Discmounts DM-6 disassembly

[casstony]

After getting some advice from Tom at Discmounts I disassembled and cleaned the AZ axis components on the mount. It's a very simple process and as long as you're careful and gentle it goes smoothly. There was a bit of debris to be cleaned off the discs and there are some scour marks on the white plastic disc. I also cleaned a few aluminium flakes out of a threaded hole drilled in the disc face.

I've been concerned that the Az axis is not quite as smooth as the Alt axis for micro movements - after cleaning it does seem smoother but I won't really be able to test it until my C11 arrives next week. I'd like to stess that the mount is generally very smooth, but was not as smooth with micro movements as the manufacturer stated it should be.

[casstony]

All back together with the addition of my home made balance shaft plate.

[Steffen]

Hi Tony,
any idea where the grit came from? Did you receive the mount like that?

Cheers
Steffen.

[casstony]

I bought the mount used off Astromart Steffen - it was built in 2006. The only place I can think of for 'grit' to come from is that threaded hole in the alloy discs (one in the top disc and one in the bottom disc); I did get some loose metal out of that hole and there did appear to be a couple of small pieces embedded in the white disc. The scraches/scour marks may be completely normal - I won't know until Tom looks at the pictures and he is away at NEAF for the week.

[Steffen]

Oh I see, it was 2nd hand. You wouldn't expect something like this to slip past QA by DiscMounts.

Cheers
Steffen.

[DiscMounts, Inc]

Tony,
I'm leaving for NEAF in about an hour.
I don't see anything unusual, the rings on the disc are normal. It's interesting to see that my sanding marks on the disc, after 5 years, are still there. it gives you an idea of how long the disc will last. I found a new source for the disc that are much flatter, so I no longer sand them. The rings in the picture are from the screw holes and are completely normal. I'm not sure why they're there, I sand each hole to make sure it's smooth. But there in every single mount.

It's very hard for anything to get in between the disc. If sand does it will lodge itself in the disc and make a new ring. My guess is the small peace of metal came from the platting hole that can be seen in the picture. There's a similar hole in each disc, that was used for the electrode to support the disc during platting. We have found another way to hold the disc so no longer put the hole there.

I don't advise taking the mount apart, you can cause serious bearing damage if it's not reassembled properly. I can't remember ever giving instructions to anyone before. My big mount (8.5" disc) which is 40 years old hasn't been dissembled since I added encoders when the Sky Commander first came out 15 years ago.

I'm out of here! Scott want's his DM-6 so I better deliver it to Him (at NEAF).

Tom

[wavelandscott]

Yes, I am getting excited about NEAF and wish you safe travels in your journey.

[casstony]

With the outlook being several days of cloudy weather I braved poor conditions tonight to test the DM-6 with my newly acquired C11. The upshot is that I didn't have any trouble making minute adjustments so cleaning the discs appears to have worked.

I did notice that the AZ motion is entirely smooth and controlable when the top metal disc is turning against the white plastic (these were in lockstep before cleaning), whereas there was still a hint of striction if the bottom metal disc turned against the white plastic. (I could get the white plastic to turn against either metal disc by holding my thumb and forefinger against it). Under normal operation the top metal disc always turned first against the white plastic, so small movements/tracking are free of striction; the bottom metal disc would also begin to slip against the plastic when the mount was moved faster. Overall I get very smooth operation in both axes now.

I tried using the C11 with and without balance weights for the AZ axis and found that the AZ motion was much nicer with the balance weights. I wasn't at all surprised by this given the weight and width of the C11.