Author Topic: Funny thing about custom alt-az made at elevation in a cooler climate...  (Read 338 times)

David Williams

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Re: Funny thing about custom alt-az made at elevation in a cooler climate...
« Reply #15 on: January 31, 2018, 01:57:09 AM »
After lots of testing under different conditions it really does seem to be ambient temperature sensitive (when it's hot and the mount head thoroughly heats up, it seizes up a bit) and specifically related to the azimuth clutch. I've noticed that when it's bad if I really tighten that clutch then fully loosen it, sometimes but not always the azimuth axis frees up a bit (i.e., the unwanted drag on when unlocked is half what it was before locking then fully loosening.

I think it is one of two things - the clutch on that axis is very close in clearance (and even audibly drags a tiny bit when loose and the mount is cold and free spinning in that axis, or the teflon bearing between the upper and lower segments below the clutch gets "pinched" when the metal of the two segments on either side expand.

Odd. Fortunately it has never been an issue at night, only during the day when the mount has sat out in heat for a long while. But at some point I may take it apart and have a look at the clutches to see if there's anything obvious amiss or otherwise anything adjustable.

Another minor issue; somehow the lower section that supplies the 3/8-16 tapping won't unscrew. There's an M10 tapping in the next segment up to allow use on different tripods with different center threaded rod specs. I'm hoping that I can secure the mount head to a tripod using the 3/8-16 connection, and then unscrew the lower segment secured to the tripod from the rest of the mount. I can't do it by hand with the mount head free from a tripod; I can't get enough leverage to do the job. Plan B would be a strap wrench on each segment, turned in opposite directions.

Regards,

Jim

Ryan Hernandez

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Re: Funny thing about custom alt-az made at elevation in a cooler climate...
« Reply #16 on: January 31, 2018, 07:35:35 AM »
Quote
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I have an AYO Master alt-az mount and adore it. Best alt-az mount I've ever used. Simple, counterweighted, massive capacity, when balanced and frictioned using clutches, one-finger movements are a piece of cake and it doesn't look like someone's science faire project or doo-doo. What's not to love?

But...

I've noticed something now that I've been using the mount for awhile. When I first received it, by day in my shed, I could hear the slightest "hiss" of friction with the clutches unlocked when I spun the mount around its azimuth axis. When I was showing it off at night to clubmates, though, and wanted to show them the slight contact on that axis, it didn't manifest. A couple of times in the shed by day of late I've attempted to rotate the mount with one hand in azimuth and even though the clutch was loose, it wouldn't budge and instead the entire mount pivoted on the workbench. Later everything was loose again with no friction on that axis.

Last night I set up to use the mount as a guiding platform for p-gram mounted big binoculars (using a GLP on a scope on the AYO Master as the "finder" for the binoculars). By day the azimuth axis with clutch loose was very stiff. So much so I almost wrote the manufacturer to ask about how I'd go about adjusting or perhaps lubricating/cleaning that bearing surface. But then when I went out after 10pm to use the mount it was again completely smooth.

Then it dawned on me: It's a temperature thing. Every instance of slight contact or tightness in the unlocked azimuth axis has been during the day, near sea level in warmer temperatures. At the same location, at night, when ambient temperatures drop into the 50s and the mount has equilibrated, it's butter smooth.

I am thinking that the tolerances are so tight that in warmer conditions than the maker could have tested (daytime use in Mediterranean climate at ~85F or warmer) there's some differential expansion of materials used in the mount that triggers contact. That contact goes away as soon as the material contracts with lower temperatures. I may have a peek inside to see if anything could be tweaked/adjusted, but for now I'll leave well enough alone since it does not interfere with any actual use I plan.

Still an odd "glitch" likely due to different geographies of maker and user.

Best,

Jim

Jim,

In about a week or so I am expecting delivery of the next smaller version, the AYO Digi II (ordered without the encoders for now) which I will also be using at essentially sea level. Albeit in the somewhat cooler climes of British Columbia, we do still get some very warm summer days. Not sure whether the Digi II and the Master have the same or different internal bearing construction. The website notes the included use of teflon for the Master but is silent as regards its use in the Digi II. But in any event I'll report back if I have a similar experience with differential ambient.

Gurm
The Master also uses Teflon simple bearings in addition to sealed bearings, so a slightly different design (albeit likely similar as far as the sealed bearings are concerned).

- Jim

engoecircming

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Re: Funny thing about custom alt-az made at elevation in a cooler climate...
« Reply #17 on: February 02, 2018, 02:23:55 PM »
If it is a temperature thing, it should be taken into account when designing. A proper astro mount should be able to accommodate at least -20° to +40° (considered normal temperature on this planet) and work without problems within that range, otherwise the manufacture should clearly specify its range.

writgobetfcoo

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Re: Funny thing about custom alt-az made at elevation in a cooler climate...
« Reply #18 on: February 03, 2018, 01:34:27 AM »
Well, I've had a chance to use my new Ayo Digi II. I think the level of friction does change with the ambient temperature, but ever so slightly and not to any degree impacting usage.

I left the mount outside after observing last night in my backyard, leaving the telescope still on the mount but covered with a cloth. I tightened both axes pretty tight, so the scope would stay put.
Today the temps got to just over 30C and the mount was in the direct sun and sure enough, I noticed the same behaviour as noted by Jim.
In my case, when I loosened the alt and azimuth knobs, the azimuth axis became totally frictionless, but it was the altitude axis that retained a very small amount of friction and it made a faint hissing noise when rotating it. What I don't know is whether the mount would have behaved identically if left in the sun but without the knobs tightened down the night before. I may give that a try some time just out of curiosity.

Anyways, about 2 hours after bringing it inside, it cooled down and returned to noiseless and totally frictionless movement when unlocked.

I should also mention noticing the same behaviour, but in reverse, while observing the evening before. As the temperature dropped over the course of the night, I found I had to tighten the knobs ever so slightly, to keep the same level of friction. I'm assuming this was due to contraction of, and therefore a bit more clearance between, the internals as they cooled.

I'm betting this temperature related expansion/contraction of internal components is normal and probably a function of very tight tolerances, but manifested only at extremes on the temp scale. Overall, I find it doesn't impact usage, even in hot daytime as the slight amount of temperature induced friction is still far less than I would normally tighten the knobs to in any event, to counteract slight imbalance issues with the scope and changing differently weighted eyepieces, moving the focus drawtube in or out, etc.

I'm very happy with this mount, about which I'll write a more complete description in a separate posting.

Gurm