuts, Washers,button,countersunk,). Quck service again, and very cheap.

J.

[Andy McK]

Thanks all. I am overwhelmed with these replys.

If all support was of this quallity, the world would be a happier place.

Andy McK

[AndyH]

Hi all.

Reads good to me, James !

I'd add the following.....

When you've got the motor out, take a carefull look at the reduction gearbox, attached to the motor. The small cog at the top of the following pic, is the one to look out for. This seems to take the brunt of the punishment....

As you can see, on mine it is partly stripped.

If it's damaged, it may completely fail to turn the motor clutch, or may do so intermittently. Replacement motor gearbox units are available from Tal in Novosibirsk.

When refitting the worm shaft, you may find it has gained some sideplay(Must admit, it's never happened to me). Tightening the threaded collar on the right hand side of the shaft, takes up any sideways play. A grub screw holds it in place. A simple snug fit is desired here.

Whilst the DEC arm is off you may as well check it's upper and lower bearings for wear too.

Cheers,

Andy.

[jamespels]

Thanks Andy, and I really should have credited you with a lot of this - thanks for the help previously!

I should have said - those bearing sizes are inner diameter x outer diameter x width. The original are all open; I am not sure if there is a benefit to geatting shielded bearings for the RA axis but it is definitely beneficial for the lower bearing on the dec axis. AndyH (I think) points out elsewhere (possibly on the defunct TAL owners club fourm - not sure if it is still accessible) that the swarf and other muck produced as the dec axis turns all falls down onto this bearing so it will probably be the one in the worst condition. Another solution posted by somebody else on the the owners club (sorry, not sure who) was to put a split fabric washer above the bearing to protect it.

J.

Edited November 9, 2011 by jamespels

[Andy McK]

Well thanks chaps, my mount is now in bits, managed to get the thrust washer off the RA axis after a bit of a faff, but it transpires that the larger of the two bearings (clutch end) seems to be ok but the smaller of the two is like a 50p piece, saying that, looking at the design, it is the bearing that takes most of the load, I'm now wondering is a tapered roller bearing might be a viable upgrade.

I had to repair my clock drive g/box, one of the shafts had sheared off the casing, but more disturbing, my g/box is an all nylon/ptfe affair. So I can see this being swapped out soon too ((

Off to find a bearing pullers now.

[jamespels]

I'm now wondering is a tapered roller bearing might be a viable upgrade.

I wouldn't bother - the bearing isn't taking any thrust as such (rotational load only - not axial) so this will detract rather than add to the performance.

Off to find a bearing pullers now.

Take one wooden spoon, feed the handle from the back and knock out the knackered bearing(s). Both came out easily in mine and it was years old with some dreadful set ex-grease. If either of the bearings are OK, just leave them, through it might be worth taking them out anyway to a soak in de-greaser and re grease them.

J.

Edited November 9, 2011 by jamespels

[Andy McK]

As you said James, I did manage to remove both bearings, without to much force, I placed the shaft in the vice, as the threaded end is of a smaller dia. then, through the large holes in the end plate, used a a piece of dowel to tap the bearing off.

Cleaned up the lot, nipped of to the local bearing supplier, (who was amused to see USSR stamped on the shells) Replaced the bearings and serverly greased the lot.

BTW. I did notice, when i stripped the RA clutch, that there was un even "polished" areas on the brass ring, sugesting that the plate and ring were not in full contact. So I have lapped them with some very fine emery sheet and oil on my table saw, (only true flat surface I have).

After re-assy. as described in one of the web sites the Tal group pointed me to, I have set up the clutches, "just to bite" and I can now balance the scope with ease, and the action on all axis' are lovely and smooth.

I am very pleased with the result, and I couldn't have done this (with confidence) without your's and AndyH's help.

The unit is now under test in the dinning room, just wait for some clear skies now.

Many Thanks

Andy McK.

[Andy McK]

Job done!!

Edited November 9, 2011 by Andy McK
Trying to add a pic

[Andy McK]

Hmmm, tried to post pics?

[Andy McK]

Drive under test. I dont know if this is the right way to go about this, just a shot in the dark, see how many deg. diff in 1 hour etc.

