CEM120 gear problems

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turboscrew
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CEM120 gear problems

#1

Post by turboscrew »

Does anyone have an idea what might be going on with my mount?

About a week ago I got a chance to try my CEM120 first time.
I aligned it and balanced both RA and DEC as well as I could, and got it polar-aligned quite well enough.
Everything started well, but then I tried to go to M106, which was much higher in the sky than the earlier targets, and
I think the DEC gear started "jumping over" in the middle of the slew. I pressed "0" in the controller to stop everything,
disengaged the DEC drive and checked that there is no obstacles anywhere and the DEC axis could move freely.

I then re-engaged the drive and went to the zero-position. No "rattling" then. The RA axis turned just right, but the DEC was a bit off - probably due to my free movement check. I didn't dare to continue.

I found this video clip where the sound is similar.


Next evening I tried again.
As long as the temperature was around +10° (50°F), all was fine, but later, when the temperature dropped to +2°C (35°F), the problem returned.

I contacted iOptron, and they told me to loosen the gear mesh a bit - the manual says max 1/4 turns total. I turned that much and expected to feel a little free play, but there was none. I tried to turn it 1/4 turns more (1/2 turn total), and still no free play.

Last night I tried again if the adjustments helped the problem, but no. It was -5°C (23°F) and now both DEC and RA axes started acting up that way.

Going to the zero position (even if now somewhat off) went fine without any noises, but from zero to Spica, which was at az 222° 18' alt +10°03' at the time, failed. Both axes stalled and made that noise.

The mount specs say:
Payload: 52kg (115 lbs), exclude counterweight
Operation temperature: -10°C ~ +40°C

My gear on top of the mount weight less than 16 kg.
Senior Embedded SW Designer
Telescope: OrionOptics XV12
Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Eyepieces: 10 mm and 25 mm Kellners, 15 mm TV Plössl, 6 mm Baader Classic Ortho, 26 mm Omegon SWAN 70°
Explore Scientific HR 2" coma corrector
Meade x3 1.25" Barlow
Some filters (#80A, ND-96, ND-09, UHC)

LAT 61° 28' 10.9" N, Bortle 5

I don't suffer from insanity. I'm enjoying every minute of it.

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turboscrew
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Re: CEM120 gear problems

#2

Post by turboscrew »

I sent an e-mail to iOptron support early this morning. I told them more about what I have tried, and what the outcomes have been. A moment ago I received an e-mail from them. They suggested to check the bearing tightnesses, and sent the instructions how to do that.

Within the same day even if it's a weekend!
Now THAT's what I call customer support!
Senior Embedded SW Designer
Telescope: OrionOptics XV12
Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Eyepieces: 10 mm and 25 mm Kellners, 15 mm TV Plössl, 6 mm Baader Classic Ortho, 26 mm Omegon SWAN 70°
Explore Scientific HR 2" coma corrector
Meade x3 1.25" Barlow
Some filters (#80A, ND-96, ND-09, UHC)

LAT 61° 28' 10.9" N, Bortle 5

I don't suffer from insanity. I'm enjoying every minute of it.

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Butterfly Maiden
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Re: CEM120 gear problems

#3

Post by Butterfly Maiden »

Let us hope that solves the problem :(

Although I have been following your frustrated efforts to get your gear working properly, I am afraid this issue is way out of my area of expertise, so I can't offer any helpful advice.
Vanessa
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Nikon D82 Fieldscope with 30x/45x/56x angled eyepiece.
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turboscrew
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Re: CEM120 gear problems

#4

Post by turboscrew »

Thanks for supportive thoughts, Vanessa.
The mount is designed and manufactured by human beings, and most of them are known to work. I know I'll get it to work eventually - whenever that is.
Senior Embedded SW Designer
Telescope: OrionOptics XV12
Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Eyepieces: 10 mm and 25 mm Kellners, 15 mm TV Plössl, 6 mm Baader Classic Ortho, 26 mm Omegon SWAN 70°
Explore Scientific HR 2" coma corrector
Meade x3 1.25" Barlow
Some filters (#80A, ND-96, ND-09, UHC)

LAT 61° 28' 10.9" N, Bortle 5

I don't suffer from insanity. I'm enjoying every minute of it.

