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iOptron CEM40 and the clutches

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#1 barnold84

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Posted 20 September 2020 - 09:39 AM

Hi,

I just ordered an iOptron CEM40 mount. In the meantime I studied the manual a bit to get acquainted with what I have to expect and be aware of.

One thing that I noticed is that iOptron seems to be obsessed about the worm gear. Contrary to some other manufacturers manuals they mention many times to open the clutches/gear locks when doing something specific.
Certainly, it’s good and reasonable to open the RA lock when attaching counterweight shaft and weight. But how about mounting the optics on the saddle?
I would assume that it’s safe and intended to close the gear locks to mount the OTA and additional equipment. If you handle some heavy equipment and try to place it on a wobbly mount, accident is preprogrammed.

Björn

#2 Michael Covington

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Posted 20 September 2020 - 10:03 AM

Here is my protocol (GEM45, which is almost identical to CEM40):  

Locks OFF when transporting the mount head in the case.
ON when lifting the mount head out of the case and putting it on the tripod.
ON when leaving the mount head on the tripod.
OFF when attaching the counterweights.
ON when attaching the telescope.
OFF when adjusting balance (of course).

ON the rest of the time.

Never put a lock HALF ON.  That would mean the gears are tooth-to-tooth instead of tooth-between-teeth.  If a lock will only go halfway on, wiggle the mount a little until it locks the rest of the way.

If leaving the mount head on the tripod, remove the counterweight bar so it doesn't get bumped.

If the mount head is on the tripod without the counterweight bar, the locks must be ON or else the head will go upside down.  On the CEM40 the mount just bumps into part of itself; on the GEM45 it can go completely upside down and unplug internal cables.


Edited by Michael Covington, 20 September 2020 - 10:04 AM.

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#3 barnold84

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Posted 20 September 2020 - 11:43 AM

Hi Michael,

 

Thanks for your prompt reply!

 

 

ON the rest of the time.

Is it possible to unlock and move the scope freely and lock again? I know after alignment, I will lose it. Besides this is there any other issue that I'm not aware of?

Usually, I'm not using the goto functionality very often. I manually move to a major star close to the final target and then slew manually with a bit of star hopping.

 

 

Never put a lock HALF ON.  That would mean the gears are tooth-to-tooth instead of tooth-between-teeth.  If a lock will only go halfway on, wiggle the mount a little until it locks the rest of the way.

Interesting to know how the gear lock works. In my LX85, it's a simple friction clutch (screw pushes rubber against the worm wheel). So, the unlocking pushes the worm out of contact. Is the worm usually spring loaded for optimal worm to wheel interlock?

 

 

If leaving the mount head on the tripod, remove the counterweight bar so it doesn't get bumped.

W/o optics I guess? I'm just asking because I might leave the mount outdoors for a few days in a row but w/o optics during the day. Typically, I leave the CW bar and CW on with RA unlocked/decoupled. If I pack the stuff indoors, I am taking the mount off the tripod. Will also have to look for a case/bag (mount will come w/o case). Also with Alt being set to the higher range, the original packaging apparently wouldn't work.

 

 

on the GEM45 it can go completely upside down and unplug internal cables.

Oops, good to know that I may never allow the RA going completely upside down. Just found another post in this forum where somebody had problems moving in DEC. The issue was that he reached some travel limit of the axis. Didn't find anything about this mentioned in the manual. Since my current mount is externally cabled, I can turn the DEC how much I want.

 

Björn



#4 Michael Covington

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Posted 20 September 2020 - 11:49 AM

Hi Michael,

 

Thanks for your prompt reply!

 

Is it possible to unlock and move the scope freely and lock again? I know after alignment, I will lose it. Besides this is there any other issue that I'm not aware of?

Usually, I'm not using the goto functionality very often. I manually move to a major star close to the final target and then slew manually with a bit of star hopping.

 

Interesting to know how the gear lock works. In my LX85, it's a simple friction clutch (screw pushes rubber against the worm wheel). So, the unlocking pushes the worm out of contact. Is the worm usually spring loaded for optimal worm to wheel interlock?

 

W/o optics I guess? I'm just asking because I might leave the mount outdoors for a few days in a row but w/o optics during the day. Typically, I leave the CW bar and CW on with RA unlocked/decoupled. If I pack the stuff indoors, I am taking the mount off the tripod. Will also have to look for a case/bag (mount will come w/o case). Also with Alt being set to the higher range, the original packaging apparently wouldn't work.

