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astrorick

mesu 200 ra

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astrorick    250
I had the the Mesu 200.  For a few years now, I noticed that when I turn the RA axis by hand the motor does not rotate even if I turn it slowly, but when I switch it on everything seems to be ok.
I was just wondering if this normal or is it a problem?  

regards  Rick

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I don't think you should move the mount by hand unless it has clutches as it could damage it. The Mesu has locks that allow the entire axis to be rotated and balanced but it does not have clutches as it is a friction drive.

Hope this helps.

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RayD    1,805
11 hours ago, astrorick said:
I had the the Mesu 200.  For a few years now, I noticed that when I turn the RA axis by hand the motor does not rotate even if I turn it slowly, but when I switch it on everything seems to be ok.
I was just wondering if this normal or is it a problem?  

regards  Rick

It is ok to spin it by hand for balancing, but just do it slowly as there is no decoupling.  I certainly wouldn't be regularly doing manual slews as a matter of course.

That's odd?  When you say the motor isn't turning, how do you know as you can't see it?  Are you saving you can't hear the servo spinning (like a kind of ticking sound)?

Having spent a bit of time with Lucas in his factory looking at and chatting about the design and coupling of the servo's I would say that if it is driving but it is not turning if you move it by hand, i.e. you can't hear the servo ticks, then it needs adjusting, which is a factory return, as there is a very specific pressure applied via eccentric keeper plates top and bottom of the servo drive shaft.  It is possible that this could happen as the gearing ratios mean it is harder to turn the servo by moving the mount than it is moving the mount by turning the servo.

It is a wonder why this would need adjusting though as there are no real wearable parts (there are technically as it is friction drive, but the grade of steel means the wear rate is incredibly low), although there are tiny bearings top and bottom of the servo drive shaft, which I guess could wear.

I would drop Lucas Mesu a line and he can advise further.

Edited by RayD

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astrorick    250

Thank you guys  

I think I will get in touch  with Lucas again and see what happen from there....

thank you again   rick

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RayD    1,805
18 hours ago, astrorick said:

Thank you guys  

I think I will get in touch  with Lucas again and see what happen from there....

thank you again   rick

Keep us updated Rick as there are quite a few of us with Mesu200 mounts who no doubt will be interested in the outcome.

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tomato    385

I have had a Mesu 200 since 2014, it goes back into a flight case after every session so once I have removed the scope I have to turn the Dec axis by hand through 90 degrees so it will go back in the case. This is done manually since all the power and connections have been removed at this point, I turn it slowly and smoothly. I must have done this dozens of times since 2014 with no apparent ill effects.

You've got me worried now....

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RayD    1,805
4 minutes ago, tomato said:

I have had a Mesu 200 since 2014, it goes back into a flight case after every session so once I have removed the scope I have to turn the Dec axis by hand through 90 degrees so it will go back in the case. This is done manually since all the power and connections have been removed at this point, I turn it slowly and smoothly. I must have done this dozens of times since 2014 with no apparent ill effects.

You've got me worried now....

No it should be absolutely fine. 

The only concern would be that as it is friction mount you can't decouple the servo from the drive controller, so when spinning by hand the servo effectively becomes a small generator.  Unless the Sitech unit is designed to cope with this back feed, which I suspect it probably is, then it could potentially cause issues with the controller.

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tomato    385

Thanks RayD for the reassurance. I’m sure I read somewhere that it was ok to move the axes by hand if the mount is powered down.

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RayD    1,805
13 minutes ago, tomato said:

Thanks RayD for the reassurance. I’m sure I read somewhere that it was ok to move the axes by hand if the mount is powered down.

Oh I'm absolutely certain it is, I do it myself, but just don't do it at the same speed you would with a mount with clutches.

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astrorick    250

Hi guys

The mesu seems ok now, all I did was slew it from east to west a few times and now the motor is rotating fine. Lucas told me that there shouldn't be anything thing to worry about and asked me if it is slipping, I don't think so but how can I tell specially if it's only a small amount, anyway things seem to be ok for now and it's guiding ok.

best regards  Rick

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kirkster501    1,624

Lucas is brilliant for after sales and answering questions.  He is a great guy, a brilliant engineer who makes a top class product.  Mine has not missed a beat.

I move mine for balance on both axis and you can hear something spinning or "notching" internally.  I never move it when it is powered up though.

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ollypenrice    18,144
22 minutes ago, kirkster501 said:

Lucas is brilliant for after sales and answering questions.  He is a great guy, a brilliant engineer who makes a top class product.  Mine has not missed a beat.

I move mine for balance on both axis and you can hear something spinning or "notching" internally.  I never move it when it is powered up though.

If you push either axis too quickly it doesn't like it and you feel a 'knotting up' of the drives. I've been moving mine manually for years because I have the internet-free ArgoNavis versions on which the first operation is to point manually at your alignment star and then power up. After that all movement is done by the drives.

Olly

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