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OhNo
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Re: CEM120 gear problems

#5

Post by OhNo »

If it is "New" I'd be a lot less than Happy! Sorry I don't own that mount but suspect something jarred it in shipping. Were the clutches engaged or dis-engaged when you opened the shipping box?
Scopes: SkyWatcher 8" Quattro, Celestron C8, SkyWatcher ST120, Orion ST80, SharpStar 61EDPH II. SLT 130 Celestron, Orion 90mm f/10
Mounts: CGEM, CG-4, EQ2, Alt Az, SLT
Cameras: ZWO ASI533MC Pro, ZWO ASI120MM, Canon 1100D
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turboscrew
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Re: CEM120 gear problems

#6

Post by turboscrew »

OhNo wrote: Sun May 02, 2021 3:58 pm If it is "New" I'd be a lot less than Happy! Sorry I don't own that mount but suspect something jarred it in shipping. Were the clutches engaged or dis-engaged when you opened the shipping box?
Gears disengaged, axle locks on, just like it says in the manual.
ONLY set the Gear Switch at locking position to engage the worm/ring gear during goto, slew or
tracking.
ALWAYS lock the Axle Locking Knob during transferring and installing.
DO NOT lock both Gear Switch and Axle Locking Knob at the same time.
And it's kind of new. I got it before Christmas, but the Tri-pier 360 arrived Mar 22th. Then there was some bad weather, so I didn't get to test things until Apr 19th.
Senior Embedded SW Designer
Telescope: OrionOptics XV12
Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Eyepieces: 10 mm and 25 mm Kellners, 15 mm TV Plössl, 6 mm Baader Classic Ortho, 26 mm Omegon SWAN 70°
Explore Scientific HR 2" coma corrector
Meade x3 1.25" Barlow
Some filters (#80A, ND-96, ND-09, UHC)

LAT 61° 28' 10.9" N, Bortle 5

I don't suffer from insanity. I'm enjoying every minute of it.

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SkyHiker
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Re: CEM120 gear problems

#7

Post by SkyHiker »

I have messed around with the G11S mesh gear a lot. I learned a lot from removing the worm gear housing, disconnecting the motors and manually running the worm. That way you can feel when it gets stuck at a high point in the ring gear. I also learned how even a slight imbalance in the direction of motion can make the whole mount vibrate. This can be solved by careful balancing then counterweighting.

For the Losmandies it is also known that a temperature change can tighten up the gear to the point where it binds up, by thermal contraction. Since you are in Finland and are outside in cold temperatures, maybe that could be the cause. Loosen the gear until you feel some backlash and leave it like that. Maybe the cold shrinks everything down so it becomes tight again and works well.
... Henk. :D Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Barndoor trackers for 10" Dob and camera, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x Pi2b all running Astroberry, Toshiba Satellite 17"
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turboscrew
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Re: CEM120 gear problems

#8

Post by turboscrew »

SkyHiker wrote: Sun May 02, 2021 6:10 pm I have messed around with the G11S mesh gear a lot. I learned a lot from removing the worm gear housing, disconnecting the motors and manually running the worm. That way you can feel when it gets stuck at a high point in the ring gear. I also learned how even a slight imbalance in the direction of motion can make the whole mount vibrate. This can be solved by careful balancing then counterweighting.

For the Losmandies it is also known that a temperature change can tighten up the gear to the point where it binds up, by thermal contraction. Since you are in Finland and are outside in cold temperatures, maybe that could be the cause. Loosen the gear until you feel some backlash and leave it like that. Maybe the cold shrinks everything down so it becomes tight again and works well.
I tried loosening the gear mesh. The document said, no more than 1/4 turns total. I turned a bit, then upto 1/4 turns, and finally 1/4 turns more (1/2 turns total). No slack, and it didn't help. I know the slack should be too small to see, but it should be felt, but that didn't happen.

The tech support at iOptron suspected (due to the temperature sensitivity) that the problem might be too tight axle end bearings, and I got instruction sheet, with pictures, how to change the worm gears. One part of putting the gears back, is tightening the axle end bearings. I'll check when I have time. At the end of weekend it's a bit too late in a house with animals (a cat and a dog).

Also, after May 5th there will be no astro dark anymore. Nautical dark is as dark as it gets.
Senior Embedded SW Designer
Telescope: OrionOptics XV12
Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Eyepieces: 10 mm and 25 mm Kellners, 15 mm TV Plössl, 6 mm Baader Classic Ortho, 26 mm Omegon SWAN 70°
Explore Scientific HR 2" coma corrector
Meade x3 1.25" Barlow
Some filters (#80A, ND-96, ND-09, UHC)

LAT 61° 28' 10.9" N, Bortle 5

I don't suffer from insanity. I'm enjoying every minute of it.

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