Disassembling an AZ EQ6 GT?

[catman161]

This is a really interesting thread. My azeq6 is brand news and works fine at present but I would certainly Pay a tenner for a comprehensive guide as I am sure in the future I may like the idea of tinkering with it.

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[mikeobrien]

Thanks Catman161 I think you have persuaded me to take my mount apart and photograph the process.

[catman161]

That's fantastic news Mike let me know when the guide is ready and I will gladly take one off your hands.

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[mikeobrien]

Will doCatman161

[Jonk]

Whilst I have mine in bits, does anyone need to know anything?!

[moriniboy]

Not currently, thanks, as long as you are taking photos that will be a great help in future.

[catman161]

One thing I would like to know-sorry this is going to seem such a dumb question and will have many rolling their eyes I imagine-how do you quantify backlash or indeed know it's present and also how do you measure how much you need to correct it by when you do find it and also how do you correct it?? Sorry, it's just it's been mentioned a few times in earlier posts in this thread and if I ever take apart my AZEQ6 id like to know how to recognise it. Cheers

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[jambouk]

The best way I know of quantifying it was described somewhere here on SGL. I can't find the thread, but someone else might be able to.

Essentially:

- slew the scope in just RA or Dec (do one at a time, though some will argue the backlash in Dec is less [un]important

- with a high power EP or reticle EP (or cam connected to computer with reticle on screen) slew on slow rate (say rate 1 or 2) so the cross hairs just go over something very distant on the horizon which isn't going to move, only do this manoever using one direction key (say the right arrow key), so if you over shoot, go much further the other way back (using the left arrow key say) and then go again to the target slowly (with the right arrow key)

- [make sure tracking is off before you start]

- then make sure you are on a very slow rate, say rate 1

- note down where the hand set thinks the scope is pointing in both RA and Dec

- now use the opposite arrow key (left arrow key in this example) at rate 1 to slew in the other direction

- you may hear the mount mechanism moving, but the image won't move for a bit

- keep going

- as soon as you see ANY movement stop pressing the arrow key

- now note down where the handset thinks it is now pointing

- the time it took from you first pressing the arrow key to when the scope first moved is the backlash in that axis

- you can roughly calculate the backlash in that axis by subtracting the first set of co-ordinates from the last set of co-ordinates

- you may want to repeat this a few times and take the average of a set of 3 or 5 observations

- then repeat as above for the other axis

Hey presto, you have a rough idea of how much backlash there is in your mount.

Make sure it is all well balance first.

Knowing this information can be useful if you subsequently make adjustments in the mount, to see if you have improved the backlash or not.

I've always been dubious about actually inputting the amount of backlash into the handset for it to make auto corrections, as I worry it would make the corrections all the time, even when at times the "cogs" may already be meshed together and so it applies a backlash compensation when it isn't needed so over compensated. If there was a feedback mechanism in the system for it to know if there was sufficient tension on the cogs then it would make sense, but I don't think it is that clever.

By following the astrobaby EQ6 page you can physically reduce the backlash on the AZEQ6, but it takes some time, and it is a balance between getting the backlash reduced, and not getting things too tight so they catch at some part of a full rotation around either axis.

For GOTO accuracy, I found that correcting my cone error made a MUCH bigger improvement than reducing my backlash.

JD

[Gembol]

I can't help thinking the same, jambouk. Great explanation!

[catman161]

Cheers james

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[Jonk]

Whilst I disassembled the mount and put it back together fine, there's one thing I don't get.

The Dec clutch locks the Dec axis fine as expected, but the axis won't turn on the motor. The brass collar turns against the worm fine as I can test this with the shaft and collar out. It appears as though there's not enough grip between the brass, the disc and the collar.

Anyone else noticed this?

[Gembol]

I haven't disassembled Dec axis... sorry... I can see what you say, but I don't know why it happens to you...

[Gembol]

Jonk, is there a locking ring like the RA one? Maybe you have to tighten it more...

[Jonk]

The Dec clutch basically pulls the whole shaft onto the brass ring when tightened and when loosened, the whole shaft is free to turn. It's as though I've left a spacer out or something and the grip just isn't enough for the brass to turn the shaft, but I can't turn it by hand.

[mikeobrien]

Monk have you tightened the black locking collar enough that's the one with grub screws to lock it on the shaft. If that's too loose the clutch won't engage.

[Jonk]

Yep, on the RA axis.. That one works a treat, nice and tight and no backlash felt.

It's the Dec axis that isn't right.

[mikeobrien]

have you left the silver clutch lock too loose when tightening the silver locking ring up to it. try setting the clutch lock so that its just close to engaged then screw the silver locking collar up to it and tighten its grub screw's.

Edited June 2, 2015 by mikeobrien

[Jonk]

I'll give that a try, but I think it was already at max.

[mikeobrien]

If its not that you need to check the order that the bearing parts have gone back in is correct. I think mine had a fiber washer that acted as a clutch plate which would need to be in the correct place for the crown gear to transfer drive power to the Dec axis drive shaft.

[Jonk]

Nope, the silver locking collar only screws on so far and it doesn't make any difference to the clutch if it's on or off.

Confused...

The problem with taking things apart for the first time is you can't always see how it's put together until you remove it!

[Jonk]

The fibre disc sits between the top of the shaft that holds the saddle and the brass gear, then the other side of the brass gear is the bearing ring, and metal washer / disc before the casting.

If that's not the right order I can't see it being another order?

[mikeobrien]

That sounds right to me

[mikeobrien]

Either take a PIC or sketch it and I'll check mine tomorrow to see if its the same.

[Jonk]

Right, I've taken some photos of the DEC axis being disassembled. The only thing I can think that isn't right, is the roller bearings only have a metal disc / washer on 1 side, whereas I'm sure on the RA axis, it had 2, 1 either side of the bearings?

The roller bearings on the clutch wheel certainly has 1 either side.

I don't really want to pull apart the RA axis again to look, but I may have to if no one else is currently doing the same.

Edited June 3, 2015 by Jonk

[mikeobrien]

In the next to last picture it looks like you have the two steel washers stuck togeather instead of one on each side of the roller bearing which incidentally I can't see in the pictures!