 

Oops, good to know that I may never allow the RA going completely upside down. Just found another post in this forum where somebody had problems moving in DEC. The issue was that he reached some travel limit of the axis. Didn't find anything about this mentioned in the manual. Since my current mount is externally cabled, I can turn the DEC how much I want.

 

Björn

(1) Yes, of course.  We do this while balancing.  It's perfectly safe to move the telescope around if the telescope and counterweight are on the mount and reasonably well balanced.

 

(2) Right, I think it's both a spring and magnet.  What you are doing is removing the worm from contact with the spur gear.

(3) Right, without optics.  If the telescope is on the mount, the counterweight must be on it.  If the counterweight is on it but no telescope, the counterweight must be straight down, to keep from applying torque.



#5 Joe Bergeron

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Posted 20 September 2020 - 04:59 PM

Here is my protocol (GEM45, which is almost identical to CEM40):  

Locks OFF when transporting the mount head in the case.
ON when lifting the mount head out of the case and putting it on the tripod.
ON when leaving the mount head on the tripod.
OFF when attaching the counterweights.
ON when attaching the telescope.
OFF when adjusting balance (of course).

ON the rest of the time.

Never put a lock HALF ON.  That would mean the gears are tooth-to-tooth instead of tooth-between-teeth.  If a lock will only go halfway on, wiggle the mount a little until it locks the rest of the way.

If leaving the mount head on the tripod, remove the counterweight bar so it doesn't get bumped.

If the mount head is on the tripod without the counterweight bar, the locks must be ON or else the head will go upside down.  On the CEM40 the mount just bumps into part of itself; on the GEM45 it can go completely upside down and unplug internal cables.

I don’t fully understand this. Why would you engage the locks while you are manhandling the mount to attach it to the tripod? Wouldn’t it be safer for the gears to leave them free? If the mount has no scope or weights, why not leave it unlocked so it can move around freely if knocked? 



#6 Michael Covington

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Posted 20 September 2020 - 06:31 PM

I don’t fully understand this. Why would you engage the locks while you are manhandling the mount to attach it to the tripod? Wouldn’t it be safer for the gears to leave them free? If the mount has no scope or weights, why not leave it unlocked so it can move around freely if knocked? 

(1) To your first point, I had the same question and asked iOptron support.  The answer is partly that it's very hard to handle the mount head when it's not locked, and the other is...

(2) The mount head is top heavy.  For CEM mounts, this means they fall over to the point that the outer bracket catches them.  For the GEM45, it's worse -- they can go upside down and unplug internal cables.  So the mount head, when there is no counterweight bar on it, needs to be locked.

I wondered about these same things.  A few minutes of actually handling a GEM45 make it evident why iOptron's recommendations are what they are.
 


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#7 barnold84

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Posted 20 September 2020 - 11:51 PM

Hi,

 

 

The answer is partly that it's very hard to handle the mount head when it's not locked, and the other is...

In the end it simply depends on the weight of the mount (actually just what may rotate freely when RA is unlocked). If you can ride a bicycle with an elephant on your back, you can mount it unlocked. I do it with my LX85 but it's more comfortable when RA is locked.

 

 

(2) The mount head is top heavy.  For CEM mounts, this means they fall over to the point that the outer bracket catches them.  For the GEM45, it's worse -- they can go upside down and unplug internal cables.  So the mount head, when there is no counterweight bar on it, needs to be locked.

I assume that the iOptron worms aren't overly more sensitive, compared to any other worm gear for astronomical mounts. They shouldn't be made out of glass and allow for normal handling. (I think they're actually brass on steel.)

It makes always sense to avoid high torque situations, especially things like having only CW bar and CWs on it. If you assemble all of your optics on top, you'll certainly be out of balance and this also experts some torque until you open the lock and balance the axes. 

That's why I started the topic. iOptron seems to be obsessive about mentioning to open clutches, while other manufacturers don't. Personally, I believe you may handle the iOptrons like any other GEM applying common sense.

 

I read about people that install their OTAs with gear unlocked. Since this is a wiggly thing they constructed some wooden support and whatsoever. If I had to do that, I would immediately return the thing.

 

@Michael: what exactly did you ask them about?

I was actually thinking if I should write them an e-mail and ask about gear lock while mounting the OTA because from the way it reads it really feels like "worm gear out of glass".