[AndyH]

Don't know if you've read this. Just some stuff I've picked up over the years of using this mount. It may be of help?

http://stargazerslounge.com/discussions-mounts/156715-adjusting-tuning-up-your-tal-mount.html

Cheers,

Andy.

[Andy McK]

Cheers Andy, all good stuff.

So chaps, if I've got this right:

The RA axis should move 15 deg in 1 hour (360 deg/24hrs)

In my pics above, I am using an angle finder and stop watch, so I recon, starting from 0 or 90 deg, i should see a 15 tilt in the OTA every hour (OTA horizontal to start)

the longer I run this, compound errors in tracking speed will become apparent. (or untill the angle finder falls off).

Motor clutch adjustment:

As stated Andy, I did notice a profound effect the tension on the motor clutch springs had on the RA adjustment, moreover, I noticed the strain put on the motor gearbox. So I backed the springs off untill there was no drive, then tightened the screws all the way in, counting the number of turnes used untill the were "snug", then backed them off total number of turns -1. I did note some slippage and adjusted the 3 screws up 1/4 turn each. I used the same process on the RA clutch. And at 12:00 today, the rig is under test, with the same apparatus as my pic. So far so good.

I will be swapping out the screws that are use the most/visable with counter sunk socket head screws when I get back to work (engineering dept have all this nice 316 stainless bits and bobs)

Btw, My daugter had a 114" Helios for her birthday, in June. We set it up quite quickly and we all saw the moon, Saturn, Jupiter etc. very impressed.

Took my TAL over there 1st night I had bought it, to compare, Just looking at the moon, I noted the improvement in image, (25mm EP) the 15mm 45mm and the 4x barlow need cleaning. But heres the point.

When my daughter came out the back garden and saw the TAL, she thought I had got it from the Taliban, as it really did look like a rocket launcher ()

pps: she did ask "who's the coffin for?" (she's 5 foot)

Thanks again all.

Andy

[Andy McK]

Sorry guys, typo, Me daughter had 114mm Helios not 114" (would have had to sell the house for that !!)

[Andy McK]

Cant remember if you sent me this Andy, but all good stuff.

THE FIRMAMENT - Solar System and Deep Sky webcam images

Very interesting with the amount of effort this chap went through to remove PE from the worm drive

[sloz1664]

Nice one Andy. I refurbished my Tal 2M mount earlier this year. Never looked back.

Cheers

Steve.

Edited November 10, 2011 by sloz1664

[AndyH]

Sounds good, Andy !

I usually run the slippage test with the scope set up at my latitude, pointing at least 45 degrees high and the DEC arm around the horizontal, so that the clutches are really having to work, so to speak. But your method sounds like it'll work just as well.

Cheers,

Andy.

[Andy McK]

Well, proof of the puddin!

We have a clear sky at Port Talbot at the mo, so I've set up outside, Going to have a crack at M32 if poss, should be good for me bout 9-10 tonite.

Andy McK (To many Andy's on this site, Think I'll change me name to Slartibartfast)

)

[jamespels]

Right, going to have to tune my mount up a bit now!!! I ned to sort out a nick in the work drive so I can tighten up the meshing a bit better - the slack is really annoying me. I missed that guide first time round, AndyH, so thanks for posting a link to it.

Anybody have any objections to me bringing this lot together into a single article on the new Peak District Dark Skies website when I get it built? All usual credits, etc.

Will have to sort out a special discount for TAL owners at PSP2012 (good luck with me pushing that past the committe!) so we can all gather in a corner and "oo" and "ahh" over how smooth we've got them

Thanks,

J.

[Andy McK]

Yer, all for that James,

BTW, skies are clearing again whoop.

did notice ealier, now the scope is in the cold, i.m getting slip in RA

Torch n screwdriver, onward.......

[AndyH]

Anybody have any objections to me bringing this lot together into a single article on the new Peak District Dark Skies website when I get it built? All usual credits, etc.

None from me.

Will have to sort out a special discount for TAL owners at PSP2012 (good luck with me pushing that past the committe!) so we can all gather in a corner and "oo" and "ahh" over how smooth we've got them

Might need a pallet full of jaffa cakes to push through that

Would be nice to see a multitude of Tal's in one field.

Andy.

Edited November 10, 2011 by AndyH