 

Björn



#8 Michael Covington

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Posted 21 September 2020 - 11:00 AM

The reason applying torque is an issue not the fragility of the worm.  It's the way it is held against the gear -- with spring tension, not by being held firmly in place.  So if you apply too much torque, the teeth will cog against each other and be damaged.



#9 ryanha

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Posted 21 September 2020 - 08:13 PM

If you are setting up and tearing down ever time you use the rig, buy yourself a 4mm ball end screwdriver.

 

The hex wrench that ships with the CEM-40 "can" be used to screw/unscrew the bolts that attach the mount to the tripod but the 90-deg angle end makes it a bit awkward. 

 

A little ball-end hex screwdriver makes this much more ergonomic. Actually surprised that they don't ship with one instead of the angled hex key.

 

--Ryan


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#10 Linwood

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Posted 21 September 2020 - 08:47 PM

Here is my protocol (GEM45, which is almost identical to CEM40):  
...

OFF when attaching the counterweights.

...

Just curious about this one.  Not that it seems a bad idea, just wouldn't have occurred to me to do it. I mean, it's just sitting there.  Or maybe the GEM45 is different? 

 

By the way, and I think it says this in the manual somewhere -- DON"T work on the mount with the RA axis unlocked and the counterweight shaft not attached.  The head flops over pretty fast and hard.  I was taking the cover off the main board (and the RA axis has to be at 90 degrees to do it) but also had the counterweight shaft off because I thought I needed to remove the iPolar (I didn't, long irrelevant story). 


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#11 cyendrey

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Posted 24 September 2020 - 05:26 PM

I don't know that is helpful, but do NOT use the term 'clutches' in regards to the Ioptron (or similarly designed mounts).  They do not have clutches; what they do is physically move the worm gear in/out of engagement with the main drive ring gear.

Synscan mounts, like the Skywatcher EQ5/6/8 series and those of similar design do have clutches, or at least a friction disk that bears the axis ring.  Overtightening has been shown to sometimes deform this ring, affecting guide performance.  However, with the clutches engaged, if excessive torque is applied, it will just slip on the ring and not damage anything (usually).  The damage usually occurs when someone tries to over tighten the clutches trying to prevent the mount from slipping why they are horsing it around..  

This is most definitely NOT the case with the gear engagement design of the Ioptron (believe this is also the case with AP and Software Bisque mount design, but don't know this for a fact).  As a consequence, since there is no inherent torque relief in the design (unlike the friction rings on Synscan designs), excessive torque can damage the worm, ring gear, or other parts of the gear/motor drive assemblies. It doesn't take very much of a 'drag' burr, scar, deformation to either gear to render tracking/guidance out of spec, and likely outside the ability of a new PEC or guide software to correct.

 

If all you've used are Orion/Skywatcher type mounts, then throw all those expectations/habits of use out because they will get you in trouble.  Yes, I just made the switch from an EQ6R Pro to an Ioptron GEM45.

 


Edited by cyendrey, 24 September 2020 - 05:29 PM.

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#12 Linwood

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Posted 24 September 2020 - 06:26 PM

I don't know that is helpful, but do NOT use the term 'clutches' in regards to the Ioptron (or similarly designed mounts).  They do not have clutches; what they do is physically move the worm gear in/out of engagement with the main drive ring gear.

Yeah, I've been told that, and I agree, and believe it.  bad habit, but I also have a least a minor excuse -- iOptron calls them clutches in the manual twice (page 5 under features and page 33 when it tells you to engage the "clutches" after each adjustment). So cut me just a little slack.  smile.gif


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#13 Michael Covington

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Posted 24 September 2020 - 06:43 PM

I'm training myself to call them the "locks" unless someone has a better idea...



#14 Linwood

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Posted 24 September 2020 - 06:58 PM

I'm training myself to call them the "locks" unless someone has a better idea...

I looked at a few other places in the manual and they call it a Gear Switch. 

 

I'm confident if we can identify the politically correct phrase, that tracking errors will be minimized. 


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#15 Michael Covington

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Posted 24 September 2020 - 07:11 PM

Noted.  Gear Switch it is!



#16 barnold84

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Posted 24 September 2020 - 11:29 PM

I don't know that is helpful, but do NOT use the term 'clutches' in regards to the Ioptron (or similarly designed mounts).  They do not have clutches; what they do is physically move the worm gear in/out of engagement with the main drive ring gear.

Synscan mounts, like the Skywatcher EQ5/6/8 series and those of similar design do have clutches, or at least a friction disk that bears the axis ring.  Overtightening has been shown to sometimes deform this ring, affecting guide performance.  However, with the clutches engaged, if excessive torque is applied, it will just slip on the ring and not damage anything (usually).  The damage usually occurs when someone tries to over tighten the clutches trying to prevent the mount from slipping why they are horsing it around..  

This is most definitely NOT the case with the gear engagement design of the Ioptron (believe this is also the case with AP and Software Bisque mount design, but don't know this for a fact).  As a consequence, since there is no inherent torque relief in the design (unlike the friction rings on Synscan designs), excessive torque can damage the worm, ring gear, or other parts of the gear/motor drive assemblies. It doesn't take very much of a 'drag' burr, scar, deformation to either gear to render tracking/guidance out of spec, and likely outside the ability of a new PEC or guide software to correct.

 

If all you've used are Orion/Skywatcher type mounts, then throw all those expectations/habits of use out because they will get you in trouble.  Yes, I just made the switch from an EQ6R Pro to an Ioptron GEM45.

 

Certainly, one can make a philosophical discussion out of this: from a mech. engineering point of view, it is valid to call both concepts a clutch since it temporarily connects and disconnects a driven element from the driving element. It doesn't matter here if its positive fit or friction based although the vast majority of clutches are realized through friction.

 

From your statement, one can see pros and cons for both ideas: the friction based connection can "protect" the form gear from excessive force (I read somewhere that Losmandy mounts rely on this to move the axis manually). With the iOptron et al. concept, you guarantee do disengage any force transmission while moving manually. The spring load also helps to have the best fit between worm and gear.

 

By the way, I just dropped a line to iOptron support asking them about their worm gears and why they mention this at every occasion and the mount-the-OTA-confusion arising sometimes. The answer took only six hours - Germany to Massachusetts. Here it is:

 

"The practice of unlock clutches applies to all mounts, not iOptron specifically. Of course, you may lock the clutch when loading OTA if you used to."

 

Long story short: if it hasn't to be locked for a reason. Keep it unlocked. Valid for any mount.

That's my conclusion.

 

Björn

 

PS: never mentioned the word "clutch" in my e-mail. iOptron did lol.gif


Edited by barnold84, 24 September 2020 - 11:31 PM.

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#17 lampcord

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Posted 28 September 2020 - 07:44 AM

Here is my protocol (GEM45, which is almost identical to CEM40):  

Locks OFF when transporting the mount head in the case.
ON when lifting the mount head out of the case and putting it on the tripod.
ON when leaving the mount head on the tripod.
OFF when attaching the counterweights.
ON when attaching the telescope.
OFF when adjusting balance (of course).

ON the rest of the time.

Never put a lock HALF ON.  That would mean the gears are tooth-to-tooth instead of tooth-between-teeth.  If a lock will only go halfway on, wiggle the mount a little until it locks the rest of the way.

If leaving the mount head on the tripod, remove the counterweight bar so it doesn't get bumped.

If the mount head is on the tripod without the counterweight bar, the locks must be ON or else the head will go upside down.  On the CEM40 the mount just bumps into part of itself; on the GEM45 it can go completely upside down and unplug internal cables.

Not to get too granular but I assume also:

 

ON before attaching the counterweight BAR.

 

Is that correct? Because my understanding is that the mount with no OTA is still top heavy until the counterweight bar is attached.


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#18 barnold84

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Posted 28 September 2020 - 07:49 AM

Not to get too granular but I assume also:

 

ON before attaching the counterweight BAR.

 

Is that correct? Because my understanding is that the mount with no OTA is still top heavy until the counterweight bar is attached.

Hi,

 

Since I got my CEM40 now: yes. I start to insert the CW bar and turn it a bit (about one turn). Then I open the lock once I'm sure that the axis wouldn't move uncontrolled.

 

Björn


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#19 Michael Covington

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Posted 28 September 2020 - 08:56 AM

Not to get too granular but I assume also:

 

ON before attaching the counterweight BAR.

 

Is that correct? Because my understanding is that the mount with no OTA is still top heavy until the counterweight bar is attached.

Right.  Sorry, I left that step out.




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